Photocrystallographic observation of halide-bridged intermediates in halogen photoeliminations.

PubMed

Powers, David C; Anderson, Bryce L; Hwang, Seung Jun; Powers, Tamara M; Pérez, Lisa M; Hall, Michael B; Zheng, Shao-Liang; Chen, Yu-Sheng; Nocera, Daniel G

2014-10-29

Polynuclear transition metal complexes, which frequently constitute the active sites of both biological and chemical catalysts, provide access to unique chemical transformations that are derived from metal-metal cooperation. Reductive elimination via ligand-bridged binuclear intermediates from bimetallic cores is one mechanism by which metals may cooperate during catalysis. We have established families of Rh2 complexes that participate in HX-splitting photocatalysis in which metal-metal cooperation is credited with the ability to achieve multielectron photochemical reactions in preference to single-electron transformations. Nanosecond-resolved transient absorption spectroscopy, steady-state photocrystallography, and computational modeling have allowed direct observation and characterization of Cl-bridged intermediates (intramolecular analogues of classical ligand-bridged intermediates in binuclear eliminations) in halogen elimination reactions. On the basis of these observations, a new class of Rh2 complexes, supported by CO ligands, has been prepared, allowing for the isolation and independent characterization of the proposed halide-bridged intermediates. Direct observation of halide-bridged structures establishes binuclear reductive elimination as a viable mechanism for photogenerating energetic bonds.

Biosensor and chemical sensor probes for calcium and other metal ions

DOEpatents

Vo-Dinh, Tuan; Viallet, Pierre

1996-01-01

The present invention relates to chemical sensor and biosensor probes for measuring low concentration of metals and metal ions in complex samples such as biological fluids, living cells, and environmental samples. More particularly the present invention relates to a gel-based Indo-1 and Fura-2 chemical sensor probes for the measurement of low concentrations of calcium, cadmium, magnesium and the like. Also disclosed is a detector device using the sensors of the present invention.

Peptide-mediated vectorization of metal complexes: conjugation strategies and biomedical applications.

PubMed

Soler, Marta; Feliu, Lidia; Planas, Marta; Ribas, Xavi; Costas, Miquel

2016-08-16

The rich chemical and structural versatility of transition metal complexes provides numerous novel paths to be pursued in the design of molecules that exert particular chemical or physicochemical effects that could operate over specific biological targets. However, the poor cell permeability of metallodrugs represents an important barrier for their therapeutic use. The conjugation between metal complexes and a functional peptide vector can be regarded as a versatile and potential strategy to improve their bioavailability and accumulation inside cells, and the site selectivity of their effect. This perspective lies in reviewing the recent advances in the design of metallopeptide conjugates for biomedical applications. Additionally, we highlight the studies where this approach has been directed towards the incorporation of redox active metal centers into living organisms for modulating the cellular redox balance, as a tool with application in anticancer therapy.

DFT study of the interaction between DOTA chelator and competitive alkali metal ions.

PubMed

Frimpong, E; Skelton, A A; Honarparvar, B

2017-09-01

1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetracetic acid (DOTA) is an important chelator for radiolabeling of pharmaceuticals. The ability of alkali metals found in the body to complex with DOTA and compete with radio metal ions can alter the radiolabeling process. Non-covalent interactions between DOTA complexed with alkali metals Li + , Na + , K + and Rb + , are investigated with density functional theory using B3LYP and ωB97XD functionals. Conformational possibilities of DOTA were explored with a varying number of carboxylic pendant arms of DOTA in close proximity to the ions. It is found that the case in which four arms of DOTA are interacting with ions is more stable than other conformations. The objective of this study is to explore the electronic structure properties upon complexation of alkali metals Li + Na + , K + and Rb + with a DOTA chelator. Interaction energies, relaxation energies, entropies, Gibbs free energies and enthalpies show that the stability of DOTA, complexed with alkali metals decreases down the group of the periodic table. Implicit water solvation affects the complexation of DOTA-ions leading to decreases in the stability of the complexes. NBO analysis through the natural population charges and the second order perturbation theory, revealed a charge transfer between DOTA and alkali metals. Conceptual DFT-based properties such as HOMO/LUMO energies, ΔE HOMO-LUMO and chemical hardness and softness indicated a decrease in the chemical stability of DOTA-alkali metal complexes down the alkali metal series. This study serves as a guide to researchers in the field of organometallic chelators, particularly, radiopharmaceuticals in finding the efficient optimal match between chelators and various metal ions. Copyright © 2017 Elsevier Inc. All rights reserved.

Synthesis and Properties of Ortho-Nitro-Fe Complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, A.; Mishra, Niyati; Sharma, R.

2011-07-15

Ortho-Nitro-Fe complex (Transition metal complex) has synthesized by chemical route method and properties of made complex has characterized by X-Ray diffraction (XRD), Moessbauer spectroscopy, Fourier transformation infra-red spectroscopy (FTIR) and X-Ray photoelectron spectroscopy (XPS). XRD analysis shows that sample is crystalline in nature and having particle size in the range of few nano meters. Moessbauer spectroscopy at room temperature shows the oxidation state of Iron (central metal ion) after complaxasion. FTIR spectra of the complex confirms the coordination of metal ion with ligand.

Impact of spreading olive mill waste water on agricultural soils for leaching of metal micronutrients and cations.

PubMed

Aharonov-Nadborny, R; Tsechansky, L; Raviv, M; Graber, E R

2017-07-01

Olive mill waste water (OMWW) is an acidic (pH 4-5), saline (EC ∼ 5-10 mS cm -1 ), blackish-red aqueous byproduct of the three phase olive oil production process, with a high chemical oxygen demand (COD) of up to 220,000 mg L -1 . OMWW is conventionally disposed of by uncontrolled dumping into the environment or by semi-controlled spreading on agricultural soils. It was hypothesized that spreading such liquids on agricultural soils could result in the release and mobilization of indigenous soil metals. The effect of OMWW spreading on leaching of metal cations (Na, K, Mg, Mn, Fe, Cu, Zn) was tested in four non-contaminated agricultural soils having different textures (sand, clay loam, clay, and loam) and chemical properties. While the OMWW contributed metals to the soil solution, it also mobilized indigenous soil metals as a function of soil clay content, cation exchange capacity (CEC), and soil pH-buffer capacity. Leaching of soil-originated metals from the sandy soil was substantially greater than from the loam and clay soils, while the clay loam was enriched with metals derived from the OMWW. These trends were attributed to cation exchange and organic-metal complex formation. The organic matter fraction of OMWW forms complexes with metal cations; these complexes may be mobile or precipitate, depending on the soil chemical and physical environment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Metal Ion Binding at the Catalytic Site Induces Widely Distributed Changes in a Sequence Specific Protein–DNA Complex

PubMed Central

2016-01-01

Metal ion cofactors can alter the energetics and specificity of sequence specific protein–DNA interactions, but it is unknown if the underlying effects on structure and dynamics are local or dispersed throughout the protein–DNA complex. This work uses EcoRV endonuclease as a model, and catalytically inactive lanthanide ions, which replace the Mg2+ cofactor. Nuclear magnetic resonance (NMR) titrations indicate that four Lu3+ or two La3+ cations bind, and two new crystal structures confirm that Lu3+ binding is confined to the active sites. NMR spectra show that the metal-free EcoRV complex with cognate (GATATC) DNA is structurally distinct from the nonspecific complex, and that metal ion binding sites are not assembled in the nonspecific complex. NMR chemical shift perturbations were determined for 1H–15N amide resonances, for 1H–13C Ile-δ-CH3 resonances, and for stereospecifically assigned Leu-δ-CH3 and Val-γ-CH3 resonances. Many chemical shifts throughout the cognate complex are unperturbed, so metal binding does not induce major conformational changes. However, some large perturbations of amide and side chain methyl resonances occur as far as 34 Å from the metal ions. Concerted changes in specific residues imply that local effects of metal binding are propagated via a β-sheet and an α-helix. Both amide and methyl resonance perturbations indicate changes in the interface between subunits of the EcoRV homodimer. Bound metal ions also affect amide hydrogen exchange rates for distant residues, including a distant subdomain that contacts DNA phosphates and promotes DNA bending, showing that metal ions in the active sites, which relieve electrostatic repulsion between protein and DNA, cause changes in slow dynamics throughout the complex. PMID:27786446

Molecular-Orbital Models for the Catayltic Activity and Selectivity of Coordinatively Unsaturated Platinum Surfaces and Complexes.

DTIC Science & Technology

1980-12-31

surfaces. Reactions involving the Pt(O)- triphenylphosphine complexes Pt(PPh 3)n, where n = 2, 3, 4, have been shown to have precise analogues on Pt...12], the triphenylphosphine (PPh 3 ) group is modeled by the simpler but chemically similar phosphine (PH3) group. The appropriate Pt-P bond distances...typically refractory oxides ) are of sufficient magnitude as to suggest significant chemical and electronic modifications of the metal at the metal-support

Use Zircon-Ilmenite Concentrate in Steelmaking

NASA Astrophysics Data System (ADS)

Fedoseev, S. N.; Volkova, T. N.

2016-08-01

Market requirements cause a constant search for new materials and technologies, for their immediate use in increasing requirements for material and energy efficiency, as well as to the quality of steel. In practice, steel production in the tended recently of more stringent requirements for the chemical composition of the steel and its contamination by nonmetallic inclusions, gas and non-ferrous metals. The main ways of increasing of strength and performance characteristics fabricated metal products related to the profound and effective influence on the crystallizing metal structure by furnace processing of the melt with refining and modifying additives. It can be argued that the furnace processing of steel and iron chemically active metals (alkali-earth metals, rare-earth metals, and others.) is an integral part of modern production of high quality products and competitive technologies. Important condition for development of methods secondary metallurgy of steel is the use of relatively inexpensive materials in a variety of complex alloys and blends, allowing targeted control of physical and chemical state of the molten metal and, therefore, receive steel with improved performance. In this connection the development of modifying natural materials metallurgy technologies presented complex ores containing titanium and zirconium, is a very urgent task.

Characterization of stainless steel surface processed using electrolytic oxidation and titanium complex ion solution

NASA Astrophysics Data System (ADS)

Kang, Yubin; Choi, Jaeyoung; Park, Jinju; Kim, Woo-Byoung; Lee, Kun-Jae

2017-09-01

This study attempts to improve the physical and chemical adhesion between metals and ceramics by using electrolytic oxidation and a titanium organic/inorganic complex ion solution on the SS-304 plate. Surface analysis confirmed the existence of the Tisbnd Osbnd Mx bonds formed by the bonding between the metal ions and the Ti oxide at the surface of the pre-processed SS plate, and improved chemical adhesion during ceramic coating was expected by confirming the presence of the carboxylic group. The adhesion was evaluated by using the ceramic coating solution in order to assess the improved adhesion of the SS plate under conditions. The results showed that both the adhesion and durability were largely improved in the sample processed with all the pre-processing steps, thus confirming that the physical and chemical adhesion between metals and ceramics can be improved by enhancing the physical roughness via electrolytic oxidation and pre-processing using a Ti complex ion solution.

Preparation, Analysis, and Characterization of Some Transition Metal Complexes--A Holistic Approach

ERIC Educational Resources Information Center

Blyth, Kristy M.; Mullings, Lindsay R.; Philips, David N.; Pritchard, David; van Bronswijk, Wilhelm

2005-01-01

The chemical and instrumental methods used in the study of transition-metal complexes provide a complete determination of their structure, bonding, and properties. It unites concepts of analytical, inorganic, and physical chemistry in a way that students might appreciate that these areas of chemistry are not different.

Increasing the reliability and quality of important cast products made of chemically active metals and alloys

NASA Astrophysics Data System (ADS)

Varfolomeev, M. S.; Moiseev, V. S.; Shcherbakova, G. I.

2017-01-01

A technology is developed to produce highly thermoresistant ceramic monoxide corundum molds using investment casting and an aluminum-organic binder. This technology is a promising trend in creating ceramic molds for precision complex-shape casting of important ingots made of high-alloy steels, high-temperature and titanium alloys, and refractory metals. The use of the casting molds that have a high thermal and chemical resistance to chemically active metals and alloys under high-temperature casting minimizes the physicochemical interaction and substantially decreases the depth of the hard-to-remove metal oxide layer on important products, which increases their service properties.

Early-Late Heterobimetallic Complexes Linked by Phosphinoamide Ligands. Tuning Redox Potentials and Small Molecule Activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, Christine M.

2015-08-01

Recent attention in the chemical community has been focused on the energy efficient and environmentally benign conversion of abundant small molecules (CO2, H2O, etc.) to useful liquid fuels. This project addresses these goals by examining fundamental aspects of catalyst design to ultimately access small molecule activation processes under mild conditions. Specifically, Thomas and coworkers have targetted heterobimetallic complexes that feature metal centers with vastly different electronic properties, dictated both by their respective positions on the periodic table and their coordination environment. Unlike homobimetallic complexes featuring identical or similar metals, the bonds between metals in early/late heterobimetallics are more polarized, withmore » the more electron-rich late metal center donating electron density to the more electron-deficient early metal center. While metal-metal bonds pose an interesting strategy for storing redox equivalents and stabilizing reactive metal fragments, the polar character of metal-metal bonds in heterobimetallic complexes renders these molecules ideally poised to react with small molecule substrates via cleavage of energy-rich single and double bonds. In addition, metal-metal interactions have been shown to dramatically affect redox potentials and promote multielectron redox activity, suggesting that metal-metal interactions may provide a mechanism to tune redox potentials and access substrate reduction/activation at mild overpotentials. This research project has provided a better fundamental understanding of how interactions between transition metals can be used as a strategy to promote and/or control chemical transformations related to the clean production of fuels. While this project focused on the study of homogeneous systems, it is anticipated that the broad conclusions drawn from these investigations will be applicable to heterogeneous catalysis as well, particularly on heterogeneous processes that occur at interfaces in multicomponent systems.« less

Metal complexes of quinolone antibiotics and their applications: an update.

PubMed

Uivarosi, Valentina

2013-09-11

Quinolones are synthetic broad-spectrum antibiotics with good oral absorption and excellent bioavailability. Due to the chemical functions found on their nucleus (a carboxylic acid function at the 3-position, and in most cases a basic piperazinyl ring (or another N-heterocycle) at the 7-position, and a carbonyl oxygen atom at the 4-position) quinolones bind metal ions forming complexes in which they can act as bidentate, as unidentate and as bridging ligand, respectively. In the polymeric complexes in solid state, multiple modes of coordination are simultaneously possible. In strongly acidic conditions, quinolone molecules possessing a basic side nucleus are protonated and appear as cations in the ionic complexes. Interaction with metal ions has some important consequences for the solubility, pharmacokinetics and bioavailability of quinolones, and is also involved in the mechanism of action of these bactericidal agents. Many metal complexes with equal or enhanced antimicrobial activity compared to the parent quinolones were obtained. New strategies in the design of metal complexes of quinolones have led to compounds with anticancer activity. Analytical applications of complexation with metal ions were oriented toward two main directions: determination of quinolones based on complexation with metal ions or, reversely, determination of metal ions based on complexation with quinolones.

Chelation technology: a promising green approach for resource management and waste minimization.

PubMed

Chauhan, Garima; Pant, K K; Nigam, K D P

2015-01-01

Green chemical engineering recognises the concept of developing innovative environmentally benign technologies to protect human health and ecosystems. In order to explore this concept for minimizing industrial waste and for reducing the environmental impact of hazardous chemicals, new greener approaches need to be adopted for the extraction of heavy metals from industrial waste. In this review, a range of conventional processes and new green approaches employed for metal extraction are discussed in brief. Chelation technology, a modern research trend, has shown its potential to develop sustainable technology for metal extraction from various metal-contaminated sites. However, the interaction mechanism of ligands with metals and the ecotoxicological risk associated with the increased bioavailability of heavy metals due to the formation of metal-chelant complexes is still not sufficiently explicated in the literature. Therefore, a need was felt to provide a comprehensive state-of-the-art review of all aspects associated with chelation technology to promote this process as a green chemical engineering approach. This article elucidates the mechanism and thermodynamics associated with metal-ligand complexation in order to have a better understanding of the metal extraction process. The effects of various process parameters on the formation and stability of complexes have been elaborately discussed with respect to optimizing the chelation efficiency. The non-biodegradable attribute of ligands is another important aspect which is currently of concern. Therefore, biotechnological approaches and computational tools have been assessed in this review to illustrate the possibility of ligand degradation, which will help the readers to look for new environmentally safe mobilizing agents. In addition, emerging trends and opportunities in the field of chelation technology have been summarized and the diverse applicability of chelation technology in metal extraction from contaminated sites has also been reviewed.

A chemical equilibrium model for metal adsorption onto bacterial surfaces

NASA Astrophysics Data System (ADS)

Fein, Jeremy B.; Daughney, Christopher J.; Yee, Nathan; Davis, Thomas A.

1997-08-01

This study quantifies metal adsorption onto cell wall surfaces of Bacillus subtilis by applying equilibrium thermodynamics to the specific chemical reactions that occur at the water-bacteria interface. We use acid/base titrations to determine deprotonation constants for the important surface functional groups, and we perform metal-bacteria adsorption experiments, using Cd, Cu, Pb, and Al, to yield site-specific stability constants for the important metal-bacteria surface complexes. The acid/base properties of the cell wall of B. subtilis can best be characterized by invoking three distinct types of surface organic acid functional groups, with pK a values of 4.82 ± 0.14, 6.9 ± 0.5, and 9.4 ± 0.6. These functional groups likely correspond to carboxyl, phosphate, and hydroxyl sites, respectively, that are displayed on the cell wall surface. The results of the metal adsorption experiments indicate that both the carboxyl sites and the phosphate sites contribute to metal uptake. The values of the log stability constants for metal-carboxyl surface complexes range from 3.4 for Cd, 4.2 for Pb, 4.3 for Cu, to 5.0 for Al. These results suggest that the stabilities of the metal-surface complexes are high enough for metal-bacterial interactions to affect metal mobilities in many aqueous systems, and this approach enables quantitative assessment of the effects of bacteria on metal mobilities.

Platinum-group elements fractionation by selective complexing, the Os, Ir, Ru, Rh-arsenide-sulfide systems above 1020 °C

NASA Astrophysics Data System (ADS)

Helmy, Hassan M.; Bragagni, Alessandro

2017-11-01

The platinum-group element (PGE) contents in magmatic ores and rocks are normally in the low μg/g (even in the ng/g) level, yet they form discrete platinum-group mineral (PGM) phases. IPGE (Os, Ir, Ru) + Rh form alloys, sulfides, and sulfarsenides while Pt and Pd form arsenides, tellurides, bismuthoids and antimonides. We experimentally investigate the behavior of Os, Ru, Ir and Rh in As-bearing sulfide system between 1300 and 1020 °C and show that the prominent mineralogical difference between IPGE (+Rh) and Pt and Pd reflects different chemical preference in the sulfide melt. At temperatures above 1200 °C, Os shows a tendency to form alloys. Ruthenium forms a sulfide (laurite RuS2) while Ir and Rh form sulfarsenides (irarsite IrAsS and hollingworthite RhAsS, respectively). The chemical preference of PGE is selective: IPGE + Rh form metal-metal, metal-S and metal-AsS complexes while Pt and Pd form semimetal complexes. Selective complexing followed by mechanical separation of IPGE (and Rh)-ligand from Pt- and Pd-ligand associations lead to PGE fractionation.

40 CFR Appendix B to Part 414 - Complexed Metal-Bearing Waste Streams

Code of Federal Regulations, 2012 CFR

2012-07-01

...) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Pt. 414, App. B... dyes, Azo (including metallized) Organic pigments, miscellaneous lakes and toners Copper Disperse dyes...-acetamidoanisole Azo dyes, metallized/Azo dye + metal acetate Direct dyes, Azo Disperse dyes, Azo and Vat Organic...

METHODS OF TREATMENT OF COMPLEX SURFACES ON METAL CUTTING MACHINES (CHAPTERS 1 AND 12),

DTIC Science & Technology

FORGING, MOLDINGS, MANDRELS, MARINE PROPELLERS, AERIAL PROPELLERS, TURBINE BLADES, ABRASIVES, IMPELLERS, AIRCRAFT PANELS, METAL PLATES, CAMS, ELECTROEROSIVE MACHINING, CHEMICAL MILLING, MAGNETOSTRICTIVE ELEMENTS, USSR.

Discovery and development of microporous metal carboxylates.

PubMed

Mori, Wasuke; Sato, Tomohiko; Kato, Chika Nozaki; Takei, Tohru; Ohmura, Tetsushi

2005-01-01

We have found a form of copper(II) terephthalate that occluded an enormous amount of gases such as N2, Ar, O2, and Xe. Copper(II) terephthalate is the first metal complex found capable of adsorbing gases. This complex has opened a new field of adsorbent chemistry and is recognized as a leader in the construction of microporous metal complexes. In extending the route for the synthesis of microporous complexes, we obtained many new porous materials that are widely recognized as useful materials for applications in areas such as gas storage, molecular sieves, catalysis, inclusion complexes, and surface science. 2005 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

Simulation of the mobility of metal - EDTA complexes in groundwater: The influence of contaminant metals

USGS Publications Warehouse

Friedly, J.C.; Kent, D.B.; Davis, J.A.

2002-01-01

Reactive transport simulations were conducted to model chemical reactions between metal - EDTA (ethylenediaminetetraacetic acid) complexes during transport in a mildly acidic quartz - sand aquifer. Simulations were compared with the results of small-scale tracer tests wherein nickel-, zinc-, and calcium - EDTA complexes and free EDTA were injected into three distinct chemical zones of a plume of sewage-contaminated groundwater. One zone had a large mass of adsorbed, sewage-derived zinc; one zone had a large mass of adsorbed manganese resulting from mildly reducing conditions created bythe sewage plume; and one zone had significantly less adsorbed manganese and negligible zinc background. The chemical model assumed that the dissolution of iron(III) from metal - hydroxypolymer coatings on the aquifer sediments by the metal - EDTA complexes was kinetically restricted. All other reactions, including metal - EDTA complexation, zinc and manganese adsorption, and aluminum hydroxide dissolution were assumed to reach equilibrium on the time scale of transport; equilibrium constants were either taken from the literature or determined independently in the laboratory. A single iron(III) dissolution rate constant was used to fit the breakthrough curves observed in the zone with negligible zinc background. Simulation results agreed well with the experimental data in all three zones, which included temporal moments derived from breakthrough curves at different distances downgradient from the injections and spatial moments calculated from synoptic samplings conducted at different times. Results show that the tracer cloud was near equilibrium with respect to Fe in the sediment after 11 m of transport in the Zn-contaminated region but remained far from equilibrium in the other two zones. Sensitivity studies showed that the relative rate of iron(III) dissolution by the different metal - EDTA complexes was less important than the fact that these reactions are rate controlled. Results suggest that the published solubility for ferrihydrite reasonably approximates the Fe solubility of the hydroxypolymer coatings on the sediments. Aluminum may be somewhat more soluble than represented by the equilibrium constant for gibbsite, and its dissolution may be rate controlled when reacting with Ca - EDTA complexes.

Density functional theory study on Herzberg-Teller contribution in Raman scattering from 4-aminothiophenol-metal complex and metal-4-aminothiophenol-metal junction

NASA Astrophysics Data System (ADS)

Liu, Shasha; Zhao, Xiuming; Li, Yuanzuo; Zhao, Xiaohong; Chen, Maodu

2009-06-01

Density functional theory (DFT) and time-dependent DFT calculations have been performed to investigate the Raman scattering spectra of metal-molecule complex and metal-molecule-metal junction architectures interconnected with 4-aminothiophenol (PATP) molecule. The simulated profiles of normal Raman scattering (NRS) spectra for the two complexes (Ag2-PATP and PATP-Au2) and the two junctions (Ag2-PATP-Au2 and Au2-PATP-Ag2) are similar to each other, but exhibit obviously different Raman intensities. Due to the lager static polarizabilities of the two junctions, which directly influence the ground state chemical enhancement in NRS spectra, the calculated normal Raman intensities of them are stronger than those of two complexes by the factor of 102. We calculate preresonance Raman scattering (RRS) spectra with incident light at 1064 nm, which is much lower than the S1 electronic transition energy of complexes and junctions. Ag2-PATP-Au2 and Au2-PATP-Ag2 junctions yield higher Raman intensities than those of Ag2-PATP and PATP-Au2 complexes, especially for b2 modes. This effect is mainly attributed to charge transfer (CT) between the metal gap and the PAPT molecule which results in the occurrence of CT resonance enhancement. The calculated pre-RRS spectra strongly depend on the electronic transition state produced by new structures. With excitation at 514.5 nm, the calculated pre-RRS spectra of two complexes and two junctions are stronger than those of with excitation at 1064 nm. A charge difference densities methodology has been used to visually describe chemical enhancement mechanism of RRS spectrum. This methodology aims at visualizing intermolecular CT which provides direct evidence of the Herzberg-Teller mechanism.

Multinuclear metal-binding ability of a carotene

PubMed Central

Horiuchi, Shinnosuke; Tachibana, Yuki; Yamashita, Mitsuki; Yamamoto, Koji; Masai, Kohei; Takase, Kohei; Matsutani, Teruo; Kawamata, Shiori; Kurashige, Yuki; Yanai, Takeshi; Murahashi, Tetsuro

2015-01-01

Carotenes are naturally abundant unsaturated hydrocarbon pigments, and their fascinating physical and chemical properties have been studied intensively not only for better understanding of the roles in biological processes but also for the use in artificial chemical systems. However, their metal-binding ability has been virtually unexplored. Here we report that β-carotene has the ability to assemble and align ten metal atoms to afford decanuclear homo- and heterometal chain complexes. The metallo–carotenoid framework shows reversible metalation–demetalation reactivity with multiple metals, which allows us to control the size of metal chains as well as the heterobimetallic composition and arrangement of the carotene-supported metal chains. PMID:25857402

Effect of Ocean Acidification on Organic and Inorganic Speciation of Trace Metals.

PubMed

Stockdale, Anthony; Tipping, Edward; Lofts, Stephen; Mortimer, Robert J G

2016-02-16

Rising concentrations of atmospheric carbon dioxide are causing acidification of the oceans. This results in changes to the concentrations of key chemical species such as hydroxide, carbonate and bicarbonate ions. These changes will affect the distribution of different forms of trace metals. Using IPCC data for pCO2 and pH under four future emissions scenarios (to the year 2100) we use a chemical speciation model to predict changes in the distribution of organic and inorganic forms of trace metals. Under a scenario where emissions peak after the year 2100, predicted free ion Al, Fe, Cu, and Pb concentrations increase by factors of up to approximately 21, 2.4, 1.5, and 2.0 respectively. Concentrations of organically complexed metal typically have a lower sensitivity to ocean acidification induced changes. Concentrations of organically complexed Mn, Cu, Zn, and Cd fall by up to 10%, while those of organically complexed Fe, Co, and Ni rise by up to 14%. Although modest, these changes may have significance for the biological availability of metals given the close adaptation of marine microorganisms to their environment.

Mechanisms for Reduction of Natural Waters Technogenic Pollution by Metals due to Complexions with Humus Substances (Zoning: Western Siberia and the European Territory of Russia)

NASA Astrophysics Data System (ADS)

Dinu, M. I.

2017-11-01

The article described the complexation of metal ions with humus substances in natural waters (small lakes). Humus substances as the major biochemical components of natural water have a significant impact on the forms and migration of metals and the toxicity of natural objects. This article presents the results of large-scale chemical experiments: the study of the structural features (zonal aspects) of humus substances extracted from soil and water natural climatic zones (more than 300 objects) in Russia (European Russia and West Siberia); the influence of structural features on the physic-chemical parameters of humus acids and, in particular, on their complexing ability. The functional specifics of humus matter extracted from soils is estimated using spectrometric techniques. The conditional stability constants for Fe(III), Cu(II), Pb(II), Cd(II), Zn(II), Ni(II), Co(II), Mn(II), Cr(III), Ca(II), Mg(II), Sr(II), and Al(III) are experimentally determined with the electrochemical, spectroscopic analysis methods. The activities of metals are classified according to their affinity to humus compounds in soils and water. The determined conditional stability constants of the complexes are tested by model experiments, and it is demonstrated that Fe and Al ions have higher conditional stability constants than the ions of alkali earth metals, Pb, Cu, and Zn. Furthermore, the influence of aluminium ions and iron on the complexation of copper and lead as well as the influence of lead and copper on complexation of cobalt and nickel have been identified. The metal forms in a large number of lakes are calculated basing on the experiments’ results. The main chemical mechanisms of the distribution of metals by forms in the water of the lakes in European Russia and West Siberia are described.

Influence of variable chemical conditions on EDTA-enhanced transport of metal ions in mildly acidic groundwater

USGS Publications Warehouse

Kent, D.B.; Davis, J.A.; Joye, J.L.; Curtis, G.P.

2008-01-01

Adsorption of Ni and Pb on aquifer sediments from Cape Cod, Massachusetts, USA increased with increasing pH and metal-ion concentration. Adsorption could be described quantitatively using a semi-mechanistic surface complexation model (SCM), in which adsorption is described using chemical reactions between metal ions and adsorption sites. Equilibrium reactive transport simulations incorporating the SCMs, formation of metal-ion-EDTA complexes, and either Fe(III)-oxyhydroxide solubility or Zn desorption from sediments identified important factors responsible for trends observed during transport experiments conducted with EDTA complexes of Ni, Zn, and Pb in the Cape Cod aquifer. Dissociation of Pb-EDTA by Fe(III) is more favorable than Ni-EDTA because of differences in Ni- and Pb-adsorption to the sediments. Dissociation of Ni-EDTA becomes more favorable with decreasing Ni-EDTA concentration and decreasing pH. In contrast to Ni, Pb-EDTA can be dissociated by Zn desorbed from the aquifer sediments. Variability in adsorbed Zn concentrations has a large impact on Pb-EDTA dissociation.

Metals, Molecules, Life and Death

DOE Office of Scientific and Technical Information (OSTI.GOV)

George, Graham

2004-08-31

In our normal everyday lives we are exposed to an incredibly complex chemical soup consisting of an enormous variety of different chemical compounds. Many of these compounds contain metal atoms which, once inside us, can either fulfill roles that are essential to health, or act as poisons. Studies at SLAC's Stanford Synchrotron Radiation Laboratory (SSRL) reveal the molecular details of metals in living systems; how they interact with one another, how they confer beneficial properties, and how they act as poisons.

Catalytic Isonitrile Insertions and Condensations Initiated by RNC–X Complexation

PubMed Central

Fleming, Fraser F.

2014-01-01

Isonitriles are delicately poised chemical entities capable of being coaxed to react as nucleophiles or electrophiles. Directing this tunable reactivity with metal and non-metal catalysts provides rapid access to a large array of complex nitrogenous structures ideally functionalized for medicinal applications. Isonitrile insertion into transition metal complexes has featured in numerous synthetic and mechanistic studies, leading to rapid deployment of isonitriles in numerous catalytic processes, including multicomponent reactions (MCR). Covering the literature from 1990–2014, the present review collates reaction types to highlight reactivity trends and allow catalyst comparison. PMID:25484847

40 CFR Appendix B to Part 414 - Complexed Metal-Bearing Waste Streams

Code of Federal Regulations, 2013 CFR

2013-07-01

... GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Pt. 414, App. B Appendix B to Part... (including metallized) Organic pigments, miscellaneous lakes and toners Copper Disperse dyes Acid dyes Direct..., metallized/Azo dye + metal acetate Direct dyes, Azo Disperse dyes, Azo and Vat Organic pigment Green 7/Copper...

40 CFR Appendix B to Part 414 - Complexed Metal-Bearing Waste Streams

Code of Federal Regulations, 2014 CFR

2014-07-01

... GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Pt. 414, App. B Appendix B to Part... (including metallized) Organic pigments, miscellaneous lakes and toners Copper Disperse dyes Acid dyes Direct..., metallized/Azo dye + metal acetate Direct dyes, Azo Disperse dyes, Azo and Vat Organic pigment Green 7/Copper...

Volatile organometallic complexes suitable for use in chemical vapor depositions on metal oxide films

DOEpatents

Giolando, Dean M.

2003-09-30

Novel ligated compounds of tin, titanium, and zinc are useful as metal oxide CVD precursor compounds without the detriments of extreme reactivity yet maintaining the ability to produce high quality metal oxide coating by contact with heated substrates.

Polymer-grafted QCM chemical sensor and application to heavy metalions real time detection.

PubMed

Sartore, Luciana; Barbaglio, Marzia; Borgese, Laura; Bontempi, Elza

2011-07-20

A flow type quartz crystal microbalance (QCM) chemical sensor was developed for monitoring of heavy metal ions in aqueous solutions (that is suitable for environmental monitoring). The sensor is based upon surface chelation of the metal ions at multifunctional polymer modified gold electrodes on 9 MHz AT-cut quartz resonators, functioning as a QCM. New processes have been developed which enable to obtain surface-modified gold electrodes with high heavy metal ions complexing ability. These polymer grafted QCM sensors can selectively adsorb heavy metal ions, such as copper lead chrome and cadmium, from solution over a wide range from 0.01 to 1000 ppm concentration by complexation with functional groups in the polymers. Cations typically present in natural water did not interfere with the detection of heavy metals. X-Ray Reflectivity (XRR) and Total Reflection X-ray Fluorescence (TXRF) were carried out to characterise the unmodified and modified gold surfaces as well as to verify the possibility to selectively bond and remove metal ions.

Selective Separation and Determination of Heavy Metals (Cd, Pb, Cr) Speciation Forms from Hortic Antrosols

NASA Astrophysics Data System (ADS)

Bulgariu, D.; Bulgariu, L.

2009-04-01

The speciation, inter-phases distribution and biodisponibility of heavy metals in soils represent one of main problem of environmental geochemistry and agro-chemistry. This problem is very important in case of hortic antrosols (soils from glasshouses) for the elimination of agricultural products (fruits, vegetables) contamination with heavy metals. In soils from glass houses, the speciation and inter-phases distribution processes of heavy metals have a particular dynamic, different in comparison with those from non-protected soils. The predominant distribution forms of heavy metals in such soils types are: complexes with low mass organic molecules, organic-mineral complexes, complexes with inorganic ligands (hydroxide-complexes, carbonate-complexes, sulphate-complexes, etc.) and basic salts. All of these have high stabilities in conditions of soils from glass houses, and in consequence, the separation and determination of speciation forms (which is directly connected with biodisponibility of heavy metals) by usual methods id very difficult and has a high uncertain degree. In this study is presented an original method for the selective separation and differentiation of speciation forms of heavy metals from glass houses soils, which is based by the combination of solid-liquid sequential extraction (SPE) with the extraction in aqueous polymer-inorganic salt two-phase systems (ABS). The soil samples used for this study have been sampled from three different locations (glass houses from Iasi, Barlad and Bacau - Romania) where the vegetables cultivation have bee performed by three different technologies. In this way was estimated the applicability and the analytical limits of method proposed by as, in function of the chemical-mineralogical and physical-chemical characteristics of soils. As heavy metals have been studied cadmium, lead and chromium, all being known for their high toxicity. The procedure used for the selective separation and differentiation of speciation forms of heavy metals from glass houses soils has two main steps: (i) non-destructive separation of chemical-mineralogical associations and aggregates from soils samples - for this the separation method with heavy liquids (bromophorme) and isodynamic magnetic method have been used; (ii) sequential extraction of heavy metals from soil fractions separated in the first step, by using combined SPE-ABS procedure. For the preparation of combined extraction systems was used polyethylene glycol (with different molecular mass: 2000, 4000 and 8000). As phase-forming inorganic salts and as selective extracting agents we have used different usual inorganic reagents. The type and concentration of phase-forming salts have been selected in function of, both nature of extracted heavy metals and chemical-mineralogical characteristics of soil samples. The experimental parameters investigated in this study are: molecular mass of polyethylene glycol and the concentration of polymeric solutions, nature and concentration of phase-forming salts, nature and concentration of extracting agents, pH in extraction system phase, type of extracted heavy metals, type of speciation forms of heavy metals and their concentrations. All these factors can influence significantly the efficiency and the selectivity of separation process. The experimental results have indicate that the combined SPE-ABS extraction systems have better separation efficiency, in comparison with traditional SPE systems and ca realized a accurate discrimination between speciation forms of heavy metals from soils. Under these conditions, the estimation of inter-phases distribution and biodisponibility of heavy metals has a high precision. On the other hand, when the combined SPE-ABS systems are used, the concomitant extraction of the elements from the same geochemical association with studied heavy metals (inevitable phenomena in case of separation by SPE procedures) is significant diminished. This increases the separation selectivity and facilitated the more accurate determination of speciation forms concentration. By adequate selection of extraction conditions can be realized the selective separation of organic-mineral complexes, which will permit to perform detailed studies about the structure and chemical composition of these. Acknowledgments The authors would like to acknowledge the financial support from Romanian Ministry of Education and Research (Project PNCDI 2-D5 no. 51045/07).

Dissolved sulfides in the oxic water column of San Francisco Bay, California

USGS Publications Warehouse

Kuwabara, J.S.; Luther, G.W.

1993-01-01

Trace contaminants enter major estuaries such as San Francisco Bay from a variety of point and nonpoint sources and may then be repartitioned between solid and aqueous phases or altered in chemical speciation. Chemical speciation affects the bioavailability of metals as well as organic ligands to planktonic and benthic organisms, and the partitioning of these solutes between phases. Our previous, work in south San Francisco Bay indicated that sulfide complexation with metals may be of particular importance because of the thermodynamic stability of these complexes. Although the water column of the bay is consistently well-oxygenated and typically unstratified with respect to dissolved oxygen, the kinetics of sulfide oxidation could exert at least transient controls on metal speciation. Our initial data on dissolved sulfides in the main channel of both the northern and southern components of the bay consistently indicate submicromolar concenrations (from <1 nM to 162 nM), as one would expect in an oxidizing environment. However, chemical speciation calculations over the range of observed sulfide concentrations indicate that these trace concentrations in the bay water column can markedly affect chemical speciation of ecologically significant trace metals such as cadmium, copper, and zinc.

Evaluation of the chelating performance of biopolyelectrolyte green complexes (NIBPEGCs) for wastewater treatment from the metal finishing industry.

PubMed

López-Maldonado, Eduardo A; Zavala García, Oscar Gabriel; Escobedo, Kevin Cruz; Oropeza-Guzman, Mercedes T

2017-08-05

In this paper nonstoichiometric interbiopolyelectrolyte green complexes (NIBPEGCs) were prepared using chitosan (Ch), alginate (AG) and poly(acrylic acid)(PAA). They are proposed as innovative formulations (polyelectrolytes and chelating agents) suitable for the elimination heavy metals contained in wastewater. This application may represent an integral solution for industries rejecting solid and aqueous metallic materials; however, it has not been previously reported. NIBPEGCs physicochemical performance was evaluated based on pH, particle size, surface charge, isoelectric point, dose, coagulation-flocculation kinetics and chemical affinity with seven metal ions. The experimental results showed that NIBPEGCs composed by AG/Ch and PAA/Chitosan have all the three complementary functions: chemical affinity, electrostatic interaction and particle entrapment anticipating more simple operation units to remove heavy metals. Complexes of AG/Ch (negative) were higher performance in removing heavy metals, with a dose window (150-180mg/L), lower dose of 410mg/L PAA/Ch (negative). Investigation of chelating performances of NIBPEGCs show that the efficiency of metal removal is: Ca˃Cr˃Cu˃Pb˃Ni˃Zn˃Cd. Transmittance vs time profiles, metals and zeta potential analysis showed that chelation capacity is the crucial factor to ensure metallic species removal, followed by physical entrapment of the metallic colloids. Integrating all presented results allow to sustain the development of excellent metals removal formulations. Copyright © 2017 Elsevier B.V. All rights reserved.

Adsorptive removal and separation of chemicals with metal-organic frameworks: Contribution of π-complexation.

PubMed

Khan, Nazmul Abedin; Jhung, Sung Hwa

2017-03-05

Efficient removal and separation of chemicals from the environment has become a vital issue from a biological and environmental point of view. Currently, adsorptive removal/separation is one of the most promising approaches for cleaning purposes. Selective adsorption/removal of various sulfur- and nitrogen-containing compounds, olefins, and π-electron-rich gases via π-complex formation between an adsorbent and adsorbate molecules is very competitive. Porous metal-organic framework (MOF) materials are very promising in the adsorption/separation of various liquids and gases owing to their distinct characteristics. This review summarizes the literature on the adsorptive removal/separation of various π-electron-rich compounds mainly from fuel and gases using MOF materials containing metal ions that are active for π-complexation. Details of the π-complexation, including mechanism, pros/cons, applications, and efficient ways to form the complex, are discussed systematically. For in-depth understanding, molecular orbital calculations regarding charge transfer between the π-complexing species are also explained in a separate section. From this review, readers will gain an understanding of π-complexation for adsorption and separation, especially with MOFs, to develop new insight for future research. Copyright © 2016 Elsevier B.V. All rights reserved.

Synthesis, Spectroscopic, and Antimicrobial Studies on Bivalent Nickel and Copper Complexes of Bis(thiosemicrbazone)

PubMed Central

Chandra, Sulekh; Raizada, Smriti; Tyagi, Monika; Gautam, Archana

2007-01-01

A series of metal complexes of Cu(II) and Ni(II) having the general composition [M(L)X2] with benzil bis(thiosemicarbazone) has been prepared and characterized by element chemical analysis, molar conductance, magnetic susceptibility measurements, and spectral (electronic, IR, EPR, mass) studies. The IR spectral data suggest the involvement of sulphur and azomethane nitrogen in coordination to the central metal ion. On the basis of spectral studies, an octahedral geometry has been assigned for Ni(II) complexes but a tetragonal geometry for Cu(II) complexes. The free ligand and its metal complexes have been tested in vitro against a number of microorganisms in order to assess their antimicrobial properties. PMID:18273385

Method for dry etching of transition metals

DOEpatents

Ashby, C.I.H.; Baca, A.G.; Esherick, P.; Parmeter, J.E.; Rieger, D.J.; Shul, R.J.

1998-09-29

A method for dry etching of transition metals is disclosed. The method for dry etching of a transition metal (or a transition metal alloy such as a silicide) on a substrate comprises providing at least one nitrogen- or phosphorus-containing {pi}-acceptor ligand in proximity to the transition metal, and etching the transition metal to form a volatile transition metal/{pi}-acceptor ligand complex. The dry etching may be performed in a plasma etching system such as a reactive ion etching (RIE) system, a downstream plasma etching system (i.e. a plasma afterglow), a chemically-assisted ion beam etching (CAIBE) system or the like. The dry etching may also be performed by generating the {pi}-acceptor ligands directly from a ligand source gas (e.g. nitrosyl ligands generated from nitric oxide), or from contact with energized particles such as photons, electrons, ions, atoms, or molecules. In some preferred embodiments of the present invention, an intermediary reactant species such as carbonyl or a halide ligand is used for an initial chemical reaction with the transition metal, with the intermediary reactant species being replaced at least in part by the {pi}-acceptor ligand for forming the volatile transition metal/{pi}-acceptor ligand complex.

Method for dry etching of transition metals

DOEpatents

Ashby, Carol I. H.; Baca, Albert G.; Esherick, Peter; Parmeter, John E.; Rieger, Dennis J.; Shul, Randy J.

1998-01-01

A method for dry etching of transition metals. The method for dry etching of a transition metal (or a transition metal alloy such as a silicide) on a substrate comprises providing at least one nitrogen- or phosphorous-containing .pi.-acceptor ligand in proximity to the transition metal, and etching the transition metal to form a volatile transition metal/.pi.-acceptor ligand complex. The dry etching may be performed in a plasma etching system such as a reactive ion etching (RIE) system, a downstream plasma etching system (i.e. a plasma afterglow), a chemically-assisted ion beam etching (CAIBE) system or the like. The dry etching may also be performed by generating the .pi.-acceptor ligands directly from a ligand source gas (e.g. nitrosyl ligands generated from nitric oxide), or from contact with energized particles such as photons, electrons, ions, atoms, or molecules. In some preferred embodiments of the present invention, an intermediary reactant species such as carbonyl or a halide ligand is used for an initial chemical reaction with the transition metal, with the intermediary reactant species being replaced at least in part by the .pi.-acceptor ligand for forming the volatile transition metal/.pi.-acceptor ligand complex.

Royal Society, Discussion on New Coal Chemistry, London, England, May 21, 22, 1980, Proceedings

NASA Astrophysics Data System (ADS)

1981-03-01

A discussion of new coal chemistry is presented. The chemical and physical structure of coal is examined in the first section, including structural studies of coal extracts, metal and metal complexes in coal and coal microporosity. The second section presents new advances in applied coal technology. The development of liquid fuels and chemicals from coal is given especial emphasis, with papers on the Sasol Synthol process, the Shell-Koppers gasification process, liquefaction and gasification in Germany, the Solvent Refined Coal process, the Exxon Donor Solvent liquefaction process and the Mobil Methanol-to-Gasoline process. Finally, some developments that will be part of the future of coal chemistry in the year 2000 are examined in the third section, including coal-based chemical complexes and the use of coal as an alternative source to oil for chemical feedstocks.

Potentiometric and spectroscopic study of the interaction of 3d transition metal ions with inositol hexakisphosphate

NASA Astrophysics Data System (ADS)

Veiga, Nicolás; Macho, Israel; Gómez, Kerman; González, Gabriel; Kremer, Carlos; Torres, Julia

2015-10-01

Among myo-inositol phosphates, the most abundant in nature is the myo-inositol hexakisphosphate, InsP6. Although it is known to be vital to cell functioning, the biochemical research into its metabolism needs chemical and structural analysis of all the protonation, complexation and precipitation processes that it undergoes in the biological media. In view of its high negative charge at physiological level, our group has been leading a thorough research into the InsP6 chemical and structural behavior in the presence of the alkali and alkaline earth metal ions essential for life. The aim of this article is to extend these studies, dealing with the chemical and structural features of the InsP6 interaction with biologically relevant 3d transition metal ions (Fe(II), Fe(III), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)), in a non-interacting medium and under simulated physiological conditions. The metal-complex stability constants were determined by potentiometry, showing under ligand-excess conditions the formation of mononuclear species in different protonation states. Under metal ion excess, polymetallic species were detected for Fe(II), Fe(III), Zn(II) and Cu(II). Additionally, the 31P NMR and UV-vis spectroscopic studies provided interesting structural aspects of the strong metal ion-InsP6 interaction.

Nanoindentation methods for wood-adhesive bond lines

Treesearch

Joseph E. Jakes; Donald S. Stone; Charles R. Frihart

2008-01-01

As an adherend, wood is structurally, chemically, and mechanically more complex than metals or plastics, and the largest source of this complexity is wood’s chemical and mechanical inhomogeneities. Understanding and predicting the performance of adhesively bonded wood requires knowledge of the interactions occurring at length scales ranging from the macro down to the...

Soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectroscopy below 100 eV: probing first-row transition-metal M-edges in chemical complexes

PubMed Central

Wang, Hongxin; Young, Anthony T.; Guo, Jinghua; Cramer, Stephen P.; Friedrich, Stephan; Braun, Artur; Gu, Weiwei

2013-01-01

X-ray absorption and scattering spectroscopies involving the 3d transition-metal K- and L-edges have a long history in studying inorganic and bioinorganic molecules. However, there have been very few studies using the M-edges, which are below 100 eV. Synchrotron-based X-ray sources can have higher energy resolution at M-edges. M-edge X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) could therefore provide complementary information to K- and L-edge spectroscopies. In this study, M 2,3-edge XAS on several Co, Ni and Cu complexes are measured and their spectral information, such as chemical shifts and covalency effects, are analyzed and discussed. In addition, M 2,3-edge RIXS on NiO, NiF2 and two other covalent complexes have been performed and different d–d transition patterns have been observed. Although still preliminary, this work on 3d metal complexes demonstrates the potential to use M-edge XAS and RIXS on more complicated 3d metal complexes in the future. The potential for using high-sensitivity and high-resolution superconducting tunnel junction X-ray detectors below 100 eV is also illustrated and discussed. PMID:23765304

Soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectroscopy below 100 eV: probing first-row transition-metal M-edges in chemical complexes.

PubMed

Wang, Hongxin; Young, Anthony T; Guo, Jinghua; Cramer, Stephen P; Friedrich, Stephan; Braun, Artur; Gu, Weiwei

2013-07-01

X-ray absorption and scattering spectroscopies involving the 3d transition-metal K- and L-edges have a long history in studying inorganic and bioinorganic molecules. However, there have been very few studies using the M-edges, which are below 100 eV. Synchrotron-based X-ray sources can have higher energy resolution at M-edges. M-edge X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) could therefore provide complementary information to K- and L-edge spectroscopies. In this study, M2,3-edge XAS on several Co, Ni and Cu complexes are measured and their spectral information, such as chemical shifts and covalency effects, are analyzed and discussed. In addition, M2,3-edge RIXS on NiO, NiF2 and two other covalent complexes have been performed and different d-d transition patterns have been observed. Although still preliminary, this work on 3d metal complexes demonstrates the potential to use M-edge XAS and RIXS on more complicated 3d metal complexes in the future. The potential for using high-sensitivity and high-resolution superconducting tunnel junction X-ray detectors below 100 eV is also illustrated and discussed.

Selective determination of heavy metals (Cd, Pb, Cr) speciation forms from hortic anthrosols

NASA Astrophysics Data System (ADS)

Bulgariu, Dumitru; Bulgariu, Laura; Filipov, Feodor; Astefanei, Dan; Stoleru, Vasile

2010-05-01

In soils from glass houses, the speciation and inter-phases distribution processes of heavy metals have a particular dynamic, different in comparison with those from non-protected soils. The predominant distribution forms of heavy metals in such soils types are: complexes with low mass organic molecules, organic-mineral complexes, complexes with inorganic ligands (hydroxide-complexes, carbonate-complexes, sulphate-complexes, etc.) and basic salts. All of these have high stabilities in conditions of soils from glass houses, and in consequence, the separation and determination of speciation forms (which is directly connected with biodisponibility of heavy metals) by usual methods id very difficult and has a high uncertain degree. In this study is presented an original method for the selective separation and differentiation of speciation forms of heavy metals from glass houses soils, which is based by the combination of solid-liquid sequential extraction (SPE) with the extraction in aqueous polymer-inorganic salt two-phase systems (ABS). The soil samples used for this study have been sampled from three different locations (glass houses from Iasi, Barlad and Bacau - Romania) where the vegetables cultivation have been performed by three different technologies. In this way was estimated the applicability and the analytical limits of method proposed by as, in function of the chemical-mineralogical and physical-chemical characteristics of soils. As heavy metals have been studied cadmium, lead and chromium, all being known for their high toxicity. The procedure used for the selective separation and differentiation of speciation forms of heavy metals from glass houses soils has two main steps: (i) non-destructive separation of chemical-mineralogical associations and aggregates from soils samples - for this the separation method with heavy liquids (bromophorme) and isodynamic magnetic method have been used; (ii) sequential extraction of heavy metals from soil fractions separated in the first step, by using combined SPE-ABS procedure. For the preparation of combined extraction systems was used polyethylene glycol (with different molecular mass: 2000, 4000 and 8000). As phase-forming inorganic salts and as selective extracting agents we have used different usual inorganic reagents. The type and concentration of phase-forming salts have been selected in function of, both nature of extracted heavy metals and chemical-mineralogical characteristics of soil samples. The experimental parameters investigated in this study are: molecular mass of polyethylene glycol and the concentration of polymeric solutions, nature and concentration of phase-forming salts, nature and concentration of extracting agents, pH in extraction system phase, type of extracted heavy metals, type of speciation forms of heavy metals and their concentrations. All these factors can influence significantly the efficiency and the selectivity of separation process. The experimental results have indicate that the combined SPE-ABS extraction systems have better separation efficiency, in comparison with traditional SPE systems and ca realized a accurate discrimination between speciation forms of heavy metals from soils. Under these conditions, the estimation of inter-phases distribution and biodisponibility of heavy metals has a high precision. On the other hand, when the combined SPE-ABS systems are used, the concomitant extraction of the elements from the same geochemical association with studied heavy metals (inevitable phenomena in case of separation by SPE procedures) is significant diminished. This increases the separation selectivity and facilitated the more accurate determination of speciation forms concentration. By adequate selection of extraction conditions can be realized the selective separation of organic-mineral complexes, which will permit to perform detailed studies about the structure and chemical composition of these. Acknowledgments The authors would like to acknowledge the financial support from Romanian Ministry of Education and Research (Project PNCDI 2-D5 no. 51045/07 and project PNCDI 2 - D5 no. 52-141 / 2008).

Identification Of (Bright) Carbon-Enhanced Metal-Poor Stars With J-Plus Photometry

NASA Astrophysics Data System (ADS)

Placco, Vinicius

2017-10-01

The chemical composition of our bodies, the Earth, the Sun, and the Universe is complex, and the end result of the formation and evolution of numerous stellar generations that contributed all of the elements heavier than helium. One way to understand the possible pathways that led to such complexity is to determine the chemical abundance patterns of ancient low-metallicity stars in the Halo of our Galaxy. However, it is impossible to observe each of the 100 billion stars in the Milky Way in sufficient detail to assess its chemical composition. Hence, astronomers have developed efficient ways to pre-select the most interesting stars for further high-resolution follow-up, based on the understanding that the colors of stars in specific regions of the optical spectrum are affected in predictable ways by changes in their chemical composition. I will discuss the importance of the J-PLUS photometry in selecting low-metallicity and carbon-enhanced stars, using its 12 magnitudes, which will fully exploit this approach, in a manner superior to all previous such efforts.

First-Principles Calculations for Chemical Reaction between Sodium Diethyldithiocarbamate and Transition-Metal (Cr) atom to Produce Cr(DDC)3 and Cr(DDC)2ODDC

NASA Astrophysics Data System (ADS)

Setiyanto, Henry; Muhida, Rifki; Kishi, Tomoya; Rempillo, Ofelia; Rahman, Mahmudur; Dipojono, Hermawan Kresno; Di\\ {n}o, Wilson Agerico; Matsumoto, Shigeno; Kasai, Hideaki

2006-10-01

We investigate the chemical reaction between a Cr transition-metal atom and sodium diethyldithiocarbamate (NaDDC), a complexing agent used to detect and extract Cr in human blood samples. Using density-functional-theory-based calculations, we determine their stable structures of Cr(DDC)2ODDC and Cr(DDC)3 complexes and obtain their dissociation energies. We found dissociation energies of -10.66 and -3.24 eV for Cr(DDC)2ODDC and Cr(DDC)3 complexes, respectively. Hence, on the basis of dissociation energies, we have verified that the reaction of NaDDC with Cr produces Cr(DDC)2ODDC as a major product.

Molecular Studies of Complex Soil Organic Matter Interactions with Metal Ions and Mineral Surfaces using Classical Molecular Dynamics and Quantum Chemistry Methods

NASA Astrophysics Data System (ADS)

Andersen, A.; Govind, N.; Laskin, A.

2017-12-01

Mineral surfaces have been implicated as potential protectors of soil organic matter (SOM) against decomposition and ultimate mineralization to small molecules which can provide nutrients for plants and soil microbes and can also contribute to the Earth's elemental cycles. SOM is a complex mixture of organic molecules of biological origin at varying degrees of decomposition and can, itself, self-assemble in such a way as to expose some biomolecule types to biotic and abiotic attack while protecting other biomolecule types. The organization of SOM and SOM with mineral surfaces and solvated metal ions is driven by an interplay of van der Waals and electrostatic interactions leading to partitioning of hydrophilic (e.g. sugars) and hydrophobic (e.g., lipids) SOM components that can be bridged with amphiphilic molecules (e.g., proteins). Classical molecular dynamics simulations can shed light on assemblies of organic molecules alone or complexation with mineral surfaces. The role of chemical reactions is also an important consideration in potential chemical changes of the organic species such as oxidation/reduction, degradation, chemisorption to mineral surfaces, and complexation with solvated metal ions to form organometallic systems. For the study of chemical reactivity, quantum chemistry methods can be employed and combined with structural insight provided by classical MD simulations. Moreover, quantum chemistry can also simulate spectroscopic signatures based on chemical structure and is a valuable tool in interpreting spectra from, notably, x-ray absorption spectroscopy (XAS). In this presentation, we will discuss our classical MD and quantum chemistry findings on a model SOM system interacting with mineral surfaces and solvated metal ions.

Characterisation of metals in the electronic waste of complex mixtures of end-of-life ICT products for development of cleaner recovery technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Z.H.I.; Xiao, Y.; Sietsma, J.

2015-01-15

Highlights: • New characterisation methodology has been established to understand an industrially processed ICT waste. • Particle size distribution, composition, thermal–chemical behaviour and occurrence of metals were considered. • The characterisation provides direct guidelines for values recovery from the waste. - Abstract: Recycling of valuable metals from electronic waste, especially complex mixtures of end-of-life information and communication technology (ICT) products, is of great difficulty due to their complexity and heterogeneity. One of the important reasons is the lack of comprehensive characterisation on such materials, i.e. accurate compositions, physical/chemical properties. In the present research, we focus on developing methodologies for themore » characterisation of metals in an industrially processed ICT waste. The morphology, particle size distribution, compositional distribution, occurrence, liberation as well as the thermo-chemical properties of the ICT waste were investigated with various characterisation techniques, including X-ray Fluorescence Spectrometry (XRF), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) with energy dispersed spectroscopy (EDS). Due to the high heterogeneity of the material, special sample preparation procedures were introduced to minimise the discrepancies during compositional analyses. As a result, a clearer overview of the ICT waste has been reached. This research provides better understanding of the extractability of each metal and improves the awareness of potential obstacles for extraction. It will lead to smarter decisions during further development of a clean and effective recovery process.« less

Chemistry of the metal-polymer interfacial region.

PubMed

Leidheiser, H; Deck, P D

1988-09-02

In many polymer-metal systems, chemical bonds are formed that involve metal-oxygen-carbon complexes. Infrared and Mössbauer spectroscopic studies indicate that carboxylate groups play an important role in some systems. The oxygen sources may be the polymer, the oxygen present in the oxide on the metal surface, or atmospheric oxygen. Diffusion of metal ions from the substrate into the polymer interphase may occur in some systems that are cured at elevated temperatures. It is unclear whether a similar, less extensive diffusion occurs over long time periods in systems maintained at room temperature. The interfacial region is dynamic, and chemical changes occur with aging at room temperature. Positron annihilation spectroscopy may have application to characterizing the voids at the metal-polymer interface.

Systems for the Storage of Molecular Oxygen - A Study.

DTIC Science & Technology

1980-11-25

form adducts with certain chemical compounds . This process, which will be called chemical absorption, generally uses a transition metal coordination... compound as the absorber. The study of oxygen binding to metal complexes has become of great interest over the past three decades (21), and some...for iron, most notably cobalt (33-35) manganese (36,37) and ruthenium (38), usually to serve as model compounds for biologically important heme

Control of a chemical reaction (photodegradation of the p3ht polymer) with nonlocal dielectric environments

PubMed Central

Peters, V. N.; Tumkur, T. U.; Zhu, G.; Noginov, M. A.

2015-01-01

Proximity to metallic surfaces, plasmonic structures, cavities and other inhomogeneous dielectric environments is known to control spontaneous emission, energy transfer, scattering, and many other phenomena of practical importance. The aim of the present study was to demonstrate that, in spirit of the Marcus theory, the rates of chemical reactions can, too, be influenced by nonlocal dielectric environments, such as metallic films and metal/dielectric bilayer or multilayer structures. We have experimentally shown that metallic, composite metal/dielectric substrates can, indeed, control ordering as well as photodegradation of thin poly-3-hexylthiophene (p3ht) films. In many particular experiments, p3ht films were separated from metal by a dielectric spacer, excluding conventional catalysis facilitated by metals and making modification of the nonlocal dielectric environment a plausible explanation for the observed phenomena. This first step toward understanding of a complex relationship between chemical reactions and nonlocal dielectric environments is to be followed by the theory development and a broader scope of thorough experimental studies. PMID:26434679

Speciation of heavy metals in landfill leachate: a review.

PubMed

Baun, Dorthe L; Christensen, Thomas H

2004-02-01

The literature was reviewed with respect to metal speciation methods in aquatic samples specifically emphasizing speciation of heavy metals in landfill leachate. Speciation here refers to physical fractionation (particulate, colloidal, dissolved), chemical fractionation (organic complexes, inorganic complexes, free metal ions), as well as computer-based thermodynamic models. Relatively few landfill leachate samples have been speciated in detail (less than 30) representing only a few landfills (less than 15). This suggests that our knowledge about metal species in landfill leachate still is indicative. In spite of the limited database and the different definitions of the dissolved fraction (< 0.45 microm or < 0.001 microm) the studies consistently show that colloids as well as organic and inorganic complexes are important for all heavy metals in landfill leachate. The free metal ion constitutes less than 30%, typically less than 10%, of the total metal concentration. This has significant implications for sampling, since no standardized procedures exist, and for assessing the content of metals in leachate in the context of its treatment, toxicity and migration in aquifers.

Orbital-specific mapping of the ligand exchange dynamics of Fe(CO)5 in solution.

PubMed

Wernet, Ph; Kunnus, K; Josefsson, I; Rajkovic, I; Quevedo, W; Beye, M; Schreck, S; Grübel, S; Scholz, M; Nordlund, D; Zhang, W; Hartsock, R W; Schlotter, W F; Turner, J J; Kennedy, B; Hennies, F; de Groot, F M F; Gaffney, K J; Techert, S; Odelius, M; Föhlisch, A

2015-04-02

Transition-metal complexes have long attracted interest for fundamental chemical reactivity studies and possible use in solar energy conversion. Electronic excitation, ligand loss from the metal centre, or a combination of both, creates changes in charge and spin density at the metal site that need to be controlled to optimize complexes for photocatalytic hydrogen production and selective carbon-hydrogen bond activation. An understanding at the molecular level of how transition-metal complexes catalyse reactions, and in particular of the role of the short-lived and reactive intermediate states involved, will be critical for such optimization. However, suitable methods for detailed characterization of electronic excited states have been lacking. Here we show, with the use of X-ray laser-based femtosecond-resolution spectroscopy and advanced quantum chemical theory to probe the reaction dynamics of the benchmark transition-metal complex Fe(CO)5 in solution, that the photo-induced removal of CO generates the 16-electron Fe(CO)4 species, a homogeneous catalyst with an electron deficiency at the Fe centre, in a hitherto unreported excited singlet state that either converts to the triplet ground state or combines with a CO or solvent molecule to regenerate a penta-coordinated Fe species on a sub-picosecond timescale. This finding, which resolves the debate about the relative importance of different spin channels in the photochemistry of Fe(CO)5 (refs 4, 16 - 20), was made possible by the ability of femtosecond X-ray spectroscopy to probe frontier-orbital interactions with atom specificity. We expect the method to be broadly applicable in the chemical sciences, and to complement approaches that probe structural dynamics in ultrafast processes.

Orbital-specific mapping of the ligand exchange dynamics of Fe(CO)5 in solution

NASA Astrophysics Data System (ADS)

Wernet, Ph.; Kunnus, K.; Josefsson, I.; Rajkovic, I.; Quevedo, W.; Beye, M.; Schreck, S.; Grübel, S.; Scholz, M.; Nordlund, D.; Zhang, W.; Hartsock, R. W.; Schlotter, W. F.; Turner, J. J.; Kennedy, B.; Hennies, F.; de Groot, F. M. F.; Gaffney, K. J.; Techert, S.; Odelius, M.; Föhlisch, A.

2015-04-01

Transition-metal complexes have long attracted interest for fundamental chemical reactivity studies and possible use in solar energy conversion. Electronic excitation, ligand loss from the metal centre, or a combination of both, creates changes in charge and spin density at the metal site that need to be controlled to optimize complexes for photocatalytic hydrogen production and selective carbon-hydrogen bond activation. An understanding at the molecular level of how transition-metal complexes catalyse reactions, and in particular of the role of the short-lived and reactive intermediate states involved, will be critical for such optimization. However, suitable methods for detailed characterization of electronic excited states have been lacking. Here we show, with the use of X-ray laser-based femtosecond-resolution spectroscopy and advanced quantum chemical theory to probe the reaction dynamics of the benchmark transition-metal complex Fe(CO)5 in solution, that the photo-induced removal of CO generates the 16-electron Fe(CO)4 species, a homogeneous catalyst with an electron deficiency at the Fe centre, in a hitherto unreported excited singlet state that either converts to the triplet ground state or combines with a CO or solvent molecule to regenerate a penta-coordinated Fe species on a sub-picosecond timescale. This finding, which resolves the debate about the relative importance of different spin channels in the photochemistry of Fe(CO)5 (refs 4, 16,17,18,19 and 20), was made possible by the ability of femtosecond X-ray spectroscopy to probe frontier-orbital interactions with atom specificity. We expect the method to be broadly applicable in the chemical sciences, and to complement approaches that probe structural dynamics in ultrafast processes.

Controlling magnetism of a complex metallic system using atomic individualism.

PubMed

Mudryk, Y; Paudyal, D; Pecharsky, V K; Gschneidner, K A; Misra, S; Miller, G J

2010-08-06

When the complexity of a metallic compound reaches a certain level, a specific location in the structure may be critically responsible for a given fundamental property of a material while other locations may not play as much of a role in determining such a property. The first-principles theory has pinpointed a critical location in the framework of a complex intermetallic compound--Gd(5)Ge(4)--that resulted in a controlled alteration of the magnetism of this compound using precise chemical tools.

Controlling Magnetism of a Complex Metallic System Using Atomic Individualism

NASA Astrophysics Data System (ADS)

Mudryk, Y.; Paudyal, D.; Pecharsky, V. K.; Gschneidner, K. A., Jr.; Misra, S.; Miller, G. J.

2010-08-01

When the complexity of a metallic compound reaches a certain level, a specific location in the structure may be critically responsible for a given fundamental property of a material while other locations may not play as much of a role in determining such a property. The first-principles theory has pinpointed a critical location in the framework of a complex intermetallic compound—Gd5Ge4—that resulted in a controlled alteration of the magnetism of this compound using precise chemical tools.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, L. X.; Zhang, X.; Lockard, J. V.

Transient molecular structures along chemical reaction pathways are important for predicting molecular reactivity, understanding reaction mechanisms, as well as controlling reaction pathways. During the past decade, X-ray transient absorption spectroscopy (XTA, or LITR-XAS, laser-initiated X-ray absorption spectroscopy), analogous to the commonly used optical transient absorption spectroscopy, has been developed. XTA uses a laser pulse to trigger a fundamental chemical process, and an X-ray pulse(s) to probe transient structures as a function of the time delay between the pump and probe pulses. Using X-ray pulses with high photon flux from synchrotron sources, transient electronic and molecular structures of metal complexes havemore » been studied in disordered media from homogeneous solutions to heterogeneous solution-solid interfaces. Several examples from the studies at the Advanced Photon Source in Argonne National Laboratory are summarized, including excited-state metalloporphyrins, metal-to-ligand charge transfer (MLCT) states of transition metal complexes, and charge transfer states of metal complexes at the interface with semiconductor nanoparticles. Recent developments of the method are briefly described followed by a future prospective of XTA. It is envisioned that concurrent developments in X-ray free-electron lasers and synchrotron X-ray facilities as well as other table-top laser-driven femtosecond X-ray sources will make many breakthroughs and realise dreams of visualizing molecular movies and snapshots, which ultimately enable chemical reaction pathways to be controlled.« less

Direct detection and characterization of bioinorganic peroxo moieties in a vanadium complex by 17O solid-state NMR and density functional theory.

PubMed

Gupta, Rupal; Stringer, John; Struppe, Jochem; Rehder, Dieter; Polenova, Tatyana

2018-07-01

Electronic and structural properties of short-lived metal-peroxido complexes, which are key intermediates in many enzymatic reactions, are not fully understood. While detected in various enzymes, their catalytic properties remain elusive because of their transient nature, making them difficult to study spectroscopically. We integrated 17 O solid-state NMR and density functional theory (DFT) to directly detect and characterize the peroxido ligand in a bioinorganic V(V) complex mimicking intermediates non-heme vanadium haloperoxidases. 17 O chemical shift and quadrupolar tensors, measured by solid-state NMR spectroscopy, probe the electronic structure of the peroxido ligand and its interaction with the metal. DFT analysis reveals the unusually large chemical shift anisotropy arising from the metal orbitals contributing towards the magnetic shielding of the ligand. The results illustrate the power of an integrated approach for studies of oxygen centers in enzyme reaction intermediates. Copyright © 2018 Elsevier Inc. All rights reserved.

Physical and Chemical Properties of Anthropogenic Aerosols: An Overview

EPA Science Inventory

Aerosol chemical composition is complex. Combustion aerosols can comprise tens of thousands of organic compounds, refractory brown and black carbon, heavy metals, cations, anions, salts, and other inorganic phases. Aerosol organic matter normally contains semivolatile material th...

Concentration, Complexation and Chemical Speciation of Zinc and Cadmium in the Western North Pacific Ocean : Exploring Sources and Transport of Trace Metals and Complexing Ligands.

NASA Astrophysics Data System (ADS)

Carrasco, G. G.; Morton, P. L.; Donat, J. R.

2008-12-01

We determined Zn and Cd total dissolved (0.45 µm-filtered) concentrations, organic complexation and chemical speciation in surface water samples collected along the transect of the 2002 IOC Baseline Contaminant Survey expedition in the Western North Pacific and in vertical profile water samples at nine stations. The goals of this work were (1) to compare and contrast various trace metal sources, including both natural and anthropogenic atmospheric deposition, upwelling, marginal seas and others; (2) to study the organic ligand sources, generally thought to be phytoplankton; and (3) to investigate metal and ligand transport mechanisms, residence times and eventual upwelling in the Eastern North Pacific. Total dissolved (TD) Zn and Cd values were obtained using a combination of differential pulse stripping anodic voltammetry (DPASV), preconcentration with 8-HQ or APDC/DDC and quantification at ICPMS or AA. Organic complexation and chemical speciation of Zn and Cd were determined simultaneously using DPASV at a thin-mercury-film, glassy-carbon-disk-electrode. Surface transect TDZn and TDCd concentrations were low in the Subtropical Gyre (STG), in contrast with high values in the Western Subarctic Gyre (WSG). Zn and Cd were organically complexed in most surface samples: at least one ligand class was detected for Zn and Cd, whose conditional stability constants (log K') averaged 10.2 and 10.5, respectively. These ligands were found in excess of the total dissolved metal throughout the region of study except in the WSG for Cd. Vertical distributions of TDZn and TDCd exhibited nutrient-type profiles for all the STG stations. While constant Zn/Si and Cd/P values were observed throughout the water column in the WSG, some deviations were observed within the STG. In addition, the mode and intermediate water masses of the STG displayed very high concentrations of a Zn-complexing ligand (log K' 10.0) in excess of TDZn. As these water masses moved eastward, we observed that the ligand concentrations decreased. In contrast to the STG, the upper 1000m of the WSG showed elevated concentrations of both metals. Despite elevated surface (0-200m) Zn concentrations (~2nM), a Zn-complexing ligand (log K' 9.8) was found in excess of TDZn; below the photic layer, even higher TDZn concentrations might have saturated the ligand. A ligand for Cd was present in lower-than-TDCd concentrations in the same surface waters; below them, organic complexation of Cd was observed rarely in both STG and WSG regions. By studying the geographic distribution of the total dissolved metals and ligands, along with other dissolved and particulate tracers, possible sources and transport mechanisms can be contrasted and evaluated. Furthermore, the influence of these sources and transport mechanisms on the distribution of Zn and Cd chemical species and, ultimately, the bioavailability of these micronutrient metals can be studied.

Agricultural waste material as potential adsorbent for sequestering heavy metal ions from aqueous solutions - a review.

PubMed

Sud, Dhiraj; Mahajan, Garima; Kaur, M P

2008-09-01

Heavy metal remediation of aqueous streams is of special concern due to recalcitrant and persistency of heavy metals in environment. Conventional treatment technologies for the removal of these toxic heavy metals are not economical and further generate huge quantity of toxic chemical sludge. Biosorption is emerging as a potential alternative to the existing conventional technologies for the removal and/or recovery of metal ions from aqueous solutions. The major advantages of biosorption over conventional treatment methods include: low cost, high efficiency, minimization of chemical or biological sludge, regeneration of biosorbents and possibility of metal recovery. Cellulosic agricultural waste materials are an abundant source for significant metal biosorption. The functional groups present in agricultural waste biomass viz. acetamido, alcoholic, carbonyl, phenolic, amido, amino, sulphydryl groups etc. have affinity for heavy metal ions to form metal complexes or chelates. The mechanism of biosorption process includes chemisorption, complexation, adsorption on surface, diffusion through pores and ion exchange etc. The purpose of this review article is to provide the scattered available information on various aspects of utilization of the agricultural waste materials for heavy metal removal. Agricultural waste material being highly efficient, low cost and renewable source of biomass can be exploited for heavy metal remediation. Further these biosorbents can be modified for better efficiency and multiple reuses to enhance their applicability at industrial scale.

Natural Indices for the Chemical Hardness/Softness of Metal Cations and Ligands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Huifang; Xu, David C.; Wang, Yifeng

Quantitative understanding of reactivity and stability for a chemical species is fundamental to chemistry. The concept has undergone many changes and additions throughout the history of chemistry, stemming from the ideas such as Lewis acids and bases. For a given complexing ligand (Lewis base) and a group of isovalent metal cations (Lewis acids), the stability constants of metal–ligand (ML) complexes can simply correlate to the known properties of metal ions [ionic radii (r Mn+), Gibbs free energy of formation (ΔG° f,Mn+), and solvation energy (ΔG° s,Mn+)] by 2.303RT log K ML = (α* MLΔG° f,Mn+ – β* MLr Mn+ +more » γ* MLΔG° s,Mn+ – δ* ML), where the coefficients (α* ML, β* ML, γ* ML, and intercept δ* ML) are determined by fitting the equation to the existing experimental data. Coefficients β* ML and γ* ML have the same sign and are in a linear relationship through the origin. Gibbs free energies of formation of cations (ΔG° f,Mn+) are found to be natural indices for the softness or hardness of metal cations, with positive values corresponding to soft acids and negative values to hard acids. The coefficient α* ML is an index for the softness or hardness of a complexing ligand. Proton (H +) with the softness index of zero is a unique acid that has strong interactions with both soft and hard bases. The stability energy resulting from the acid–base interactions is determined by the term α* MLΔG° f,Mn+; a positive product of α* ML and ΔG° f,Mn+ indicates that the acid–base interaction between the metal cation and the complexing ligand stabilizes the complex. The terms β* MLr Mn+ and γ* MLΔG° s,Mn+, which are related to ionic radii of metal cations, represent the steric and solvation effects of the cations. The new softness indices proposed here will help to understand the interactions of ligands (Lewis bases) with metal cations (Lewis acids) and provide guidelines for engineering materials with desired chemical reactivity and selectivity. As a result, the new correlation can also enhance our ability for predicting the speciation, mobility, and toxicity of heavy metals in the earth environments and biological systems.« less

Natural Indices for the Chemical Hardness/Softness of Metal Cations and Ligands

DOE PAGES

Xu, Huifang; Xu, David C.; Wang, Yifeng

2017-10-26

Quantitative understanding of reactivity and stability for a chemical species is fundamental to chemistry. The concept has undergone many changes and additions throughout the history of chemistry, stemming from the ideas such as Lewis acids and bases. For a given complexing ligand (Lewis base) and a group of isovalent metal cations (Lewis acids), the stability constants of metal–ligand (ML) complexes can simply correlate to the known properties of metal ions [ionic radii (r Mn+), Gibbs free energy of formation (ΔG° f,Mn+), and solvation energy (ΔG° s,Mn+)] by 2.303RT log K ML = (α* MLΔG° f,Mn+ – β* MLr Mn+ +more » γ* MLΔG° s,Mn+ – δ* ML), where the coefficients (α* ML, β* ML, γ* ML, and intercept δ* ML) are determined by fitting the equation to the existing experimental data. Coefficients β* ML and γ* ML have the same sign and are in a linear relationship through the origin. Gibbs free energies of formation of cations (ΔG° f,Mn+) are found to be natural indices for the softness or hardness of metal cations, with positive values corresponding to soft acids and negative values to hard acids. The coefficient α* ML is an index for the softness or hardness of a complexing ligand. Proton (H +) with the softness index of zero is a unique acid that has strong interactions with both soft and hard bases. The stability energy resulting from the acid–base interactions is determined by the term α* MLΔG° f,Mn+; a positive product of α* ML and ΔG° f,Mn+ indicates that the acid–base interaction between the metal cation and the complexing ligand stabilizes the complex. The terms β* MLr Mn+ and γ* MLΔG° s,Mn+, which are related to ionic radii of metal cations, represent the steric and solvation effects of the cations. The new softness indices proposed here will help to understand the interactions of ligands (Lewis bases) with metal cations (Lewis acids) and provide guidelines for engineering materials with desired chemical reactivity and selectivity. As a result, the new correlation can also enhance our ability for predicting the speciation, mobility, and toxicity of heavy metals in the earth environments and biological systems.« less

Versatile nature of hetero-chitosan based derivatives as biodegradable adsorbent for heavy metal ions; a review.

PubMed

Ahmad, Mudasir; Manzoor, Kaiser; Ikram, Saiqa

2017-12-01

The polyfunctional chitosan can act as the biological macromolecule ligand not only for the adsorption and the recovery of metal ions from an aqueous media, but also for the fabrication of novel adsorbents which shows selectivity and better adsorption properties. The unmodified chitosan itself, a single cationic polysaccharide, has hydroxyl and amine groups carrying complex properties with the metal ions. In addition, the selectivity of metal ions, the adsorption efficiency and adsorption capacity of the adsorbent can be modified chemically. This review covers the synthetic strategies of chitosan towards the synthesis of hetero-chitosan based adsorbents via chemical modifications in past two decades. It also includes how chemical modification influences the metal adsorption with N, O, S and P containing chitosan derivatives. Hope this review article provides an opportunity for researchers in the future to explore the potential of chitosan as an adsorbent for removal of metal ions from wastewater. Copyright © 2017 Elsevier B.V. All rights reserved.

Investigation of DOTA-Metal Chelation Effects on the Chemical Shift of 129 Xe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeong, Keunhong; Slack, Clancy C.; Vassiliou, Christophoros C.

2015-09-17

Recent work has shown that xenon chemical shifts in cryptophane-cage sensors are affected when tethered chelators bind to metals. Here in this paper, we explore the xenon shifts in response to a wide range of metal ions binding to diastereomeric forms of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) linked to cryptophane-A. The shifts induced by the binding of Ca 2+, Cu 2+, Ce 3+, Zn 2+, Cd 2+, Ni 2+, Co 2+, Cr 2+, Fe 3+, and Hg 2+ are distinct. In addition, the different responses of the diastereomers for the same metal ion indicate that shifts are affected by partial folding withmore » a correlation between the expected coordination number of the metal in the DOTA complex and the chemical shift of 129Xe. Lastly, these sensors may be used to detect and quantify many important metal ions, and a better understanding of the basis for the induced shifts could enhance future designs.« less

Synthetic humic substances and their use for remediation of contaminated environments

NASA Astrophysics Data System (ADS)

Dudare, Diana; Klavins, Maris

2014-05-01

Soils are increasingly subjected to different chemical stresses, because of increasing industrialization process and other factors. Different anthropogenic compounds (organic or inorganic in nature) upon entering the soil, may not only influence its productivity potential, but may also affect the quality of groundwater and food chain. Consequently, soils of different environments contain a complex mixture of contaminants, such as oil products, metals, organic solvents, acids, bases and radionuclides. Thereby greater focus should be paid to risk assessment and evaluation of remedial techniques in order to restore the quality of the soil and groundwater. The treatment technologies presently used to remove contaminants are physical, chemical and biological technologies. Many functional groups in the structure of humic substances determine their ability to interact with metal ions forming stable complexes and influencing speciation of metal ions in the environment, as well mobility, behaviour and speciation forms in the environment. Humic substances are suggested for use in the remediation of environments contaminated with metals, owing to complex forming properties. Several efforts have been undertaken with respect to synthesize humic substances for their structural studies. At the same time the real number of methods suggested for synthesis of humic substances is highly limited and their synthesis in general has been used mostly for their structural analysis. The present study deals with development of approaches for synthesis of humic substances with increased complex forming ability in respect to metal ions. Industrially produced humic substances (TEHUM) were used for comparison and after their modification their properties were analyzed for their elemental composition; functional group content changes in spectral characteristics. Synthetic humic substances showed significant differences in the number of functional groups and in ability to interact with the metal ions, which were reflected in their complexation properties towards metal ions. FTIR spectra gave evidence of the presence of metal ions, strongly bound and protected in inner sphere complexes. Considering a large scale of production of humic substances, the obtained synthetic humic substances with modified properties are perspective and sustainable areas of use. The obtained results of this study showed that synthetic humic substances can be used for remediation of environments contaminated with heavy metal ions.

TREATMENT OF METAL-LADEN HAZARDOUS WASTES WITH ADVANCED CLEAN COAL TECHNOLOGY BY-PRODUCTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

James T. Cobb, Jr.

2003-09-12

Metal-laden wastes can be stabilized and solidified using advanced clean coal technology by-products (CCTBs)--fluid bed combustor ash and spray drier solids. These utility-generated treatment chemicals are available for purchase through brokers, and commercial applications of this process are being practiced by treaters of metal-laden hazardous waste. A complex of regulations governs this industry, and sensitivities to this complex has discouraged public documentation of treatment of metal-laden hazardous wastes with CCTBs. This report provides a comprehensive public documentation of laboratory studies that show the efficacy of the stabilization and solidification of metal-laden hazardous wastes--such as lead-contaminated soils and sandblast residues--through treatmentmore » with CCTBs. It then describes the extensive efforts that were made to obtain the permits allowing a commercial hazardous waste treater to utilize CCTBs as treatment chemicals and to install the equipment required to do so. It concludes with the effect of this lengthy process on the ability of the treatment company to realize the practical, physical outcome of this effort, leading to premature termination of the project.« less

Heavy metal contamination and ecological risk assessment in the surface sediments of the coastal area surrounding the industrial complex of Gabes city, Gulf of Gabes, SE Tunisia.

PubMed

El Zrelli, Radhouan; Courjault-Radé, Pierre; Rabaoui, Lotfi; Castet, Sylvie; Michel, Sylvain; Bejaoui, Nejla

2015-12-30

In the present study, the concentrations of 6 trace metals (Hg, Cd, Cu, Pb, Cr and Zn) were assessed in the surface sediments of the central coastal area of Gabes Gulf to determine their contamination status, source, spatial distribution and ecological risks. The ranking of metal contents was found to be Zn>Cd>Cr>Pb>Cu>Hg. Correlation analysis indicated that Cd and Zn derived mainly from the Tunisian Chemical Group phosphogypsum. The other pollutants may originate from other industrial wastes. Metallic contamination was detected in the south of chemical complex, especially in the inter-harbor zone, where the ecological risk of surface sediments is the highest, implying potential negative impacts of industrial pollutants. The spatial distribution of pollutants seems to be due to the effect of harbor installations and coastal currents. The metallic pollution status of surface sediments of Gabes Gulf is obvious, very worrying and requires rapid intervention. Copyright © 2015 Elsevier Ltd. All rights reserved.

EPR, UV-vis, magnetic, spectral studies and electrochemical behaviour of mononuclear transition metal complexes derived from novel hexa-aza-macrotricyclic ligand

NASA Astrophysics Data System (ADS)

Chandra, Sulekh; Gupta, Nidhi; Gupta, Rachna; Bawa, Sukhwant Singh

2005-11-01

Aza-macrocyclic complexes have gained importance because of their pharmacological properties [N.K. Singh, Srivastava, Trans. Met. Chem. 25 (2000) 133]. Hexa-aza-macrocyles containing glutarimide efficiently coordinate as hexa-dentate ligand, to give complexes of Cu(II) possessing tetragonal structure and Mn(II), Co(II) and Ni(II) metal ions that are essentially octahedral. Spectroscopic, and chemical characterizations of these systems are presented in this article. For Ni(II) complexes results on electron transfer processes measured by cyclic voltammetry and colourimetry have been studied.

Chemical activation of molecules by metals: Experimental studies of electron distributions and bonding

NASA Astrophysics Data System (ADS)

Lichtenberg, Dennis L.

During this period some important breakthroughs were accomplished in understanding the relationships between molecular ionization energies and bond energies in transition metal complexes, in understanding the electronic factors of carbon-hydrogen bond activation by transition metals, in characterizing small molecule bonding interactions with transition metals, and in investigating intermolecular interactions in thin films of transition metal complexes. The formal relationship between measured molecular ionization energies and thermodynamic bond dissociation energies was developed into a single equation which unifies the treatment of covalent bonds, ionic bonds, and partially ionic bonds. The relationship was used to clarify the fundamental thermodynamic information relating to metal-hydrogen, metal-alkyl, and metal-metal bond energies. The ionization energies were also used to correlate the rates of carbonyl substitution reactions of (eta(sup 5)-C5H4X)Rh(CO)2 complexes, and to reveal the factors that control the stability of the transition state. The investigations of the fundamental interactions of C-H sigma and sigma* orbitals metals were continued with study of eta(sup 3)-1-methylallyl metal complexes. Direct observation and measurement of the stabilization energy provided by the agostic interaction of the C-H bond with the metal was obtained. The ability to observe the electronic effects of intermolecular interactions by comparing the ionizations of metal complexes in the gas phase with the ionizations of thin solid organometallic films prepared in ultra-high vacuum was established. Most significantly, the scanning tunneling microscope imaging of these thin films was accomplished.

Metal species involved in long distance metal transport in plants

PubMed Central

Álvarez-Fernández, Ana; Díaz-Benito, Pablo; Abadía, Anunciación; López-Millán, Ana-Flor; Abadía, Javier

2014-01-01

The mechanisms plants use to transport metals from roots to shoots are not completely understood. It has long been proposed that organic molecules participate in metal translocation within the plant. However, until recently the identity of the complexes involved in the long-distance transport of metals could only be inferred by using indirect methods, such as analyzing separately the concentrations of metals and putative ligands and then using in silico chemical speciation software to predict metal species. Molecular biology approaches also have provided a breadth of information about putative metal ligands and metal complexes occurring in plant fluids. The new advances in analytical techniques based on mass spectrometry and the increased use of synchrotron X-ray spectroscopy have allowed for the identification of some metal-ligand species in plant fluids such as the xylem and phloem saps. Also, some proteins present in plant fluids can bind metals and a few studies have explored this possibility. This study reviews the analytical challenges researchers have to face to understand long-distance metal transport in plants as well as the recent advances in the identification of the ligand and metal-ligand complexes in plant fluids. PMID:24723928

Analysis of the chemical and physical properties of combustion aerosols: Properties overview

EPA Science Inventory

Aerosol chemical composition is remarkably complex. Combustion aerosols can comprise tens of thousands of organic compounds and fragments, refractory carbon, metals, cations, anions, salts, and other inorganic phases and substituents [Hays et al., 2004]. Aerosol organic matter no...

Soluble collagen approach to a combination tannage mechanism

USDA-ARS?s Scientific Manuscript database

Although complex salts of Cr(III) sulfate are currently the most effective tanning agents, salts of other metals, including aluminum, have been used either alone or in combination with vegetable tannins or other organic chemicals. In the present study, the interactions of metallic sulfates, and cond...

A Heterobimetallic Complex With an Unsupported Uranium(III)-Aluminum(I) Bond: (CpSiMe3)3U-AlCp* (Cp* = C5Me5)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Minasian, Stefan; Krinsky Ph.D., Jamin; Williams, Valerie

2008-07-23

The discovery of molecular metal-metal bonds has been of fundamental importance to the understanding of chemical bonding. For the actinides, examples of unsupported metal-metal bonds are relatively uncommon, consisting of Cp{sub 3}U-SnPh{sub 3}, and several actinide-transition metal complexes. Traditionally, bonding in the f-elements has been described as electrostatic; however, elucidating the degree of covalency is a subject of recent research. In carbon monoxide complexes of the trivalent uranium metallocenes, decreased {nu}{sub CO} values relative to free CO suggest that the U(III) atom acts as a {pi}-donor. Ephritikhine and coworkers have demonstrated that {pi}-accepting ligands can differentiate trivalent lanthanide and actinidemore » ions, an effect that renders this chemistry of interest in the context of nuclear waste separation technology.« less

Geochemical behaviour of palladium in soils and Pd/PdO model substances in the presence of the organic complexing agents L-methionine and citric acid.

PubMed

Zereini, Fathi; Wiseman, Clare L S; Vang, My; Albers, Peter; Schneider, Wolfgang; Schindl, Roland; Leopold, Kerstin

2016-01-01

Risk assessments of platinum group metal (PGE) emissions, notably those of platinum (Pt), palladium (Pd) and rhodium (Rh), have been mostly based on data regarding the metallic forms used in vehicular exhaust converters, known to be virtually biologically inert and immobile. To adequately assess the potential impacts of PGE, however, data on the chemical behaviour of these metals under ambient conditions post-emission is needed. Complexing agents with a high affinity for metals in the environment are hypothesized to contribute to an increased bioaccessibility of PGE. The purpose of this study is to examine the modulating effects of the organic complexing agents, L-methionine and citric acid, on the geochemical behavior of Pd in soils and model substances (Pd black and PdO). Batch experimental tests were conducted with soils and model substances to examine the impacts of the concentration of complexing agents, pH and length of extraction period on Pd solubility and its chemical transformation. Particle surface chemistry was examined using X-ray photoelectron spectroscopy (XPS) on samples treated with solutions under various conditions, including low and high O2 levels. Pd was observed to be more soluble in the presence of organic complexing agents, compared to Pt and Rh. Pd in soils was more readily solubilized with organic complexing agents compared to the model substances. After 7 days of extraction, L-methionine (0.1 M) treated soil and Pd black samples, for instance, had mean soluble Pd fractions of 12.4 ± 5.9% and 0.554 ± 0.024%, respectively. Surface chemistry analyses (XPS) confirmed the oxidation of metallic Pd surfaces when treated with organic complexing agents. The type of organic complexing agent used for experimental purposes was observed to be the most important factor influencing solubility, followed by solution pH and time of extraction. The results demonstrate that metallic Pd can be transformed into more bioaccessible species in the presence of organic complexing agents which are ubiquitous in the environment.

Catalysts Based on Earth-Abundant Metals for Visible Light-Driven Water Oxidation Reaction.

PubMed

Lin, Junqi; Han, Qing; Ding, Yong

2018-06-04

Exploration of water oxidation catalyst (WOC) with excellent performance is the key for the overall water splitting reaction, which is a feasible strategy to convert solar energy to chemical energy. Although some compounds composed of noble metals, mainly Ru and Ir, have been reported to catalyze water oxidation with high efficiency, catalysts based on low-cost and earth-abundant transition metals are essential for realizing economical and large-scale light-driven water splitting. Various WOCs containing earth-abundant metals (mainly Mn, Fe, Co, Ni, Cu) have been utilized for visible light-driven water oxidation in recent years. In this Personal Account, we summarize our recent developments in WOCs based on earth-abundant transition metals including polyoxometalates (POMs), metal oxides or bimetal oxides, and metal complexes containing multidentate ligand scaffolds for visible light-driven water oxidation reaction. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modelling removal mechanisms of Pb, Cu, Zn and Cd in acidic groundwater during the neutralization by ambient surface and ground waters

USGS Publications Warehouse

Paulson, Anthony J.; Balistrieri, Laurie S.

1999-01-01

Removal of Pb, Cu, Zn, and Cd during neutralization of acid rock drainage is examined using model simulations of field conditions and laboratory experiments involving mixing of natural drainage and surface waters or groundwaters. The simulations consider sorption onto hydrous Fe and Al oxides and particulate organic carbon, mineral precipitation, and organic and inorganic solution complexation of metals for two physical systems where newly formed oxides and particulate organic matter are either transported or retained along the chemical pathway. The calculations indicate that metal removal is a strong function of the physical system. Relative to direct discharge of ARD into streams, lower metal removals are observed where ARD enters streamwaters during the latter stages of neutralization by ambient groundwater after most of the Fe has precipitated and been retained in the soils. The mixing experiments, which represent the field simulations, also demonstrated the importance of dissolved metal to particle Fe ratios in controlling dissolved metal removal along the chemical pathway. Finally, model calculations indicate that hydrous Fe oxides and particulate organic carbon are more important than hydrous Al oxides in removing metals and that both inorganic and organic complexation must be considered when modeling metal removal from aquatic systems that are impacted by sulfide oxidation.

Process for the conversion of and aqueous biomass hydrolyzate into fuels or chemicals by the selective removal of fermentation inhibitors

DOEpatents

Hames, Bonnie R.; Sluiter, Amie D.; Hayward, Tammy K.; Nagle, Nicholas J.

2004-05-18

A process of making a fuel or chemical from a biomass hydrolyzate is provided which comprises the steps of providing a biomass hydrolyzate, adjusting the pH of the hydrolyzate, contacting a metal oxide having an affinity for guaiacyl or syringyl functional groups, or both and the hydrolyzate for a time sufficient to form an adsorption complex; removing the complex wherein a sugar fraction is provided, and converting the sugar fraction to fuels or chemicals using a microorganism.

Mineralogy controls on reactive transport of Marcellus Shale waters.

PubMed

Cai, Zhang; Wen, Hang; Komarneni, Sridhar; Li, Li

2018-07-15

Produced or flowback waters from Marcellus Shale gas extraction (MSWs) typically are highly saline and contain chemicals including trace metals, which pose significant concerns on water quality. The natural attenuation of MSW chemicals in groundwater is poorly understood due to the complex interactions between aquifer minerals and MSWs, limiting our capabilities to monitor and predict. Here we combine flow-through experiments and process-based reactive transport modeling to understand mechanisms and quantify the retention of MSW chemicals in a quartz (Qtz) column, a calcite-rich (Cal) column, and a clay-rich (Vrm, vermiculite) column. These columns were used to represent sand, carbonate, and clay-rich aquifers. Results show that the types and extent of water-rock interactions differ significantly across columns. Although it is generally known that clay-rich media retard chemicals and that quartz media minimize water-rock interactions, results here have revealed insights that differ from previous thoughts. We found that the reaction mechanisms are much more complex than merely sorption and mineral precipitation. In clay rich media, trace metals participate in both ion exchange and mineral precipitation. In fact, the majority of metals (~50-90%) is retained in the solid via mineral precipitation, which is surprising because we typically expect the dominance of sorption in clay-rich aquifers. In the Cal column, trace metals are retained not only through precipitation but also solid solution partitioning, leading to a total of 75-99% retention. Even in the Qtz column, trace metals are retained at unexpectedly high percentages (~20-70%) due to precipitation. The reactive transport model developed here quantitatively differentiates the relative importance of individual processes, and bridges a limited number of experiments to a wide range of natural conditions. This is particularly useful where relatively limited knowledge and data prevent the prediction of complex rock-contaminant interactions and natural attenuation. Copyright © 2018 Elsevier B.V. All rights reserved.

Foam and gel methods for the decontamination of metallic surfaces

DOEpatents

Nunez, Luis; Kaminski, Michael Donald

2007-01-23

Decontamination of nuclear facilities is necessary to reduce the radiation field during normal operations and decommissioning of complex equipment. In this invention, we discuss gel and foam based diphosphonic acid (HEDPA) chemical solutions that are unique in that these solutions can be applied at room temperature; provide protection to the base metal for continued applications of the equipment; and reduce the final waste form production to one step. The HEDPA gels and foams are formulated with benign chemicals, including various solvents, such as ionic liquids and reducing and complexing agents such as hydroxamic acids, and formaldehyde sulfoxylate. Gel and foam based HEDPA processes allow for decontamination of difficult to reach surfaces that are unmanageable with traditional aqueous process methods. Also, the gel and foam components are optimized to maximize the dissolution rate and assist in the chemical transformation of the gel and foam to a stable waste form.

Molecular Speciation of Trace Metal Organic Complexes in the Pacific Ocean

NASA Astrophysics Data System (ADS)

Repeta, D.; Boiteau, R. M.; Bundy, R. M.; Babcock-Adams, L.

2017-12-01

Microbial production across approximately one third of the surface ocean is limited by extraordinarily low (picomolar) concentrations of dissolved iron, essentially all of which is complexed to strong organic ligands of unknown composition. Other biologically important trace metals (cobalt, copper, zinc, nickel) are also complexed to strong organic ligands, which again have not been extensively characterized. Nevertheless, organic ligands exert a strong influence on metal bioavailability and toxicity. For example, amendment experiments using commercially available siderophores, organic compounds synthesized by microbes to facilitate iron uptake, show these ligands can both facilitate or impede iron uptake depending on the siderophore composition and available uptake pathways. Over the past few years we have developed analytical techniques using high pressure liquid chromatography interfaced with inductively coupled plasma and electrospray ionization mass spectrometry to identify and quantify trace metal organic complexes in laboratory cultures of marine microbes and in seawater. We found siderophores to be widely distributed in the ocean, particularly in regions characterized by low iron concentrations. We also find chemically distinct complexes of copper, zinc, colbalt and nickel that we have yet to fully characterize. We will discuss some of our recent work on trace metal organic speciation in seawater and laboratory cultures, and outline future efforts to better understand the microbial cycling of trace metal organic complexes in the sea.

Understanding M-ligand bonding and mer-/fac-isomerism in tris(8-hydroxyquinolinate) metallic complexes.

PubMed

Lima, Carlos F R A C; Taveira, Ricardo J S; Costa, José C S; Fernandes, Ana M; Melo, André; Silva, Artur M S; Santos, Luís M N B F

2016-06-28

Tris(8-hydroxyquinolinate) metallic complexes, Mq3, are one of the most important classes of organic semiconductor materials. Herein, the nature of the chemical bond in Mq3 complexes and its implications on their molecular properties were investigated by a combined experimental and computational approach. Various Mq3 complexes, resulting from the alteration of the metal and substitution of the 8-hydroxyquinoline ligand in different positions, were prepared. The mer-/fac-isomerism in Mq3 was explored by FTIR and NMR spectroscopy, evidencing that, irrespective of the substituent, mer- and fac-are the most stable molecular configurations of Al(iii) and In(iii) complexes, respectively. The relative M-ligand bond dissociation energies were evaluated experimentally by electrospray ionization tandem mass spectrometry (ESI-MS-MS), showing a non-monotonous variation along the group (Al > In > Ga). The results reveal a strong covalent character in M-ligand bonding, which allows for through-ligand electron delocalization, and explain the preferred molecular structures of Mq3 complexes as resulting from the interplay between bonding and steric factors. The mer-isomer reduces intraligand repulsions, being preferred for smaller metals, while the fac-isomer is favoured for larger metals where stronger covalent M-ligand bonds can be formed due to more extensive through-ligand conjugation mediated by metal "d" orbitals.

Comparison of energy interaction parameters for the complexation of Pr(III) with glutathione reduced (GSH) in absence and presence of Zn(II) in aqueous and aquated organic solvents using 4f?4f transition spectra as PROBE

NASA Astrophysics Data System (ADS)

Singh, Th. David; Sumitra, Ch.; Yaiphaba, N.; Devi, H. Debecca; Devi, M. Indira; Singh, N. Rajmuhon

2005-04-01

The coordination chemistry of glutathione reduced (GSH) is of great importance as it acts as excellent model system for the binding of metal ions. The GSH complexation with metal ions is involved in the toxicology of different metal ions. Its coordination behaviour for soft metal ions and hard metal ions is found different because of the structure of GSH and its different potential binding sites. In our work we have studied two chemically dissimilar metal ions viz. Pr(III), which prefer hard donor site like carboxylic groups and Zn(II) the soft metal ion which prefer peptide-NH and sulphydryl groups. The absorption difference and comparative absorption spectroscopy involving 4f-4f transitions of the heterobimetallic Complexation of GSH with Pr(III) and Zn(II) has been explored in aqueous and aquated organic solvents. The variation in the energy parameters like Slater-Condon ( F K), Racah ( E K) and Lande ( ξ4f), Nephelauxetic parameter ( β) and bonding parameter ( b1/2) are computed to explain the nature of complexation.

Intercalation of Transition Metals into Stacked Benzene Rings: A Model Study of the Intercalation of Transition Metals into Bilayered Graphene.

PubMed

Youn, Il Seung; Kim, Dong Young; Singh, N Jiten; Park, Sung Woo; Youn, Jihee; Kim, Kwang S

2012-01-10

Structures of neutral metal-dibenzene complexes, M(C6H6)2 (M = Sc-Zn), are investigated by using Møller-Plesset second order perturbation theory (MP2). The benzene molecules change their conformation and shape upon complexation with the transition metals. We find two types of structures: (i) stacked forms for early transition metal complexes and (ii) distorted forms for late transition metal ones. The benzene molecules and the metal atom are bound together by δ bonds which originate from the interaction of π-MOs and d orbitals. The binding energy shows a maximum for Cr(C6H6)2, which obeys the 18-electron rule. It is noticeable that Mn(C6H6)2, a 19-electron complex, manages to have a stacked structure with an excess electron delocalized. For other late transition metal complexes having more than 19 electrons, the benzene molecules are bent or stray away from each other to reduce the electron density around a metal atom. For the early transition metals, the M(C6H6) complexes are found to be more weakly bound than M(C6H6)2. This is because the M(C6H6) complexes do not have enough electrons to satisfy the 18-electron rule, and so the M(C6H6)2 complexes generally tend to have tighter binding with a shorter benzene-metal length than the M(C6H6) complexes, which is quite unusual. The present results could provide a possible explanation of why on the Ni surface graphene tends to grow in a few layers, while on the Cu surface the weak interaction between the copper surface and graphene allows for the formation of a single layer of graphene, in agreement with chemical vapor deposition experiments.

HM{sup +} and HM{sup +}‑He (M = Group 2 metal): Chemical or physical interactions?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, Joe P.; Dodson, Hannah; Wright, Timothy G., E-mail: Tim.Wright@nottingham.ac.uk

2014-09-07

We investigate the HM{sup +}‑He complexes (M = Group 2 metal) using quantum chemistry. Equilibrium geometries are linear for M = Be and Mg, and bent for M = Ca–Ra; the explanation for this lies in the differing nature of the highest occupied molecular orbitals in the two sets of complexes. The difference primarily occurs as a result of the formation of the H–M{sup +} bond, and so the HM{sup +} diatomics are also studied as part of the present work. The position of the He atom in the complexes is largely determined by the form of the electron density.more » HM{sup +}…He binding energies are obtained and are surprisingly high for a helium complex. The HBe{sup +}…He value is almost 3000 cm{sup −1}, which is high enough to suspect contributions from chemical bonding. This is explored by examining the natural orbital density and by population analyses.« less

Relevant role of dissolved humic matter in phosphorus bioavailability in natural and agronomical ecosystems through the formation of Humic-(Metal)-Phosphate complexes

NASA Astrophysics Data System (ADS)

Baigorri, Roberto; Urrutia, Óscar; Erro, Javier; Pazos-Pérez, Nicolás; María García-Mina, José

2016-04-01

Natural Organic Matter (NOM) and the NOM fraction present in soil solution (dissolved organic matter: DOM) are currently considered as fundamental actors in soil fertility and crop mineral nutrition. Indeed, decreases in crop yields as well as soil erosion are closely related to low values of NOM and, in fact, the use of organic amendments as both soil improvers and plant growth enhancers is very usual in countries with soils poor in NOM. This role of NOM (and DOM) seems to be associated with the presence of bio-transformed organic molecules (humic substances) with high cation chelating-complexing ability. In fact, bioavailable micronutrients with metallic character in soil solutions of alkaline and calcareous soils are forming stable complexes with DOM. This beneficial action of DOM also concerns other plant nutrients such as inorganic phosphate (Pi). Among the different mechanisms involved in the beneficial action of DOM on P bioavailability, the possible formation of poly-nuclear complexes including stable chemical bonds between negative binding sites in humic substances and Pi through metal bridges in soil solution might be relevant, especially in acidic soils. In fact, several studies have proven that these complexes can be obtained in the laboratory and are very efficient in prevent Pi soil fixation and improve Pi root uptake. However, clear experimental evidence about their presence in soil solutions of natural and agronomical soil ecosystems has not published yet. We present here experimental results supporting the real presence of stable Pi-metal-Humic (PMH) complexes in the soil solution of several acidic soils. The study is based on the physico-chemical characterization (31P-NMR, FTIR, TEM-EDAX, ICP-OES) of the DOM fraction isolated by ultrafiltration from the soil solution of several representative acidic soils. In average, more than 60 % of Pi was found in the soil solution humic fraction forming stable humic-metal (Fe, Al) complexes.

Electronic Structure and Bonding in Transition Metal Inorganic and Organometallic Complexes: New Basis Sets, Linear Semibridging Carbonyls and Thiocarbonyls, and Oxidative Addition of Molecular Hydrogen to Square - Iridium Complexes.

NASA Astrophysics Data System (ADS)

Sargent, Andrew Landman

Approximate molecular orbital and ab initio quantum chemical techniques are used to investigate the electronic structure, bonding and reactivity of several transition metal inorganic and organometallic complexes. Modest-sized basis sets are developed for the second-row transition metal atoms and are designed for use in geometry optimizations of inorganic and organometallic complexes incorporating these atoms. The basis sets produce optimized equilibrium geometries which are slightly better than those produced with standard 3-21G basis sets, and which are significantly better than those produced with effective core potential basis sets. Linear semibridging carbonyl ligands in heterobimetallic complexes which contain a coordinatively unsaturated late transition metal center are found to accept electron density from, rather than donate electron density to, these centers. Only when the secondary metal center is a coordinatively unsaturated early transition metal center does the semibridging ligand donate electron density to this center. Large holes in the d shell around the metal center are more prominent and prevalent in early than in late transition metal centers, and the importance of filling in these holes outweighs the importance of mitigating the charge imbalance due to the dative metal-metal interaction. Semibridging thiocarbonyl ligands are more effective donors of electron density than the carbonyl ligands since the occupied donor orbitals of pi symmetry are higher in energy. The stereoselectivity of H_2 addition to d^8 square-planar transition metal complexes is controlled by the interactions between the ligands in the plane of addition and the concentrations of electronic charge around the metal center as the complex evolves from a four-coordinate to a six-coordinate species. Electron -withdrawing ligands help stabilize the five-coordinate species while strong electron donor ligands contribute only to the destabilizing repulsive interactions. The relative thermodynamic stabilities of the final complexes can be predicted based on the relative orientations of the strongest sigma-donor ligands.

Some difficulties in the assessment of electric arc welding fume.

PubMed

Hewitt, P J; Gray, C N

1983-10-01

During electric arc welding of metals, particulate fume in a variety of chemical compositions and physical forms is produced with consequent complex solution chemistry. Mechanisms of fume formation include condensation of vaporized metals to produce submicron diameter chains, and spatter of larger particles with subsequent oxidation to yield mixed metal oxide fumes in the respirable range. Complete dissolution of certain constituent metals such as chromium, can be achieved by fusion with potassium hydrogen sulphate. Extraction of hexavalent chromium by sodium carbonate/hydroxide solution is efficient and rapid, while some other extractants give erroneous results. Investigations show that constituent metals are released from the fume at different rates both in vitro and in vivo. The implications arising from the complex nature of welding fume for industrial hygiene assessment are discussed.

Precious Metals Recovery from Electroplating Wastewater: A Review

NASA Astrophysics Data System (ADS)

Azmi, A. A.; Jai, J.; Zamanhuri, N. A.; Yahya, A.

2018-05-01

Metal bearing electroplating wastewater posts great health and environmental concerns, but could also provide opportunities for precious and valuable metal recovery, which can make the treatment process more cost-effective and sustainable. Current conventional electroplating wastewater treatment and metal recovery methods include chemical precipitation, coagulation and flocculation, ion exchange, membrane filtration, adsorption, electrochemical treatment and photocatalysis. However, these physico-chemical methods have several disadvantages such as high initial capital cost, high operational cost due to expensive chemical reagents and electricity supply, generation of metal complexes sludge which requires further treatment, ineffective in diluted and/or concentrated wastewater, low precious metal selectivity, and slow recovery process. On the other hand, metal bio-reduction assisted by bioactive phytochemical compounds extracted from plants and plant parts is a new found technology explored by several researchers in recent years aiming to recover precious and valuable metals from secondary sources mainly industrial wastewater by utilizing low-cost and eco-friendly biomaterials as reagents. Extract of plants contains polyphenolic compounds which have great antioxidant properties and reducing capacities, able to reduce metal ions into zerovalent metal atoms and stabilize the metal particles formed. This green bio-recovery method has a value added in their end products since the metals are recovered in nano-sized particles which are more valuable and have high commercial demand in other fields ranging from electrochemistry to medicine.

Characterisation of metals in the electronic waste of complex mixtures of end-of-life ICT products for development of cleaner recovery technology.

PubMed

Sun, Z H I; Xiao, Y; Sietsma, J; Agterhuis, H; Visser, G; Yang, Y

2015-01-01

Recycling of valuable metals from electronic waste, especially complex mixtures of end-of-life information and communication technology (ICT) products, is of great difficulty due to their complexity and heterogeneity. One of the important reasons is the lack of comprehensive characterisation on such materials, i.e. accurate compositions, physical/chemical properties. In the present research, we focus on developing methodologies for the characterisation of metals in an industrially processed ICT waste. The morphology, particle size distribution, compositional distribution, occurrence, liberation as well as the thermo-chemical properties of the ICT waste were investigated with various characterisation techniques, including X-ray Fluorescence Spectrometry (XRF), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) with energy dispersed spectroscopy (EDS). Due to the high heterogeneity of the material, special sample preparation procedures were introduced to minimise the discrepancies during compositional analyses. As a result, a clearer overview of the ICT waste has been reached. This research provides better understanding of the extractability of each metal and improves the awareness of potential obstacles for extraction. It will lead to smarter decisions during further development of a clean and effective recovery process. Copyright © 2014 Elsevier Ltd. All rights reserved.

Anticancer activity of metal complexes: involvement of redox processes.

PubMed

Jungwirth, Ute; Kowol, Christian R; Keppler, Bernhard K; Hartinger, Christian G; Berger, Walter; Heffeter, Petra

2011-08-15

Cells require tight regulation of the intracellular redox balance and consequently of reactive oxygen species for proper redox signaling and maintenance of metal (e.g., of iron and copper) homeostasis. In several diseases, including cancer, this balance is disturbed. Therefore, anticancer drugs targeting the redox systems, for example, glutathione and thioredoxin, have entered focus of interest. Anticancer metal complexes (platinum, gold, arsenic, ruthenium, rhodium, copper, vanadium, cobalt, manganese, gadolinium, and molybdenum) have been shown to strongly interact with or even disturb cellular redox homeostasis. In this context, especially the hypothesis of "activation by reduction" as well as the "hard and soft acids and bases" theory with respect to coordination of metal ions to cellular ligands represent important concepts to understand the molecular modes of action of anticancer metal drugs. The aim of this review is to highlight specific interactions of metal-based anticancer drugs with the cellular redox homeostasis and to explain this behavior by considering chemical properties of the respective anticancer metal complexes currently either in (pre)clinical development or in daily clinical routine in oncology.

Anticancer Activity of Metal Complexes: Involvement of Redox Processes

PubMed Central

Jungwirth, Ute; Kowol, Christian R.; Keppler, Bernhard K.; Hartinger, Christian G.; Berger, Walter; Heffeter, Petra

2012-01-01

Cells require tight regulation of the intracellular redox balance and consequently of reactive oxygen species for proper redox signaling and maintenance of metal (e.g., of iron and copper) homeostasis. In several diseases, including cancer, this balance is disturbed. Therefore, anticancer drugs targeting the redox systems, for example, glutathione and thioredoxin, have entered focus of interest. Anticancer metal complexes (platinum, gold, arsenic, ruthenium, rhodium, copper, vanadium, cobalt, manganese, gadolinium, and molybdenum) have been shown to strongly interact with or even disturb cellular redox homeostasis. In this context, especially the hypothesis of “activation by reduction” as well as the “hard and soft acids and bases” theory with respect to coordination of metal ions to cellular ligands represent important concepts to understand the molecular modes of action of anticancer metal drugs. The aim of this review is to highlight specific interactions of metal-based anticancer drugs with the cellular redox homeostasis and to explain this behavior by considering chemical properties of the respective anticancer metal complexes currently either in (pre)clinical development or in daily clinical routine in oncology. PMID:21275772

An absorption spectral study of Nd (III) with glutathione (reduced), GSH in aqueous and aquated organic solvent in presence and absence of Zn (II)

NASA Astrophysics Data System (ADS)

Mehta, Jignasu P.; Bhatt, Prashant N.; Misra, Sudhindra N.

2003-02-01

The coordination chemistry of glutathione (reduced) GSH is of great importance as it acts as an excellent model system for the binding of metal ions. The GSH complexation with metal ions is involved in the toxicology of different metal ions. Its coordination behaviour for soft metal ions and hard metal ions is found different because of the structure of GSH and its different potential binding sites. We have studied two chemically dissimilar metal ions viz. Nd (III) being hard metal ion, which will prefer hard donor sites like carboxylic groups, and Zn (II) the soft metal ion more suited to peptide-NH and sulfhydryl groups. The absorption difference and comparative absorption spectroscopy involving 4f-4f transitions of the heterobimetallic complexation of GSH with Nd (III) and Zn (II) has been explored in aqueous and aquated organic solvents. The changes in the oscillator strengths of different 4f-4f bands and Judd-Ofelt intensity (Tλ) parameters determined experimentally is being used to investigate the complexation of GSH. The in vivo intracellular complexation of GSH with Ca (II) in presence of Zn (II) ion has been mimicked through Nd (III)-GSH-Zn (II) absorption spectral studies in vitro.

Energetic Ionic Liquids Based on Anionic Rare Earth Nitrate Complexes (Preprint)

DTIC Science & Technology

2008-07-10

a glass transition temperature (Tg) at -46 oC. However, it is only stable in dry air, and thus must be protected from water. At 75 oC, clear weight...involved highly toxic and corrosive chemicals, N2O4 and NOCl. Ligands which coordinate via oxygen atoms to a rare earth metal ion give rise to stable...complexes. Thus higher air and thermal stabilities may be obtained by introducing rare earth metal nitrates as main components of ionic liquids. We

THE MUTAGENICITY OF METALLIZED AND UNMETALLIZED AZO AND FORMAZAN DYES IN THE SALMONELLA MUTAGENICITY ASSAY

EPA Science Inventory

The mutagenicity of metallized and unmetallized azo and formazan dyes in the Salmonella mutagenicity
Laura. C. Edwards', Harold S. Freeman'*, and Larry D. Claxton2

Abstract
In previous papers, the synthesis and chemical properties of iron complexed azo and formazan d...

Fate of Pharmaceuticals and Personal Care Products (PPCPs) in Saturated Soil Under Various Redox Conditions

NASA Astrophysics Data System (ADS)

Dror, I.; Menahem, A.; Berkowitz, B.

2014-12-01

The growing use of PPCPs results in their increasing release to the aquatic environment. Consequently, understanding the fate of PPCPs under environmentally relevant conditions that account for dynamic flow and varying redox states is critical. In this study, the transport of two organometallic PPCPs, Gd-DTPA and Roxarsone (As complex) and their metal salts (Gd(NO3)3, AsNaO2), is investigated. The former is used widely as a contrasting agent for MRI, while the latter is applied extensively as a food additive in the broiler poultry industry. Both of these compounds are excreted from the body, almost unchanged chemically. Gadolinium complexes are not fully eliminated in wastewater treatment and can reach groundwater via irrigation with treated wastewater; Roxarsone can enter groundwater via leaching from manure used as fertilizer. Studies have shown that the transport of PPCPs in groundwater is affected by environmental conditions such as redox states, pH, and soil type. For this study, column experiments using sand or Mediterranean red sandy clay soil were performed under several redox conditions: aerobic, nitrate-reducing, iron-reducing, sulfate-reducing, methanogenic, and very strongly chemical reducing. Batch experiments to determine adsorption isotherms were also performed for the complexes and metal salts. We found that Gd-DTPA transport was affected by the soil type and was not affected by the redox conditions. In contrast, Roxarsone transport was affected mainly by the different redox conditions, showing delayed breakthrough curves as the conditions became more biologically reduced (strong chemical reducing conditions did not affect the transport). We also observed that the metal salts show essentially no transport while the organic complexes display much faster breakthrough. The results suggest that transport of these PPCPs through soil and groundwater is determined by the redox conditions, as well as by soil type and the form of the applied metal (as salt or organic complex).

Modifications of chemical functional groups of Pandanus amaryllifolius Roxb and its effect towards biosorption of heavy metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdullah, Mohd Zamri, E-mail: zamriab@petronas.com.my; Ismail, Siti Salwa

2015-07-22

The utilization of non-living biomass as an alternative biosorbent for heavy metal removal has gain a tremendous consideration through the years. Pandanus amaryllifolius Roxb or pandan leaves, which is widely used as food additives in the South East Asia region, has been selected for its viability in the said effort due to the presence of chemical functional groups on its cellular network that enables the sorption to occur. In order to elucidate the possible mechanisms participated during the heavy metal removal process, the biosorbent undergone a series of modification techniques to alter the chemical functional groups present on its constituent.more » From the outcome of the chemically-modified biosorbent being subjected to the contact with metal cations, nitrogen- and oxygen-containing groups present on the biosorbent are believed to be responsible for the metal uptake to occur through complexation mechanism. Modifying amine groups causes 14% reduction of Cu(II) uptake, whereas removing protein element increases the uptake to 26% as compared to the unmodified biosorbent. Also, scanning electron micrographs further suggested that the adsorption mechanism could perform in parallel, as attributed to the evidence of porous structure throughout the biosorbent fibrous nature.« less

Modifications of chemical functional groups of Pandanus amaryllifolius Roxb and its effect towards biosorption of heavy metals

NASA Astrophysics Data System (ADS)

Abdullah, Mohd. Zamri; Ismail, Siti Salwa

2015-07-01

The utilization of non-living biomass as an alternative biosorbent for heavy metal removal has gain a tremendous consideration through the years. Pandanus amaryllifolius Roxb or pandan leaves, which is widely used as food additives in the South East Asia region, has been selected for its viability in the said effort due to the presence of chemical functional groups on its cellular network that enables the sorption to occur. In order to elucidate the possible mechanisms participated during the heavy metal removal process, the biosorbent undergone a series of modification techniques to alter the chemical functional groups present on its constituent. From the outcome of the chemically-modified biosorbent being subjected to the contact with metal cations, nitrogen- and oxygen-containing groups present on the biosorbent are believed to be responsible for the metal uptake to occur through complexation mechanism. Modifying amine groups causes 14% reduction of Cu(II) uptake, whereas removing protein element increases the uptake to 26% as compared to the unmodified biosorbent. Also, scanning electron micrographs further suggested that the adsorption mechanism could perform in parallel, as attributed to the evidence of porous structure throughout the biosorbent fibrous nature.

Metals and lipid oxidation. Contemporary issues.

PubMed

Schaich, K M

1992-03-01

Lipid oxidation is now recognized to be a critically important reaction in physiological and toxicological processes as well as in food products. This provides compelling reasons to understand what causes lipid oxidation in order to be able to prevent or control the reactions. Redox-active metals are major factors catalyzing lipid oxidation in biological systems. Classical mechanisms of direct electron transfer to double bonds by higher valence metals and of reduction of hydroperoxides by lower valence metals do not always account for patterns of metal catalysis of lipid oxidation in multiphasic or compartmentalized biological systems. To explain why oxidation kinetics, mechanisms, and products in molecular environments which are both chemically and physically complex often do not follow classical patterns predicted by model system studies, increased consideration must be given to five contemporary issues regarding metal catalysis of lipid oxidation: hypervalent non-heme iron or iron-oxygen complexes, heme catalysis mechanism(s), compartmentalization of reactions and lipid phase reactions of metals, effects of metals on product mixes, and factors affecting the mode of metal catalytic action.

Reactive metal-oxide interfaces: A microscopic view

NASA Astrophysics Data System (ADS)

Picone, A.; Riva, M.; Brambilla, A.; Calloni, A.; Bussetti, G.; Finazzi, M.; Ciccacci, F.; Duò, L.

2016-03-01

Metal-oxide interfaces play a fundamental role in determining the functional properties of artificial layered heterostructures, which are at the root of present and future technological applications. Magnetic exchange and magnetoelectric coupling, spin filtering, metal passivation, catalytic activity of oxide-supported nano-particles are just few examples of physical and chemical processes arising at metal-oxide hybrid systems, readily exploited in working devices. These phenomena are strictly correlated with the chemical and structural characteristics of the metal-oxide interfacial region, making a thorough understanding of the atomistic mechanisms responsible of its formation a prerequisite in order to tailor the device properties. The steep compositional gradient established upon formation of metal-oxide heterostructures drives strong chemical interactions at the interface, making the metal-oxide boundary region a complex system to treat, both from an experimental and a theoretical point of view. However, once properly mastered, interfacial chemical interactions offer a further degree of freedom for tuning the material properties. The goal of the present review is to provide a summary of the latest achievements in the understanding of metal/oxide and oxide/metal layered systems characterized by reactive interfaces. The influence of the interface composition on the structural, electronic and magnetic properties will be highlighted. Particular emphasis will be devoted to the discussion of ultra-thin epitaxial oxides stabilized on highly oxidizable metals, which have been rarely exploited as oxide supports as compared to the much more widespread noble and quasi noble metallic substrates. In this frame, an extensive discussion is devoted to the microscopic characterization of interfaces between epitaxial metal oxides and the Fe(001) substrate, regarded from the one hand as a prototypical ferromagnetic material and from the other hand as a highly oxidizable metal.

Simulating Valence-to-Core X-ray Emission Spectroscopy of Transition Metal Complexes with Time-Dependent Density Functional Theory.

PubMed

Zhang, Yu; Mukamel, Shaul; Khalil, Munira; Govind, Niranjan

2015-12-08

Valence-to-core (VtC) X-ray emission spectroscopy (XES) has emerged as a powerful technique for the structural characterization of complex organometallic compounds in realistic environments. Since the spectrum represents electronic transitions from the ligand molecular orbitals to the core holes of the metal centers, the approach is more chemically sensitive to the metal-ligand bonding character compared with conventional X-ray absorption techniques. In this paper we study how linear-response time-dependent density functional theory (LR-TDDFT) can be harnessed to simulate K-edge VtC X-ray emission spectra reliably. LR-TDDFT allows one to go beyond the single-particle picture that has been extensively used to simulate VtC-XES. We consider seven low- and high-spin model complexes involving chromium, manganese, and iron transition metal centers. Our results are in good agreement with experiment.

Density Functional Study for Chemical Reaction between Cr and Fe with Sodium Diethyldithiocarbamate (NaDDC)

NASA Astrophysics Data System (ADS)

Setiyanto, Henry; Muhida, Rifki; Kishi, Tomoya; Rahman, Md. Mahmudur; Dipojono, Hermawan K.; Diño, Wilson A.; Matsumoto, Shigeno; Kasai, Hideaki

Analytical chemistry in the perspective of ab initio molecular orbital calculation is introduced by investigating the chemical reaction between transition metals Cr and Fe with sodium diethyldithiocarbamate (NaDDC), a complexing agent to detect and extract Cr in human blood sample. Using density functional theory—based calculations, we determine the stable structure of the Cr-DDC and Fe-DDC complexes and obtain its dissociation energies. We found dissociation energy values of -3.24 and -2.67 eV for Cr and Fe complexes, respectively; and hence the formation of the former complex is more favorable than the formation of the latter.

Nanoscale patterning of two metals on silicon surfaces using an ABC triblock copolymer template.

PubMed

Aizawa, Masato; Buriak, Jillian M

2006-05-03

Patterning technologically important semiconductor interfaces with nanoscale metal films is important for applications such as metallic interconnects and sensing applications. Self-assembling block copolymer templates are utilized to pattern an aqueous metal reduction reaction, galvanic displacement, on silicon surfaces. Utilization of a triblock copolymer monolayer film, polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (PS-b-P2VP-b-PEO), with two blocks capable of selective transport of different metal complexes to the surface (PEO and P2VP), allows for chemical discrimination and nanoscale patterning. Different regions of the self-assembled structure discriminate between metal complexes at the silicon surface, at which time they undergo the spontaneous reaction at the interface. Gold deposition from gold(III) compounds such as HAuCl4(aq) in the presence of hydrofluoric acid mirrors the parent block copolymer core structure, whereas silver deposition from Ag(I) salts such as AgNO3(aq) does the opposite, localizing exclusively under the corona. By carrying out gold deposition first and silver second, sub-100-nm gold features surrounded by silver films can be produced. The chemical selectivity was extended to other metals, including copper, palladium, and platinum. The interfaces were characterized by a variety of methods, including scanning electron microscopy, scanning Auger microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy.

Nickel Complexes of a Binucleating Ligand Derived from an SCS Pincer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peterson, Sonja M.; Helm, Monte L.; Appel, Aaron M.

2015-01-01

A binucleating ligand has been prepared that contains an SCS pincer and three oxygen donor ligands in a partial crown ether loop. To enable metalation with Ni0, a bromoarene precursor was used and resulted in the formation of a nickel-bromide complex in the SCS pincer. Reaction of the nickel complex with a lithium salt yielded a heterobimetallic complex with bromide bridging the two metal centers. The solid-state structures were determined for this heterobimetallic complex and the nickel-bromide precursor, and the two complexes were characterized electrochemically to determine the influence of coordinating the second metal. This research was supported by themore » US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. MLH was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle.« less

Using Metal Complex Ion-Molecule Reactions in a Miniature Rectilinear Ion Trap Mass Spectrometer to Detect Chemical Warfare Agents

NASA Astrophysics Data System (ADS)

Graichen, Adam M.; Vachet, Richard W.

2013-06-01

The gas-phase reactions of a series of coordinatively unsaturated [Ni(L)n]y+ complexes, where L is a nitrogen-containing ligand, with chemical warfare agent (CWA) simulants in a miniature rectilinear ion trap mass spectrometer were investigated as part of a new approach to detect CWAs. Results show that upon entering the vacuum system via a poly(dimethylsiloxane) (PDMS) membrane introduction, low concentrations of several CWA simulants, including dipropyl sulfide (simulant for mustard gas), acetonitrile (simulant for the nerve agent tabun), and diethyl phosphite (simulant for nerve agents sarin, soman, tabun, and VX), can react with metal complex ions generated by electrospray ionization (ESI), thereby providing a sensitive means of detecting these compounds. The [Ni(L)n]2+ complexes are found to be particularly reactive with the simulants of mustard gas and tabun, allowing their detection at low parts-per-billion (ppb) levels. These detection limits are well below reported exposure limits for these CWAs, which indicates the applicability of this new approach, and are about two orders of magnitude lower than electron ionization detection limits on the same mass spectrometer. The use of coordinatively unsaturated metal complexes as reagent ions offers the possibility of further tuning the ion-molecule chemistry so that desired compounds can be detected selectively or at even lower concentrations.

Spectroscopic, thermal analysis and DFT computational studies of salen-type Schiff base complexes.

PubMed

Ebrahimi, Hossein Pasha; Hadi, Jabbar S; Abdulnabi, Zuhair A; Bolandnazar, Zeinab

2014-01-03

A new series of metal(II) complexes of Co(II), Ni(II), Cu(II), Zn(II), and Pb(II) have been synthesized from a salen-type Schiff base ligand derived from o-vanillin and 4-methyl-1,2-phenylenediamine and characterized by elemental analysis, spectral (IR, UV-Vis, (1)H NMR, (13)C NMR and EI-mass), molar conductance measurements and thermal analysis techniques. Coats-Redfern method has been utilized to calculate the kinetic and thermodynamic parameters of the metal complexes. The molecular geometry, Mulliken atomic charges of the studied compounds were investigated theoretically by performing density functional theory (DFT) to access reliable results to the experimental values. The theoretical (13)C chemical shift results of the studied compounds have been calculated at the B3LYP, PBEPBE and PW91PW91 methods and standard 6-311+G(d,p) basis set starting from optimized geometry. The comparison of the results indicates that B3LYP/6-311+G(d,p) yields good agreement with the observed chemical shifts. The measured low molar conductance values in DMF indicate that the metal complexes are non-electrolytes. The spectral and thermal analysis reveals that all complexes have octahedral geometry except Cu(II) complex which can attain the square planner arrangement. The presence of lattice and coordinated water molecules are indicated by thermograms of the complexes. The thermogravimetric (TG/DTG) analyses confirm high stability for all complexes followed by thermal decomposition in different steps. Copyright © 2013 Elsevier B.V. All rights reserved.

Prediction of Combustion Gas Deposit Compositions

NASA Technical Reports Server (NTRS)

Kohl, F. J.; Mcbride, B. J.; Zeleznik, F. J.; Gordon, S.

1985-01-01

Demonstrated procedure used to predict accurately chemical compositions of complicated deposit mixtures. NASA Lewis Research Center's Computer Program for Calculation of Complex Chemical Equilibrium Compositions (CEC) used in conjunction with Computer Program for Calculation of Ideal Gas Thermodynamic Data (PAC) and resulting Thermodynamic Data Base (THDATA) to predict deposit compositions from metal or mineral-seeded combustion processes.

Synthesis of first row transition metal selenomaltol complexes.

PubMed

Spiegel, Michael T; Hoogerbrugge, Amanda; Truksa, Shamus; Smith, Andrew G; Shuford, Kevin L; Klausmeyer, Kevin K; Farmer, Patrick J

2018-06-21

We report an efficient, one-step synthesis of the chelator 3-hydroxy-2-methyl-4-selenopyrone (selenomaltol). Complexes of selenomaltol with Fe(iii), Ni(ii), Cu(ii) and Zn(ii) have been prepared and studied by NMR, X-ray crystallography, cyclic voltammetry, EPR and electronic absorption. The Ni(ii) and Cu(ii) complexes show chemically reversible oxidations which are suggested to be ligand-based. Nuclear independent chemical shifts (NICS) analysis is used to compare aromaticity of the heterocyclic rings of selenomaltol and its chelates. The compounds described here should significantly expand the scope and utility of unusual O,Se-donor chelates.

Mechanisms of lichen resistance to metallic pollution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarret, C.; Manceau, A.; Eybert-Berard, L.

1998-11-01

Some lichens have a unique ability to grow in heavily contaminated areas due to the development of adaptative mechanisms allowing a high tolerance to metals. Here the authors report on the chemical forms of Pb and Zn in the metal hyperaccumulator Diploschistes muscorum and of Pb in the metal tolerant lichen Xanthoria parietina. The speciation of Zn and Pb has been investigated by powder X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopy using the advanced third-generation synchrotron radiation source of the European synchrotron radiation facility (ESRF in Grenoble). This study reveals that in both lichens cells aremore » protected from toxicity by complexation of heavy metals, but the strategies differ: in D. muscorum, Pb and Zn are accumulated through an enhanced synthesis of oxalate, which precipitates toxic elements as insoluble salts, whereas in X. parietina, Pb is complexed to carboxylic groups of the fungal cell walls. The authors conclude that hyperaccumulation of metals results from a reactive mechanism of organic acid production, whereas metallo-tolerance is achieved by a passive complexation to existing functional groups.« less

Solution-phase electronegativity scale: insight into the chemical behaviors of metal ions in solution.

PubMed

Li, Keyan; Li, Min; Xue, Dongfeng

2012-04-26

By incorporating the solvent effect into the Born effective radius, we have proposed an electronegativity scale of metal ions in aqueous solution with the most common oxidation states and hydration coordination numbers in terms of the effective ionic electrostatic potential. It is found that the metal ions in aqueous solution are poorer electron acceptors compared to those in the gas phase. This solution-phase electronegativity scale shows its efficiency in predicting some important properties of metal ions in aqueous solution such as the aqueous acidities of the metal ions, the stability constants of metal complexes, and the solubility product constants of the metal hydroxides. We have elaborated that the standard reduction potential and the solution-phase electronegativity are two different quantities for describing the processes of metal ions in aqueous solution to soak up electrons with different final states. This work provides a new insight into the chemical behaviors of the metal ions in aqueous solution, indicating a potential application of this electronegativity scale to the design of solution reactions.

Chemical Sensors Based on Cyclodextrin Derivatives.

PubMed

Ogoshi, Tomoki; Harada, Akira

2008-08-25

This review focuses on chemical sensors based on cyclodextrin (CD) derivatives. This has been a field of classical interest, and is now of current interest for numerous scientists. First, typical chemical sensors using chromophore appended CDs are mentioned. Various "turn-off" and "turn-on" fluorescent chemical sensors, in which fluorescence intensity was decreased or increased by complexation with guest molecules, respectively, were synthesized. Dye modified CDs and photoactive metal ion-ligand complex appended CDs, metallocyclodextrins, were also applied for chemical sensors. Furthermore, recent novel approaches to chemical sensing systems using supramolecular structures such as CD dimers, trimers and cooperative binding systems of CDs with the other macrocycle [2]rotaxane and supramolecular polymers consisting of CD units are mentioned. New chemical sensors using hybrids of CDs with p-conjugated polymers, peptides, DNA, nanocarbons and nanoparticles are also described in this review.

Uranium extraction by complexation with siderophores

NASA Astrophysics Data System (ADS)

Bahamonde Castro, Cristina

One of the major concerns of energy production is the environmental impact associated with the extraction of natural resources. Nuclear energy fuel is obtained from uranium, an abundant and naturally occurring element in the environment, but the currently used techniques for uranium extraction leave either a significant fingerprint (open pit mines) or a chemical residue that alters the pH of the environment (acid or alkali leaching). It is therefore clear that a new and greener approach to uranium extraction is needed. Bioleaching is one potential alternative. In bioleaching, complexants naturally produced from fungi or bacteria may be used to extract the uranium. In the following research, the siderophore enterobactin, which is naturally produced by bacteria to extract and solubilize iron from the environment, is evaluated to determine its potential for complexing with uranium. To determine whether enterobactin could be used for uranium extraction, its acid dissociation and its binding strength with the metal of interest must be determined. Due to the complexity of working with radioactive materials, lanthanides were used as analogs for uranium. In addition, polyprotic acids were used as structural and chemical analogs for the siderophore during method development. To evaluate the acid dissociation of enterobactin and the subsequent binding constants with lanthanides, three different analytical techniques were studied including: potentiometric titration, UltraViolet Visible (UV-Vis) spectrophotometry and Isothermal Titration Calorimetry (ITC). After evaluation of three techniques, a combination of ITC and potentiometric titrations was deemed to be the most viable way for studying the siderophore of interest. The results obtained from these studies corroborate the ideal pH range for enterobactin complexation to the lanthanide of interest and pave the way for determining the strength of complexation relative to other naturally occurring metals. Ultimately, this fundamental research enhances our current understanding of heavy metal complexation to naturally occurring complexants, which may enhance the metals mobility in the environment or potentially be used as a greener alternative in uranium extraction or remediation.

The Toxicological Geochemistry of Dusts, Soils, and Other Earth Materials: Insights From In Vitro Physiologically-based Geochemical Leach Tests

NASA Astrophysics Data System (ADS)

Plumlee, G. S.; Ziegler, T. L.; Lamothe, P.; Meeker, G. P.; Sutley, S.

2003-12-01

Exposure to mineral dusts, soils, and other earth materials results in chemical reactions between the materials and different body fluids that include, depending upon the exposure route, lung fluids, gastrointestinal fluids, and perspiration. In vitro physiologically-based geochemical leach tests provide useful insights into these chemical reactions and their potential toxicological implications. We have conducted such leach tests on a variety of earth materials, including asbestos, volcanic ash, dusts from dry lake beds, mine wastes, wastes left from the roasting of mercury ores, mineral processing wastes, coal dusts and coal fly ash, various soils, and complex dusts generated by the World Trade Center collapse. Size-fractionated samples of earth materials that have been well-characterized mineralogically and chemically are reacted at body temperature (37 C) for periods from 2 hours up to multiple days with various proportions of simulated lung, gastric, intestinal, and/or plasma-based fluids. Results indicate that different earth materials may have quite different solubility and dissolution behavior in vivo, depending upon a) the mineralogic makeup of the material, and b) the exposure route. For example, biodurable minerals such as asbestos and volcanic ash particles, whose health effects result because they dissolve very slowly in vivo, bleed off low levels of trace metals into the simulated lung fluids; these include metals such as Fe and Cr that are suspected by health scientists of contributing to the generation of reactive oxygen species and resulting DNA damage in vivo. In contrast, dry lake bed dusts and concrete-rich dusts are highly alkaline and bioreactive, and cause substantial pH increases and other chemical changes in the simulated body fluids. Many of the earth materials tested contain a variety of metals that can be quite soluble (bioaccessible), depending upon the material and the simulated body fluid composition. For example, due to their acidic pH and high chloride concentrations, simulated gastric fluids are most efficient at solubilizing metals such as Hg, Pb, Zn, and others that form strong chloride complexes; although these metals tend to partially reprecipitate in the near-neutral simulated intestinal fluids, complexes with organic ligands (i.e., amino and carboxylic acids) enhance their solubility. These metals are also quite soluble in near-neutral, protein-rich plasma-based fluids because they form strong complexes with the proteins. In contrast, metalloids that form oxyanion species (such as As, Cr, Mo, W) are commonly more soluble in near-neutral pH simulated lung fluids than in simulated gastric fluids.

Modeling of Heavy Metal Transformation in Soil Ecosystem

NASA Astrophysics Data System (ADS)

Kalinichenko, Kira; Nikovskaya, Galina N.

2017-04-01

The intensification of industrial activity leads to an increase in heavy metals pollution of soils. In our opinion, sludge from biological treatment of municipal waste water, stabilized under aerobic-anaerobic conditions (commonly known as biosolid), may be considered as concentrate of natural soil. In their chemical, physical and chemical and biological properties these systems are similar gel-like nanocomposites. These contain microorganisms, humic substances, clay, clusters of nanoparticles of heavy metal compounds, and so on involved into heteropolysaccharides matrix. It is known that microorganisms play an important role in the transformation of different nature substances in soil and its health maintenance. The regularities of transformation of heavy metal compounds in soil ecosystem were studied at the model of biosolid. At biosolid swelling its structure changing (gel-sol transition, weakening of coagulation contacts between metal containing nanoparticles, microbial cells and metabolites, loosening and even destroying of the nanocomposite structure) can occur [1, 2]. The promotion of the sludge heterotrophic microbial activities leads to solubilization of heavy metal compounds in the system. The microbiological process can be realized in alcaligeneous or acidogeneous regimes in dependence on the type of carbon source and followed by the synthesis of metabolites with the properties of flocculants and heavy metals extragents [3]. In this case the heavy metals solubilization (bioleaching) in the form of nanoparticles of hydroxycarbonate complexes or water soluble complexes with oxycarbonic acids is observed. Under the action of biosolid microorganisms the heavy metals-oxycarbonic acids complexes can be transformed (catabolised) into nano-sizing heavy metals- hydroxycarbonates complexes. These ecologically friendly complexes and microbial heteropolysaccharides are able to interact with soil colloids, stay in the top soil profile, and improve soil structure due to the formation of water-stable aggregates. The alkaligeneous microbiological process in natural ecosystems by co-metabolism of appropriate carbon source is more advantages for environment. Thus the possibility of solubilization of heavy metal compounds in the soil due to stimulating its biological activities of native microorganisms is proved. The studies on the interactions in the system of sludge solid has allowed to develop the "green" biotechnological process of heavy metals solubilization in contaminated soils and sludges. 1. Kalinichenko KV, Nikovskaya GN, and Ulberg ZR (2012) Bioextraction of heavy metals from colloidal sludge systems. Colloid Journ. 74(5) : 553-557. 2. Kalinichenko KV, Nikovskaya GN, and Ulberg ZR (2013) Changes in the surface properties and stability of biocolloids of a sludge system upon extraction of heavy metals. Colloid Journ. 75(3) : 274-278. 3. Nikovskaya GN, Kalinichenko KV (2013) Bioleaching of heavy metals from sludge after biological treatment of municipal effluent. Journ. of Water Chem. and Techn. 35(2) : 80-85.

School-Based Study of Complex Environmental Exposures and Related Health Effects in Children: Part A - Exposure. Final Report and Executive Summary.

ERIC Educational Resources Information Center

Minnesota Univ., Minneapolis. School of Public Health.

The School Health Initiative: Environment, Learning, and Disease (SHIELD) study examined children's exposure to complex mixtures of environmental agents (i.e., volatile organic chemicals, environmental tobacco smoke, allergens, bioaerosols, metals, and pesticides). Environmental, personal, and biological data were collected on ethnically and…

Chemistry of carcinogenic metals.

PubMed Central

Martell, A E

1981-01-01

The periodic distribution of known and suspected carcinogenic metal ions is described, and the chemical behavior of various types of metal ions is explained in terms of the general theory of hard and soft acids and bases. The chelate effect is elucidated, and the relatively high stability of metal chelates in very dilute solutions is discussed. The concepts employed for the chelate effect are extended to explain the high stabilities of macrocyclic and cryptate complexes. Procedures for the use of equilibrium data to determine the speciation of metal ions and complexes under varying solution conditions are described. Methods for assessing the interferences by hydrogen ion, competing metal ions, hydrolysis, and precipitation are explained, and are applied to systems containing iron(III) chelates of fourteen chelating agents designed for effective binding of the ferric ion. The donor groups available for the building up of multidentate ligands are presented, and the ways in which they may be combined to achieve high affinity and selectivity for certain types of metal ions are explained. PMID:6791915

Waste treatment process for removal of contaminants from aqueous, mixed-waste solutions using sequential chemical treatment and crossflow microfiltration, followed by dewatering

DOEpatents

Vijayan, S.; Wong, C.F.; Buckley, L.P.

1994-11-22

In processes of this invention aqueous waste solutions containing a variety of mixed waste contaminants are treated to remove the contaminants by a sequential addition of chemicals and adsorption/ion exchange powdered materials to remove the contaminants including lead, cadmium, uranium, cesium-137, strontium-85/90, trichloroethylene and benzene, and impurities including iron and calcium. Staged conditioning of the waste solution produces a polydisperse system of size enlarged complexes of the contaminants in three distinct configurations: water-soluble metal complexes, insoluble metal precipitation complexes, and contaminant-bearing particles of ion exchange and adsorbent materials. The volume of the waste is reduced by separation of the polydisperse system by cross-flow microfiltration, followed by low-temperature evaporation and/or filter pressing. The water produced as filtrate is discharged if it meets a specified target water quality, or else the filtrate is recycled until the target is achieved. 1 fig.

Waste treatment process for removal of contaminants from aqueous, mixed-waste solutions using sequential chemical treatment and crossflow microfiltration, followed by dewatering

DOEpatents

Vijayan, Sivaraman; Wong, Chi F.; Buckley, Leo P.

1994-01-01

In processes of this invention aqueous waste solutions containing a variety of mixed waste contaminants are treated to remove the contaminants by a sequential addition of chemicals and adsorption/ion exchange powdered materials to remove the contaminants including lead, cadmium, uranium, cesium-137, strontium-85/90, trichloroethylene and benzene, and impurities including iron and calcium. Staged conditioning of the waste solution produces a polydisperse system of size enlarged complexes of the contaminants in three distinct configurations: water-soluble metal complexes, insoluble metal precipitation complexes, and contaminant-bearing particles of ion exchange and adsorbent materials. The volume of the waste is reduced by separation of the polydisperse system by cross-flow microfiltration, followed by low-temperature evaporation and/or filter pressing. The water produced as filtrate is discharged if it meets a specified target water quality, or else the filtrate is recycled until the target is achieved.

On the structure of transition metals complexes with the new tridentate dye of thiazole series: Theoretical and experimental studies

NASA Astrophysics Data System (ADS)

Fizer, Maksym; Sidey, Vasyl; Tupys, Andrii; Ostapiuk, Yurii; Tymoshuk, Oleksandr; Bazel, Yaroslav

2017-12-01

The 1-[(5-Benzyl-1,3-thiazol-2-yl)diazenyl]naphthalene-2-ol (BnTAN) is a recently synthesized azo dye that can act as a tridentate ligand in complexes with transition metals. In a series of previous works, this analytical reagent was shown to be applicable for selective, reliable, express and relatively inexpensive determination of heavy metals in different objects through the spectrophotometric technique. Although the action of 1-(2-thiazolylazo)-2-naphthol (TAN) dyes as tridentate ligands has been suggested in the literature long time ago, due to the lack of experimental data, it was necessary to investigate the mechanism of formation and the structure of BnTAN complexes with the such transition metals as Cu(II), Zn(II) and Cd(II). Furthermore, the reactivity and properties of different acidity forms and conformers of BnTAN and related TAN dyes were not fully defined, so the determination of these properties by analysis of wavefunction was also necessary. Two standard spectrophotometric methods and voltammetric technique were used to determine the composition of complex of BnTAN with metals ions. All three experimental methods indicate that coordination ratio of metal:dye is equal to 1:2. Moreover, this study reports the stability and geometry of conformers of different forms (anionic/neutral/cationic) of BnTAN, along with a detailed analysis of electronic properties, reactivity and aromaticity of the most stable conformers of BnTAN forms. Each of the above forms has some difference in position of benzyl ring against the thiazole moiety, which is explained in terms of attraction and repulsion of these two fragments induced by partial atomic charges. The crucial influence of hydrogen bond and weak non-covalent interactions between naphthyl, aza- and thiazolyl fragments has been established. The quantum chemical calculations have shown that partial atomic charges of anionic, neutral and cationic forms can explain the reactivity of each BnTAN form, and have also clarified the mechanism of formation of metal complex through the connection of metal with phenol oxygen, thiazolyl nitrogen and one nitrogen of aza group - thus giving two five-membered metal-containing cycles and confirming that BnTAN acts as a tridentate ligand. The obtained results introduce novel and crucial information which can assist in understanding the mechanism of complex formation of BnTAN and display the strength and level of detail of applying quantum chemical methods to reveal the reactivity, energy properties, and electronic properties of this new dye.

A primer on trace metal-sediment chemistry

USGS Publications Warehouse

Horowitz, Arthur J.

1985-01-01

In most aquatic systems, concentrations of trace metals in suspended sediment and the top few centimeters of bottom sediment are far greater than concentrations of trace metals dissolved in the water column. Consequently, the distribution, transport, and availability of these constituents can not be intelligently evaluated, nor can their environmental impact be determined or predicted solely through the sampling and analysis of dissolved phases. This Primer is designed to acquaint the reader with the basic principles that govern the concentration and distribution of trace metals associated with bottom and suspended sediments. The sampling and analysis of suspended and bottom sediments are very important for monitoring studies, not only because trace metal concentrations associated with them are orders of magnitude higher than in the dissolved phase, but also because of several other factors. Riverine transport of trace metals is dominated by sediment. In addition, bottom sediments serve as a source for suspended sediment and can provide a historical record of chemical conditions. This record will help establish area baseline metal levels against which existing conditions can be compared. Many physical and chemical factors affect a sediment's capacity to collect and concentrate trace metals. The physical factors include grain size, surface area, surface charge, cation exchange capacity, composition, and so forth. Increases in metal concentrations are strongly correlated with decreasing grain size and increasing surface area, surface charge, cation exchange capacity, and increasing concentrations of iron and manganese oxides, organic matter, and clay minerals. Chemical factors are equally important, especially for differentiating between samples having similar bulk chemistries and for inferring or predicting environmental availability. Chemical factors entail phase associations (with such sedimentary components as interstitial water, sulfides, carbonates, and organic matter) and ways in which the metals are entrained by the sediments (such as adsorption, complexation, and within mineral lattices).

Integrated copper-containing wastewater treatment using xanthate process.

PubMed

Chang, Yi-Kuo; Chang, Juu-En; Lin, Tzong-Tzeng; Hsu, Yu-Ming

2002-09-02

Although, the xanthate process has been shown to be an effective method for heavy metal removal from contaminated water, a heavy metal contaminated residual sludge is produced by the treatment process and the metal-xanthate sludge must be handled in accordance with the Taiwan EPA's waste disposal requirements. This work employed potassium ethyl xanthate (KEX) to remove copper ions from wastewater. The toxicity characteristic leaching procedure (TCLP) and semi-dynamic leaching test (SDLT) were used to determine the leaching potential and stability characteristics of the residual copper xanthate (Cu-EX) complexes. Results from metal removal experiments showed that KEX was suitable for the treatment of copper-containing wastewater over a wide copper concentration range (50, 100, 500, and 1000 mg/l) to the level that meets the Taiwan EPA's effluent regulations (3mg/l). The TCLP results of the residual Cu-EX complexes could meet the current regulations and thus the Cu-EX complexes could be treated as a non-hazardous material. Besides, the results of SDLT indicated that the complexes exhibited an excellent performance for stabilizing metals under acidic conditions, even slight chemical changes of the complexes occurred during extraction. The xanthate process, mixing KEX with copper-bearing solution to form Cu-EX precipitates, offered a comprehensive strategy for solving both copper-containing wastewater problems and subsequent sludge disposal requirements.

Electroreduction of CO 2 Catalyzed by a Heterogenized Zn–Porphyrin Complex with a Redox-Innocent Metal Center

DOE PAGES

Wu, Yueshen; Jiang, Jianbing; Weng, Zhe; ...

2017-07-26

Transition-metal-based molecular complexes are a class of catalyst materials for electrochemical CO 2 reduction to CO that can be rationally designed to deliver high catalytic performance. One common mechanistic feature of these electrocatalysts developed thus far is an electrogenerated reduced metal center associated with catalytic CO 2 reduction. Here in this paper, we report a heterogenized zinc–porphyrin complex (zinc(II) 5,10,15,20-tetramesitylporphyrin) as an electrocatalyst that delivers a turnover frequency as high as 14.4 site –1 s –1 and a Faradaic efficiency as high as 95% for CO 2 electroreduction to CO at -1.7 V vs the standard hydrogen electrode in anmore » organic/water mixed electrolyte. While the Zn center is critical to the observed catalysis, in situ and operando X-ray absorption spectroscopic studies reveal that it is redox-innocent throughout the potential range. Cyclic voltammetry indicates that the porphyrin ligand may act as a redox mediator. Chemical reduction of the zinc–porphyrin complex further confirms that the reduction is ligand-based and the reduced species can react with CO 2. This represents the first example of a transition-metal complex for CO 2 electroreduction catalysis with its metal center being redox-innocent under working conditions.« less

Electroreduction of CO2 Catalyzed by a Heterogenized Zn–Porphyrin Complex with a Redox-Innocent Metal Center

PubMed Central

2017-01-01

Transition-metal-based molecular complexes are a class of catalyst materials for electrochemical CO2 reduction to CO that can be rationally designed to deliver high catalytic performance. One common mechanistic feature of these electrocatalysts developed thus far is an electrogenerated reduced metal center associated with catalytic CO2 reduction. Here we report a heterogenized zinc–porphyrin complex (zinc(II) 5,10,15,20-tetramesitylporphyrin) as an electrocatalyst that delivers a turnover frequency as high as 14.4 site–1 s–1 and a Faradaic efficiency as high as 95% for CO2 electroreduction to CO at −1.7 V vs the standard hydrogen electrode in an organic/water mixed electrolyte. While the Zn center is critical to the observed catalysis, in situ and operando X-ray absorption spectroscopic studies reveal that it is redox-innocent throughout the potential range. Cyclic voltammetry indicates that the porphyrin ligand may act as a redox mediator. Chemical reduction of the zinc–porphyrin complex further confirms that the reduction is ligand-based and the reduced species can react with CO2. This represents the first example of a transition-metal complex for CO2 electroreduction catalysis with its metal center being redox-innocent under working conditions. PMID:28852698

Electroreduction of CO 2 Catalyzed by a Heterogenized Zn–Porphyrin Complex with a Redox-Innocent Metal Center

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Yueshen; Jiang, Jianbing; Weng, Zhe

Transition-metal-based molecular complexes are a class of catalyst materials for electrochemical CO 2 reduction to CO that can be rationally designed to deliver high catalytic performance. One common mechanistic feature of these electrocatalysts developed thus far is an electrogenerated reduced metal center associated with catalytic CO 2 reduction. Here in this paper, we report a heterogenized zinc–porphyrin complex (zinc(II) 5,10,15,20-tetramesitylporphyrin) as an electrocatalyst that delivers a turnover frequency as high as 14.4 site –1 s –1 and a Faradaic efficiency as high as 95% for CO 2 electroreduction to CO at -1.7 V vs the standard hydrogen electrode in anmore » organic/water mixed electrolyte. While the Zn center is critical to the observed catalysis, in situ and operando X-ray absorption spectroscopic studies reveal that it is redox-innocent throughout the potential range. Cyclic voltammetry indicates that the porphyrin ligand may act as a redox mediator. Chemical reduction of the zinc–porphyrin complex further confirms that the reduction is ligand-based and the reduced species can react with CO 2. This represents the first example of a transition-metal complex for CO 2 electroreduction catalysis with its metal center being redox-innocent under working conditions.« less

Electroreduction of CO 2 Catalyzed by a Heterogenized Zn–Porphyrin Complex with a Redox-Innocent Metal Center

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Yueshen; Jiang, Jianbing; Weng, Zhe

Transition-metal-based molecular complexes are a class of catalyst materials for electrochemical CO2 reduction to CO that can be rationally designed to deliver high catalytic performance. One common mechanistic feature of these electrocatalysts developed thus far is an electrogenerated reduced metal center associated with catalytic CO2 reduction. Here we report a heterogenized zinc–porphyrin complex (zinc(II) 5,10,15,20-tetramesitylporphyrin) as an electrocatalyst that delivers a turnover frequency as high as 14.4 site–1 s–1 and a Faradaic efficiency as high as 95% for CO2 electroreduction to CO at -1.7 V vs the standard hydrogen electrode in an organic/water mixed electrolyte. While the Zn center ismore » critical to the observed catalysis, in situ and operando X-ray absorption spectroscopic studies reveal that it is redox-innocent throughout the potential range. Cyclic voltammetry indicates that the porphyrin ligand may act as a redox mediator. Chemical reduction of the zinc–porphyrin complex further confirms that the reduction is ligand-based and the reduced species can react with CO2. This represents the first example of a transition-metal complex for CO2 electroreduction catalysis with its metal center being redox-innocent under working conditions.« less

40 CFR Appendix A to Part 414 - Non-Complexed Metal-Bearing Waste Streams and Cyanide-Bearing Waste Streams

Code of Federal Regulations, 2014 CFR

2014-07-01

... PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC... Picolines, mixed/Condensation of acetaldehyde + formaldehyde + ammonia Organic pigments, Azo/Diazotization...

40 CFR Appendix A to Part 414 - Non-Complexed Metal-Bearing Waste Streams and Cyanide-Bearing Waste Streams

Code of Federal Regulations, 2011 CFR

2011-07-01

... PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC... Picolines, mixed/Condensation of acetaldehyde + formaldehyde + ammonia Organic pigments, Azo/Diazotization...

40 CFR Appendix A to Part 414 - Non-Complexed Metal-Bearing Waste Streams and Cyanide-Bearing Waste Streams

Code of Federal Regulations, 2013 CFR

2013-07-01

... PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC... Picolines, mixed/Condensation of acetaldehyde + formaldehyde + ammonia Organic pigments, Azo/Diazotization...

40 CFR Appendix A to Part 414 - Non-Complexed Metal-Bearing Waste Streams and Cyanide-Bearing Waste Streams

Code of Federal Regulations, 2012 CFR

2012-07-01

... PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC... Picolines, mixed/Condensation of acetaldehyde + formaldehyde + ammonia Organic pigments, Azo/Diazotization...

Rhodium complexes as therapeutic agents.

PubMed

Ma, Dik-Lung; Wang, Modi; Mao, Zhifeng; Yang, Chao; Ng, Chan-Tat; Leung, Chung-Hang

2016-02-21

The landscape of inorganic medicinal chemistry has been dominated by the investigation of platinum, and to a lesser extent ruthenium, complexes over the past few decades. Recently, complexes based on other metal centers such as rhodium have attracted attention due to their tunable chemical and biological properties as well as distinct mechanisms of action. This perspective highlights recent examples of rhodium complexes that show diverse biological activities against various targets, including enzymes and protein-protein interactions.

Ligational behavior of Schiff bases towards transition metal ion and metalation effect on their antibacterial activity

NASA Astrophysics Data System (ADS)

Devi, Jai; Batra, Nisha; Malhotra, Rajesh

2012-11-01

New Schiff bases pyrazine-2-carboxylicacid (phenyl-pyridin-2-yl-methylene)-hydrazide (Hpch-bp) HL1 and pyrazine-2-carboxylicacid (pyridin-2-ylmethylene)-hydrazide (Hpch-pc) HL2 derived from condensation of pyrazine carboxylic hydrazide (Hpch) with 2-benzoyl pyridine (bp) or pyridine 2-carbaldehyde (pc) and their transition metal complexes of type ML(1-2)2 have been synthesized, where M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). Characterization of ligands and their metal complexes was carried out by elemental analysis, conductimetric studies, magnetic susceptibility, spectroscopic techniques (IR, UV-VIS, NMR, ESR, Mass) and thermogravimetric analysis. The physico-chemical studies revealed octahedral geometry or distorted octahedral geometry around metal ion. These azomethine Schiff base ligands acted as tridentate ? coordinating through carbonyl, azomethine and pyridine nitrogen present in the ligand. The thermodynamic and thermal properties of the complexes have been investigated and it was observed on the basis of these studies that thermal stability of complexes follows the order Mn < Zn < Cu < Co < Ni. The ligands and their complexes were tested for in vitro antibacterial activity at different concentrations against bacteria viz. Gram positive Bacillus subtilis, Micrococcus luteus and Gram negative Pseudomonas aeruginosa, Pseudomonas mendocina. A marked enhancement in biocidal activity of the ligands under similar experimental conditions was observed as a consequence of coordination with metal ions. The trend of growth inhibition in the complexes was found to be in the order: Cu > Mn > Ni > Co > Zn.

Modeling Biogeochemical Cycling of Heavy Metals in Lake Coeur d'Alene Sediments

NASA Astrophysics Data System (ADS)

Sengor, S. S.; Spycher, N.; Belding, E.; Curthoys, K.; Ginn, T. R.

2005-12-01

Mining of precious metals since the late 1800's have left Lake Coeur d'Alene (LCdA) sediments heavily enriched with toxic metals, including Cd, Cu, Pb, and Zn. Indigenous microbes however are capable of catalyzing reactions that detoxify the benthic and aqueous lake environments, and thus constitute an important driving component in the biogeochemical cycles of these metals. Here we report on the development of a quantitative model of transport, fate, exposure and effects of toxic compounds on benthic microbial communities at LCdA. First, chemical data from the LCdA area have been compiled from multiple sources to investigate trends in chemical occurrence, as well as to define model boundary conditions. The model is structured as 1-D diffusive reactive transport model to simulate spatial and temporal distribution of metals through the benthic sediments. Inorganic reaction processes included in the model are aqueous speciation, surface complexation, mineral precipitation/dissolution and abiotic redox reactions. Simulations with and without surface complexation are carried out to evaluate the effect of sorption and the conservative behaviour of metals within the benthic sediments under abiotic and purely diffusive transport. The 1-D inorganic diffusive transport model is then coupled to a biotic reaction network including consortium biodegradation kinetics with multiple electron acceptors, product toxicity, and energy partitioning. Multiyear simulations are performed, with water column chemistry established as a boundary condition from extant data, to explore the role of biogeochemical dynamics on benthic fluxes of metals in the long term.

Electronic structures and magnetic/optical properties of metal phthalocyanine complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baba, Shintaro; Suzuki, Atsushi, E-mail: suzuki@mat.usp.ac.jp; Oku, Takeo

2016-02-01

Electronic structures and magnetic / optical properties of metal phthalocyanine complexes were studied by quantum calculations using density functional theory. Effects of central metal and expansion of π orbital on aromatic ring as conjugation system on the electronic structures, magnetic, optical properties and vibration modes of infrared and Raman spectra of metal phthalocyanines were investigated. Electron and charge density distribution and energy levels near frontier orbital and excited states were influenced by the deformed structures varied with central metal and charge. The magnetic parameters of chemical shifts in {sup 13}C-nuclear magnetic resonance ({sup 13}C-NMR), principle g-tensor, A-tensor, V-tensor of electricmore » field gradient and asymmetry parameters derived from the deformed structures with magnetic interaction of nuclear quadruple interaction based on electron and charge density distribution with a bias of charge near ligand under crystal field.« less

VizieR Online Data Catalog: Abundances of M33 HII regions (Magrini+, 2010)

NASA Astrophysics Data System (ADS)

Magrini, L.; Stanghellini, L.; Corbelli, E.; Galli, D.; Villaver, E.

2009-11-01

We analyze the spatial distribution of metals in M33 using a new sample and literature data of HII regions, constraining a model of galactic chemical evolution with HII region and planetary nebula (PN) abundances. We consider chemical abundances of a new sample of HII regions complemented with previous literature data-sets. Supported by a uniform sample of nebular spectroscopic observations, we conclude that: i) the metallicity distribution in M33 is very complex, showing a central depression in metallicity probably due to observational bias; ii) the metallicity gradient in the disk of M33 has a slope of -0.037+/-0.009dex/kpc in the whole radial range up to ~8kpc, and -0.044+/-0.009dex/kpc excluding the central kpc; iii) there is a small evolution of the slope with time from the epoch of PN progenitor formation to the present-time. Description: Emission line fluxes, observed and dereddened of 33 HII regions are presented. Physical and chemical properties, such as electron temperatures and density, ionic and total chemical abundances of He, O, N, Ne, Ar, S, are derived. (3 data files).

Engineering the oxygen coordination in digital superlattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cook, Seyoung; Andersen, Tassie K.; Hong, Hawoong

The oxygen sublattice in the complex oxides is typically composed of corner-shared polyhedra, with transition metals at their centers. The electronic and chemical properties of the oxide depend on the type and geometric arrangement of these polyhedra, which can be controlled through epitaxial synthesis. Here, we use oxide molecular beam epitaxy to create SrCoOx:SrTiO3 superlattices with tunable oxygen coordination environments and sublattice geometries. Using soft X-ray spectroscopy, we find that the chemical state of Co can be varied with the polyhedral arrangement, demonstrating a new strategy for achieving unique electronic properties in the transition metal oxides.

[Influence of the earthworm Lumbricus terrestris on soil solution complexation capacity].

PubMed

el Gharmali, A; Rada, A; el Meray, M; Nejmeddine, A

2001-04-01

Four soil samples highly contaminated with metals of urban and mine origin (SE1, SE2, SM1, SM2) and having different physico-chemical proprieties were selected to study copper complexation capacity (LT) of soil solution. The effect of Lumbricus terrestris on copper complexation capacity of soil solution was investigated on SE1 and SE2. The complexation capacity was estimated by amperometric titration of soil solution by copper. Free hydrated cation and labile complexes of copper were determined by DPASV. The results show that the copper complexation capacity variation depends on the physico-chemical characteristics of soils, particularly pH. Thus, the values of copper complexation capacity are 0; 0.6 x 10(-7); 1.8 x 10(-7) and 5.5 x 10(-7) mol l-1 respectively for SM2; SM1; SE1 and SE2 which are pH 5; 5.4; 6.5 and 7.4. Based on these results, the bioavailability levels of heavy metals show the following pool ranking: SM2 > SM1 > SE1 > SE2. The copper complexation capacity of soil solution increases with the soil disturbance by Lumbricus terrestris. This is more obvious when the time of disturbance by lumbrics is longer. Indeed, average values determined for 1 month and 3 months are 3.8 x 10(-7) and 7.8 x 10(-7) mol l-1 for SE1; 7.7 x 10(-7) and 15.2 x 10(-7) mol l-1 for SE2 respectively. It seems that the action of earthworm on soil can contribute to the decrease of bioavailability of heavy metals, particularly copper.

Biocompatible nanocarriers that respond to oxidative environments via interactions between chitosan and multiple metal ions

PubMed Central

Zhang, Shichang; Xia, Liye; Ding, Chenchen; Wen, Lu; Wan, Weihua; Chen, Gang

2016-01-01

Hydrogen peroxide (H2O2) functions as an early damage signal contributing to the oxidative stress response and can act as a trigger in smart oxidation-responsive drug delivery systems that are currently in development. Current H2O2-triggered oxidation-responsive polymeric systems are usually derived from chemical synthesis and rarely include natural polymers. Herein, we report two series of nanoparticle (NP) complexes prepared with the biopolymer chitosan (CS) and four different metal ions (Cu2+, Ca2+, Zn2+, and Fe3+), defined as CSNPs-metal complexes (Series 1) and CS-metal complexes NPs (Series 2), which responded to oxidation by dissolving upon H2O2 exposure. Experiments examining Nile red release and H2O2-triggered degradation confirmed that both series of complexes showed better sensitivity to oxidation than the CSNPs alone. Furthermore, preliminary cytotoxicity and histological observations indicated that the two series exhibited little or no cytotoxicity and generated a mild inflammatory response. Our work provides a novel and promising strategy for developing NPs for use as intelligent oxidation-responsive systems. PMID:27358564

A Review: Advances on Absorption of Heavy Metals in the Waste Water by Biochar

NASA Astrophysics Data System (ADS)

Chen, Hao; Xie, Anbin; You, Shaohong

2018-01-01

Biochar as a new type of adsorbent, its physical and chemical characteristics and adsorption of heavy metal has been widely studied. Based on the current studies, the article reviewed the main characteristics of biochar, its influencing factors (preparation temperature, feed stocks, functional group et.) on adsorption of heavy metals in water and its mechanism of adsorption (ion exchange adsorption, complexation, precipitation sedimentation et.). Briefly summarize unresolved issues for potential applications of biochar in the future.

Understanding interaction of curcumin and metal ions on electrode surfaces using EDXRF

NASA Astrophysics Data System (ADS)

Joseph, Daisy; Kumar, K. Krishna; Narayanan, S. Sriman

2018-04-01

A chemically modified electrode was developed for determination of metal ions (Cd, Pb, Zn, Co, Hg). The modifier used for the study was Curcumin. Curcumin acts as a complexing agent at the surface of the electrode for preconcentration of metal ions from electrolyte to electrode surface and stripped back to electrolyte during analysis. EDXRF was used to analyze these electrodes and it was concluded that the PCR modified electrode favored effective chelation for lead and mercury.

Zinc complexes developed as metallopharmaceutics for treating diabetes mellitus based on the bio-medicinal inorganic chemistry.

PubMed

Yoshikawa, Yutaka; Yasui, Hiroyuki

2012-01-01

Biological trace metals such as iron, zinc, copper, and manganese are essential to life and health of humans, and the success of platinum drugs in the cancer chemotherapy has rapidly grown interest in developing inorganic pharmaceutical agents in medicinal chemistry, that is, medicinal inorganic chemistry, using essential elements and other biological trace metals. Transition metal complexes with unique chemical structures may be useful alternatives to the drugs available to address some of the incurable diseases. In this review, we emphasize that metal complexes are an expanding of interest in the research field of treatment of diabetes mellitus. Especially, orally active anti-diabetic and anti-metabolic syndrome zinc complexes have been developed and progressed since the discovery in 2001, where several highly potent anti-diabetic zinc complexes with different coordination structures have quite recently been disclosed, using experimental diabetic animals. In all of the complexes discussed, zinc is found to be biologically active and function by interacting with some target proteins related with diabetes mellitus. The design and screening of zinc complexes with higher activity is not efficient without consideration of the translational research. For the development of a clinically useful metallopharmaceutics, the research of zinc complexes on the long-term toxicity including side effects, clear-cut evidence of target molecule for the in vivo pharmacological action, and good pharmacokinetic property are essential in the current and future studies.

Progress of Chiral Schiff Bases with C1 Symmetry in Metal-Catalyzed Asymmetric Reactions.

PubMed

Hayashi, Masahiko

2016-12-01

In this Personal Account, various chiral Schiff base-metal-catalyzed enantioselective organic reactions are reported; the Schiff bases used were O,N,O- as well as N,N,P-tridentate ligands and N,N-bidentate ligands having C 1 symmetry. In particular, the enantioselective addition of trimethylsilyl cyanide, dialkylzinc, and organozinc halides to aldehydes, enantioselective 1,4-addition of dialkylzinc to cyclic and acyclic enones, and asymmetric allylic oxidation are reported. Typically, ketimine-type Schiff base-metal complexes exhibited higher reactivity and enantioselectivity compared with the corresponding aldimine-type Schiff base-metal complexes. Notably, remarkable ligand acceleration was observed for all reactions. The obtained products can be used as key intermediates for optically active natural products and pharmaceuticals. © 2016 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Recycle of radioactive scrap metal from the Oak Ridge Gaseous Diffusion Plant (K-25 Site)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meehan, R.W.

1997-02-01

The scale of the metal available for reuse at the plant includes 22 million pounds of Ni, 17 million pounds of Al, 47 million pounds of copper, and 835 million pounds of steels. In addition there is a wide range of industrial equipment and other items of value. The author describes small bench scale and pilot plant scale efforts made at treating metal for decontamination and fabrication into cast stock or specialized containers for reuse within the DOE complex or release. These projects show that much of the material can be cleaned or chemically decontaminated to a level where itmore » can be free released to various markets. Of the remaining metals, much of it can be cast into products which can be absorbed within the DOE complex.« less

Molecular engineering of sensitizers for dye-sensitized solar cell applications.

PubMed

Giribabu, Lingamallu; Kanaparthi, Ravi Kumar; Velkannan, Veerapandian

2012-06-01

Dye-sensitized solar cells (DSSCs) have attracted considerable attention in recent years as they offer the possibility of low-cost conversion of photovoltaic energy. This account focuses on recent advances in molecular design and technological aspects of sensitizers based on metal complexes, metal-free organics and tetrapyrrolic compounds which include porphyrins, phthalocyanines as well as corroles. Special attention has been paid to the design principles of these dyes, and co-sensitization, an emerging technique to extend the absorption range, is also discussed as a way to improve the performance of the device. This account also focuses on recent advances of efficient ruthenium sensitizers as well as other metal complexes and their applications in DSSCs. Recent developments in the area of metal-free organic and tetrapyrrolic sensitizers are also discussed. Copyright © 2012 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

Chemical reactivity parameters (HSAB) applied to magma evolution and ore formation

NASA Astrophysics Data System (ADS)

Vigneresse, Jean-Louis

2012-11-01

Magmas are commonly described through the usual content of 10 major oxides. This requires a complex dimensional plot. Concepts of hard-soft acid-base (HSAB) interactions allow estimating chemical reactivity of elements, such as electronegativity, i.e. the chemical potential changed of sign, hardness and electrophilicity. For complex system, those values result from equalization methods, i.e. the equalization of the respective chemical potentials, or from ab-initio computations through density functional theory (DFT). They help to characterize silicate magmas by a single value describing their reactivity. Principles of minimum electrophilicity (mEP), maximum hardness (MHP) and minimum polarizability (mPP) indicate trends towards regions of higher stability. Those parameters are plotted within a fitness landscape diagram, highlighting toward which principle reactions trend. Major oxides, main minerals and magmas determine the respective fields in which evolve natural rocks. Three poles are identified, represented by silica and alkalis, whereas oxidation forms the third trend. Mantle-derived rocks show a large variation in electrophilicity compared to hardness. They present all characters of a closed chemical system, being simply described by the free Gibbs energy. Conversely, rocks contaminated within the continental crust show a large variation in hardness between a silica pole and an alkaline, defining two separate trends. The trends show the character of an open chemical system, requiring a Grand Potential description (i.e. taking into account the difference in chemical potential). The terms open and closed systems refer to thermodynamical description, implying contamination for the crust and recycling for the mantle. The specific role of alkalis contrasts with other cations, pointing to their behavior in modifying silicate polymer structures. A second application deals with the reactivity of the melt and its fluid phase. It leads to a better understanding on the mechanisms that control sequestration and transport of metals within the different phases during igneous activity. Based on high gas/melt partitioning for metals and similar reactivity, the gaseous phase is more attractive for metals than silicate melts. The presence of halogens in the fluid phase tends to reinforce hardness, making the fluid phase attractive for hard metals such as Sn or W. Conversely, the presence of S decreases hardness of the fluid phase that becomes attractive for soft metals such as Au, Ag and Cu.

Ammonia and hydrazine. Transition-metal-catalyzed hydroamination and metal-free catalyzed functionalization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bertrand, Guy

2012-06-29

The efficient and selective preparation of organic molecules is critical for mankind. For the future, it is of paramount importance to find catalysts able to transform abundant and cheap feedstocks into useful compounds. Acyclic and heterocyclic nitrogen-containing derivatives are common components of naturally occurring compounds, agrochemicals, cosmetics, and pharmaceuticals; they are also useful intermediates in a number of industrial processes. One of the most widely used synthetic strategies, allowing the formation of an N-C bond, is the addition of an N-H bond across a carbon-carbon multiple bond, the so-called hydroamination reaction. This chemical transformation fulfills the principle of “green chemistry”more » since it ideally occurs with 100% atom economy. Various catalysts have been found to promote this reaction, although many limitations remain; one of the most prominent is the lack of methods that permit the use of NH 3 and NH 2NH 2 as the amine partners. In fact, ammonia and hydrazine have rarely succumbed to homogeneous catalytic transformations. Considering the low cost and abundance of ammonia (136 million metric tons produced in 2011) and hydrazine, catalysts able to improve the reactivity and selectivity of the NH 3- and NH 2NH 2-hydroamination reaction, and more broadly speaking the functionalization of these chemicals, are highly desirable. In the last funded period, we discovered the first homogeneous catalysts able to promote the hydroamination of alkynes and allenes with ammonia and the parent hydrazine. The key feature of our catalytic systems is that the formation of catalytically inactive Werner complexes is reversible, in marked contrast to most of the known ammonia and hydrazine transition metal complexes. This is due to the peculiar electronic properties of our neutral ancillary ligands, especially their strong donating capabilities. However, our catalysts currently require high temperatures and long reaction times. To address this issue, we have developed several new families of carbon- and boron-based ligands, which are even better donors. The corresponding metal complexes (particularly gold, rhodium, iridium, and ruthenium) of all these species will be tested in the Markovnikov and anti-Markovnikov hydroamination of alkynes, allenes, and also alkenes with ammonia and hydrazine. We will also develop metal-free catalytic processes for the functionalization of ammonia and hydrazine. By possessing both a lone pair of electrons and an accessible vacant orbital, singlet carbenes resemble and can mimic the chemical behavior of transition metals. Our preliminary results demonstrate that specially designed carbenes can split the N–H bond of ammonia by an initial nucleophilic activation that prevents the formation of Lewis acid-base adducts, which is the major hurdle for the transition metal catalyzed functionalization of NH 3. The use of purely organic compounds as catalysts will eliminate the major drawbacks of transition-metal-catalysis technology, which are the excessive cost of metal complexes (metal + ligands) and in many cases the toxicity of the metal.« less

New Possibilities for Understanding Complex Metal Hydrides via Synchrotron X-ray Studies

NASA Astrophysics Data System (ADS)

Dobbins, Tabbetha

2008-03-01

Ultrasmall-angle x-ray scattering (USAXS) and X-ray absorption spectroscopy (XAS) are used for the study of chemical and morphological changes in metal hydride powder (e.g. NaAlH4) both before and after transition metal salt catalytic dopant additions by high energy ball milling. The variation in surface fractal dimension and particle size with milling time and dopant content were tracked. These studies show that dopant content level (e.g. 2 mol % and 4 mol %) and dopant type (i.e. TiCl2, TiCl3, VCl3, and ZrCl4) markedly affects NaAlH4 powder particle surface area (determined using USAXS surface fractal dimension). As well, the chemical reaction between the catalyst and hydride powder was further elucidated using XAS. Ti-metal reacts with the Al desorption product (from NaAlH4) to form TiAlx product phases. These studies were able to link powder particle surface area to catalytic doping and were able to link dopant chemical state with dehydrogenation reactant and product phases.

Synthesis, spectroscopic characterization, electrochemistry and biological evaluation of some metal (II) complexes with ONO donor ligand containing benzo[b]thiophene and coumarin moieties

NASA Astrophysics Data System (ADS)

Mahendra Raj, K.; Mruthyunjayaswamy, B. H. M.

2014-09-01

Schiff base ligand 3-chloro-N‧-((7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)benzo[b]thiophene-2-carbohydrazide and its Cu(II), Co(II), Ni(II) and Zn(II) complexes were synthesized, characterized by elemental analysis and various physico-chemical techniques like, IR, 1H NMR, ESI-mass, UV-Visible, thermogravimetry - differential thermal analysis, magnetic measurements and molar conductance. Spectral analysis indicates octahedral geometry for all the complexes. Cu(II) complex have 1:1 stoichiometry of the type [M(L)(Cl)(H2O)2], whereas Co(II), Ni(II) and Zn(II) complexes have 1:2 stoichiometric ratio of the type [M(L)2]. The bonding sites are the oxygen atom of amide carbonyl, nitrogen of azomethine function and phenolic oxygen of the Schiff base ligand via deprotonation. The thermogravimetry - differential thermal analysis studies gave evidence for the presence of coordinated water molecules in the composition of Cu(II) complex which was further supported by IR measurements. All the complexes were investigated for their electrochemical activity, but only the Cu(II) complex showed the redox property. In order to evaluate the effect of antimicrobial potency of metal ions upon chelation, ligand and its metal complexes along with their respective metal chlorides were screened for their antibacterial and antifungal activities by minimum inhibitory concentration (MIC) method. The results showed that the metal complexes were found to be more active than free ligand. Ligand and its complexes were screened for free radical scavenging activity by DPPH method and DNA cleavage activity using Calf-thymus DNA (Cat. No-105850).

A novel type of matrix for surface-assisted laser desorption-ionization mass spectrometric detection of biomolecules using metal-organic frameworks.

PubMed

Fu, Chien-Ping; Lirio, Stephen; Liu, Wan-Ling; Lin, Chia-Her; Huang, Hsi-Ya

2015-08-12

A 3D metal-organic framework (MOF) nanomaterial as matrix for surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) and tandem mass spectrometry (MS/MS) was developed for the analysis of complex biomolecules. Unlike other nanoparticle matrices, this MOF nanomaterial does not need chemical modification prior to use. An exceptional signal reproducibility as well as very low background interferences in analyzing mono-/di-saccharides, peptides and complex starch digests demonstrate its high potential for biomolecule assays, especially for small molecules. Copyright © 2015 Elsevier B.V. All rights reserved.

Ring-Opening Copolymerization of Epoxides and Cyclic Anhydrides with Discrete Metal Complexes: Structure-Property Relationships.

PubMed

Longo, Julie M; Sanford, Maria J; Coates, Geoffrey W

2016-12-28

Polyesters synthesized through the alternating copolymerization of epoxides and cyclic anhydrides compose a growing class of polymers that exhibit an impressive array of chemical and physical properties. Because they are synthesized through the chain-growth polymerization of two variable monomers, their syntheses can be controlled by discrete metal complexes, and the resulting materials vary widely in their functionality and physical properties. This polymer-focused review gives a perspective on the current state of the field of epoxide/anhydride copolymerization mediated by discrete catalysts and the relationships between the structures and properties of these polyesters.

Partitioning of Dissolved Metals (Fe, Mn, Cu, Cd, Zn, Ni, and Pb) into Soluble and Colloidal Fractions in Continental Shelf and Offshore Waters, Northern California

NASA Astrophysics Data System (ADS)

Fitzsimmons, J. N.; Parker, C.; Sherrell, R. M.

2016-02-01

The physicochemical speciation of trace metals in seawater influences their cycling as essential micronutrients for microorganisms or as tracers of anthropogenic influences on the marine environment. While chemical speciation affects lability, the size of metal complexes influences their ability to be accessed biologically and also influences their fate in the aggregation pathway to marine particles. In this study, we show that multiple trace metals in shelf and open ocean waters off northern California (IRN-BRU cruise, July 2014) have colloidal-sized components. Colloidal fractions were operationally defined using two ultrafiltration methods: a 0.02 µm Anopore membrane and a 10 kDa ( 0.003 µm) cross flow filtration (CFF) system. Together these two methods distinguished small (0.003 - 0.02 µm) and large (0.02 µm - 0.2 µm) colloids. As has been found previously for seawater in other ocean regimes, dissolved Fe had a broad size distribution with 50% soluble (<10 kDa) complexes and both small and large colloidal species. Dissolved Mn had no measurable colloidal component, consistent with its predicted chemical speciation as free Mn(II). Dissolved Cu, which like Fe is thought to be nearly fully organically bound in seawater, was only 25% colloidal, and these colloids were all small. Surprisingly Cd, Ni, and Pb also showed colloidal components (8-20%, 25-40%, and 10-50%) despite their hypothesized low organic speciation. Zn and Pb were nearly completely sorbed onto the Anopore membrane, making CFF the only viable ultrafiltration method for those elements. Zn suffered incomplete recovery ( 50-75%) through the CFF system but showed 30-85% colloidal contribution; thus, verifying a Zn colloidal phase with these methods is challenging. Conclusions will reveal links between the physical and chemical speciation for these metals and what role these metal colloids might have on trace metal exchange between the ocean margin and offshore waters.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kattel, Shyam; Liu, Ping; Chen, Jingguang G.

The chemical transformation of CO 2 not only mitigates the anthropogenic CO 2 emission into the Earth’s atmosphere but also produces carbon compounds that can be used as precursors for the production of chemicals and fuels. The activation and conversion of CO 2 can be achieved on multifunctional catalytic sites available at the metal/oxide interface by taking advantage of the synergy between the metal nanoparticles and oxide support. In this paper, we look at the recent progress in mechanistic studies of CO 2 hydrogenation to C1 (CO, CH 3OH, and CH 4) compounds on metal/oxide catalysts. On this basis, wemore » are able to provide a better understanding of the complex reaction network, grasp the capability of manipulating structure and combination of metal and oxide at the interface in tuning selectivity, and identify the key descriptors to control the activity and, in particular, the selectivity of catalysts. In conclusion, we also discuss challenges and future research opportunities for tuning the selective conversion of CO 2 on metal/oxide catalysts.« less

Chemistry of Marine Ligands and Siderophores

PubMed Central

Vraspir, Julia M.; Butler, Alison

2011-01-01

Marine microorganisms are presented with unique challenges to obtain essential metal ions required to survive and thrive in the ocean. The production of organic ligands to complex transition metal ions is one strategy to both facilitate uptake of specific metals, such as iron, and to mitigate the potential toxic effects of other metal ions, such as copper. A number of important trace metal ions are complexed by organic ligands in seawater, including iron, cobalt, nickel, copper, zinc, and cadmium, thus defining the speciation of these metal ions in the ocean. In the case of iron, siderophores have been identified and structurally characterized. Siderophores are low molecular weight iron-binding ligands produced by marine bacteria. Although progress has been made toward the identity of in situ iron-binding ligands, few compounds have been identified that coordinate the other trace metals. Deciphering the chemical structures and production stimuli of naturally produced organic ligands and the organisms they come from is fundamental to understanding metal speciation and bioavailability. The current evidence for marine ligands, with an emphasis on siderophores, and discussion of the importance and implications of metal-binding ligands in controlling metal speciation and cycling within the world’s oceans are presented. PMID:21141029

The reactivity of sodium alanates with O[2], H[2]O, and CO[2] : an investigation of complex metal hydride contamination in the context of automotive systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dedrick, Daniel E.; Bradshaw, Robert W.; Behrens, Richard, Jr.

2007-08-01

Safe and efficient hydrogen storage is a significant challenge inhibiting the use of hydrogen as a primary energy carrier. Although energy storage performance properties are critical to the success of solid-state hydrogen storage systems, operator and user safety is of highest importance when designing and implementing consumer products. As researchers are now integrating high energy density solid materials into hydrogen storage systems, quantification of the hazards associated with the operation and handling of these materials becomes imperative. The experimental effort presented in this paper focuses on identifying the hazards associated with producing, storing, and handling sodium alanates, and thus allowingmore » for the development and implementation of hazard mitigation procedures. The chemical changes of sodium alanates associated with exposure to oxygen and water vapor have been characterized by thermal decomposition analysis using simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) and X-ray diffraction methods. Partial oxidation of sodium alanates, an alkali metal complex hydride, results in destabilization of the remaining hydrogen-containing material. At temperatures below 70 C, reaction of sodium alanate with water generates potentially combustible mixtures of H{sub 2} and O{sub 2}. In addition to identifying the reaction hazards associated with the oxidation of alkali-metal containing complex hydrides, potential treatment methods are identified that chemically stabilize the oxidized material and reduce the hazard associated with handling the contaminated metal hydrides.« less

Immobilization of heavy metals in electroplating sludge by biochar and iron sulfide.

PubMed

Lyu, Honghong; Gong, Yanyan; Tang, Jingcshun; Huang, Yao; Wang, Qilin

2016-07-01

Electroplating sludge (ES) containing large quantities of heavy metals is regarded as a hazardous waste in China. This paper introduced a simple method of treating ES using environmentally friendly fixatives biochar (BC) and iron sulfide (FeS), respectively. After 3 days of treatment with FeS at a FeS-to-ES mass ratio of 1:5, the toxicity characteristic leaching procedure (TCLP)-based leachability of total Cr (TCr), Cu(II), Ni(II), Pb(II), and Zn(II) was decreased by 59.6, 100, 63.8, 73.5, and 90.5 %, respectively. After 5 days of treatment with BC at a BC-to-ES mass ratio of 1:2, the TCLP-based leachability was declined by 35.1, 30.6, 22.3, 23.1, and 22.4 %, respectively. Pseudo first-order kinetic model adequately simulated the sorption kinetic data. Structure and morphology analysis showed that adsorption, electrostatic attraction, surface complexation, and chemical precipitation were dominant mechanisms for heavy metals immobilization by BC, and that chemical precipitation (formation of metal sulfide and hydroxide precipitates), iron exchange (formation of CuFeS2), and surface complexation were mainly responsible for heavy metals removal by FeS. Economic costs of BC and FeS were 500 and 768 CNY/t, lower than that of Na2S (940 CNY/t). The results suggest that BC and FeS are effective, economic, and environmentally friendly fixatives for immobilization of heavy metals in ES before landfill disposal.

Biosorptive recovery of platinum from platinum group metal refining wastewaters by immobilised Saccharomyces cerevisiae.

PubMed

Mack, C L; Wilhelmi, B; Duncan, J R; Burgess, J E

2011-01-01

The process of platinum group metal (PGM) refining can be up to 99.99% efficient at best, and although it may seem small, the amount of valuable metal lost to waste streams is appreciable enough to warrant recovery. The method currently used to remove entrained metal ions from refinery wastewaters, chemical precipitation, is not effective for selective recovery of PGMs. The yeast Saccharomyces cerevisiae has been found capable of sorbing numerous precious and base metals, and is a cheap and abundant source of biomass. In this investigation, S. cerevisiae was immobilised using polyethyleneimine and glutaraldehyde to produce a suitable sorbent, capable of high platinum uptake (150-170 mg/g) at low pH (<2). The sorption mechanism was found to be a chemical reaction, which made effective desorption impossible. When applied to PGM refinery wastewater, two key wastewater characteristics limited the success of the sorption process; high inorganic ion content and complex speciation of the platinum ions. The results proved the concept principle of platinum recovery by immobilised yeast biosorption and indicated that a more detailed understanding of the platinum speciation within the wastewater is required before biosorption can be applied. Overall, the sorption of platinum by the S. cerevisiae sorbent was demonstrated to be highly effective in principle, but the complexity of the wastewater requires that pretreatment steps be taken before the successful application of this process to industrial wastewater.

Intrinsic Atomic Orbitals: An Unbiased Bridge between Quantum Theory and Chemical Concepts.

PubMed

Knizia, Gerald

2013-11-12

Modern quantum chemistry can make quantitative predictions on an immense array of chemical systems. However, the interpretation of those predictions is often complicated by the complex wave function expansions used. Here we show that an exceptionally simple algebraic construction allows for defining atomic core and valence orbitals, polarized by the molecular environment, which can exactly represent self-consistent field wave functions. This construction provides an unbiased and direct connection between quantum chemistry and empirical chemical concepts, and can be used, for example, to calculate the nature of bonding in molecules, in chemical terms, from first principles. In particular, we find consistency with electronegativities (χ), C 1s core-level shifts, resonance substituent parameters (σR), Lewis structures, and oxidation states of transition-metal complexes.

Selective CO2 reduction conjugated with H2O oxidation utilizing semiconductor/metal-complex hybrid photocatalysts

NASA Astrophysics Data System (ADS)

Morikawa, T.; Sato, S.; Arai, T.; Uemura, K.; Yamanaka, K. I.; Suzuki, T. M.; Kajino, T.; Motohiro, T.

2013-12-01

We developed a new hybrid photocatalyst for CO2 reduction, which is composed of a semiconductor and a metal complex. In the hybrid photocatalyst, ΔG between the position of conduction band minimum (ECBM) of the semiconductor and the CO2 reduction potential of the complex is an essential factor for realizing fast electron transfer from the conduction band of semiconductor to metal complex leading to high photocatalytic activity. On the basis of this concept, the hybrid photocatalyst InP/Ru-complex, which functions in aqueous media, was developed. The photoreduction of CO2 to formate using water as an electron donor and a proton source was successfully achieved as a Z-scheme system by functionally conjugating the InP/Ru-complex photocatalyst for CO2 reduction with a TiO2 photocatalyst for water oxidation. The conversion efficiency from solar energy to chemical energy was ca. 0.04%, which approaches that for photosynthesis in a plant. Because this system can be applied to many other inorganic semiconductors and metal-complex catalysts, the efficiency and reaction selectivity can be enhanced by optimization of the electron transfer process including the energy-band configurations, conjugation conformations, and catalyst structures. This electrical-bias-free reaction is a huge leap forward for future practical applications of artificial photosynthesis under solar irradiation to produce organic species.

Metal sulfide thin films by chemical spray pyrolysis

NASA Astrophysics Data System (ADS)

Krunks, Malle; Mellikov, Enn

2001-04-01

CdS, ZnS and CuS thin films were prepared by spray pyrolysis method using metal chlorides and thiourea (tu) as starting materials. Metal sulfide films form as products of thermal decomposition of complexes Cd(tu)2Cl2, Zn(tu)2Cl2 and Cu(tu)Cl(DOT)1/2H2O, originally formed in aqueous solution at precursors molar ratio 1:2. The metal-ligand bonding is thermally stable up to 220 degrees Celsius, followed by multistep degradation process of complexes. The TG/DTA analysis show similar thermal behavior of complexes up to 300 degrees Celsius with the formation of metal sulfides in this decomposition step. In air intensive oxidation processes are detected close to 400, 600 and 720 degrees Celsius for Cu, Cd and Zn complexes, respectively. The results of thermoanalytical study and XRD of sprayed films show that CdS and ZnS films could be grown at 450 degrees Celsius even in air while deposition of copper sulfide films should be performed in an inert atmosphere. High total impurities content of 10 wt% in CdS films prepared at 240 degrees Celsius is originated from the precursor and reduced to 2 wt% by increasing the growth temperature up to 400 degrees Celsius.

Domain growth of carbon nanotubes assisted by dewetting of thin catalyst precursor films

NASA Astrophysics Data System (ADS)

Srivastava, Alok Kumar; Sachan, Priyanka; Samanta, Chandan; Mukhopadhyay, Kingsuk; Sharma, Ashutosh

2014-01-01

We explore self-organized dewetting of ultrathin films of a novel metal complex as a one step surface patterning method to create nanoislands of iron, using which spatially separated carbon nanostructures were synthesized. Dewetting of ultrathin metal complex films was induced by two different methods: liquid solvent exposure and thermal annealing to engender surface patterning. For thermal dewetting, thin films of the iron oleate complex were dewetted at high temperature. In the case of liquid solvent assisted dewetting, the metal complex, mixed with a sacrificial polymer (polystyrene) was spin coated as thin films (<40 nm) and then dewetted under an optimal solution mixture consisting of methyl ethyl ketone, acetone and water. The carrier polymer was then selectively removed to produce the iron metal islands. These metal islands were used for selective growth of discrete patches of multiwall CNTs and CNFs by a chemical vapor deposition (CVD) process. Solvent induced dewetting showed clear advantages over thermal dewetting owing to reduced size of catalyst domains formed by dewetting, an improved control over CNT growth as well as in its ability to immobilize the seed particles. The generic solution mediated dewetting and pattern generation in thin films of various catalytic precursors can thus be a powerful method for selective domain growth of a variety of functional nanomaterials.

Aquatic Humic Substances: Relationship Between Origin and Complexing Capacity.

PubMed

González-Guadarrama, María de Jesús; Armienta-Hernández, Ma Aurora; Rosa, André H

2018-05-01

Aiming to determine the relationship between source and complexing capacity, humic substances obtained from three sites (Sorocaba and Itapanhau Brasilian rivers, and Xochimilco Lake in Mexico) were studied. Copper, manganese, zinc and arsenic complexing capacity were determined for the three substances under various pH conditions. Results showed similar complexing capacity for the three elements depending on the chemistry of each one and on the physico-chemical conditions. Speciation diagrams showed that these conditions affect both, the humic substances, and the transition metals and arsenic.

Tuning Selectivity of CO 2 Hydrogenation Reactions at the Metal/Oxide Interface

DOE PAGES

Kattel, Shyam; Liu, Ping; Chen, Jingguang G.

2017-06-26

The chemical transformation of CO 2 not only mitigates the anthropogenic CO 2 emission into the Earth’s atmosphere but also produces carbon compounds that can be used as precursors for the production of chemicals and fuels. The activation and conversion of CO 2 can be achieved on multifunctional catalytic sites available at the metal/oxide interface by taking advantage of the synergy between the metal nanoparticles and oxide support. In this paper, we look at the recent progress in mechanistic studies of CO 2 hydrogenation to C1 (CO, CH 3OH, and CH 4) compounds on metal/oxide catalysts. On this basis, wemore » are able to provide a better understanding of the complex reaction network, grasp the capability of manipulating structure and combination of metal and oxide at the interface in tuning selectivity, and identify the key descriptors to control the activity and, in particular, the selectivity of catalysts. In conclusion, we also discuss challenges and future research opportunities for tuning the selective conversion of CO 2 on metal/oxide catalysts.« less

Student Misinterpretations and Misconceptions Based on Their Explanations of Two Computer Animations of Varying Complexity Depicting the Same Oxidation-Reduction Reaction

ERIC Educational Resources Information Center

Rosenthal, Deborah P.; Sanger, Michael J.

2012-01-01

A group of 55 students were shown unnarrated versions of two different particulate-level computer animations of varying complexity depicting the oxidation-reduction reaction of aqueous silver nitrate and solid copper metal. These students were asked to explain their understanding of the chemical reaction based on their interpretations of these…

Dynamic NMR of Intramolecular Exchange Processes in EDTA Complexes of Sc[superscript 3+], Y[superscript 3+], and La[superscript 3+

ERIC Educational Resources Information Center

Ba, Yong; Han, Steven; Ni, Lily; Su, Tony; Garcia, Andres

2006-01-01

Dynamic NMR makes use of the effect of chemical exchanges on NMR spectra to study kinetics and thermodynamics. An advanced physical chemistry lab experiment was developed to study the intramolecular exchange processes of EDTA (the disodium salt of ethylenediaminetetraacetic acid) metal complexes. EDTA is an important chelating agent, used in…

Iron Isotope Systematics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dauphas, Nicolas; John, Seth G.; Rouxel, Olivier

Iron is a ubiquitous element with a rich (i.e., complex) chemical behavior. It possesses three oxidation states, metallic iron (Fe0), ferrous iron (Fe2+) and ferric iron (Fe3+). The distribution of these oxidation states is markedly stratified in the Earth.

75 FR 66352 - Glycine From the People's Republic of China: Initiation of Antidumping Anti-circumvention Inquiry

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-28

... agent, re-absorbable amino acid, chemical intermediate, and a metal complexing agent. Glycine is... and Chiyuen International Trading Ltd., a manufacturer in the PRC of amino acetic acid (i.e., glycine...

Synthesis, characterization and cytotoxicity of rare earth metal ion complexes of N,N‧-bis-(2-thiophenecarboxaldimine)-3,3‧-diaminobenzidene, Schiff base ligand

NASA Astrophysics Data System (ADS)

Shakir, Mohammad; Abbasi, Ambreen; Faraz, Mohammad; Sherwani, Asif

2015-12-01

Lanthanide complexes of La3+, Pr3+, Nd3+, Gd3+, Er3+ of general formula [Ln2 L(H2O)4(NO3)4](NO3)2·2H2O have been synthesized from Schiff base, N,N‧-bis-(2-thiophenecarboxaldimine)-3,3‧-diaminobenzidene. The complexes were characterized by elemental analysis, molar conductance, UV-Vis, fluorescence, FT-IR,1H NMR, mass spectroscopy, EDX, SEM and thermal analysis. FT-IR spectral data suggested that ligand coordinate with metal ions through azomethine nitrogen and uncondensed amino group. Molar conductance data revealed 1:2 electrolytic nature of complexes. From the analytical data, the stoichiometry of the complexes was found to be 1:2 (ligand:metal). Thephysico-chemical data suggested eight coordination number for Ln(III)Schiffbase complexes. SEM analysis shows morphological changes in the surfaces of complexes as compared to free ligand. Thermal decomposition profiles were consistent with proposed formulations. The anticancer activity of the complexes and theSchiffbase ligand has been studied towards human cervical cancer celllines (HeLa) and human breast cancer cell lines (MCF-7) and it was found that complexes exhibited greater activity than theSchiffbase.

Balancing Near-Field Enhancement, Absorption, and Scattering for Effective Antenna-Reactor Plasmonic Photocatalysis.

PubMed

Li, Kun; Hogan, Nathaniel J; Kale, Matthew J; Halas, Naomi J; Nordlander, Peter; Christopher, Phillip

2017-06-14

Efficient photocatalysis requires multifunctional materials that absorb photons and generate energetic charge carriers at catalytic active sites to facilitate a desired chemical reaction. Antenna-reactor complexes are an emerging multifunctional photocatalytic structure where the strong, localized near field of the plasmonic metal nanoparticle (e.g., Ag) is coupled to the catalytic properties of the nonplasmonic metal nanoparticle (e.g., Pt) to enable chemical transformations. With an eye toward sustainable solar driven photocatalysis, we investigate how the structure of antenna-reactor complexes governs their photocatalytic activity in the light-limited regime, where all photons need to be effectively utilized. By synthesizing core@shell/satellite (Ag@SiO 2 /Pt) antenna-reactor complexes with varying Ag nanoparticle diameters and performing photocatalytic CO oxidation, we observed plasmon-enhanced photocatalysis only for antenna-reactor complexes with antenna components of intermediate sizes (25 and 50 nm). Optimal photocatalytic performance was shown to be determined by a balance between maximized local field enhancements at the catalytically active Pt surface, minimized collective scattering of photons out of the catalyst bed by the complexes, and minimal light absorption in the Ag nanoparticle antenna. These results elucidate the critical aspects of local field enhancement, light scattering, and absorption in plasmonic photocatalyst design, especially under light-limited illumination conditions.

Switchable molecular magnets

PubMed Central

SATO, Osamu

2012-01-01

Various molecular magnetic compounds whose magnetic properties can be controlled by external stimuli have been developed, including electrochemically, photochemically, and chemically tunable bulk magnets as well as a phototunable antiferromagnetic phase of single chain magnet. In addition, we present tunable paramagnetic mononuclear complexes ranging from spin crossover complexes and valence tautomeric complexes to Co complexes in which orbital angular momentum can be switched. Furthermore, we recently developed several switchable clusters and one-dimensional coordination polymers. The switching of magnetic properties can be achieved by modulating metals, ligands, and molecules/ions in the second sphere of the complexes. PMID:22728438

Homo- and Heterometallic Bis(Pentafluorobenzoyl)Methanide Complexes of Copper(II) and Cobalt(II)

NASA Astrophysics Data System (ADS)

Crowder, Janell M.

beta-Diketones are well known to form metal complexes with practically every known metal and metalloid. Metal complexes of fluorinated beta-diketones generally exhibit increased volatility and thermal stability compared to the non-fluorinated analogues, and thus are used extensively in various chemical vapor deposition (CVD) processes for the deposition of metal, simple or mixed metal oxides, and fluorine-doped metal oxide thin films. Furthermore, the electron-withdrawing nature of the fluorinated ligand enhances the Lewis acidity of a coordinatively unsaturated metal center which facilitates additional coordination reactions. The physical and structural properties of fluorinated beta-diketonate complexes are discussed in Chapter 1 and a few key application examples are given. The focus of this work is the synthesis and single crystal X-ray structural characterization of unsolvated and coordinatively unsaturated metal complexes of bis(pentafluorobenzoyl)- methanide (L, C6F5COCHCOC 6F5-). In Chapter 2, we present the preparation and isolation of the unsolvated complex [Cu(L)2] in pure crystalline form for the first time. We subsequently investigated the reaction of unsolvated [Cu(L)2] with sodium hexafluoroacetylacetonate [Na(hfac)] in a solvent-free environment. This reaction allowed the isolation of the first heterometallic Na-Cu diketonate [Na2Cu2(L) 4(hfac)2] structurally characterized by single crystal X-ray crystallography. Thermal decomposition of [Na2Cu2(L) 4(hfac)2] was investigated for its potential application in MOCVD processes. In the final chapter, we present the first exploration of the anhydrous synthesis of Co(II) complexed with bis(pentafluorobenzoyl)methanide in order to produce a complex without ligated water. Single crystal X-ray crystallographic investigations revealed the isolation of the ethanol adduct, [Co2(L)4(C2H5OH)2], and following the removal of ethanol, a 1,4-dioxane adduct, [{Co 2(L)4}2(C4H8O2)]. In this work, we have provided the first investigation of the synthesis, isolation and single crystal X-ray structural characterization of unsolvated and coordinatively unsaturated Cu(II) and Co(II) complexes of bis(pentafluorobenzoyl)methanide ligand. These studies demonstrate how the electrophilicity of a coordinatively unsaturated metal complexed to highly-fluorinated â-diketone ligands can be utilized for the formation of new adducts or new and interesting heterometallic complexes. This body of work provides a basis upon which future research into unsolvated and unligated bis(pentafluorobenzoyl)methanide metal complexes can expand.

Synthesis, spectroscopic, molecular orbital calculation, cytotoxic, molecular docking of DNA binding and DNA cleavage studies of transition metal complexes with N-benzylidene-N'-salicylidene-1,1-diaminopropane

NASA Astrophysics Data System (ADS)

Al-Mogren, Muneerah M.; Alaghaz, Abdel-Nasser M. A.; Elbohy, Salwa A. H.

2013-10-01

Eight mononuclear chromium(III), manganese(II), iron(III), cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes of Schiff's base ligand were synthesized and determined by different physical techniques. The complexes are insoluble in common organic solvents but soluble in DMF and DMSO. The measured molar conductance values in DMSO indicate that the complexes are non-electrolytic in nature. All the eight metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic data. The analytical data helped to elucidate the structure of the metal complexes. The Schiff base is found to act as tridentate ligand using N2O donor set of atoms leading to an octahedral geometry for the complexes around all the metal ions. Quantum chemical calculations were performed with semi-empirical method to find the optimum geometry of the ligand and its complexes. Additionally in silico, the docking studies and the calculated pharmacokinetic parameters show promising futures for application of the ligand and complexes as high potency agents for DNA binding activity. The interaction of the complexes with calf thymus DNA (CT-DNA) has been investigated by UV absorption method, and the mode of CT-DNA binding to the complexes has been explored. Furthermore, the DNA cleavage activity by the complexes was performed. The Schiff base and their complexes have been screened for their antibacterial activity against bacterial strains [Staphylococcus aureus (RCMB010027), Staphylococcus epidermidis (RCMB010024), Bacillis subtilis (RCMB010063), Proteous vulgaris (RCMB 010085), Klebsiella pneumonia (RCMB 010093) and Shigella flexneri (RCMB 0100542)] and fungi [(Aspergillus fumigates (RCMB 02564), Aspergillus clavatus (RCMB 02593) and Candida albicans (RCMB05035)] by disk diffusion method. All the metal complexes have potent biocidal activity than the free ligand.

Synthesis and characterization of heterometallic uranyl pyridinedicarboxylate compounds

NASA Astrophysics Data System (ADS)

Jayasinghe, Ashini S.; Payne, Maurice K.; Forbes, Tori Z.

2017-10-01

The incorporation of transition metals into hybrid uranyl materials can result in more diverse structural topologies and variations in physical and chemical properties. To explore the impact of transition metals on the uranyl cation, five uranium containing bimetallic chain compounds, [(UO2)M(PDC)2(H2O)4]·4(H2O) (PDC = 2,6 pyridinedicarboxylate; M = Ni2+, Co2+, Fe2+, Zn2+, and Cu2+) were synthesized by evaporation of aqueous solutions at room temperature. The uranyl cation is complex by two PDC ligands and the transition metal cations bond to the complex to form a one-dimensional chain topology. The presence of the transition metal leads to the presence of a stronger uranyl oxo bonds as shown by the single-crystal X-ray diffraction data and the Raman spectra. Solid state diffuse reflectance UV/Visible spectra confirmed the presence of the transition metals in the structure by the broad bands that appeared at relevant wavelengths.

Catalytic Deoxydehydration of Carbohydrates and Polyols to Chemicals and Fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nicholas, Kenneth M.

As the world's fossil fuel resources are being depleted and their costs increase, there is an urgent need to discover and develop new processes for the conversion of renewable, biomass resources into fuels and chemical feedstocks. Research and development in this area have been given high priority by both governmental agencies and industry. To increase the energy content and decrease the boiling points of biomass-derived carbohydrates and polyols to the useful liquid range it is necessary to chemically remove water (dehydrate) and, preferably, oxygen (deoxygenate/reduce). The poly-hydroxylic nature of carbohydrates is attractive for their use as functionalized chemical building blocks,more » but it presents a daunting challenge for their selective conversion to single product chemicals or fuels. The long term, practical objective of this project is to develop catalytic processes for the deoxydehydration (DODH) of biomass-derived carbohydrates and polyols to produce unsaturated alcohols and hydrocarbons of value as chemical feedstocks and fuels; DODH: polyol + reductant --(LMOx catalyst)--> unsaturate + oxidized reductant + H2O. Limited prior studies have established the viability of the DODH process with expensive phosphine reductants and rhenium-catalysts. Initial studies in the PI's laboratory have now demonstrated: 1) the moderately efficient conversion of glycols to olefins by the economical sulfite salts is catalyzed by MeReO3 and Z+ReO4-; 2) effective phosphine-based catalytic DODH of representative glycols to olefins by cheap LMoO2 complexes; and 3) computational studies (with K. Houk, UCLA) have identified several Mo-, W-, and V-oxo complexes that are likely to catalyze glycol DODH. Seeking practically useful DODH reactions of complex polyols and new understanding of the reactivity of polyoxo-metal species with biomass-oxygenates we will employ a two-pronged approach: 1) investigate experimentally the reactivity, both stoichiometric and catalytic, of polyoxo-complexes and practical reductants with representative polyols to establish structure/reactivity relationships and reaction mechanisms; and b) carry out parallel computational studies of these reactions and their mechanisms- both analytical and predictive. Our prioritized action plan is: (1) to optimize the catalytic efficiency, assess the substrate scope/selectivity, and address key mechanistic aspects of Re-catalyzed, sulfite-driven DODH reactions; (2) use the findings from (1), together with computational predictions, to discover new, effective non-precious metal catalysts for sulfite-driven DODH reactions; and 3) to initiate exploratory studies of CO- and H2-driven DODH. Successful execution of this research project will: 1) provide practical chemical processes for the conversion of biomass into useful chemicals and fuels: 2) bring fundamental new understanding of chemical reactions involving metal-oxo catalysts; and 3) provide educational and technical training of future energy scientists.« less

Goldilocks and the three inorganic equilibria: how Earth's chemistry and life coevolve to be nearly in tune.

PubMed

Rickaby, R E M

2015-03-13

Life and the chemical environment are united in an inescapable feedback cycle. The periodic table of the elements essential for life has transformed over Earth's history, but, as today, evolved in tune with the elements available in abundance in the environment. The most revolutionary time in life's history was the advent and proliferation of oxygenic photosynthesis which forced the environment towards a greater degree of oxidation. Consideration of three inorganic chemical equilibria throughout this gradual oxygenation prescribes a phased release of trace metals to the environment, which appear to have coevolved with employment of these new chemicals by life. Evolution towards complexity was chemically constrained, and changes in availability of notably Fe, Zn and Cu paced the systematic development of complex organisms. Evolving life repeatedly catalysed its own chemical challenges via the unwitting release of new and initially toxic chemicals. Ultimately, the harnessing of these allowed life to advance to greater complexity, though the mechanism responsible for translating novel chemistry to heritable use remains elusive. Whether a chemical acts as a poison or a nutrient lies both in the dose and in its environmental history. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Communication: Enhanced chemical reactivity of graphene on a Ni(111) substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ambrosetti, Alberto; Silvestrelli, Pier Luigi

2016-03-21

Due to the unique combination of structural, mechanical, and transport properties, graphene has emerged as an exceptional candidate for catalysis applications. The low chemical reactivity caused by sp{sup 2} hybridization and strongly delocalized π electrons, however, represents a main challenge for straightforward use of graphene in its pristine, free-standing form. Following recent experimental indications, we show that due to charge hybridization, a Ni(111) substrate can enhance the chemical reactivity of graphene, as exemplified by the interaction with the CO molecule. While CO only physisorbs on free-standing graphene, chemisorption of CO involving formation of ethylene dione complexes is predicted in Ni(111)-graphene.more » Higher chemical reactivity is also suggested in the case of oxidized graphene, opening the way to a simple and efficient control of graphene chemical properties, devoid of complex defect patterning or active metallic structures deposition.« less

DFT Studies on Interaction between Lanthanum and Hydroxyamide

NASA Astrophysics Data System (ADS)

Pati, Anindita; Kundu, T. K.; Pal, Snehanshu

2018-03-01

Extraction and separation of individual rare earth elements has been a challenge as they are chemically very similar. Solvent extraction is the most suitable way for extraction of rare earth elements. Acidic, basic, neutral, chelating are the major classes of extractants for solvent extraction of rare earth elements. The coordination complex of chelating extractants is very selective with positively charged metal ion. Hence they are widely used. Hydroxyamide is capable of forming chelates with metal cations. In this present study interactions of hydroxyamide ligand with lanthanum have been investigated using density functional theory (DFT). Two different functional such as raB97XD and B3LYP are applied along with 6-31+G(d,p) basis set for carbon, nitrogen, hydrogen and SDD basis set for lanthanum. Stability of formed complexes has been evaluated based on calculated interaction energies and solvation energies. Frontier orbital (highest occupied molecular orbital or HOMO and lowest unoccupied molecular orbital or LUMO) energies of the molecule have also been calculated. Electronegativity, chemical hardness, chemical softness and chemical potential are also determined for these complexes to get an idea about the reactivity. From the partial charge distribution it is seen that oxygen atoms in hydroxyamide have higher negative charge. The double bonded oxygen atom present in the hydroxyamide structure has higher electron density and so it forms bond with lanthanum but the singly bonded oxygen atom in the hydroxyamide structure is weaker donor atom and so it is less available for interaction with lanthanum.

‘… a metal conducts and a non-metal doesn't’

PubMed Central

Edwards, P. P.; Lodge, M. T. J.; Hensel, F.; Redmer, R.

2010-01-01

In a letter to one of the authors, Sir Nevill Mott, then in his tenth decade, highlighted the fact that the statement ‘… a metal conducts, and a non-metal doesn’t’ can be true only at the absolute zero of temperature, T=0 K. But, of course, experimental studies of metals, non-metals and, indeed, the electronic and thermodynamic transition between these canonical states of matter must always occur above T=0 K, and, in many important cases, for temperatures far above the absolute zero. Here, we review the issues—theoretical and experimental—attendant on studies of the metal to non-metal transition in doped semiconductors at temperatures close to absolute zero (T=0.03 K) and fluid chemical elements at temperatures far above absolute zero (T>1000 K). We attempt to illustrate Mott’s insights for delving into such complex phenomena and experimental systems, finding intuitively the dominant features of the science, and developing a coherent picture of the different competing electronic processes. A particular emphasis is placed on the idea of a ‘Mott metal to non-metal transition’ in the nominally metallic chemical elements rubidium, caesium and mercury, and the converse metallization transition in the nominally non-metal elements hydrogen and oxygen. We also review major innovations by D. A. Goldhammer (Goldhammer 1913 Dispersion und absorption des lichtes) and K. F. Herzfeld (Herzfeld 1927 Phys. Rev. 29, 701–705. (doi:10.1103/PhysRev.29.701)) in a pre-quantum theory description of the metal–non-metal transition, which emphasize the pivotal role of atomic properties in dictating the metallic or non-metallic status of the chemical elements of the periodic table under ambient and extreme conditions; a link with Pauling’s ‘metallic orbital’ is also established here. PMID:20123742

Chemistry Notes.

ERIC Educational Resources Information Center

School Science Review, 1984

1984-01-01

Presents an experiment which links mass spectrometry to gas chromatography. Also presents a simulation of iron extraction using a ZX81 computer and discussions of Fehling versus Benedict's solutions, transition metal ammine complexes, electrochemical and other chemical series, and a simple model of dynamic equilibria. (JN)

Computational approaches for de novo design and redesign of metal-binding sites on proteins.

PubMed

Akcapinar, Gunseli Bayram; Sezerman, Osman Ugur

2017-04-28

Metal ions play pivotal roles in protein structure, function and stability. The functional and structural diversity of proteins in nature expanded with the incorporation of metal ions or clusters in proteins. Approximately one-third of these proteins in the databases contain metal ions. Many biological and chemical processes in nature involve metal ion-binding proteins, aka metalloproteins. Many cellular reactions that underpin life require metalloproteins. Most of the remarkable, complex chemical transformations are catalysed by metalloenzymes. Realization of the importance of metal-binding sites in a variety of cellular events led to the advancement of various computational methods for their prediction and characterization. Furthermore, as structural and functional knowledgebase about metalloproteins is expanding with advances in computational and experimental fields, the focus of the research is now shifting towards de novo design and redesign of metalloproteins to extend nature's own diversity beyond its limits. In this review, we will focus on the computational toolbox for prediction of metal ion-binding sites, de novo metalloprotein design and redesign. We will also give examples of tailor-made artificial metalloproteins designed with the computational toolbox. © 2017 The Author(s).

Ecological risk assessment on heavy metals in soils: Use of soil diffuse reflectance mid-infrared Fourier-transform spectroscopy

PubMed Central

Wang, Cheng; Li, Wei; Guo, Mingxing; Ji, Junfeng

2017-01-01

The bioavailability of heavy metals in soil is controlled by their concentrations and soil properties. Diffuse reflectance mid-infrared Fourier-transform spectroscopy (DRIFTS) is capable of detecting specific organic and inorganic bonds in metal complexes and minerals and therefore, has been employed to predict soil composition and heavy metal contents. The present study explored the potential of DRIFTS for estimating soil heavy metal bioavailability. Soil and corresponding wheat grain samples from the Yangtze River Delta region were analyzed by DRIFTS and chemical methods. Statistical regression analyses were conducted to correlate the soil spectral information to the concentrations of Cd, Cr, Cu, Zn, Pb, Ni, Hg and Fe in wheat grains. The principal components in the spectra influencing soil heavy metal bioavailability were identified and used in prediction model construction. The established soil DRIFTS-based prediction models were applied to estimate the heavy metal concentrations in wheat grains in the mid-Yangtze River Delta area. The predicted heavy metal concentrations of wheat grain were highly consistent with the measured levels by chemical analysis, showing a significant correlation (r2 > 0.72) with acceptable root mean square error RMSE. In conclusion, DRIFTS is a promising technique for assessing the bioavailability of soil heavy metals and related ecological risk. PMID:28198802

Recovery of heavy metals from spent Ni-Cd batteries by a potentiostatic electrodeposition technique

NASA Astrophysics Data System (ADS)

Yang, Chun-Chen

Two heavy metals, Cd and Ni, have been separately recovered from spent AA-size Ni-Cd batteries by the potentiostatic electrodeposition and chemical precipitation methods, respectively. Various types and concentrations of HCl, H 2SO 4, and HNO 3 acids had been used as leach extractants. Experimental results indicate that the acid with the best leach capability is 4 M HCl. Three complexing reagents of NH 3, sodium acetate, sodium citrate have been chosen and tested. The most effective buffer is sodium citrate. The optimum mole ratio of metallic ion to citrate ion is 1:1. The recovery process for Cd metal is conducted by the potentiostatic electrodeposition in a leach electrolyte with a sodium citrate complex. The optimum applied potential for Cd recovery is in the range -1100 to -1120 mV (versus saturated calomel electrode (SCE)). The current efficiency for the recovery process is between 70 and 90% and depends strongly on the process parameters, e.g. liquor, concentration, applied potential, temperature, type of complex reagents, mole ratio, mass-transfer rate.

Complexation studies with lanthanides and humic acid analyzed by ultrafiltration and capillary electrophoresis-inductively coupled plasma mass spectrometry.

PubMed

Kautenburger, Ralf; Beck, Horst Philipp

2007-08-03

For the long-term storage of radioactive waste, detailed information about geo-chemical behavior of radioactive and toxic metal ions under environmental conditions is necessary. Humic acid (HA) can play an important role in the immobilisation or mobilisation of metal ions due to complexation and colloid formation. Therefore, we investigate the complexation behavior of HA and its influence on the migration or retardation of selected lanthanides (europium and gadolinium as homologues of the actinides americium and curium). Two independent speciation techniques, ultrafiltration and capillary electrophoresis coupled with inductively coupled plasma mass spectrometry (CE-ICP-MS) have been compared for the study of Eu and Gd interaction with (purified Aldrich) HA. The degree of complexation of Eu and Gd in 25 mg l(-1) Aldrich HA solutions was determined with a broad range of metal loading (Eu and Gd total concentration between 10(-6) and 10(-4) mol l(-1)), ionic strength of 10 mM (NaClO4) and different pH-values. From the CE-ICP-MS electropherograms, additional information on the charge of the Eu species was obtained by the use of 1-bromopropane as neutral marker. To detect HA in the ICP-MS and separate between HA complexed and non complexed metal ions in the CE-ICP-MS, we have halogenated the HA with iodine as ICP-MS marker.

Redox-activated MRI contrast agents based on lanthanide and transition metal ions.

PubMed

Tsitovich, Pavel B; Burns, Patrick J; McKay, Adam M; Morrow, Janet R

2014-04-01

The reduction/oxidation (redox) potential of tissue is tightly regulated in order to maintain normal physiological processes, but is disrupted in disease states. Thus, the development of new tools to map tissue redox potential may be clinically important for the diagnosis of diseases that lead to redox imbalances. One promising area of chemical research is the development of redox-activated probes for mapping tissue through magnetic resonance imaging (MRI). In this review, we summarize several strategies for the design of redox-responsive MRI contrast agents. Our emphasis is on both lanthanide(III) and transition metal(II/III) ion complexes that provide contrast either as T1 relaxivity MRI contrast agents or as paramagnetic chemical exchange saturation transfer (PARACEST) contrast agents. These agents are redox-triggered by a variety of chemical reactions or switches including redox-activated thiol groups, and heterocyclic groups that interact with the metal ion or influence properties of other ancillary ligands. Metal ion centered redox is an approach which is ripe for development by coordination chemists. Redox-triggered metal ion approaches have great potential for creating large differences in magnetic properties that lead to changes in contrast. An attractive feature of these agents is the ease of fine-tuning the metal ion redox potential over a biologically relevant range. Copyright © 2014 Elsevier Inc. All rights reserved.

Fe N-Heterocyclic Carbene Complexes as Promising Photosensitizers.

PubMed

Liu, Yizhu; Persson, Petter; Sundström, Villy; Wärnmark, Kenneth

2016-08-16

The photophysics and photochemistry of transition metal complexes (TMCs) has long been a hot field of interdisciplinary research. Rich metal-based redox processes, together with a high variety in electronic configurations and excited-state dynamics, have rendered TMCs excellent candidates for interconversion between light, chemical, and electrical energies in intramolecular, supramolecular, and interfacial arrangements. In specific applications such as photocatalytic organic synthesis, photoelectrochemical cells, and light-driven supramolecular motors, light absorption by a TMC-based photosensitizer and subsequent excited-state energy or electron transfer constitute essential steps. In this context, TMCs based on rare and expensive metals, such as ruthenium and iridium, are frequently employed as photosensitizers, which is obviously not ideal for large-scale implementation. In the search for abundant and environmentally benign solutions, six-coordinate Fe(II) complexes (Fe(II)L6) have been widely considered as highly desirable alternatives. However, not much success has been achieved due to the extremely short-lived triplet metal-to-ligand charge transfer ((3)MLCT) excited state that is deactivated by low-lying metal-centered (MC) states on a 100 fs time scale. A fundamental strategy to design useful Fe-based photosensitizers is thus to destabilize the MC states relative to the (3)MLCT state by increasing the ligand field strength, with special focus on making eg σ* orbitals on the Fe center energetically less accessible. Previous efforts to directly transplant successful strategies from Ru(II)L6 complexes unfortunately met with limited success in this regard, despite their close chemical kinship. In this Account, we summarize recent promising results from our and other groups in utilizing strongly σ-donating N-heterocyclic carbene (NHC) ligands to make strong-field Fe(II)L6 complexes with significantly extended (3)MLCT lifetimes. Already some of the first homoleptic bis(tridentate) complexes incorporating (CNHC^Npyridine^CNHC)-type ligands gratifyingly resulted in extension of the (3)MLCT lifetime by more than 2 orders of magnitude compared to the parental [Fe(tpy)2](2+) (tpy = 2,2':6',2″-terpyridine) complex. Quantum chemical (QC) studies also revealed that the (3)MC instead of the (5)MC state likely dictates the deactivation of the (3)MLCT state, a behavior distinct from traditional Fe(II)L6 complexes but rather resembling Ru analogues. A heteroleptic Fe(II) NHC complex featuring mesoionic bis(1,2,3-triazol-5-ylidene) (btz) ligands also delivered a 100-fold elongation of the (3)MLCT lifetime relative to its parental [Fe(bpy)3](2+) (bpy = 2,2'-bipyridine) complex. Again, a Ru-like deactivation mechanism of the (3)MLCT state was indicated by QC studies. With a COOH-functionalized homoleptic complex, a record (3)MLCT lifetime of 37 ps was recently observed on an Al2O3 nanofilm. As a proof of concept, it was further demonstrated that the significant improvement in the (3)MLCT lifetime indeed benefits efficient light harvesting with Fe(II) NHC complexes. For the first time, close-to-unity electron injection from the lowest-energy (3)MLCT state to a TiO2 nanofilm was achieved by a stable Fe(II) complex. This is in complete contrast to conventional Fe(II)L6-derived photosensitizers that could only make use of high-energy photons. These exciting results significantly broaden the understanding of the fundamental photophysics and photochemistry of d(6) Fe(II) complexes. They also open up new possibilities to develop solar energy-converting materials based on this abundant, inexpensive, and intrinsically nontoxic element.

Structures of Hydrated Alkali Metal Cations, M+(H2O)nAr (m = Li, Na, K, rb and Cs, n = 3-5), Using Infrared Photodissociation Spectroscopy and Thermodynamic Analysis

NASA Astrophysics Data System (ADS)

Ke, Haochen; van der Linde, Christian; Lisy, James M.

2014-06-01

Alkali metal cations play vital roles in chemical and biochemical systems. Lithium is widely used in psychiatric treatment of manic states and bipolar disorder; Sodium and potassium are essential elements, having major biological roles as electrolytes, balancing osmotic pressure on body cells and assisting the electroneurographic signal transmission; Rubidium has seen increasing usage as a supplementation for manic depression and depression treatment; Cesium doped compounds are used as essential catalysts in chemical production and organic synthesis. Since hydrated alkali metal cations are ubiquitous and the basic form of the alkali metal cations in chemical and biochemical systems, their structural and thermodynamic properties serve as the foundation for modeling more complex chemical and biochemical processes, such as ion transport and ion size-selectivity of ionophores and protein channels. By combining mass spectrometry and infrared photodissociation spectroscopy, we have characterized the structures and thermodynamic properties of the hydrated alkali metal cations, i.e. M+(H2O)nAr, (M = Li, Na, K, Rb and Cs, n = 3-5). Ab initio calculations and RRKM-EE (evaporative ensemble) calculations were used to assist in the spectral assignments and thermodynamic analysis. Results showed that the structures of hydrated alkali metal cations were determined predominantly by the competition between non-covalent interactions, i.e. the water---water hydrogen bonding interactions and the water---cation electrostatic interactions. This balance, however, is very delicate and small changes, i.e. different cations, different levels of hydration and different effective temperatures clearly impact the balance.

Kinetic and energetic paradigms for dye-sensitized solar cells: moving from the ideal to the real.

PubMed

O'Regan, Brian C; Durrant, James R

2009-11-17

Dye-sensitized solar cells (DSSCs) are photoelectrochemical solar cells. Their function is based on photoinduced charge separation at a dye-sensitized interface between a nanocrystalline, mesoporous metal oxide electrode and a redox electrolyte. They have been the subject of substantial academic and commercial research over the last 20 years, motivated by their potential as a low-cost solar energy conversion technology. Substantial progress has been made in enhancing the efficiency, stability, and processability of this technology and, in particular, the interplay between these technology drivers. However, despite intense research efforts, our ability to identify predictive materials and structure/device function relationships and, thus, achieve the rational optimization of materials and device design, remains relatively limited. A key challenge in developing such predictive design tools is the chemical complexity of the device. DSSCs comprise distinct materials components, including metal oxide nanoparticles, a molecular sensitizer dye, and a redox electrolyte, all of which exhibit complex interactions with each other. In particular, the electrolyte alone is chemically complex, including not only a redox couple (almost always iodide/iodine) but also a range of additional additives found empirically to enhance device performance. These molecular solutes make up typically 20% of the electrolyte by volume. As with most molecular systems, they exhibit complex interactions with both themselves and the other device components (e.g., the sensitizer dye and the metal oxide). Moreover, these interactions can be modulated by solar irradiation and device operation. As such, understanding the function of these photoelectrochemical solar cells requires careful consideration of the chemical complexity and its impact upon device operation. In this Account, we focus on the process by which electrons injected into the nanocrystalline electrode are collected by the external electrical circuit in real devices under operating conditions. We first of all summarize device function, including the energetics and kinetics of the key processes, using an "idealized" description, which does not fully account for much of the chemical complexity of the system. We then go on to consider recent advances in our understanding of the impact of these complexities upon the efficiency of electron collection. These include "catalysis" of interfacial recombination losses by surface adsorption processes and the influence of device operating conditions upon the recombination rate constant and conduction band energy, both attributed to changes in the chemical composition of the interface. We go on to discuss appropriate methodologies for quantifying the efficiency of electron collection in devices under operation. Finally, we show that, by taking into account these advances in our understanding of the DSSC function, we are able to recreate the current/voltage curves of both efficient and degraded devices without any fitting parameters and, thus, gain significant insight into the determinants of DSSC performance.

Photodissociation Spectroscopy of Anionic Transition Metal Complexes

NASA Astrophysics Data System (ADS)

Kaufman, Sydney Hamilton

Transition metal complexes play an important role in many aspects of chemistry; whether in supporting biological functions, as catalysts for organic reactions, in the environment, or in industry. This thesis is comprised of gas-phase spectroscopic studies of four transition metal species with implications for many different chemical applications. Most knowledge of the target molecules in this thesis are derived from studies in the condensed phase, where the chemical environment can change molecular properties. As a result, it is difficult to gain an understanding of the intrinsic properties in solution as well as a molecular-level picture of chemical reactions that take place where many oxidation states, molecular species, and solvent interactions occur. By isolating one particular species in the gas phase, we are able to observe how each species interacts with light independent of perturbing effects of solvent and counter ions. In this thesis, we perform spectroscopic experiments on mass-selected ions in the gas phase, where we are able to gain information on intrinsic molecular properties without the influence of a condensed phase chemical environment. We employ photodissociation spectroscopy, where we mass-select a particular ionic species from solution and irradiate that molecular ion with the output of a tunable laser in the ultraviolet and visible regions. By monitoring the fragments produced, we can obtain an electronic absorption spectrum of the isolated species as well as gain insight into the photochemistry of the ions under study from the fragmentation pathways observed. We combine this method with solution absorption spectra as well as electronic structure calculations.

Design and characterization of α-melanotropin peptide analogs cyclized through rhenium and technetium metal coordination

PubMed Central

Giblin, Michael F.; Wang, Nannan; Hoffman, Timothy J.; Jurisson, Silvia S.; Quinn, Thomas P.

1998-01-01

α-Melanocyte stimulating hormone (α-MSH) analogs, cyclized through site-specific rhenium (Re) and technetium (Tc) metal coordination, were structurally characterized and analyzed for their abilities to bind α-MSH receptors present on melanoma cells and in tumor-bearing mice. Results from receptor-binding assays conducted with B16 F1 murine melanoma cells indicated that receptor-binding affinity was reduced to approximately 1% of its original levels after Re incorporation into the cyclic Cys4,10, d-Phe7–α-MSH4-13 analog. Structural analysis of the Re–peptide complex showed that the disulfide bond of the original peptide was replaced by thiolate–metal–thiolate cyclization. A comparison of the metal-bound and metal-free structures indicated that metal complexation dramatically altered the structure of the receptor-binding core sequence. Redesign of the metal binding site resulted in a second-generation Re–peptide complex (ReCCMSH) that displayed a receptor-binding affinity of 2.9 nM, 25-fold higher than the initial Re–α-MSH analog. Characterization of the second-generation Re–peptide complex indicated that the peptide was still cyclized through Re coordination, but the structure of the receptor-binding sequence was no longer constrained. The corresponding 99mTc- and 188ReCCMSH complexes were synthesized and shown to be stable in phosphate-buffered saline and to challenges from diethylenetriaminepentaacetic acid (DTPA) and free cysteine. In vivo, the 99mTcCCMSH complex exhibited significant tumor uptake and retention and was effective in imaging melanoma in a murine-tumor model system. Cyclization of α-MSH analogs via 99mTc and 188Re yields chemically stable and biologically active molecules with potential melanoma-imaging and therapeutic properties. PMID:9788997

Modelling of trace metal uptake by roots taking into account complexation by exogenous organic ligands

NASA Astrophysics Data System (ADS)

Jean-Marc, Custos; Christian, Moyne; Sterckeman, Thibault

2010-05-01

The context of this study is phytoextraction of soil trace metals such as Cd, Pb or Zn. Trace metal transfer from soil to plant depends on physical and chemical processes such as minerals alteration, transport, adsorption/desorption, reactions in solution and biological processes including the action of plant roots and of associated micro-flora. Complexation of metal ions by organic ligands is considered to play a role on the availability of trace metals for roots in particular in the event that synthetic ligands (EDTA, NTA, etc.) are added to the soil to increase the solubility of the contaminants. As this role is not clearly understood, we wanted to simulate it in order to quantify the effect of organic ligands on root uptake of trace metals and produce a tool which could help in optimizing the conditions of phytoextraction.We studied the effect of an aminocarboxilate ligand on the absorption of the metal ion by roots, both in hydroponic solution and in soil solution, for which we had to formalize the buffer power for the metal. We assumed that the hydrated metal ion is the only form which can be absorbed by the plants. Transport and reaction processes were modelled for a system made up of the metal M, a ligand L and the metal complex ML. The Tinker-Nye-Barber model was adapted to describe the transport of solutes M, L and ML in the soil and absorption of M by the roots. This allowed to represent the interactions between transport, chelating reactions, absorption of the solutes at the root surface, root growth with time, in order to simulate metal uptake by a whole root system.Several assumptions were tested such as i) absorption of the metal by an infinite sink and according to a Michaelis-Menten kinetics, solutes transport by diffusion with and without ii) mass flow and iii) soil buffer power for the ligand L. In hydroponic solution (without soil buffer power), ligands decreased the trace metal flux towards roots, as they reduced the concentration of hydrated metal ion. In soil, depending on the L/M ratio, the presence of metal complexes could increase the metal flux taken up by roots since the ligand desorbed the metal on soil solid phase while the complex dissociated and provided metal ions to the solution in the vicinity of the root.The model enabled to surround the conditions in which phytoextraction is thus optimized. In addition of complexation by organic ligands added to the soil, we expect to integrate complexation by roots organic exudates and by soil organic matter, as well as the competition of the metal ions with Ca2+ et H+.

State of research: environmental pathways and food chain transfer.

PubMed Central

Vaughan, B E

1984-01-01

Data on the chemistry of biologically active components of petroleum, synthetic fuel oils, certain metal elements and pesticides provide valuable generic information needed for predicting the long-term fate of buried waste constituents and their likelihood of entering food chains. Components of such complex mixtures partition between solid and solution phases, influencing their mobility, volatility and susceptibility to microbial transformation. Estimating health hazards from indirect exposures to organic chemicals involves an ecosystem's approach to understanding the unique behavior of complex mixtures. Metabolism by microbial organisms fundamentally alters these complex mixtures as they move through food chains. Pathway modeling of organic chemicals must consider the nature and magnitude of food chain transfers to predict biological risk where metabolites may become more toxic than the parent compound. To obtain predictions, major areas are identified where data acquisition is essential to extend our radiological modeling experience to the field of organic chemical contamination. PMID:6428875

A Combined Theoretical and Experimental Study for Silver Electroplating

PubMed Central

Liu, Anmin; Ren, Xuefeng; An, Maozhong; Zhang, Jinqiu; Yang, Peixia; Wang, Bo; Zhu, Yongming; Wang, Chong

2014-01-01

A novel method combined theoretical and experimental study for environmental friendly silver electroplating was introduced. Quantum chemical calculations and molecular dynamic (MD) simulations were employed for predicting the behaviour and function of the complexing agents. Electronic properties, orbital information, and single point energies of the 5,5-dimethylhydantoin (DMH), nicotinic acid (NA), as well as their silver(I)-complexes were provided by quantum chemical calculations based on density functional theory (DFT). Adsorption behaviors of the agents on copper and silver surfaces were investigated using MD simulations. Basing on the data of quantum chemical calculations and MD simulations, we believed that DMH and NA could be the promising complexing agents for silver electroplating. The experimental results, including of electrochemical measurement and silver electroplating, further confirmed the above prediction. This efficient and versatile method thus opens a new window to study or design complexing agents for generalized metal electroplating and will vigorously promote the level of this research region. PMID:24452389

Interaction of Tryptophane and Phenylalanine with Cadmium and Molybdenum Ferrocyanides and Its Implications in Chemical Evolution and Origins of Life.

NASA Astrophysics Data System (ADS)

Tewari, Brij

2016-07-01

Insoluble metal hexacyanoferrate(II) complexes could have concentrated biomonomers from dilute prebiotic soup during course of chemical evolution and origin of life or primitive earth. In the light of above hypothesis, adsorption of tryptophane and phenylalanine was studied on cadmium and molybdenum ferrocyanides at neutral pH (7.0 ± 0.01) and at a temperature of 30 ± 1º C. Interaction of amino acids with metal ferrocyanides are found to be maximum at neutral pH. Neutral pH is chosen for the adsorption studies because most of the reactions in biological systems taken place at neutral pH range. Adsorption trend follow Langmuir isotherm model. The Langmuir constants b and Qo were calculated at neutral pH, tryptophane was found to more adsorbed than phenylalanine on both metal ferrocyanides studied. Molybdenum ferrocyanides studied. Molybdenum ferrocyanides was found to have more uptake capacity for both adsorbates than cadmium ferrocyanides. The present study suggests that metal ferrocyanides might have played a role in the stabilization of biomolecules through their surface activity during course of chemical solution and origins of life on primitive earth.

DEMONSTRATION BULLETIN: COLLOID POLISHING FILTER METHOD - FILTER FLOW TECHNOLOGY, INC.

EPA Science Inventory

The Filter Flow Technology, Inc. (FFT) Colloid Polishing Filter Method (CPFM) was tested as a transportable, trailer mounted, system that uses sorption and chemical complexing phenomena to remove heavy metals and nontritium radionuclides from water. Contaminated waters can be pro...

Role of surfaces and interfaces in controlling the mechanical properties of metallic alloys.

PubMed

Lee, Won-Jong; Chia, Wen-Jui; Wang, Jinliu; Chen, Yanfeng; Vaynman, Semyon; Fine, Morris E; Chung, Yip-Wah

2010-11-02

This article explores the subtle effects of surfaces and interfaces on the mechanical properties of bulk metallic alloys using three examples: environmental effects on fatigue life, hydrogen embrittlement effects on the ductility of intermetallics, and the role of coherent precipitates in the toughness of steels. It is demonstrated that the marked degradation of the fatigue life of metals is due to the strong chemisorption of adsorbates on exposed slip steps that are formed during fatigue deformation. These adsorbates reduce the reversibility of slip, thus accelerating fatigue damage in a chemically active gas environment. For certain intermetallic alloys such as Ni(3)Al and Ni(3)Fe, the ductility depends on the ambient gas composition and the atomic ordering in these alloys, both of which govern the complex surface chemical reactions taking place in the vicinity of crack tips. Finally, it is shown that local stresses at a coherent precipitate-matrix interface can activate dislocation motion at low temperatures, thus improving the fracture toughness of bulk alloys such as steels at cryogenic temperatures. These examples illustrate the complex interplay between surface chemistry and mechanics, often yielding unexpected results.

Flow microcapillary plasma mass spectrometry-based investigation of new Al-Cr-Fe complex metallic alloy passivation.

PubMed

Ott, N; Beni, A; Ulrich, A; Ludwig, C; Schmutz, P

2014-03-01

Al-Cr-Fe complex metallic alloys are new intermetallic phases with low surface energy, low friction, and high corrosion resistance down to very low pH values (0-2). Flow microcapillary plasma mass spectrometry under potentiostatic control was used to characterize the dynamic aspect of passivation of an Al-Cr-Fe gamma phase in acidic electrolytes, allowing a better insight on the parameters inducing chemical stability at the oxyhydroxide-solution interface. In sulfuric acid pH 0, low element dissolution rates (in the µg cm(-2) range after 60 min) evidenced the passive state of the Al-Cr-Fe gamma phase with a preferential over-stoichiometric dissolution of Al and Fe cations. Longer air-aging was found to be beneficial for stabilizing the passive film. In chloride-containing electrolytes, ten times higher Al dissolution rates were detected at open-circuit potential (OCP), indicating that the spontaneously formed passive film becomes unstable. However, electrochemical polarization at low passive potentials induces electrical field generated oxide film modification, increasing chemical stability at the oxyhydroxide-solution interface. In the high potential passive region, localized attack is initiated with subsequent active metal dissolution. © 2013 Published by Elsevier B.V.

A quantum informational approach for dissecting chemical reactions

NASA Astrophysics Data System (ADS)

Duperrouzel, Corinne; Tecmer, Paweł; Boguslawski, Katharina; Barcza, Gergely; Legeza, Örs; Ayers, Paul W.

2015-02-01

We present a conceptionally different approach to dissect bond-formation processes in metal-driven catalysis using concepts from quantum information theory. Our method uses the entanglement and correlation among molecular orbitals to analyze changes in electronic structure that accompany chemical processes. As a proof-of-principle example, the evolution of nickel-ethene bond-formation is dissected, which allows us to monitor the interplay of back-bonding and π-donation along the reaction coordinate. Furthermore, the reaction pathway of nickel-ethene complexation is analyzed using quantum chemistry methods, revealing the presence of a transition state. Our study supports the crucial role of metal-to-ligand back-donation in the bond-forming process of nickel-ethene.

Synthesis, structural, optical band gap and biological studies on iron (III), nickel (II), zinc (II) and mercury (II) complexes of benzyl α-monoxime pyridyl thiosemicarbazone

NASA Astrophysics Data System (ADS)

Bedier, R. A.; Yousef, T. A.; Abu El-Reash, G. M.; El-Gammal, O. A.

2017-07-01

New ligand, (E)-2-((E)-2-(hydroxyimino)-1,2-diphenylethylidene)-N-(pyridin-2 yl) hydrazinecarbothioamide (H2DPPT) and its complexes [Fe(DPPT)Cl(H2O)], [Ni(H2DPPT)2Cl2], [Zn(HDPPT)(OAc)] and [Hg(HDPPT)Cl](H2O)4 were isolated and characterized by various of physico-chemical techniques. IR spectra show that H2DPPT coordinates to the metal ions as neutral NN bidentate, mononegative NNS tridentate and binegative NNSN tetradentate, respectively. From the modeling studies, the bond length, bond angle, HOMO, LUMO and dipole moment had been calculated to confirm the geometry of the ligands and their investigated complexes. The thermal studies showed the type of water molecules involved in metal complexes Furthermore, the kinetic and thermodynamic parameters for the different decomposition steps were calculated using the Coats-Redfern and Horowitz-Metzger methods. Also, the optical band gap (Eg) has been calculated to elucidate the conductivity of the isolated complexes. The optical transition energy (Eg) is direct and equals 3.34 and 3.44 ev for Ni and Fe complexes, respectively. The ligand and their metal complexes were screened for antibacterial activity against the following bacterial species, Bacillus thuringiensis, Staphylococcus aureus, Pseudomonas aeuroginosa and Escherichia coli. The results revealed that the metal complexes have more potent antibacterial compared with the ligand. Also, the degradation effect of the investigated compounds was tested showing that, Ni complex exhibited powerful and complete degradation effect on DNA.

Selective CO{sub 2} reduction conjugated with H{sub 2}O oxidation utilizing semiconductor/metal-complex hybrid photocatalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morikawa, T., E-mail: morikawa@mosk.tytlabs.co.jp; Sato, S., E-mail: morikawa@mosk.tytlabs.co.jp; Arai, T., E-mail: morikawa@mosk.tytlabs.co.jp

2013-12-10

We developed a new hybrid photocatalyst for CO{sub 2} reduction, which is composed of a semiconductor and a metal complex. In the hybrid photocatalyst, ΔG between the position of conduction band minimum (E{sub CBM}) of the semiconductor and the CO{sub 2} reduction potential of the complex is an essential factor for realizing fast electron transfer from the conduction band of semiconductor to metal complex leading to high photocatalytic activity. On the basis of this concept, the hybrid photocatalyst InP/Ru-complex, which functions in aqueous media, was developed. The photoreduction of CO{sub 2} to formate using water as an electron donor andmore » a proton source was successfully achieved as a Z-scheme system by functionally conjugating the InP/Ru-complex photocatalyst for CO{sub 2} reduction with a TiO{sub 2} photocatalyst for water oxidation. The conversion efficiency from solar energy to chemical energy was ca. 0.04%, which approaches that for photosynthesis in a plant. Because this system can be applied to many other inorganic semiconductors and metal-complex catalysts, the efficiency and reaction selectivity can be enhanced by optimization of the electron transfer process including the energy-band configurations, conjugation conformations, and catalyst structures. This electrical-bias-free reaction is a huge leap forward for future practical applications of artificial photosynthesis under solar irradiation to produce organic species.« less

Redox-switchable copper(I) metallogel: a metal-organic material for selective and naked-eye sensing of picric acid.

PubMed

Sarkar, Sougata; Dutta, Soumen; Chakrabarti, Susmita; Bairi, Partha; Pal, Tarasankar

2014-05-14

Thiourea (TU), a commercially available laboratory chemical, has been discovered to introduce metallogelation when reacted with copper(II) chloride in aqueous medium. The chemistry involves the reduction of Cu(II) to Cu(I) with concomitant oxidation of thiourea to dithiobisformamidinium dichloride. The gel formation is triggered through metal-ligand complexation, i.e., Cu(I)-TU coordination and extensive hydrogen bonding interactions involving thiourea, the disulfide product, water, and chloride ions. Entangled network morphology of the gel selectively develops in water, maybe for its superior hydrogen-bonding ability, as accounted from Kamlet-Taft solvent parameters. Complete and systematic chemical analyses demonstrate the importance of both Cu(I) and chloride ions as the key ingredients in the metal-organic coordination gel framework. The gel is highly fluorescent. Again, exclusive presence of Cu(I) metal centers in the gel structure makes the gel redox-responsive and therefore it shows reversible gel-sol phase transition. However, the reversibility does not cause any morphological change in the gel phase. The gel practically exhibits its multiresponsive nature and therefore the influences of different probable interfering parameters (pH, selective metal ions and anions, selective complexing agents, etc.) have been studied mechanistically and the results might be promising for different applications. Finally, the gel material shows a highly selective visual response to a commonly used nitroexplosive, picric acid among a set of 19 congeners and the preferred selectivity has been mechanistically interpreted with density functional theory-based calculations.

Feasibility analysis of EDXRF method to detect heavy metal pollution in ecological environment

NASA Astrophysics Data System (ADS)

Hao, Zhixu; Qin, Xulei

2018-02-01

The change of heavy metal content in water environment, soil and plant can reflect the change of heavy metal pollution in ecological environment, and it is important to monitor the trend of heavy metal pollution in eco-environment by using water environment, soil and heavy metal content in plant. However, the content of heavy metals in nature is very low, the background elements of water environment, soil and plant samples are complex, and there are many interfering factors in the EDXRF system that will affect the spectral analysis results and reduce the detection accuracy. Through the contrastive analysis of several heavy metal elements detection methods, it is concluded that the EDXRF method is superior to other chemical methods in testing accuracy and method feasibility when the heavy metal pollution in soil is tested in ecological environment.

A IAB-Complex Iron Meteorite Containing Low-Ca Clinopyroxene: Northwest Africa 468 and its Relationship to Iodranites and Formation by Impact Melting

NASA Technical Reports Server (NTRS)

Rubin, Alan E.; Kallemeyn, Gregory W.; Wasson, John T.

2002-01-01

Northwest Africa 468 (NWA 468) is a new ungrouped, silicate-rich member of the IAB complex of nonmagmatic iron meteorites. The silicates contain relatively coarse (approximately 300 micron-size) grains of low-Ca clinopyroxene with polysynthetic twinning and inclined extinction. Low-Ca clinopyroxene is indicative of quenching from high temperatures (either from protoenstatite in a few seconds or high-temperature clinoenstatite in a few hours). It seems likely that NWA 468 formed by impact melting followed by rapid cooling to less than or equal to 660 C. After the loss of a metal-sulfide melt from the silicates, sulfide was reintroduced, either from impact-mobilized FeS or as an S2 vapor that combined with metallic Fe to produce FeS. The O-isotopic composition (delta O-17 = -1.39 %) indicates that the precursor material of NWA 468 was a metal-rich (e.g., CR) carbonaceous chondrite. Lodranites are similar in bulk chemical and O-isotopic composition to the silicates in NWA 468; the MAC 88177 lodranite (which also contains low-Ca clinopyroxene) is close in bulk chemical composition. Both NWA 468 and MAC 88177 have relatively low abundances of REE (rare earth elements) and plagiophile elements. Siderophiles in the metal-rich areas of NWA 468 are similar to those in the MAC 88177 whole rock; both samples contain low Ir and relatively high Fe, Cu and Se. Most unweathered lodranites contain approximately 20 - 38 wt. % metallic Fe-Ni. These rocks may have formed in an analogous manner to NWA 468 (i.e., by impact melting of metal-rich carbonaceous-chondrite precursors) but with less separation of metal-rich melts from silicates.

Vadose Zone Fate and Transport Simulation of Chemicals Associated with Coal Seam Gas Extraction

NASA Astrophysics Data System (ADS)

Simunek, J.; Mallants, D.; Jacques, D.; Van Genuchten, M.

2017-12-01

The HYDRUS-1D and HYDRUS (2D/3D) computer software packages are widely used finite element models for simulating the one-, and two- or three-dimensional movement of water, heat, and multiple solutes in variably-saturated media, respectively. While the standard HYDRUS models consider only the fate and transport of individual solutes or solutes subject to first-order degradation reactions, several specialized HYDRUS add-on modules can simulate far more complex biogeochemical processes. The objective of this presentation is to provide an overview of the HYDRUS models and their add-on modules, and to demonstrate applications of the software to the subsurface fate and transport of chemicals involved in coal seam gas extraction and water management operations. One application uses the standard HYDRUS model to evaluate the natural soil attenuation potential of hydraulic fracturing chemicals and their transformation products in case of an accidental release. By coupling the processes of retardation, first-order degradation and convective-dispersive transport of the biocide bronopol and its degradation products, we demonstrated how natural attenuation reduces initial concentrations by more than a factor of hundred in the top 5 cm of the vadose zone. A second application uses the UnsatChem module to explore the possible use of coal seam gas produced water for sustainable irrigation. Simulations with different irrigation waters (untreated, amended with surface water, and reverse osmosis treated) provided detailed results regarding chemical indicators of soil and plant health, notably SAR, EC and sodium concentrations. A third application uses the coupled HYDRUS-PHREEQC module to analyze trace metal transport involving cation exchange and surface complexation sorption reactions in the vadose zone leached with coal seam gas produced water following some accidental water release scenario. Results show that the main process responsible for trace metal migration is complexation of naturally present trace metals with inorganic ligands such as (bi)carbonate that enter the soil upon infiltration with alkaline produced water.

Redox Active Transition Metal ions Make Melanin Susceptible to Chemical Degradation Induced by Organic Peroxide.

PubMed

Zadlo, Andrzej; Pilat, Anna; Sarna, Michal; Pawlak, Anna; Sarna, Tadeusz

2017-12-01

With aging, retinal pigment epithelium melanosomes, by fusion with the age pigment lipofuscin, form complex granules called melanolipofuscin. Lipofuscin granules may contain oxidized proteins and lipid hydroperoxides, which in melanolipofuscin could chemically modify melanin polymer, while transition metal ions present in melanin can accelerate such oxidative modifications. The aim of this research was to examine the effect of selected transition metal ions on melanin susceptibility to chemical modification induced by the water-soluble tert-butyl hydroperoxide used as an oxidizing agent. Synthetic melanin obtained by DOPA autooxidation and melanosomes isolated from bovine retinal pigment epithelium were analyzed. To monitor tert-butyl hydroperoxide-induced oxidative changes of DMa and BMs, electron paramagnetic resonance spectroscopy, UV-vis absorption spectroscopy, dynamic light scattering, atomic force microscopy and electron paramagnetic resonance oximetry were employed. These measurements revealed that both copper and iron ions accelerated chemical degradation induced by tert-butyl hydroperoxide, while zinc ions had no effect. Strong prooxidant action was detected only in the case of melanosomes and melanin degraded in the presence of iron. It can be postulated that similar chemical processes, if they occur in situ in melanolipofuscin granules of the human retinal pigment epithelium, would modify antioxidant properties of melanin and its reactivity.

Ultrafast Transient Absorption Spectroscopy of Polymer-Based Organophotoredox Catalysts Mimicking Transition-Metal Complexes

NASA Astrophysics Data System (ADS)

Jamhawi, Abdelqader; Paul, Anam C.; Smith, Justin D.; Handa, Sachin; Liu, Jinjun

2017-06-01

Transition-metal complexes of rare earth metals including ruthenium and iridium are most commonly employed as visible-light photocatalysts. Despite their highly important and broad applications, they have many disadvantages including high cost associated with low abundance in earth crust, potential toxicity, requirement of specialized ligands for desired activity, and difficulty in recycling of metal contents as well as associated ligands. Polymer-based organophotoredox catalysts are promising alternatives and possess unique advantages such as easier synthesis from inexpensive starting material, longer excited state life time, broad range of activity, sustainability, and recyclability. In this research talk, time-resolved photoluminescence and femtosecond transient absorption (TA) spectroscopy measurements of three novel polymer-based organophotoredox catalysts will be presented. By our synthetic team, their catalytic activity has been proven in some highly valuable chemical transformations, that otherwise require transition metal complexes. Time-resolved spectroscopic investigations have demonstrated that photoinduced processes in these catalysts are similar to the transition metal complexes. Especially, intramolecular vibrational relaxation, internal conversion, and intersystem crossing from the S1 state to the T1 state all occur on a sub-picosecond timescale. The long lifetime of the T1 state ( 2-3 microsecond) renders these polymers potent oxidizing and reducing agents. A spectroscopic and kinetic model has been developed for global fitting of TA spectra in both the frequency and time domains. Implication of the current ultrafast spectroscopy studies of these novel molecules to their roles in photocatalysis will be discussed.

Investigation of chemical vapor deposition of garnet films for bubble domain memories

NASA Technical Reports Server (NTRS)

Besser, P. J.; Hamilton, T. N.

1973-01-01

The important process parameters and control required to grow reproducible device quality ferrimagnetic films by chemical vapor deposition (CVD) were studied. The investigation of the critical parameters in the CVD growth process led to the conclusion that the required reproducibility of film properties cannot be achieved with individually controlled separate metal halide sources. Therefore, the CVD growth effort was directed toward replacement of the halide sources with metallic sources with the ultimate goal being the reproducible growth of complex garnet compositions utilizing a single metal alloy source. The characterization of the YGdGaIG films showed that certain characteristics of this material, primarily the low domain wall energy and the large temperature sensitivity, severely limited its potential as a useful material for bubble domain devices. Consequently, at the time of the change from halide to metallic sources, the target film compositions were shifted to more useful materials such as YGdTmGaIG, YEuGaIG and YSmGaIG.

Iterative reactions of transient boronic acids enable sequential C-C bond formation

NASA Astrophysics Data System (ADS)

Battilocchio, Claudio; Feist, Florian; Hafner, Andreas; Simon, Meike; Tran, Duc N.; Allwood, Daniel M.; Blakemore, David C.; Ley, Steven V.

2016-04-01

The ability to form multiple carbon-carbon bonds in a controlled sequence and thus rapidly build molecular complexity in an iterative fashion is an important goal in modern chemical synthesis. In recent times, transition-metal-catalysed coupling reactions have dominated in the development of C-C bond forming processes. A desire to reduce the reliance on precious metals and a need to obtain products with very low levels of metal impurities has brought a renewed focus on metal-free coupling processes. Here, we report the in situ preparation of reactive allylic and benzylic boronic acids, obtained by reacting flow-generated diazo compounds with boronic acids, and their application in controlled iterative C-C bond forming reactions is described. Thus far we have shown the formation of up to three C-C bonds in a sequence including the final trapping of a reactive boronic acid species with an aldehyde to generate a range of new chemical structures.

Nicotianamine forms complexes with Zn(II) in vivo.

PubMed

Trampczynska, Aleksandra; Küpper, Hendrik; Meyer-Klaucke, Wolfram; Schmidt, Holger; Clemens, Stephan

2010-01-01

The non-proteinogenic amino acid nicotianamine (NA) is a major player in plant metal homeostasis. It is known to form complexes with different transition metals in vitro. Available evidence associates NA with translocation of Fe, and possibly other micronutrients, to and between different plant cells and tissues. To date, however, it is still extremely challenging to detect metal-ligand complexes in vivo because tissue disruption immediately changes the chemical environment and thereby the availability of binding partners. In order to overcome this limitation we used various Schizosaccharomyces pombe strains expressing a plant NAS gene to study formation of metal-NA complexes in vivo. Tolerance, accumulation and competition data clearly indicated formation of Zn(ii)-NA but not of Cu(ii)-NA complexes. Zn(ii)-NA was then identified by X-ray absorption spectroscopy (XAS). About half of the cellular Zn was found to be bound by NA in NAS-expressing cells while no NA-like ligands were detected by XAS in control cells not expressing NAS. Given the high conservation of eukaryotic metal homeostasis components, these results strongly suggest the possible existence of Zn(ii)-NA complexes also in planta. Reported observations implicating NA in plant Zn homeostasis would then indeed be attributable to direct interaction of Zn(ii) with NA rather than only indirectly to perturbations in Fe metabolism. Re-evaluation of extended X-ray absorption fine structure (EXAFS) spectra for the Zn hyperaccumulator Thlaspi caerulescens showed that NA is as expected not a major storage ligand for Zn. Instead it is hypothesized to be involved in efficient translocation of Zn to above-ground tissues in hyperaccumulators.

Metal cation controls phosphate release in the myosin ATPase.

PubMed

Ge, Jinghua; Huang, Furong; Nesmelov, Yuri E

2017-11-01

Myosin is an enzyme that utilizes ATP to produce a conformational change generating a force. The kinetics of the myosin reverse recovery stroke depends on the metal cation complexed with ATP. The reverse recovery stroke is slow for MgATP and fast for MnATP. The metal ion coordinates the γ phosphate of ATP in the myosin active site. It is accepted that the reverse recovery stroke is correlated with the phosphate release; therefore, magnesium "holds" phosphate tighter than manganese. Magnesium and manganese are similar ions in terms of their chemical properties and the shell complexation; hence, we propose to use these ions to study the mechanism of the phosphate release. Analysis of octahedral complexes of magnesium and manganese show that the partial charge of magnesium is higher than that of manganese and the slightly larger size of manganese ion makes its ionic potential smaller. We hypothesize that electrostatics play a role in keeping and releasing the abstracted γ phosphate in the active site, and the stronger electric charge of magnesium ion holds γ phosphate tighter. We used stable myosin-nucleotide analog complex and Raman spectroscopy to examine the effect of the metal cation on the relative position of γ phosphate analog in the active site. We found that in the manganese complex, the γ phosphate analog is 0.01 nm further away from ADP than in the magnesium complex. We conclude that the ionic potential of the metal cation plays a role in the retention of the abstracted phosphate. © 2017 The Protein Society.

A theory for bioinorganic chemical reactivity of oxometal complexes and analogous oxidants: the exchange and orbital-selection rules.

PubMed

Usharani, Dandamudi; Janardanan, Deepa; Li, Chunsen; Shaik, Sason

2013-02-19

Over the past decades metalloenzymes and their synthetic models have emerged as an area of increasing research interest. The metalloenzymes and their synthetic models oxidize organic molecules using oxometal complexes (OMCs), especially oxoiron(IV)-based ones. Theoretical studies have helped researchers to characterize the active species and to resolve mechanistic issues. This activity has generated massive amounts of data on the relationship between the reactivity of OMCs and the transition metal's identity, oxidation state, ligand sphere, and spin state. Theoretical studies have also produced information on transition state (TS) structures, reaction intermediates, barriers, and rate-equilibrium relationships. For example, the experimental-theoretical interplay has revealed that nonheme enzymes carry out H-abstraction from strong C-H bonds using high-spin (S = 2) oxoiron(IV) species with four unpaired electrons on the iron center. However, other reagents with higher spin states and more unpaired electrons on the metal are not as reactive. Still other reagents carry out these transformations using lower spin states with fewer unpaired electrons on the metal. The TS structures for these reactions exhibit structural selectivity depending on the reactive spin states. The barriers and thermodynamic driving forces of the reactions also depend on the spin state. H-Abstraction is preferred over the thermodynamically more favorable concerted insertion into C-H bonds. Currently, there is no unified theoretical framework that explains the totality of these fascinating trends. This Account aims to unify this rich chemistry and understand the role of unpaired electrons on chemical reactivity. We show that during an oxidative step the d-orbital block of the transition metal is enriched by one electron through proton-coupled electron transfer (PCET). That single electron elicits variable exchange interactions on the metal, which in turn depend critically on the number of unpaired electrons on the metal center. Thus, we introduce the exchange-enhanced reactivity (EER) principle, which predicts the preferred spin state during oxidation reactions, the dependence of the barrier on the number of unpaired electrons in the TS, and the dependence of the deformation energy of the reactants on the spin state. We complement EER with orbital-selection rules, which predict the structure of the preferred TS and provide a handy theory of bioinorganic oxidative reactions. These rules show how EER provides a Hund's Rule for chemical reactivity: EER controls the reactivity landscape for a great variety of transition-metal complexes and substrates. Among many reactivity patterns explained, EER rationalizes the abundance of high-spin oxoiron(IV) complexes in enzymes that carry out bond activation of the strongest bonds. The concepts used in this Account might also be applicable in other areas such as in f-block chemistry and excited-state reactivity of 4d and 5d OMCs.

Quantum chemical studies on hypothetical Fischer type Mo(CO)5[C(OEt)Me] and Mo(CO)5[C(OMe)Et] carbene complexes

NASA Astrophysics Data System (ADS)

Gövdeli, Nezafet; Karakaş, Duran

2018-07-01

Quantum chemical calculations at B3LYP/LANL2DZ/6-31G(d) level were made on anti-eclipsed, anti-staggered, syn-eclipsed, syn-staggered conformers of hypothetical Fischer type Mo(CO)5[C(OEt)Me] and Mo(CO)5[C(OMe)Et] carbene complexes in the gas phase. The most stable conformer of the complexes was found to be anti-staggered according to the total energy values calculated at given level. Structural parameters, vibration spectra, charge distributions, molecular orbital energy diagrams, contour diagrams of frontier orbitals, molecular electrostatic potential maps and some electronic structure descriptors were obtained for the most stable conformers. NMR spectra of the most stable conformers were calculated at GIAO/B3LYP/LANL2DZ level. The most stable conformer geometry was found to be distorted octahedral. IR and NMR spectra of the complexes are consistent with their geometry. HOMOs of the complexes were found to be center-atomic character and LUMOs were carbene-carbon character. From the calculated charge analysis and molecular electrostatic potential maps, it is found that carbene-carbon acts as electrofil and metal center nucleophile. It is suggested that the catalytic properties of the carbene complexes may be due to the fact that the carbene-carbon behave as electrophile and metal center nucleophile. Some electronic structure descriptors of the complexes were calculated and the molecular properties were estimated.

The ongoing search for small molecules to study metal-associated amyloid-β species in Alzheimer's disease.

PubMed

Savelieff, Masha G; DeToma, Alaina S; Derrick, Jeffrey S; Lim, Mi Hee

2014-08-19

The development of a cure for Alzheimer's disease (AD) has been impeded by an inability to pinpoint the root cause of this disorder. Although numerous potential pathological factors have been indicated, acting either individually or mutually, the molecular mechanisms leading to disease onset and progression have not been clear. Amyloid-β (Aβ), generated from proteolytic processing of the amyloid precursor protein (APP), and its aggregated forms, particularly oligomers, are suggested as key pathological features in AD-affected brains. Historically, highly concentrated metals are found colocalized within Aβ plaques. Metal binding to Aβ (metal-Aβ) generates/stabilizes potentially toxic Aβ oligomers, and produces reactive oxygen species (ROS) in vitro (redox active metal ions; plausible contribution to oxidative stress). Consequently, clarification of the relationship between Aβ, metal ions, and toxicity, including oxidative stress via metal-Aβ, can lead to a deeper understanding of AD development. To probe the involvement of metal-Aβ in AD pathogenesis, rationally designed and naturally occurring molecules have been examined as chemical tools to target metal-Aβ species, modulate the interaction between the metal and Aβ, and subsequently redirect their aggregation into nontoxic, off-pathway unstructured aggregates. These ligands are also capable of attenuating the generation of redox active metal-Aβ-induced ROS to mitigate oxidative stress. One rational design concept, the incorporation approach, installs a metal binding site into a framework known to interact with Aβ. This approach affords compounds with the simultaneous ability to chelate metal ions and interact with Aβ. Natural products capable of Aβ interaction have been investigated for their influence on metal-induced Aβ aggregation and have inspired the construction of synthetic analogues. Systematic studies of these synthetic or natural molecules could uncover relationships between chemical structures, metal/Aβ/metal-Aβ interactions, and inhibition of Aβ/metal-Aβ reactivity (i.e., aggregation modes of Aβ/metal-Aβ; associated ROS production), suggesting mechanisms to refine the design strategy. Interdisciplinary investigations have demonstrated that the designed molecules and natural products control the aggregation pathways of metal-Aβ species transforming their size/conformation distribution. The aptitude of these molecules to impact metal-Aβ aggregation pathways, either via inhibition of Aβ aggregate formation, most importantly of oligomers, or disaggregation of preformed fibrils, could originate from their formation of complexes with metal-Aβ. Potentially, these molecules could direct metal-Aβ size/conformational states into alternative nontoxic unstructured oligomers, and control the geometry at the Aβ-ligated metal center for limited ROS formation to lessen the overall toxicity induced by metal-Aβ. Complexation between small molecules and Aβ/metal-Aβ has been observed by nuclear magnetic resonance spectroscopy (NMR) and ion mobility-mass spectrometry (IM-MS) pointing to molecular level interactions, validating the design strategy. In addition, these molecules exhibit other attractive properties, such as antioxidant capacity, prevention of ROS production, potential blood-brain barrier (BBB) permeability, and reduction of Aβ-/metal-Aβ-induced cytotoxicity, making them desirable tools for unraveling AD complexity. In this Account, we summarize the recent development of small molecules, via both rational design and the selection and modification of natural products, as tools for investigating metal-Aβ complexes, to advance our understanding of their relation to AD pathology.

Functionalized Derivatives of Benzo-Crown Ethers. Part 4. Antifungal Macrocyclic Supramolecular Complexes of Transition Metal Ions Acting as Lanosterol-14-α-Demethylase Ihibitors

PubMed Central

Barboiu, Mihai; Scozzafava, Andrea; Guran, Cornelia; Diaconescu, Paula; Bojin, Mihaela; Iluc, Vlad; Cot, Louis

1999-01-01

Poly- and mononuclear metal complexes of 2,3,11,12-bis[4-(10-aminodecylcarbonyl)]benzo-18- crown-6 (L) and Cu(II); Ni(II); Co(II) and Cr(III) have been synthesized and characterized by standard physico-chemical procedures. In the newly prepared complexes the crown moiety oxygen atoms of the macrocyclic host did not generally interact with metal ions, whereas the two amino groups of the ligand always did. Several of the newly synthesized compounds act as effective antifungal agents against Aspergillus and Candida spp., some of them showing activities comparable to ketoconazole, with minimum inhibitory concentrations in the range of 0.3−0.5 μg/mL. The mechanism of antifungal action of these coordination compounds is probably connected to an inhibition of lanosterol-14-α-demethylase, a metallo-enzyme playing a key role in sterol biosynthesis in fungi, bacteria and eukariotes. PMID:18475888

Photochemical Reactions of (n(5)-Pentamethylcyclpentadienyl)-Dicarbonyliron-Alkyl and -Silyl Complexes: Reversible Ethylene Insertion into an Iron-Silicon Bond and Implications for the Mechanism of Transition Metal-Catalyzed Hydrosilation of Alkenes.

DTIC Science & Technology

1985-12-11

RD-R162 462 PHOTOCHEMICAL REACTIONS OF(N(S)-P NTANETNYLCVCLPENTADIENYL)-DICARRONVLIR.. (U) MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY...34 Photochemical Reactions of (n5-Pentamethylcyclpentadienyl)- Dicarbonyliron-Alkyl and -Silyl Complexes: Reversible Ethylene Insertion into an Iron-Silicon Bond...Chemical Society) PHOTOCHEMICAL REACTIONS OF (n5-PENTAMETHYLCYCLOPENTADIENYL)- DICARBONYLIRON-ALKYL AND -SILYL COMPLEXES: REVERSIBLE ETHYLENE INSERTION INTO

Synthesis of platinum nanowheels using a bicellar template.

PubMed

Song, Yujiang; Dorin, Rachel M; Garcia, Robert M; Jiang, Ying-Bing; Wang, Haorong; Li, Peng; Qiu, Yan; van Swol, Frank; Miller, James E; Shelnutt, John A

2008-09-24

Disk-like surfactant bicelles provide a unique meso-structured reaction environment for templating the wet-chemical reduction of platinum(II) salt by ascorbic acid to produce platinum nanowheels. The Pt wheels are 496 +/-55 nm in diameter and possess thickened centers and radial dendritic nanosheets (about 2-nm in thickness) culminating in flared dendritic rims. The structural features of the platinum wheels arise from confined growth of platinum within the bilayer that is also limited at edges of the bicelles. The size of CTAB/FC7 bicelles is observed to evolve with the addition of Pt(II) complex and ascorbic acid. Synthetic control is demonstrated by varying the reaction parameters including metal salt concentration, temperature, and total surfactant concentration. This study opens up opportunities for the use of other inhomogeneous soft templates for synthesizing metals, metal alloys, and possibly semiconductors with complex nanostructures.

LABORATORY STUDIES ON THE REMEDIATION OF MERCURY-CONTAMINATED SOILS

EPA Science Inventory

Mercury, in contrast to other toxic metals, cycles between the atmosphere, land, and water. During this cycle, it undergoes a series of complex chemical and physical transformations. Because of these transformations, it is found in the environment not only as simple inorganic and...

In situ Raman cell for high pressure and temperature studies of metal and complex hydrides.

PubMed

Domènech-Ferrer, Roger; Ziegs, Frank; Klod, Sabrina; Lindemann, Inge; Voigtländer, Ralf; Dunsch, Lothar; Gutfleisch, Oliver

2011-04-15

A novel cell for in situ Raman studies at hydrogen pressures up to 200 bar and at temperatures as high as 400 °C is presented. This device permits in situ monitoring of the formation and decomposition of chemical structures under high pressure via Raman scattering. The performance of the cell under extreme conditions is stable as the design of this device compensates much of the thermal expansion during heating which avoids defocusing of the laser beam. Several complex and metal hydrides were analyzed to demonstrate the advantageous use of this in situ cell. Temperature calibration was performed by monitoring the structural phase transformation and melting point of LiBH(4). The feasibility of the cell in hydrogen atmosphere was confirmed by in situ studies of the decomposition of NaAlH(4) with added TiCl(3) at different hydrogen pressures and the decomposition and rehydrogenation of MgH(2) and LiNH(2). © 2011 American Chemical Society

Characterization of synergistic embryotoxicity of nickel and buprofezin in zebrafish.

PubMed

Ku, Tingting; Yan, Wei; Jia, Wuyao; Yun, Yang; Zhu, Na; Li, Guangke; Sang, Nan

2015-04-07

Multiple pollutants, usually at low levels, coexist and may interact in the environment. It is therefore important to analyze the toxicity of mixtures of coexisting chemicals to evaluate the potential ecological risk. Concern regarding the co-occurrence and combined bioeffects of heavy metals and organic insecticides in aquatic settings has existed for many years, but a clear understanding of the interactions between and potential combined toxicity of these chemicals remains elusive. In the present study, the combined effects of the heavy metal nickel (NiSO4) and insect growth regulator buprofezin on the induction of embryo toxicity in zebrafish were assessed. By applying nonlinear regression to the concentration-response data with each of the chemicals using the Hill and Langmuir functions and computing the predictions using the model of concentration addition (CA), we confirmed that NiSO4 and buprofezin acted together to produce synergistic embryotoxicity in zebrafish. Subsequently, we further found that the combination of NiSO4 and buprofezin formed a complex that facilitated the uptake of nickel (Ni) and buprofezin by the embryos. Following this, we clarified that an oxidative mechanism of the complex might underlie the synergistic embryotoxicity of NiSO4 and buprofezin.

Assessment of heavy metals contamination in sediments from three adjacent regions of the Yellow River using metal chemical fractions and multivariate analysis techniques.

PubMed

Ma, Xiaoling; Zuo, Hang; Tian, Mengjing; Zhang, Liyang; Meng, Jia; Zhou, Xuening; Min, Na; Chang, Xinyuan; Liu, Ying

2016-02-01

Metal chemical fractions obtained by optimized BCR three-stage extraction procedure and multivariate analysis techniques were exploited for assessing 7 heavy metals (Cr, Pb, Cd, Co, Cu, Zn and Ni) in sediments from Gansu province, Ningxia and Inner Mongolia Autonomous Regions of the Yellow River in Northern China. The results indicated that higher susceptibility and bioavailability of Cr and Cd with a strong anthropogenic source were due to their higher availability in the exchangeable fraction. A portion of Pb, Cd, Co, Zn, and Ni in reducible fraction may be due to the fact that they can form stable complexes with Fe and Mn oxides. Substantial amount of Pb, Co, Ni and Cu was observed as oxidizable fraction because of their strong affinity to the organic matters so that they can complex with humic substances in sediments. The high geo-accumulation indexes (I(geo)) for Cr and Cd showed their higher environmental risk to the aquatic biota. Principal component analysis (PCA) revealed that high toxic Cr and Cd in polluted sites (Cd in S10, S11 and Cr in S13) may be contributed to anthropogenic sources, it was consistent with the results of dual hierarchical clustering analysis (DHCA), which could give more details about contributing sources. Copyright © 2015 Elsevier Ltd. All rights reserved.

About complex refractive index of black Si

NASA Astrophysics Data System (ADS)

Pinčík, Emil; Brunner, Robert; Kobayashi, Hikaru; Mikula, Milan

2017-12-01

The paper deals with the complex refractive index in the IR light region of two types of samples (i) as prepared black silicon, and (ii) thermally oxidized black silicon (BSi) nano-crystalline specimens produced both by the surface structure chemical transfer method using catalytic Ag evaporated spots (as prepared sample) and by the catalytic Pt catalytic mesh (thermally oxidized sample). We present, compare, and discuss the values of the IR complex refractive index obtained by calculation using the Kramers-Krönig transformation. Results indicate that small differences between optical properties of as prepared black Si and thermally oxidized BSi are given by: (i) - oxidation procedure, (ii) - thickness of the formed black Si layer, mainly, not by utilization of different catalytic metals, and by iii) the different thickness. Contamination of the surface by different catalytic metals contributes almost equally to the calculated values of the corresponding complex refractive index.

Module degradation catalyzed by metal-encapsulation reactions

NASA Technical Reports Server (NTRS)

Gallagher, B. D.

1983-01-01

Four major properties are considered to be relevant in determining service life of a photovoltaic module: (1) Mechanical: creep resistance, modulus, tensile strength; (2) Optical: integrated transmission at 0.4 to 1.1 m wavelength; (3) Chemical: inertness with respect to metals and other components, retention of stabilizers, etc. and (4) Electrical; maintaining effective isolation of conductive components. These properties were measured after exposing polymer specimens to three types of accelerated stress: thermal, ultraviolet radiation and metal catalysts. These conditions give rise to a large number of complex interrelated free-radical reactions that result in the deterioration of polymeric materials.

Formation of high-temperature superconductor films during the nonstationary laser heating of liquid metal carboxylate solutions

NASA Astrophysics Data System (ADS)

Borman, V. D.; Dudko, S. A.; Sinitsyn, I. V.; Troian, V. I.; Filippov, E. A.

1989-01-01

It has been shown in earlier studies that high-temperature superconductor films can be produced through the decomposition of metal (Y, Ba, Cu) carboxylates in a liquid solution film. In the present study, the effect of nonstationary laser heating on the composition and properties of the complex oxide films formed by this method is examined with reference to experimental results obtained for YBa2Cu3O(x) films. It is shown that the chemical composition and properties of films formed in metal carboxylate solutions can be controlled by varying the time of laser heating.

BOND: A quantum of solace for nebular abundance determinations

NASA Astrophysics Data System (ADS)

Vale Asari, N.; Stasińska, G.; Morisset, C.; Cid Fernandes, R.

2017-11-01

The abundances of chemical elements other than hydrogen and helium in a galaxy are the fossil record of its star formation history. Empirical relations such as mass-metallicity relation are thus seen as guides for studies on the history and chemical evolution of galaxies. Those relations usually rely on nebular metallicities measured with strong-line methods, which assume that H II regions are a one- (or at most two-) parameter family where the oxygen abundance is the driving quantity. Nature is however much more complex than that, and metallicities from strong lines may be strongly biased. We have developed the method BOND (Bayesian Oxygen and Nitrogen abundance Determinations) to simultaneously derive oxygen and nitrogen abundances in giant H II regions by comparing strong and semi-strong observed emission lines to a carefully-defined, finely-meshed grid of photoionization models. Our code and results are public and available at http://bond.ufsc.br.

In situ ceramic layer growth on coated fuel particles dispersed in a zirconium metal matrix

DOE Office of Scientific and Technical Information (OSTI.GOV)

Terrani, Kurt A; Silva, G W Chinthaka M; Kiggans, Jim

2013-01-01

The extent and nature of the chemical interaction between the outermost coating layer of coated fuel particles embedded in zirconium metal during fabrication of metal matrix microencapsulated fuels was examined. Various particles with outermost coating layers of pyrocarbon, SiC, and ZrC have been investigated in this study. ZrC-Zr interaction was least substantial while PyC-Zr reaction can be exploited to produce a ZrC layer at the interface in an in situ manner. The thickness of the ZrC layer in the latter case can be controlled by adjusting the time and temperature during processing. The kinetics of ZrC layer growth is significantlymore » faster from what is predicted using literature carbon diffusivity data in ZrC. SiC-Zr interaction is more complex and results in formation of various chemical phases in a layered aggregate morphology at the interface.« less

Analysis of molecular structure, spectroscopic properties (FT-IR, micro-Raman and UV-vis) and quantum chemical calculations of free and ligand 2-thiopheneglyoxylic acid in metal halides (Cd, Co, Cu, Ni and Zn).

PubMed

Gökce, Halil; Bahçeli, Semiha

2013-12-01

In this study, molecular geometries, experimental vibrational wavenumbers, electronic properties and quantum chemical calculations of 2-thiopheneglyoxylic acid molecule, (C6H4O3S), and its metal halides (Cd, Co, Cu, Ni and Zn) which are used as pharmacologic agents have been investigated experimentally by FT-IR, micro-Raman and UV-visible spectroscopies and elemental analysis. Meanwhile the vibrational calculations were verified by DFT/B3LYP method with 6-311++G(d,p) and LANL2DZ basis sets in the ground state, for free TPGA molecule and its metal halide complexes, respectively, for the first time. The calculated fundamental vibrational frequencies for the title compounds are in a good agreement with the experimental data. Copyright © 2013 Elsevier B.V. All rights reserved.

NMR shielding calculations across the periodic table: diamagnetic uranium compounds. 2. Ligand and metal NMR.

PubMed

Schreckenbach, Georg

2002-12-16

In this and a previous article (J. Phys. Chem. A 2000, 104, 8244), the range of application for relativistic density functional theory (DFT) is extended to the calculation of nuclear magnetic resonance (NMR) shieldings and chemical shifts in diamagnetic actinide compounds. Two relativistic DFT methods are used, ZORA ("zeroth-order regular approximation") and the quasirelativistic (QR) method. In the given second paper, NMR shieldings and chemical shifts are calculated and discussed for a wide range of compounds. The molecules studied comprise uranyl complexes, [UO(2)L(n)](+/-)(q); UF(6); inorganic UF(6) derivatives, UF(6-n)Cl(n), n = 0-6; and organometallic UF(6) derivatives, UF(6-n)(OCH(3))(n), n = 0-5. Uranyl complexes include [UO(2)F(4)](2-), [UO(2)Cl(4)](2-), [UO(2)(OH)(4)](2-), [UO(2)(CO(3))(3)](4-), and [UO(2)(H(2)O)(5)](2+). For the ligand NMR, moderate (e.g., (19)F NMR chemical shifts in UF(6-n)Cl(n)) to excellent agreement [e.g., (19)F chemical shift tensor in UF(6) or (1)H NMR in UF(6-n)(OCH(3))(n)] has been found between theory and experiment. The methods have been used to calculate the experimentally unknown (235)U NMR chemical shifts. A large chemical shift range of at least 21,000 ppm has been predicted for the (235)U nucleus. ZORA spin-orbit appears to be the most accurate method for predicting actinide metal chemical shifts. Trends in the (235)U NMR chemical shifts of UF(6-n)L(n) molecules are analyzed and explained in terms of the calculated electronic structure. It is argued that the energy separation and interaction between occupied and virtual orbitals with f-character are the determining factors.

Synthesis, Characterization, and Antibacterial Studies of Mixed Ligand Dioxouranium Complexes with 8-Hydroxyquinoline and Some Amino Acids

PubMed Central

Patil, Sunil S.; Thakur, Ganesh A.; Shaikh, Manzoor M.

2011-01-01

Mixed ligand complexes of dioxouranium (VI) of the type [UO2(Q)(L)·2H2O] have been synthesized using 8-hydroxyquinoline (HQ) as a primary ligand and amino acids (HL) such as L-threonine, L-tryptophan, and L-isoleucine as secondary ligands. The metal complexes have been characterized by elemental analysis, electrical conductance, magnetic susceptibility measurements, and spectral and thermal studies. The electrical conductance studies of the complexes indicate their nonelectrolytic nature. Magnetic susceptibility measurements revealed diamagnetic nature of the complexes. Electronic absorption spectra of the complexes show intraligand and charge transfer transitions, respectively. Bonding of the metal ion through N- and O-donor atoms of the ligands is revealed by IR studies, and the chemical environment of the protons is confirmed by NMR studies. The thermal analysis data of the complexes indicate the presence of coordinated water molecules. The agar cup and tube dilution methods have been used to study the antibacterial activity of the complexes against the pathogenic bacteria S. aureus, C. diphtheriae, S. typhi, and E. coli. PMID:22389843

Interplay between theory and experiment: computational organometallic and transition metal chemistry.

PubMed

Lin, Zhenyang

2010-05-18

Computational and theoretical chemistry provide fundamental insights into the structures, properties, and reactivities of molecules. As a result, theoretical calculations have become indispensable in various fields of chemical research and development. In this Account, we present our research in the area of computational transition metal chemistry, using examples to illustrate how theory impacts our understanding of experimental results and how close collaboration between theoreticians and experimental chemists can be mutually beneficial. We begin by examining the use of computational chemistry to elucidate the details of some unusual chemical bonds. We consider the three-center, two-electron bonding in titanocene sigma-borane complexes and the five-center, four-electron bonding in a rhodium-bismuth complex. The bonding in metallabenzene complexes is also examined. In each case, theoretical calculations provide particular insight into the electronic structure of the chemical bonds. We then give an example of how theoretical calculations aided the structural determination of a kappa(2)-N,N chelate ruthenium complex formed upon heating an intermediate benzonitrile-coordinated complex. An initial X-ray diffraction structure proposed on the basis of a reasonable mechanism appeared to fit well, with an apparently acceptable R value of 0.0478. But when DFT calculations were applied, the optimized geometry differed significantly from the experimental data. By combining experimental and theoretical outlooks, we posited a new structure. Remarkably, a re-refining of the X-ray diffraction data based on the new structure resulted in a slightly lower R value of 0.0453. We further examine the use of computational chemistry in providing new insight into C-H bond activation mechanisms and in understanding the reactivity properties of nucleophilic boryl ligands, addressing experimental difficulties with calculations and vice versa. Finally, we consider the impact of theoretical insights in three very specific experimental studies of chemical reactions, illustrating how theoretical results prompt further experimental studies: (i) diboration of aldehydes catalyzed by copper(I) boryl complexes, (ii) ruthenium-catalyzed C-H amination of arylazides, and (iii) zinc reduction of a vinylcarbyne complex. The concepts and examples presented here are intended for nonspecialists, particularly experimentalists. Together, they illustrate some of the achievements that are possible with a fruitful union of experiment and theory.

Towards Rational Design of Functional Fluoride and Oxyfluoride Materials from First Principles

NASA Astrophysics Data System (ADS)

Charles, Nenian

Complex transition metal compounds (TMCs) research has produced functional materials with a range of properties, including ferroelectricity, colossal magnetoresistance, nonlinear optical activity and high-temperature superconductivity. Conventional routes to tune properties in transition metal oxides, for example, have relied primarily on cation chemical substitution and interfacial effects in thin film heterostructures. In heteroanionic TMCs, exhibiting two chemically distinct anions coordinating the same or different cations, engineering of the anion sub-lattice for property control is a promising alternative approach. The presence of multiple anions provides additional design variables, such as anion order, that are absent in homoanionic counterparts. The more complex structural and chemical phase space of heteroanionic materials provides a unique opportunity to realize enhanced or unanticipated electronic, optical, and magnetic responses. Although there is growing interest in heteroanionic materials, and synthetic and characterization advances are occurring for these materials, the crystal-chemistry principles for realizing structural and property control are only slowing emerging. This dissertation employs anion engineering to investigate phenomena in transition metal fluorides and oxyfluorides compounds using first principles density functional theory calculations. Oxyfluorides are particularly intriguing owing their tendency to stabilize highly ordered anion sublattices as well as the potential to combine the advantageous properties of transition metal oxides and fluorides. This work 1) addresses the challenges of studying fluorides and oxyfluorides using first principles calculations; 2) evaluates the feasibility of using external stimuli, such as epitaxial strain and hydrostatic pressure, to control properties of fluorides and oxyfluorides; and 3) formulates a computational workflow based on multiple levels of theory and computation to elucidate structure-property relationships and anion-order descriptors. The insights gained in this work advance the understanding of oxide-fluoride anion engineered materials and we anticipate that it will motivate novel experimental efforts and materials by design in the future.

Study of the chemical chelates and anti-microbial effect of some metal ions in nanostructural form on the efficiency of antibiotic therapy "norfloxacin drug"

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; El-Hawary, W. F.; Mohamed, Mahmoud A.

2012-04-01

This paper has reviewed the chemical and biological impact resulting from the interaction between norfloxacin (norH) antibiotic drug and two lanthanide (lanthanum(III) and cerium(III)) metal ions, which prepared in normal and nano-features. La(III) and Ce(III) complexes were synthesized with chemical formulas [La(nor)3]·3H2O and [Ce(nor)3]·2H2O. Lanthanum and cerium(III) ions coordinated toward norH with a hexadentate geometry. The norH acts as deprotonated bidentate ligand through the oxygen atom of carbonyl group and the oxygen atom of carboxylic group. Elemental analysis, FT-IR spectral, electrical conductivity, thermal analysis (TG/DTA), X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) measurements have been used to characterize the mentioned isolated complexes. The Coats-Redfern and Horowitz-Metzger integral methods are used to estimate the kinetic parameters for the major successive steps detectable in the TG curve. The brightness side in this study is to take advantage for the preparation and characterization of single phases of La2O3 and CeO2 nanoparticles using urea as precursors via a solid-state decomposition procedure. The norH ligand in comparison with both cases (normal and nano-particles) of lanthanide complexes were screened against for antibacterial (Escherichia Coli, Staphylococcus Aureus, Bacillus subtilis and Pseudomonas aeruginosa) and antifungal (Aspergillus Flavus and Candida Albicans) activities. The highest antibacterial and antifungal activities data of the nano-particles complexes were observed with more potent than the free norH and normal lanthanide complexes.

Structural, theoretical and corrosion inhibition studies on some transition metal complexes derived from heterocyclic system

NASA Astrophysics Data System (ADS)

Gupta, Shraddha Rani; Mourya, Punita; Singh, M. M.; Singh, Vinod P.

2017-06-01

A Schiff base, (E)-N‧-((1H-indol-3-yl)methylene)-2-aminobenzohydrazide (Iabh) and its Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes have been synthesized. These compounds have been characterized by different physico-chemical and spectroscopic tools (UV-Vis, IR, NMR and ESI-Mass). The molecular structure of Iabh is determined by single crystal X-ray diffraction technique. The ligand Iabh displays E-configuration about the >Cdbnd N- bond. The structure of ligand is stabilized by intra-molecular H-bonding. In all the metal complexes the ligand coordinates through azomethine-N and carbonyl-O resulting a distorted octahedral geometry for Mn(II), Co(II) and Cu(II) complexes in which chloride ions occupy axial positions. Ni(II) and Zn(II) complexes, however, form 4-coordinate distorted square planer and tetrahedral geometry around metal ion, respectively. The structures of the complexes have been satisfactorily modeled by calculations based on density functional theory (DFT) and time dependent-DFT (TD-DFT). The corrosion inhibition study of the compounds have been performed against mild steel in 0.5 M H2SO4 solution at 298 K by using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). They show appreciable corrosion inhibition property.

Antimicrobial Polymer

DOEpatents

McDonald, William F.; Wright, Stacy C.; Taylor, Andrew C.

2004-09-28

A polymeric composition having antimicrobial properties and a process for rendering the surface of a substrate antimicrobial are disclosed. The polymeric composition comprises a crosslinked chemical combination of (i) a polymer having amino group-containing side chains along a backbone forming the polymer, (ii) an antimicrobial agent selected from metals, metal alloys, metal salts, metal complexes and mixtures thereof, and (iii) a crosslinking agent containing functional groups capable of reacting with the amino groups. In one example embodiment, the polymer is a polyamide formed from a maleic anhydride or maleic acid ester monomer and alkylamines thereby producing a polyamide having amino substituted alkyl chains on one side of the polyamide backbone; the crosslinking agent is a phosphine having the general formula (A).sub.3 P wherein A is hydroxyalkyl; and the metallic antimicrobial agent is selected from chelated silver ions, silver metal, chelated copper ions, copper metal, chelated zinc ions, zinc metal and mixtures thereof.

Predicting the potentials, solubilities and stabilities of metal-acetylacetonates for non-aqueous redox flow batteries using density functional theory calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kucharyson, J. F.; Cheng, L.; Tung, S. O.

New active materials are needed to improve the performance and reduce the cost of non-aqueous redox flow batteries (RFBs) for grid-scale energy storage applications. Efforts to develop better performing materials, which have largely been empirical, would benefit from a better understanding of relationships between structural, electronic and RFB-relevant functional properties. This paper focuses on metal-acetylacetonates, a class of metal coordination complexes that has shown promise for use in RFBs, and describes correlations between their experimentally measured standard potentials, solubilities, and stabilities (cycle lifes), and selected chemical, structural and electronic properties determined from Density Functional Theory (DFT) calculations. The training setmore » consisted of 16 complexes including 5 different metals and 11 different substituents on the acetylacetonate ligand. Standard potentials for those compounds were calculated and are in good agreement with experimentally measured results. A predictive equation based on the solvation energies and dipole moments, two easily computed properties, reasonably modeled the experimentally determined solubilities. Importantly, we were able to identify a descriptor for the stability of acetylacetonates. The experimentally determined stability, quantified as the cycle life to a given degree of degradation, correlated with the percentage of the highest occupied (HOMO) or lowest unoccupied molecular orbital (LUMO) on the metal of the complex. This percentage is influenced by the degree of ligand innocence (irreducibility), and complexes with the most innocent ligands yielded the most stable redox reactions. To this end, VO(acetylacetonate)(2) and Fe(acetylacetonate)(3), with nearly 80% of the HOMO and LUMO on the metal, possessed the most stable oxidation and reduction half-reactions, respectively. The structure-function relationships and correlations presented in this paper could be used to predict new, highly soluble and stable complexes for RFB applications.« less

Unifying Exchange Sensitivity in Transition-Metal Spin-State Ordering and Catalysis through Bond Valence Metrics.

PubMed

Gani, Terry Z H; Kulik, Heather J

2017-11-14

Accurate predictions of spin-state ordering, reaction energetics, and barrier heights are critical for the computational discovery of open-shell transition-metal (TM) catalysts. Semilocal approximations in density functional theory, such as the generalized gradient approximation (GGA), suffer from delocalization error that causes them to overstabilize strongly bonded states. Descriptions of energetics and bonding are often improved by introducing a fraction of exact exchange (e.g., erroneous low-spin GGA ground states are instead correctly predicted as high-spin with a hybrid functional). The degree of spin-splitting sensitivity to exchange can be understood based on the chemical composition of the complex, but the effect of exchange on reaction energetics within a single spin state is less well-established. Across a number of model iron complexes, we observe strong exchange sensitivities of reaction barriers and energies that are of the same magnitude as those for spin splitting energies. We rationalize trends in both reaction and spin energetics by introducing a measure of delocalization, the bond valence of the metal-ligand bonds in each complex. The bond valence thus represents a simple-to-compute property that unifies understanding of exchange sensitivity for catalytic properties and spin-state ordering in TM complexes. Close agreement of the resulting per-metal-organic-bond sensitivity estimates, together with failure of alternative descriptors demonstrates the utility of the bond valence as a robust descriptor of how differences in metal-ligand delocalization produce differing relative energetics with exchange tuning. Our unified description explains the overall effect of exact exchange tuning on the paradigmatic two-state FeO + /CH 4 reaction that combines challenges of spin-state and reactivity predictions. This new descriptor-sensitivity relationship provides a path to quantifying how predictions in transition-metal complex screening are sensitive to the method used.

The role of metals in protein conformational disorders - The case of prion protein and Aβ -peptide

NASA Astrophysics Data System (ADS)

De Santis, E.; Minicozzi, V.; Morante, S.; Rossi, G. C.; Stellato, F.

2016-02-01

Protein conformational disorders are members of a vast class of pathologies in which endogenous proteins or peptides undergo a misfolding process by switching from the physiological soluble configuration to a pathological fibrillar insoluble state. An important, but not yet fully elucidated, role in the process appears to be played by transition metal ions, mainly copper and zinc. X-ray absorption spectroscopy is one of the most suitable techniques for the structural characterization of biological molecules in complex with metal. Owing to its chemical selectivity and sensitivity to the local atomic geometry around the absorber, it can be successfully used to study the environment of metal ions in complex with proteins and peptides in physiological conditions. In this paper we present X-ray absorption spectroscopy studies of the metal ions coordination modes in systems where metals are complexed with specific amyloidogenic proteins and peptides. In particular, we show results concerning the Amyloid β peptide, that is involved in Alzheimer's disease, and the Prion protein, that is responsible for the Transmissible Spongiform Encephalopathy. Our findings suggest that the copper and zinc ions may play a crucial role in the aggregation and fibril formation process of these two biomolecules. Elucidating this kind of interaction could be a key preliminary step before any viable therapy can be conceived or designed.

Soluble collagen approach to a combination tannage mechanism

USDA-ARS?s Scientific Manuscript database

Although complex salts of Cr(III) sulfate are currently the most effective tanning agents, salts of other metals, including aluminum, have been used either alone or in combination with vegetable tannins or other organic chemicals. In the present study, the interactions of aluminum sulfate, and quebr...

Bioinorganic Chemical Modeling of Dioxygen-Activating Copper Proteins.

ERIC Educational Resources Information Center

Karlin, Kenneth D.; Gultneh, Yilma

1985-01-01

Discusses studies done in modeling the copper centers in the proteins hemocyanin (a dioxygen carrier), tyrosinase, and dopamine beta-hydroxylase. Copper proteins, model approach in copper bioinorganic chemistry, characterization of reversible oxygen carriers and dioxygen-metal complexes, a copper mono-oxygenase model reaction, and other topics are…

A Bimetallic Nickel-Gallium Complex Catalyzes CO2 Hydrogenation via the Intermediacy of an Anionic d10 Nickel Hydride.

PubMed

Cammarota, Ryan C; Vollmer, Matthew V; Xie, Jing; Ye, Jingyun; Linehan, John C; Burgess, Samantha A; Appel, Aaron M; Gagliardi, Laura; Lu, Connie C

2017-10-11

Large-scale CO 2 hydrogenation could offer a renewable stream of industrially important C 1 chemicals while reducing CO 2 emissions. Critical to this opportunity is the requirement for inexpensive catalysts based on earth-abundant metals instead of precious metals. We report a nickel-gallium complex featuring a Ni(0)→Ga(III) bond that shows remarkable catalytic activity for hydrogenating CO 2 to formate at ambient temperature (3150 turnovers, turnover frequency = 9700 h -1 ), compared with prior homogeneous Ni-centered catalysts. The Lewis acidic Ga(III) ion plays a pivotal role in stabilizing catalytic intermediates, including a rare anionic d 10 Ni hydride. Structural and in situ characterization of this reactive intermediate support a terminal Ni-H moiety, for which the thermodynamic hydride donor strength rivals those of precious metal hydrides. Collectively, our experimental and computational results demonstrate that modulating a transition metal center via a direct interaction with a Lewis acidic support can be a powerful strategy for promoting new reactivity paradigms in base-metal catalysis.

Pushing the frontiers of first-principles based computer simulations of chemical and biological systems.

PubMed

Brunk, Elizabeth; Ashari, Negar; Athri, Prashanth; Campomanes, Pablo; de Carvalho, F Franco; Curchod, Basile F E; Diamantis, Polydefkis; Doemer, Manuel; Garrec, Julian; Laktionov, Andrey; Micciarelli, Marco; Neri, Marilisa; Palermo, Giulia; Penfold, Thomas J; Vanni, Stefano; Tavernelli, Ivano; Rothlisberger, Ursula

2011-01-01

The Laboratory of Computational Chemistry and Biochemistry is active in the development and application of first-principles based simulations of complex chemical and biochemical phenomena. Here, we review some of our recent efforts in extending these methods to larger systems, longer time scales and increased accuracies. Their versatility is illustrated with a diverse range of applications, ranging from the determination of the gas phase structure of the cyclic decapeptide gramicidin S, to the study of G protein coupled receptors, the interaction of transition metal based anti-cancer agents with protein targets, the mechanism of action of DNA repair enzymes, the role of metal ions in neurodegenerative diseases and the computational design of dye-sensitized solar cells. Many of these projects are done in collaboration with experimental groups from the Institute of Chemical Sciences and Engineering (ISIC) at the EPFL.

Mechanistic Insights and Computational Design of Transition-Metal Catalysts for Hydrogenation and Dehydrogenation Reactions.

PubMed

Chen, Xiangyang; Yang, Xinzheng

2016-10-01

Catalytic hydrogenation and dehydrogenation reactions are fundamentally important in chemical synthesis and industrial processes, as well as potential applications in the storage and conversion of renewable energy. Modern computational quantum chemistry has already become a powerful tool in understanding the structures and properties of compounds and elucidating mechanistic insights of chemical reactions, and therefore, holds great promise in the design of new catalysts. Herein, we review our computational studies on the catalytic hydrogenation of carbon dioxide and small organic carbonyl compounds, and on the dehydrogenation of amine-borane and alcohols with an emphasis on elucidating reaction mechanisms and predicting new catalytic reactions, and in return provide some general ideas for the design of high-efficiency, low-cost transition-metal complexes for hydrogenation and dehydrogenation reactions. © 2016 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A simple scheme to determine potential aquatic metal toxicity from mining wastes

USGS Publications Warehouse

Wildeman, T.R.; Smith, K.S.; Ranville, J.F.

2007-01-01

A decision tree (mining waste decision tree) that uses simple physical and chemical tests has been developed to determine whether effluent from mine waste material poses a potential toxicity threat to the aquatic environment. For the chemical portion of the tree, leaching tests developed by the United States Geological Survey, the Colorado Division of Minerals and Geology (Denver, CO), and a modified 1311 toxicity characteristic leaching procedure (TCLP) test of the United States Environmental Protection Agency have been extensively used as a surrogate for readily available metals that can be released into the environment from mining wastes. To assist in the assessment, element concentration pattern graphs (ECPG) are produced that compare concentrations of selected groups of elements from the three leachates and any water associated with the mining waste. The MWDT makes a distinction between leachates or waters with pH less than or greater than 5. Generally, when the pH values are below 5, the ECPG of the solutions are quite similar, and potential aquatic toxicity from cationic metals, such as Pb, Cu, Zn, Cd, and Al, is assumed. Below pH 5, these metals are mostly dissolved, generally are not complexed with organic or inorganic ligands, and hence are more bioavailable. Furthermore, there is virtually no carbonate alkalinity at pH less than 5. All of these factors promote metal toxicity to aquatic organisms. On the other hand, when the pH value of the water or the leachates is above 5, the ECPG from the solutions are variable, and inferred aquatic toxicity depends on factors in addition to the metals released from the leaching tests. Hence, leachates and waters with pH above 5 warrant further examination of their chemical composition. Physical ranking criteria provide additional information, particularly in areas where waste piles exhibit similar chemical rankings. Rankings from physical and chemical criteria generally are not correlated. Examples of how this decision tree has been applied in assessing mine sites are discussed. Copyright ?? Taylor & Francis Group, LLC.

Synthesis and Characterization of Cluster-Derived Supported Bimetallic Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adams, Richard D; Amiridis, Michael D

2008-10-10

New procedures have been developed for synthesizing di- and tri-metallic cluster complexes. The chemical properties of the new complexes have been investigated, particularly toward the activation of molecular hydrogen. These complexes were then converted into bi- and tri-metallic nanoparticles on silica and alumina supports. These nanoparticles were characterized by electron microscopy and were then tested for their ability to produce catalytic hydrogenation of unsaturated hydrocarbons and for the preferential oxidation of CO in the presence of hydrogen. The bi- and tri-metallic nanoparticles exhibited far superior activity and selectivity as hydrogenation catalysts when compared to the individual metallic components. It wasmore » found that the addition of tin greatly improved the selectivity of the catalysts for the hydrogenation of polyolefins. The addition of iron improves the catalysts for the selective oxidation of CO by platinum in the presence of hydrogen. The observations should lead to the development of lower cost routes to molecules that can be used to produce polymers and plastics for use by the general public and for procedures to purify hydrogen for use as an alternative energy in the hydrogen economy of the future.« less

Engineering the oxygen coordination in digital superlattices

NASA Astrophysics Data System (ADS)

Cook, Seyoung; Andersen, Tassie K.; Hong, Hawoong; Rosenberg, Richard A.; Marks, Laurence D.; Fong, Dillon D.

2017-12-01

The oxygen sublattice in complex oxides is typically composed of corner-shared polyhedra, with transition metals at their centers. The electronic and chemical properties of the oxide depend on the type and geometric arrangement of these polyhedra, which can be controlled through epitaxial synthesis. Here, we use oxide molecular beam epitaxy to create SrCoOx:SrTiO3 superlattices with tunable oxygen coordination environments and sublattice geometries. Using synchrotron X-ray scattering in combination with soft X-ray spectroscopy, we find that the chemical state of Co can be varied with the polyhedral arrangement, with higher Co oxidation states increasing the valence band maximum. This work demonstrates a new strategy for engineering unique electronic structures in the transition metal oxides using short-period superlattices.

Final Technical Report: Metal—Organic Surface Catalyst for Low-temperature Methane Oxidation: Bi-functional Union of Metal—Organic Complex and Chemically Complementary Surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tait, Steven L.

Stabilization and chemical control of transition metal centers is a critical problem in the advancement of heterogeneous catalysts to next-generation catalysts that exhibit high levels of selectivity, while maintaining strong activity and facile catalyst recycling. Supported metal nanoparticle catalysts typically suffer from having a wide range of metal sites with different coordination numbers and varying chemistry. This project is exploring new possibilities in catalysis by combining features of homogeneous catalysts with those of heterogeneous catalysts to develop new, bi-functional systems. The systems are more complex than traditional heterogeneous catalysts in that they utilize sequential active sites to accomplish the desiredmore » overall reaction. The interaction of metal—organic catalysts with surface supports and their interactions with reactants to enable the catalysis of critical reactions at lower temperatures are at the focus of this study. Our work targets key fundamental chemistry problems. How do the metal—organic complexes interact with the surface? Can those metal center sites be tuned for selectivity and activity as they are in the homogeneous system by ligand design? What steps are necessary to enable a cooperative chemistry to occur and open opportunities for bi-functional catalyst systems? Study of these systems will develop the concept of bringing together the advantages of heterogeneous catalysis with those of homogeneous catalysis, and take this a step further by pursuing the objective of a bi-functional system. The use of metal-organic complexes in surface catalysts is therefore of interest to create well-defined and highly regular single-site centers. While these are not likely to be stable in the high temperature environments (> 300 °C) typical of industrial heterogeneous catalysts, they could be applied in moderate temperature reactions (100-300 °C), made feasible by lowering reaction temperatures by better catalyst control. They also serve as easily tuned model systems for exploring the chemistry of single-site transition metals and tandem catalysts that could then be developed into a zeolite or other stable support structures. In this final technical report, three major advances our described that further these goals. The first is a study demonstrating the ability to tune the oxidation state of V single-site centers on a surface by design of the surrounding ligand field. The synthesis of the single-site centers was developed in a previous reporting period of this project and this new advance shows a distinct new ability of the systems to have a designed oxidation state of the metal center. Second, we demonstrate metal complexation at surfaces using vibrational spectroscopy and also show a metal replacement reaction on Ag surfaces. Third, we demonstrate a surface-catalyzed dehydrocyclization reaction important for metal-organic catalyst design at surfaces.« less

Computational Investigations of Potential Energy Function Development for Metal--Organic Framework Simulations, Metal Carbenes, and Chemical Warfare Agents

NASA Astrophysics Data System (ADS)

Cioce, Christian R.

Metal-Organic Frameworks (MOFs) are three-dimensional porous nanomaterials with a variety of applications, including catalysis, gas storage and separation, and sustainable energy. Their potential as air filtration systems is of interest for designer carbon capture materials. The chemical constituents (i.e. organic ligands) can be functionalized to create rationally designed CO2 sequestration platforms, for example. Hardware and software alike at the bleeding edge of supercomputing are utilized for designing first principles-based molecular models for the simulation of gas sorption in these frameworks. The classical potentials developed herein are named PHAST --- Potentials with High Accuracy, Speed, and Transferability, and thus are designed via a "bottom-up" approach. Specifically, models for N2 and CH4 are constructed and presented. Extensive verification and validation leads to insights and range of applicability. Through this experience, the PHAST models are improved upon further to be more applicable in heterogeneous environments. Given this, the models are applied to reproducing high level ab initio energies for gas sorption trajectories of helium atoms in a variety of rare-gas clusters, the geometries of which being representative of sorption-like environments commonly encountered in a porous nanomaterial. This work seeks to push forward the state of classical and first principles materials modeling. Additionally, the characterization of a new type of tunable radical metal---carbene is presented. Here, a cobalt(II)---porphyrin complex, [Co(Por)], was investigated to understand its role as an effective catalyst in stereoselective cyclopropanation of a diazoacetate reagent. Density functional theory along with natural bond order analysis and charge decomposition analysis gave insight into the electronics of the catalytic intermediate. The bonding pattern unveiled a new class of radical metal---carbene complex, with a doublet cobalt into which a triplet carbene sigma donates, and subsequent back-bonding occurs into a pi* antibonding orbital. This is a different type of interaction not seen in the three existing classes of metal-carbene complexes, namely Fischer, Schrock, and Grubbs. Finally, the virtual engineering of enhanced chemical warfare agent (CWA) detection systems is discussed. As part of a U.S. Department of Defense supported research project, in silico chemical modifications to a previously synthesized zinc-porphyrin, ZnCS1, were made to attempt to achieve preferential binding of the nerve agent sarin versus its simulant, DIMP (diisopropyl methylphosphonate). Upon modification, a combination of steric effects and induced hydrogen bonding allowed for the selective binding of sarin. The success of this work demonstrates the role that high performance computing can play in national security research, without the associated costs and high security required for experimentation.

Waveguide analysis of heat-drawn and chemically etched probe tips for scanning near-field optical microscopy.

PubMed

Moar, Peter N; Love, John D; Ladouceur, François; Cahill, Laurence W

2006-09-01

We analyze two basic aspects of a scanning near-field optical microscope (SNOM) probe's operation: (i) spot-size evolution of the electric field along the probe with and without a metal layer, and (ii) a modal analysis of the SNOM probe, particularly in close proximity to the aperture. A slab waveguide model is utilized to minimize the analytical complexity, yet provides useful quantitative results--including losses associated with the metal coating--which can then be used as design rules.

Iron piano-stool complexes containing NHC ligands outfitted with pendent arms: synthesis, characterization, and screening for catalytic transfer hydrogenation

Treesearch

Parthapratim Das; Thomas Elder; William W. Brennessel; Stephen C. Chmely

2016-01-01

Catalysis is a fundamental technology that is widely used in the food, petrochemical, pharmaceutical, and agricultural sectors to produce chemical products on an industrial scale. Well-defined molecular organometallic species are a cornerstone of catalytic methodology, and the activity and selectivity of these complexes can be modulated by judicious choice of metal and...

Redox-inactive metal ions promoted the catalytic reactivity of non-heme manganese complexes towards oxygen atom transfer.

PubMed

Choe, Cholho; Yang, Ling; Lv, Zhanao; Mo, Wanling; Chen, Zhuqi; Li, Guangxin; Yin, Guochuan

2015-05-21

Redox-inactive metal ions can modulate the reactivity of redox-active metal ions in a variety of biological and chemical oxidations. Many synthetic models have been developed to help address the elusive roles of these redox-inactive metal ions. Using a non-heme manganese(II) complex as the model, the influence of redox-inactive metal ions as a Lewis acid on its catalytic efficiency in oxygen atom transfer was investigated. In the absence of redox-inactive metal ions, the manganese(II) catalyst is very sluggish, for example, in cyclooctene epoxidation, providing only 9.9% conversion with 4.1% yield of epoxide. However, addition of 2 equiv. of Al(3+) to the manganese(II) catalyst sharply improves the epoxidation, providing up to 97.8% conversion with 91.4% yield of epoxide. EPR studies of the manganese(II) catalyst in the presence of an oxidant reveal a 16-line hyperfine structure centered at g = 2.0, clearly indicating the formation of a mixed valent di-μ-oxo-bridged diamond core, Mn(III)-(μ-O)2-Mn(IV). The presence of a Lewis acid like Al(3+) causes the dissociation of this diamond Mn(III)-(μ-O)2-Mn(IV) core to form monomeric manganese(iv) species which is responsible for improved epoxidation efficiency. This promotional effect has also been observed in other manganese complexes bearing various non-heme ligands. The findings presented here have provided a promising strategy to explore the catalytic reactivity of some di-μ-oxo-bridged complexes by adding non-redox metal ions to in situ dissociate those dimeric cores and may also provide clues to understand the mechanism of methane monooxygenase which has a similar diiron diamond core as the intermediate.

Preparation, spectral, X-ray powder diffraction and computational studies and genotoxic properties of new azo-azomethine metal chelates

NASA Astrophysics Data System (ADS)

Bitmez, Şirin; Sayin, Koray; Avar, Bariş; Köse, Muhammet; Kayraldız, Ahmet; Kurtoğlu, Mükerrem

2014-11-01

A new tridentate azo-azomethine ligand, N‧-[{2-hydroxy-5-[(4-nitrophenyl)diazenyl]phenyl}methylidene]benzohydrazidemonohydrate, (sbH·H2O) (1), is prepared by condensation of benzohydrazide and 2-hydroxy-5-[(4-nitrophenyl)diazenyl]benzaldehyde (a) with treatment of a solution of diazonium salt of p-nitroaniline and 2-hydroxybenzaldehyde in EtOH. The five coordination compounds, [Co(sb)2]·4H2O (2), [Ni(sb)2]·H2O (3), [Cu(sb)2]·4H2O (4), [Zn(sb)2]·H2O (5) and [Cd(sb)2]·H2O (6) are prepared by reacting the Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) ions with the ligand. The structures of the compounds are elucidated from the elemental analyses data and spectroscopic studies. It is found the ligand acts as a tridentate bending through phenolic and carbonyl oxygens and nitrogen atom of the Cdbnd Nsbnd group similar to the most of salicylaldimines. Comparison of the infrared spectra of the ligand and its metal complexes confirm that azo-Schiff base behaves as a monobasic tridentate ligand towards the central metal ion with an ONO donor sequence. Upon complexation with the ligand, the Cd(II), and Zn(II) ions form monoclinic structures, while Co(II), Cu(II) and Ni(II) ions form orthorhombic structures. Quantum chemical calculations are performed on tautomers and its metal chelates by using DFT/B3LYP method. Most stable tautomer is determined as tautomer (1a). The geometrical parameters of its metal chelates are obtained as theoretically. The NLO properties of tautomer (1a) and its metal complexes are investigated. Finally, the ligand and its metal complexes are assessed for their genotoxicity.

DEVELOPING AZO AND FORMAZAN DYES BASED ON ENVIRONMENTAL CONSIDERATIONS: SALMONELLA MUTAGENICITY

EPA Science Inventory

Abstract
In previous papers, the synthesis and chemical properties of iron-complexed azo and formazan dyes were reported. In this regard, it was shown that in certain cases iron could be substituted for the traditionally used metals, chromium and cobalt, without having an adve...

Chemical and Physical Analysis Methods for Characterizing Tire Crumb Rubber Used in Synthetic Turf Fields

EPA Science Inventory

Tire crumb rubber from recycled tires is widely used as infill material in synthetic turf fields in the United States. Recycled crumb rubber is a complex and potentially variable matrix with many metal, VOC, and SVOC constituents, presenting challenges for characterization and ex...

PSMA-Targeted Polygadolinium Clusters: A Novel Agent for Imaging Prostate Cancer

DTIC Science & Technology

2007-01-01

Los Alamos, NM, February 23, 2006 “A Smorgasbord of Half-Sandwiches and Meatballs of the Early Transition Metals, Lanthanides, and Bismuth” 62. Mark...Twain Section Meeting, American Chemical Society, April 1, 2005, Culver-Stockton College, MO. “New Vistas in Half-Sandwich and Meatball Complexes

Ambient Air Pollution and Increases in Blood Pressure: Role for biological constituents of particulate matter

EPA Science Inventory

Particulate matter (PM) is a complex mixture of extremely small particles and liquid droplets made up of a number of components including elemental carbon, organic chemicals, metals, acids (such as nitrates and sulfates), and soil and dust particles. Epidemiological studies con...

Structural plasticity: how intermetallics deform themselves in response to chemical pressure, and the complex structures that result.

PubMed

Berns, Veronica M; Fredrickson, Daniel C

2014-10-06

Interfaces between periodic domains play a crucial role in the properties of metallic materials, as is vividly illustrated by the way in which the familiar malleability of many metals arises from the formation and migration of dislocations. In complex intermetallics, such interfaces can occur as an integral part of the ground-state crystal structure, rather than as defects, resulting in such marvels as the NaCd2 structure (whose giant cubic unit cell contains more than 1000 atoms). However, the sources of the periodic interfaces in intermetallics remain mysterious, unlike the dislocations in simple metals, which can be associated with the exertion of physical stresses. In this Article, we propose and explore the concept of structural plasticity, the hypothesis that interfaces in complex intermetallic structures similarly result from stresses, but ones that are inherent in a defect-free parent structure, rather than being externally applied. Using DFT-chemical pressure analysis, we show how the complex structures of Ca2Ag7 (Yb2Ag7 type), Ca14Cd51 (Gd14Ag51 type), and the 1/1 Tsai-type quasicrystal approximant CaCd6 (YCd6 type) can all be traced to large negative pressures around the Ca atoms of a common progenitor structure, the CaCu5 type with its simple hexagonal 6-atom unit cell. Two structural paths are found by which the compounds provide relief to the Ca atoms' negative pressures: a Ca-rich pathway, where lower coordination numbers are achieved through defects eliminating transition metal (TM) atoms from the structure; and a TM-rich path, along which the addition of spacer Cd atoms provides the Ca coordination environments greater independence from each other as they contract. The common origins of these structures in the presence of stresses within a single parent structure highlights the diverse paths by which intermetallics can cope with competing interactions, and the role that structural plasticity may play in navigating this diversity.

From which soil metal fractions Fe, Mn, Zn and Cu are taken up by olive trees (Olea europaea L., cv. 'Chondrolia Chalkidikis') in organic groves?

PubMed

Chatzistathis, T; Papaioannou, A; Gasparatos, D; Molassiotis, A

2017-12-01

Organic farming has been proposed as an alternative agricultural system to help solve environmental problems, like the sustainable management of soil micronutrients, without inputs of chemical fertilizers. The purposes of this study were: i) to assess Fe, Mn, Zn and Cu bioavailability through the determination of sequentially extracted chemical forms (fractions) and their correlation with foliar micronutrient concentrations in mature organic olive (cv. 'Chondrolia Chalkidikis') groves; ii) to determine the soil depth and the available forms (fractions) by which the 4 metals are taken up by olive trees. DTPA extractable (from the soil layers 0-20, 20-40 and 40-60 cm) and foliar micronutrient concentrations were determined in two organic olive groves. Using the Tessier fractionation, five fractions, for all the metals, were found: exchangeable, bound to carbonates (acid-soluble), bound to Fe-Mn oxides (reducible), organic (oxidizable), as well as residual form. Our results indicated that Fe was taken up by the olive trees as organic complex, mainly from the soil layer 40-60 cm. Manganese was taken up from the exchangeable fraction (0-20 cm); Zinc was taken up as organic complex from the layers 0-20 and 40-60 cm, as well as in the exchangeable form from the upper 20 cm. Copper was taken up from the soil layers 0-20 and 40-60 cm as soluble organic complex, and as exchangeable ion from the upper 20 cm. Our data reveal the crucial role of organic matter to sustain metal (Fe, Zn and Cu) uptake -as soluble complexes-by olive trees, in mature organic groves grown on calcareous soils; it is also expected that these data will constitute a thorough insight and useful tool towards a successful nutrient and organic C management for organic olive groves, since no serious nutritional deficiencies were found. Copyright © 2017 Elsevier Ltd. All rights reserved.

Porous-Hybrid Polymers as Platforms for Heterogeneous Photochemical Catalysis.

PubMed

Haikal, Rana R; Wang, Xia; Hassan, Youssef S; Parida, Manas R; Murali, Banavoth; Mohammed, Omar F; Pellechia, Perry J; Fontecave, Marc; Alkordi, Mohamed H

2016-08-10

A number of permanently porous polymers containing Ru(bpy)n photosensitizer or a cobaloxime complex, as a proton-reduction catalyst, were constructed via one-pot Sonogashira-Hagihara (SH) cross-coupling reactions. This process required minimal workup to access porous platforms with control over the apparent surface area, pore volume, and chemical functionality from suitable molecular building blocks (MBBs) containing the Ru or Co complexes, as rigid and multitopic nodes. The cobaloxime molecular building block, generated through in situ metalation, afforded a microporous solid that demonstrated noticeable catalytic activity toward hydrogen-evolution reaction (HER) with remarkable recyclability. We further demonstrated, in two cases, the ability to affect the excited-state lifetime of the covalently immobilized Ru(bpy)3 complex attained through deliberate utilization of the organic linkers of variable dimensions. Overall, this approach facilitates construction of tunable porous solids, with hybrid composition and pronounced chemical and physical stability, based on the well-known Ru(bpy)nor the cobaloxime complexes.

Effect of salinity on the precipitation of dissolved metals in the wastewater that produced during fly ash disposal

NASA Astrophysics Data System (ADS)

Lv, Lina; Yang, Yanling; Tian, Junguo; Li, Yaojian; Li, Jun; Yan, Shengjun

2018-02-01

In this study, a salinity wastewater was produced during the fly ash treatment in the waste incineration plant. Chemical precipitation method was applied for heavy metals removal in the salinity wastewater. The effect of salinity on the removal of dissolved heavy metal ions (Zn2+, Cu2+, Pb2+, Ni2+ and Cd2+) was studied, especially on the removal of Pb2+ and Cd2+. Because of the formation of [PbCl3]- and [PbCl4]2- complexes, the residual concentration of dissolved Pb2+ increased from 0.02 mg/L to 4.08 mg/L, as the NaCl concentration increased from 0 % to 10 %. And the residual concentration of dissolved Cd2+ increased from 0.02 mg/L to 1.39 mg/L, due to the formation of [CdCl3]-, [CdCl4]2- and [CdCl6]4- complexes.

Stable dimeric magnesium(I) compounds: from chemical landmarks to versatile reagents.

PubMed

Stasch, Andreas; Jones, Cameron

2011-06-07

The chemistry of the s-block metals is dominated by the +1 oxidation state for the Alkali metals (group 1) and the +2 oxidation state for the Alkaline Earth metals (group 2). In recent years, a series of stable dimeric magnesium(I) compounds has been prepared and their chemistry has started to develop. These complexes feature "deformable" Mg-Mg single bonds and are stabilised by sterically demanding and chelating anionic N-ligands that prevent their disproportionation. They have rapidly proven useful in organic and organometallic/inorganic reduction reactions as hydrocarbon soluble, stoichiometric, selective and safe reducing agents. The scope of this perspective focuses on stable molecular compounds of the general type LMgMgL and describes their synthesis, structures, theoretical and spectroscopic studies as well as their further chemistry. Also, comparisons are drawn with related complexes including magnesium(II) hydrides and dimeric zinc(I) compounds.

Interaction of glutathione reductase with heavy metal: the binding of Hg(II) or Cd(II) to the reduced enzyme affects both the redox dithiol pair and the flavin.

PubMed

Picaud, Thierry; Desbois, Alain

2006-12-26

To determine the inhibition mechanism of yeast glutathione reductase (GR) by heavy metal, we have compared the electronic absorption and resonance Raman (RR) spectra of the enzyme in its oxidized (Eox) and two-electron reduced (EH2) forms, in the absence and the presence of Hg(II) or Cd(II). The spectral data clearly show a redox dependence of the metal binding. The metal ions do not affect the absorption and RR spectra of Eox. On the contrary, the EH2 spectra, generated by addition of NADPH, are strongly modified by the presence of heavy metal. The absorption changes of EH2 are metal-dependent. On the one hand, the main flavin band observed at 450 nm for EH2 is red-shifted at 455 nm for the EH2-Hg(II) complex and at 451 nm for the EH2-Cd(II) complex. On the other hand, the characteristic charge-transfer (CT) band at 540 nm is quenched upon metal binding to EH2. In NADPH excess, a new CT band is observed at 610 nm for the EH2-Hg(II)-NADPH complex and at 590 nm for EH2-Cd(II)-NADPH. The RR spectra of the EH2-metal complexes are not sensitive to the NADPH concentration. With reference to the RR spectra of EH2 in which the frequencies of bands II and III were observed at 1582 and 1547 cm-1, respectively, those of the EH2-metal complexes are detected at 1577 and 1542 cm-1, indicating an increased flavin bending upon metal coordination to EH2. From the frequency shifts of band III, a concomitant weakening of the H-bonding state of the N5 atom is also deduced. Taking into account the different chemical properties of Hg(II) and Cd(II), the coordination number of the bound metal ion was deduced to be different in GR. A mechanism of the GR inhibition is proposed. It proceeds primarily by a specific binding of the metal to the redox thiol/thiolate pair and the catalytic histidine of EH2. The bound metal ion then acts on the bending of the isoalloxazine ring of FAD as well as on the hydrophobicity of its microenvironment.

Operando Multi-modal Synchrotron Investigation for Structural and Chemical Evolution of Cupric Sulfide (CuS) Additive in Li-S battery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Ke; Zhao, Chonghang; Lin, Cheng-Hung

Conductive metal sulfides are promising multi-functional additives for future lithium-sulfur (Li-S) batteries. These can increase the sulfur cathode’s electrical conductivity to improve the battery’s power capability, as well as contribute to the overall cell-discharge capacity. This multi-functional electrode design showed initial promise; however, complicated interactions at the system level are accompanied by some detrimental side effects. The metal sulfide additives with a chemical conversion as the reaction mechanism, e.g., CuS and FeS 2, can increase the theoretical capacity of the Li-S system. However, these additives may cause undesired parasitic reactions, such as the dissolution of the additive in the electrolyte.more » Studying such complex reactions presents a challenge because it requires experimental methods that can track the chemical and structural evolution of the system during an electrochemical process. To address the fundamental mechanisms in these systems, we employed an operando multimodal x-ray characterization approach to study the structural and chemical evolution of the metal sulfide—utilizing powder diffraction and fluorescence imaging to resolve the former and absorption spectroscopy the latter—during lithiation and de-lithiation of a Li-S battery with CuS as the multi-functional cathode additive. The resulting elucidation of the structural and chemical evolution of the system leads to a new description of the reaction mechanism.« less

Operando Multi-modal Synchrotron Investigation for Structural and Chemical Evolution of Cupric Sulfide (CuS) Additive in Li-S battery

DOE PAGES

Sun, Ke; Zhao, Chonghang; Lin, Cheng-Hung; ...

2017-10-11

Conductive metal sulfides are promising multi-functional additives for future lithium-sulfur (Li-S) batteries. These can increase the sulfur cathode’s electrical conductivity to improve the battery’s power capability, as well as contribute to the overall cell-discharge capacity. This multi-functional electrode design showed initial promise; however, complicated interactions at the system level are accompanied by some detrimental side effects. The metal sulfide additives with a chemical conversion as the reaction mechanism, e.g., CuS and FeS 2, can increase the theoretical capacity of the Li-S system. However, these additives may cause undesired parasitic reactions, such as the dissolution of the additive in the electrolyte.more » Studying such complex reactions presents a challenge because it requires experimental methods that can track the chemical and structural evolution of the system during an electrochemical process. To address the fundamental mechanisms in these systems, we employed an operando multimodal x-ray characterization approach to study the structural and chemical evolution of the metal sulfide—utilizing powder diffraction and fluorescence imaging to resolve the former and absorption spectroscopy the latter—during lithiation and de-lithiation of a Li-S battery with CuS as the multi-functional cathode additive. The resulting elucidation of the structural and chemical evolution of the system leads to a new description of the reaction mechanism.« less

Spectroscopic studies and thermal analysis of mononuclear metal complexes with moxifloxacin and 2,2‧-bipyridine and their effects on acute lung injury induced by hydrochloric acid in rats

NASA Astrophysics Data System (ADS)

El-Hamid, S. M. Abd; El-Demerdash, R. S.; Arafat, H. F. H.; Sadeek, S. A.

2017-12-01

The article describes the interaction of Y(III), Zr(IV), La(III), Ce(IV) and U(VI) with moxifloxacin hydrochloride and 2,2‧-bipyridine. Characterization of complexes was made by elemental analyses, molar conductivity, magnetic moment measurements and spectral measurements e.g. IR, UV-Vis., 1H NMR and mass as well as thermal analyses (TG and DTG). The molar conductivity shows that the complexes are electrolytes nature. Spectroscopic investigation of the solid complexes studied here indicate that moxifloxacin hydrochloride and 2,2‧-bipyridine are coordinated to the metal ions in a neutral bidentate manner. After complete characterization, the chemical formulae of the complexes were established. The calculated bond length and force constant, F(Udbnd O), in the uranyl complex are 1.756 Å and 637.90 Nm-1, respectively. Kinetic and thermodynamic parameters were determined using Coats-Redfern and Horowitz-Metzger equations. Establishment of hydrochloric acid that induce acute lung injury (ALI) in rats by intratracheal administration through damaging the alveolar epithelium and activation of the neutrophil and subsequent oxidative stress by increasing malondialdehyde (MDA), tumor necrosis factor (TNF-α) and neutrophil, which were confirmed by histopathological investigation while decreasing in antioxidant enzymes and lymphocytes. Whereas treatment with mixed-ligand metal complexes significantly decrease MDA, TNF-α and neutrophils and increase antioxidant and lymphocytes.

Chitosan-bound pyridinedicarboxylate Ni(II) and Fe(III) complex biopolymer films as waste water decyanidation agents.

PubMed

Adewuyi, Sheriff; Jacob, Julianah Modupe; Olaleye, Oluwatoyin Omolola; Abdulraheem, Taofiq Olanrewaju; Tayo, Jubril Ayopo; Oladoyinbo, Fatai Oladipupo

2016-10-20

Chitosan is a biopolymer with immense structural advantage for chemical and mechanical modifications to generate novel properties, functions and applications. This work depicts new pyridinedicarboxylicacid (PDC) crosslinked chitosan-metal ion films as veritable material for cyanide ion removal from aqueous solution. The PDC-crosslinked chitosan-metal films (PDC-Chit-Ni(II) and PDC-Chit-Fe(III)) were formed by complexing PDC-crosslinked chitosan film with anhydrous nickel(II) and iron(III) chloride salts respectively. The PDC-Chit and its metal films were characterized employing various analytical and spectroscopic techniques. The FT-IR, UV-vis and the XRD results confirm the presence of the metal ions in the metal coordinated PDC-crosslinked chitosan film. The surface morphological difference of PDC-Chit-Ni(II) film before and after decyanidation was explored with scanning electron microscopy. Furthermore, the quantitative amount of nickel(II) and iron(III) present in the complex were determined using Atomic Absorption Spectrophotometer as 32.3 and 37.2μg/g respectively which portends the biopolymer film as a good complexing agent. Removal of cyanide from aqueous solution with PDC-Chit, PDC-Chit-Ni(II) and PDC-Chit-Fe(III) films was studied with batch equilibrium experiments. At equilibrium, decyanidation capacity (DC) followed the order PDC-Chit-Ni (II)≈PDC-Chit-Fe(III)>PDC-Chit. PDC-Chit-Ni(II) film gave 100% CN(-) removal within 40min decyanidation owing to favorable coordination geometry. Copyright © 2016 Elsevier Ltd. All rights reserved.

Synthesis, spectral and theoretical studies of Ni(II), Pd(II) and Pt(II) complexes of 5-mercapto-1,2,4-triazole-3-imine-2‧-hydroxynaphyhaline

NASA Astrophysics Data System (ADS)

Gaber, Mohamed; El-Ghamry, Hoda; Atlam, Faten; Fathalla, Shaimaa

2015-02-01

Ni(II), Pd(II) and Pt(II) complexes of 5-mercapto-1,2,4-triazole-3-imine-2‧-hydroxynaphthaline have been isolated and characterized by elemental analysis, IR, 1H NMR, EI-mass, UV-vis, molar conductance, magnetic moment measurements and thermogravimetric analysis. The molar conductance values indicated that the complexes are non-electrolytes. The magnetic moment values of the complexes displayed diamagnetic behavior for Pd(II) and Pt(II) complexes and tetrahedral geometrical structure for Ni(II) complex. From the bioinorganic applications point of view, the interaction of the ligand and its metal complexes with CT-DNA was investigated using absorption and viscosity titration techniques. The Schiff-base ligand and its metal complexes have also been screened for their antimicrobial and antitumor activities. Also, theoretical investigation of molecular and electronic structures of the studied ligand and its metal complexes has been carried out. Molecular orbital calculations were performed using DFT (density functional theory) at B3LYP level with standard 6-31G(d,p) and LANL2DZ basis sets to access reliable results to the experimental values. The calculations were performed to obtain the optimized molecular geometry, charge density distribution, extent of distortion from regular geometry, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), Mulliken atomic charges, reactivity index (ΔE), dipole moment (D), global hardness (η), softness (σ), electrophilicity index (ω), chemical potential and Mulliken electronegativity (χ).

Chemical Interaction-Guided, Metal-Free Growth of Large-Area Hexagonal Boron Nitride on Silicon-Based Substrates.

PubMed

Behura, Sanjay; Nguyen, Phong; Debbarma, Rousan; Che, Songwei; Seacrist, Michael R; Berry, Vikas

2017-05-23

Hexagonal boron nitride (h-BN) is an ideal platform for interfacing with two-dimensional (2D) nanomaterials to reduce carrier scattering for high-quality 2D electronics. However, scalable, transfer-free growth of hexagonal boron nitride (h-BN) remains a challenge. Currently, h-BN-based 2D heterostructures require exfoliation or chemical transfer of h-BN grown on metals resulting in small areas or significant interfacial impurities. Here, we demonstrate a surface-chemistry-influenced transfer-free growth of large-area, uniform, and smooth h-BN directly on silicon (Si)-based substrates, including Si, silicon nitride (Si 3 N 4 ), and silicon dioxide (SiO 2 ), via low-pressure chemical vapor deposition. The growth rates increase with substrate electronegativity, Si < Si 3 N 4 < SiO 2 , consistent with the adsorption rates calculated for the precursor molecules via atomistic molecular dynamics simulations. Under graphene with high grain density, this h-BN film acts as a polymer-free, planar-dielectric interface increasing carrier mobility by 3.5-fold attributed to reduced surface roughness and charged impurities. This single-step, chemical interaction guided, metal-free growth mechanism of h-BN for graphene heterostructures establishes a potential pathway for the design of complex and integrated 2D-heterostructured circuitry.

Crystal and electronic structures of magnesium(II), copper(II), and mixed magnesium(II)-copper(II) complexes of the quinoline half of styrylquinoline-type HIV-1 integrase inhibitors.

PubMed

Courcot, B; Firley, D; Fraisse, B; Becker, P; Gillet, J-M; Pattison, P; Chernyshov, D; Sghaier, M; Zouhiri, F; Desmaële, D; d'Angelo, J; Bonhomme, F; Geiger, S; Ghermani, N E

2007-05-31

A new target in AIDS therapy development is HIV-1 integrase (IN). It was proven that HIV-1 IN required divalent metal cations to achieve phosphodiester bond cleavage of DNA. Accordingly, all newly investigated potent IN inhibitors contain chemical fragments possessing a high ability to chelate metal cations. One of the promising leads in the polyhydroxylated styrylquinolines (SQLs) series is (E)-8-hydroxy-2-[2-(4,5-dihydroxy-3-methoxyphenyl)-ethenyl]-7-quinoline carboxylic acid (1). The present study focuses on the quinoline-based progenitor (2), which is actually the most probable chelating part of SQLs. Conventional and synchrotron low-temperature X-ray crystallographic studies were used to investigate the chelating power of progenitor 2. Mg2+ and Cu2+ cations were selected for this purpose, and three types of metal complexes of 2 were obtained: Mg(II) complex (4), Cu(II) complex (5) and mixed Mg(II)-Cu(II) complexes (6 and 7). The analysis of the crystal structure of complex 4 indicates that two tridentate ligands coordinate two Mg2+ cations, both in octahedral geometry. The Mg-Mg distance was found equal to 3.221(1) A, in agreement with the metal-metal distance of 3.9 A encountered in the crystal structure of Escherichia coli DNA polymerase I. In 5, the complex is formed by two bidentate ligands coordinating one copper ion in tetrahedral geometry. Both mixed Mg(II)-Cu(II) complexes, 6 and 7 exhibit an original arrangement of four ligands linked to a central heterometallic cluster consisting of three octahedrally coordinated magnesium ions and one tetrahedrally coordinated copper ion. Quantum mechanics calculations were also carried out in order to display the electrostatic potential generated by the dianionic ligand 2 and complex 4 and to quantify the binding energy (BE) during the formation of the magnesium complex of progenitor 2. A comparison of the binding energies of two hypothetical monometallic Mg(II) complexes with that found in the bimetallic magnesium complex 4 was made.

In silico strategies for the selection of chelating compounds with potential application in metal-promoted neurodegenerative diseases

NASA Astrophysics Data System (ADS)

Rodríguez-Rodríguez, Cristina; Rimola, Albert; Alí-Torres, Jorge; Sodupe, Mariona; González-Duarte, Pilar

2011-01-01

The development of new strategies to find commercial molecules with promising biochemical features is a main target in the field of biomedicine chemistry. In this work we present an in silico-based protocol that allows identifying commercial compounds with suitable metal coordinating and pharmacokinetic properties to act as metal-ion chelators in metal-promoted neurodegenerative diseases (MpND). Selection of the chelating ligands is done by combining quantum chemical calculations with the search of commercial compounds on different databases via virtual screening. Starting from different designed molecular frameworks, which mainly constitute the binding site, the virtual screening on databases facilitates the identification of different commercial molecules that enclose such scaffolds and, by imposing a set of chemical and pharmacokinetic filters, obey some drug-like requirements mandatory to deal with MpND. The quantum mechanical calculations are useful to gauge the chelating properties of the selected candidate molecules by determining the structure of metal complexes and evaluating their stability constants. With the proposed strategy, commercial compounds containing N and S donor atoms in the binding sites and capable to cross the BBB have been identified and their chelating properties analyzed.

Randic and Schultz molecular topological indices and their correlation with some X-ray absorption parameters

NASA Astrophysics Data System (ADS)

Khatri, Sunil; Kekre, Pravin A.; Mishra, Ashutosh

2016-10-01

The properties of a molecular system are affected by the topology of molecule. Therefore many studies have been made where the various physic-chemical properties are correlated with the topological indices. These studies have shown a very good correlation demonstrating the utility of the graph theoretical approach. It is, therefore, very natural to expect that the various physical properties obtained by the X-ray absorption spectra may also show correlation with the topological indices. Some complexes were used to establish correlation between topological indices and some X-ray absorption parameters like chemical shift. The chemical shift is on the higher energy side of the metal edge in these complexes. The result obtained in these studies shows that the topological indices of organic molecule acting as a legands can be used for estimating edge shift theoretically.

High density crystalline boron prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, C.L.

1993-08-31

Boron powder is hot isostatically pressed in a refractory metal container to produce a solid boron monolith with a bulk density at least 2.22 g/cc and up to or greater than 2.34 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed or chemical vapor deposited onto a powder compact. Hot isostatic pressing at 1,800 C and 30 PSI (206.8 MPa) argon pressure for four hours produces a bulk density of 2.34 g/cc. Complex shapes can be made.

High density crystalline boron prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, Clarence L.

1993-01-01

Boron powder is hot isostatically pressed in a refractory metal container to produce a solid boron monolith with a bulk density at least 2.22 g/cc and up to or greater than 2.34 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed or chemical vapor deposited onto a powder compact. Hot isostatic pressing at 1800.degree. C. and 30 KSI (206.8 MPa) argon pressure for four hours produces a bulk density of 2.34 g/cc. Complex shapes can be made.

High density-high purity graphite prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, Clarence L.

1994-01-01

Porous graphite in solid form is hot isostatically pressed in a refractory metal container to produce a solid graphite monolith with a bulk density greater than or equal to 2.10 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed, chemically vapor deposited, or coated by some other suitable means onto graphite. Hot isostatic pressing at 2200.degree. C. and 30 KSI (206.8 MPa) argon pressure for two hours produces a bulk density of 2.10 g/cc. Complex shapes can be made.

High density-high purity graphite prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, C.L.

1994-08-09

Porous graphite in solid form is hot isostatically pressed in a refractory metal container to produce a solid graphite monolith with a bulk density greater than or equal to 2.10 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed, chemically vapor deposited, or coated by some other suitable means onto graphite. Hot isostatic pressing at 2,200 C and 30 KSI (206.8 MPa) argon pressure for two hours produces a bulk density of 2.10 g/cc. Complex shapes can be made. 1 fig.

Pt(II) and Pd(II) complexes with ibuprofen hydrazide: Characterization, theoretical calculations, antibacterial and antitumor assays and studies of interaction with CT-DNA

NASA Astrophysics Data System (ADS)

Manzano, Carlos M.; Bergamini, Fernando R. G.; Lustri, Wilton R.; Ruiz, Ana Lúcia T. G.; de Oliveira, Ellen C. S.; Ribeiro, Marcos A.; Formiga, André L. B.; Corbi, Pedro P.

2018-02-01

Palladium(II) and platinum(II) complexes with a hydrazide derivative of ibuprofen (named HIB) were synthesized and characterized by chemical and spectroscopic methods. Elemental and thermogravimetric analyses, as well as ESI-QTOF-MS studies for both complexes, confirmed a 1:2:2 metal/HIB/Cl- molar ratio. The crystal structure of the palladium(II) complex was solved by single crystal X-ray diffractometric analysis, which permitted identifying the coordination formula [PdCl2(HIB)2]. Crystallographic studies also indicate coordination of HIB to the metal by the NH2 group. Nuclear magnetic resonance and infrared spectroscopies reinforced the coordination observed in the crystal structure and suggested that the platinum(II) complex presents similar coordination modes and structure when compared with the Pd(II) complex. The complexes had their structures optimized with the aid of DFT methods. In vitro antiproliferative assays showed that the [PdCl2(HIB)2] complex is active over ovarian cancer cell line OVCAR-03, while biophysical studies indicated its capacity to interact with CT-DNA. The complexes were inactive over Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa bacterial strains.

Cp[prime]M(NO)R[sub 2]: 16-electron piano-stool molecules of molybdenum and tungsten

DOE Office of Scientific and Technical Information (OSTI.GOV)

Legzdins, P.; Veltheer, J.E.

1993-02-01

A long-term goal of this research program is the development of organometallic nitrosyl complexes as specific reactants or selective catalysts for organic or organometallic transformations of practical significance. To attain this goal specifically with Cp[prime]M(NO)R[sub 2] system the authors developed new methods for their synthesis, established their characteristic physical and chemical properties, and are currently endeavoring to exploit those properties which are unique to the complexes. During our investigations, the authors have discovered that the Cp[prime]M(NO)R[sub 2] complexes react with a variety of small molecules, often in an unprecedented manner. The authors have also established several unique transformations that aremore » not exhibited by all members of this group of complexes. Indeed, the authors found that the chemical properties of these systems are often dependent on the metal, the nature of the R groups, and the type of Cp[prime] ligand. In this Account the authors summarize the synthesis, characterization, comparative reactivity, and distinctive chemical properties of the 16-electron Cp[prime]M(NO)R[sub 2] complexes known to date. 35 refs., 7 figs.« less

Novel approach to investigation of semiconductor MOCVD by microreactor technology

NASA Astrophysics Data System (ADS)

Konakov, S. A.; Krzhizhanovskaya, V. V.

2017-11-01

Metal-Organic Chemical Vapour Deposition is a very complex technology that requires further investigation and optimization. We propose to apply microreactors to (1) replace multiple expensive time-consuming macroscale experiments by just one microreactor deposition with many points on one substrate; (2) to derive chemical reaction rates from individual deposition profiles using theoretical analytical solution. In this paper we also present the analytical solution of a simplified equation describing the deposition rate dependency on temperature. It allows to solve an inverse problem and to obtain detailed information about chemical reaction mechanism of MOCVD process.

Half-sandwich rare-earth-catalyzed olefin polymerization, carbometalation, and hydroarylation.

PubMed

Nishiura, Masayoshi; Guo, Fang; Hou, Zhaomin

2015-08-18

The search for new catalysts for more efficient, selective chemical transformations and for the synthesis of new functional materials has been a long-standing research subject in both academia and industry. To develop new generations of catalysts that are superior or complementary to the existing ones, exploring the potential of untapped elements is an important strategy. Rare-earth elements, including scandium, yttrium, and the lanthanides (La-Lu), constitute one important frontier in the periodic table. Rare-earth elements possess unique chemical and physical properties that are different from those of main-group and late-transition metals. The development of rare-earth-based catalysts by taking the advantage of these unique properties is of great interest and importance. The most stable oxidation state of rare-earth metals is 3+, which is difficult to change under many reaction conditions. The oxidative addition and reductive elimination processes often observed in catalytic cycles involving late transition metals are generally difficult in the case of rare-earth complexes. The 18-electron rule that is applicable to late-transition-metal complexes does not fit rare-earth complexes, whose structures are mainly governed by the sterics (rather than the electron numbers) of the ligands. In the lanthanide series (La-Lu), the ionic radius gradually decreases with increasing atomic number because of the influence of the 4f electrons, which show poor shielding of nuclear charge. Rare-earth metal ions generally show strong Lewis acidity and oxophilicity. Rare-earth metal alkyl and hydride species are highly reactive, showing both nucleophilicity and basicity. The combination of these features, such as the strong nucleophilicity and moderate basicity of the alkyl and hydride species and the high stability, strong Lewis acidity, and unsaturated C-C bond affinity of the 3+ metal ions, can make rare-earth metals unique candidates for the formation of excellent single-site catalysts. This Account is intended to give an overview of our recent studies on organo rare-earth catalysis, in particular the synthesis and application of half-sandwich rare-earth alkyl complexes bearing monocyclopentadienyl ligands for olefin polymerization, carbometalation, and hydroarylation. Treatment of half-sandwich rare-earth dialkyl complexes having the general formula CpMR2 with an equimolar amount of an appropriate borate compound such as [Ph3C][B(C6F5)4] can generate the corresponding cationic monoalkyl species, which serve as excellent single-site catalysts for the polymerization and copolymerization of a wide range of olefin monomers such as ethylene, 1-hexene, styrene, conjugated and nonconjugated dienes, and cyclic olefins. The cationic half-sandwich rare-earth alkyl complexes can also catalyze the regio- and stereoselective alkylative alumination of alkenes and alkynes through insertion of the unsaturated C-C bond into the metal-alkyl bond followed by transmetalation between the resulting new alkyl or alkenyl species and an alkylaluminum compound. Moreover, a combination of deprotonative C-H bond activation of appropriate organic compounds such as anisoles and pyridines by the rare-earth alkyl species and insertion of alkenes into the resulting new metal-carbon bond can lead to catalytic C-H bond alkylation of the organic substrates. Most of these transformations are unique to the rare-earth catalysts with selectivity and functional group tolerance different from those of late-transition-metal catalysts.

Understanding Metal Sources and Transport Processes in Watersheds: a Hydropedologic Approach (Invited)

NASA Astrophysics Data System (ADS)

Bullen, T. D.; Bailey, S. W.; McGuire, K. J.; Brousseau, P.; Ross, D. S.; Bourgault, R.; Zimmer, M. A.

2010-12-01

Understanding the origin of metals in watersheds, as well as the transport and cycling processes that affect them is of critical importance to watershed science. Metals can be derived both from weathering of minerals in the watershed soils and bedrock and from atmospheric deposition, and can have highly variable residence times in the watershed due to cycling through plant communities and retention in secondary mineral phases prior to release to drainage waters. Although much has been learned about metal cycling and transport through watersheds using simple “box model” approaches that define unique input, output and processing terms, the fact remains that watersheds are inherently complex and variable in terms of substrate structure, hydrologic flowpaths and the influence of plants, all of which affect the chemical composition of water that ultimately passes through the watershed outlet. In an effort to unravel some of this complexity at a watershed scale, we have initiated an interdisciplinary, hydropedology-focused study of the hydrologic reference watershed (Watershed 3) at the Hubbard Brook Experimental Forest in New Hampshire, USA. This 41 hectare headwater catchment consists of a beech-birch-maple-spruce forest growing on soils developed on granitoid glacial till that mantles Paleozoic metamorphic bedrock. Soils vary from lateral spodosols downslope from bedrock exposures near the watershed crest to vertical and bi-modal spodosols along hillslopes to umbrepts at toe-slope positions and inferred hydrologic pinch points created by bedrock and till structure. Using a variety of chemical and isotope tracers (e.g., K/Na, Ca/Sr, Sr/Ba, Fe/Mn, 87Sr/86Sr, Ca-Sr-Fe stable isotopes) on water, soil and plant samples in an end-member mixing analysis approach, we are attempting to discretize the watershed according to soil types encountered along determined hydrologic flowpaths in order better constrain the various biogeochemical processes that control the delivery of metals to the watershed outlet. Our initial results reveal that along the numerous first-order streams that drain the watershed, chemical and Sr isotope compositions are highly variable from sample point to sample point on a given day and from season to season, reflecting the complex nature of hydrologic flowpaths that deliver water to the streams and hinting at the importance of groundwater seeps that appear to concentrate along the central axis of the watershed.

Multifaceted Modularity: A Key for Stepwise Building of Hierarchical Complexity in Actinide Metal-Organic Frameworks.

PubMed

Dolgopolova, Ekaterina A; Ejegbavwo, Otega A; Martin, Corey R; Smith, Mark D; Setyawan, Wahyu; Karakalos, Stavros G; Henager, Charles H; Zur Loye, Hans-Conrad; Shustova, Natalia B

2017-11-22

Growing necessity for efficient nuclear waste management is a driving force for development of alternative architectures toward fundamental understanding of mechanisms involved in actinide (An) integration inside extended structures. In this manuscript, metal-organic frameworks (MOFs) were investigated as a model system for engineering radionuclide containing materials through utilization of unprecedented MOF modularity, which cannot be replicated in any other type of materials. Through the implementation of recent synthetic advances in the MOF field, hierarchical complexity of An-materials was built stepwise, which was only feasible due to preparation of the first examples of actinide-based frameworks with "unsaturated" metal nodes. The first successful attempts of solid-state metathesis and metal node extension in An-MOFs are reported, and the results of the former approach revealed drastic differences in chemical behavior of extended structures versus molecular species. Successful utilization of MOF modularity also allowed us to structurally characterize the first example of bimetallic An-An nodes. To the best of our knowledge, through combination of solid-state metathesis, guest incorporation, and capping linker installation, we were able to achieve the highest Th wt % in mono- and biactinide frameworks with minimal structural density. Overall, the combination of a multistep synthetic approach with homogeneous actinide distribution and moderate solvothermal conditions could make MOFs an exceptionally powerful tool to address fundamental questions responsible for chemical behavior of An-based extended structures and, therefore, shed light on possible optimization of nuclear waste administration.

Complex Nanostructures from Materials based on Metal-Organic Frameworks for Electrochemical Energy Storage and Conversion.

PubMed

Guan, Bu Yuan; Yu, Xin Yao; Wu, Hao Bin; Lou, Xiong Wen David

2017-12-01

Metal-organic frameworks (MOFs) have drawn tremendous attention because of their abundant diversity in structure and composition. Recently, there has been growing research interest in deriving advanced nanomaterials with complex architectures and tailored chemical compositions from MOF-based precursors for electrochemical energy storage and conversion. Here, a comprehensive overview of the synthesis and energy-related applications of complex nanostructures derived from MOF-based precursors is provided. After a brief summary of synthetic methods of MOF-based templates and their conversion to desirable nanostructures, delicate designs and preparation of complex architectures from MOFs or their composites are described in detail, including porous structures, single-shelled hollow structures, and multishelled hollow structures, as well as other unusual complex structures. Afterward, their applications are discussed as electrode materials or catalysts for lithium-ion batteries, hybrid supercapacitors, water-splitting devices, and fuel cells. Lastly, the research challenges and possible development directions of complex nanostructures derived from MOF-based-templates for electrochemical energy storage and conversion applications are outlined. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microemulsions and Aggregation Formation in Extraction Processes for Used Nuclear Fuel: Thermodynamic and Structural Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nilsson, Mikael

Advanced nuclear fuel cycles rely on successful chemical separation of various elements in the used fuel. Numerous solvent extraction (SX) processes have been developed for the recovery and purification of metal ions from this used material. However, the predictability of process operations has been challenged by the lack of a fundamental understanding of the chemical interactions in several of these separation systems. For example, gaps in the thermodynamic description of the mechanism and the complexes formed will make predictions very challenging. Recent studies of certain extraction systems under development and a number of more established SX processes have suggested thatmore » aggregate formation in the organic phase results in a transformation of its selectivity and efficiency. Aggregation phenomena have consistently been interfering in SX process development, and have, over the years, become synonymous with an undesirable effect that must be prevented. This multiyear, multicollaborative research effort was carried out to study solvation and self-organization in non-aqueous solutions at conditions promoting aggregation phenomena. Our approach to this challenging topic was to investigate extraction systems comprising more than one extraction reagent where synergy of the metal ion could be observed. These systems were probed for the existence of stable microemulsions in the organic phase, and a number of high-end characterization tools were employed to elucidate the role of the aggregates in metal ion extraction. The ultimate goal was to find connections between synergy of metal ion extraction and reverse micellar formation. Our main accomplishment for this project was the expansion of the understanding of metal ion complexation in the extraction system combining tributyl phosphate (TBP) and dibutyl phosphoric acid (HDBP). We have found that for this system no direct correlation exists for the metal ion extraction and the formation of aggregates, meaning that the metal ion is not solubilized in a reverse micelle core. Rather we have found solid evidence that the metal ions are extracted and coordinated by the organic ligands as suggested by classic SX theories. However, we have challenged the existence of mixed complexes that have been suggested to exist in this particular extraction system. Most importantly we have generated a wealth of information and trained students on important lab techniques and strengthened the collaboration between the DOE national laboratories and US educational institution involved in this work.« less

Emergence of complex chemistry on an organic monolayer.

PubMed

Prins, Leonard J

2015-07-21

In many origin-of-life scenarios, inorganic materials, such as FeS or mineral clays, play an important role owing to their ability to concentrate and select small organic molecules on their surface and facilitate their chemical transformations into new molecules. However, considering that life is made up of organic matter, at a certain stage during the evolution the role of the inorganic material must have been taken over by organic molecules. How this exactly happened is unclear, and, indeed, a big gap separates the rudimentary level of organization involving inorganic materials and the complex organization of cells, which are the building blocks of life. Over the past years, we have extensively studied the interaction of small molecules with monolayer-protected gold nanoparticles (Au NPs) for the purpose of developing innovative sensing and catalytic systems. During the course of these studies, we realized that the functional role of this system is very similar to that typically attributed to inorganic surfaces in the early stages of life, with the important being difference that the functional properties (molecular recognition, catalysis, signaling, adaptation) originate entirely from the organic monolayer rather than the inorganic support. This led us to the proposition that this system may serve as a model that illustrates how the important role of inorganic surfaces in dictating chemical processes in the early stages of life may have been taken over by organic matter. Here, we reframe our previously obtained results in the context of the origin-of-life question. The following functional roles of Au NPs will be discussed: the ability to concentrate small molecules and create different local populations, the ability to catalyze the chemical transformation of bound molecules, and, finally, the ability to install rudimentary signaling pathways and display primitive adaptive behavior. In particular, we will show that many of the functional properties of the system originate from two features: the presence of metal ions that are complexed in the organic monolayer and the multivalent nature of the system. Complexed metal ions play an important role in determining the affinity and selectivity of the interaction with small molecules, but serve also as regulatory elements for determining how many molecules are bound simultaneously. Importantly, neighboring metal ion complexes also create catalytic pockets in which two metal ions cooperatively catalyze the cleavage of an RNA-model compound. The multivalent nature of the system permits multiple noncovalent interactions with small molecules that enhances the affinity, but is also at the basis of simple signal transduction pathways and adaptive behavior.

Contribution of radiation chemistry to the study of metal clusters.

PubMed

Belloni, J

1998-11-01

Radiation chemistry dates from the discovery of radioactivity one century ago by H. Becquerel and P. and M. Curie. The complex phenomena induced by ionizing radiation have been explained progressively. At present, the methodology of radiation chemistry, particularly in the pulsed mode, provides a powerful means to study not only the early processes after the energy absorption, but more generally a broad diversity of chemical and biochemical reaction mechanisms. Among them, the new area of metal cluster chemistry illustrates how radiation chemistry contributed to this field in suggesting fruitful original concepts, in guiding and controlling specific syntheses, and in the detailed elaboration of the mechanisms of complex and long-unsolved processes, such as the dynamics of nucleation, electron transfer catalysis and photographic development.

Towards an ab initio theory for metal L-edge soft X-ray spectroscopy of molecular aggregates.

PubMed

Preuße, Marie; Bokarev, Sergey I; Aziz, Saadullah G; Kühn, Oliver

2016-11-01

The Frenkel exciton model was adapted to describe X-ray absorption and resonant inelastic scattering spectra of polynuclear transition metal complexes by means of the restricted active space self-consistent field method. The proposed approach allows to substantially decrease the requirements on computational resources if compared to a full supermolecular quantum chemical treatment. This holds true, in particular, in cases where the dipole approximation to the electronic transition charge density can be applied. The computational protocol was applied to the calculation of X-ray spectra of the hemin complex, which forms dimers in aqueous solution. The aggregation effects were found to be comparable to the spectral alterations due to the replacement of the axial ligand by solvent molecules.

High-Valent Organometallic Copper and Palladium in Catalysis

PubMed Central

Hickman, Amanda J.; Sanford, Melanie S.

2015-01-01

Preface Copper and palladium catalysts are critically important for numerous commercial chemical processes. Improvements in the activity, selectivity, and scope of these catalysts have the potential to dramatically reduce the environmental impact and increase the sustainability of chemical reactions. One rapidly emerging strategy to achieve these goals is to exploit “high-valent” copper and palladium intermediates in catalysis. This review describes exciting recent advances involving both the fundamental chemistry and the applications of these high-valent metal complexes in numerous synthetically useful catalytic transformations. PMID:22498623

One-electron oxidation of electronically diverse manganese(III) and nickel(II) salen complexes: transition from localized to delocalized mixed-valence ligand radicals.

PubMed

Kurahashi, Takuya; Fujii, Hiroshi

2011-06-01

Ligand radicals from salen complexes are unique mixed-valence compounds in which a phenoxyl radical is electronically linked to a remote phenolate via a neighboring redox-active metal ion, providing an opportunity to study electron transfer from a phenolate to a phenoxyl radical mediated by a redox-active metal ion as a bridge. We herein synthesize one-electron-oxidized products from electronically diverse manganese(III) salen complexes in which the locus of oxidation is shown to be ligand-centered, not metal-centered, affording manganese(III)-phenoxyl radical species. The key point in the present study is an unambiguous assignment of intervalence charge transfer bands by using nonsymmetrical salen complexes, which enables us to obtain otherwise inaccessible insight into the mixed-valence property. A d(4) high-spin manganese(III) ion forms a Robin-Day class II mixed-valence system, in which electron transfer is occurring between the localized phenoxyl radical and the phenolate. This is in clear contrast to a d(8) low-spin nickel(II) ion with the same salen ligand, which induces a delocalized radical (Robin-Day class III) over the two phenolate rings, as previously reported by others. The present findings point to a fascinating possibility that electron transfer could be drastically modulated by exchanging the metal ion that bridges the two redox centers. © 2011 American Chemical Society

Development of luminescent sensors based on transition metal complexes for the detection of nitroexplosives.

PubMed

Sathish, Veerasamy; Ramdass, Arumugam; Velayudham, Murugesan; Lu, Kuang-Lieh; Thanasekaran, Pounraj; Rajagopal, Seenivasan

2017-12-12

The detection of chemical explosives is a major area of research interest and is essential for the military as well as homeland security to counter the catastrophic effects of global terrorism. In recent years, tremendous effort has been devoted to the development of luminescent materials for the detection of explosives in the vapor, solution, and solid states with a high degree of selectivity and sensitivity and a rapid response time. Apart from the wide range of organic fluorescent chemosensors, transition metal complexes play a prominent role in the sensing of nitroaromatic explosives owing to their rich photophysical characteristics. This review briefly summarizes the salient features of the design and preparation of transition metal (Zn(ii), Ir(iii), Pd(ii), Pt(ii), Re(i) and Ru(ii)) complexes/metallacycles/metallosupramolecules with emphasis on their photophysical properties, sensing behavior, mechanism of action, and the driving forces for detecting explosives and future prospects and challenges. Most of the probes that have been reported to date act as "turn-off" luminescent sensors because their emission (intensity, lifetime, and quantum yield) is eventually quenched upon sensing with nitroaromatic compounds (NACs) through photo-induced electron or energy transfer. These unique properties of transition metal complexes in response to explosives open up new vistas for the development of real world applications such as on-site detection, in-field security, forensic research, etc.

Speciation, photosensitivity, and reactions of transition metal ions in atmospheric droplets

NASA Astrophysics Data System (ADS)

Weschler, C. J.; Mandich, M. L.; Graedel, T. E.

1986-04-01

Dissolved transition metal ions (TMI) are common constituents of atmospheric droplets. They are known to catalyze sulfur oxidation in droplets and are suspected of being involved in other chemical processes as well. We have reviewed the relevant equilibrium constants and chemical reactions of the major TMI (iron, manganese, copper, and nickel), their ability to form complexes in aqueous solution, and their potential involvement in photochemical processes in atmospheric droplets. Among the results are the following: (1) The major Fe(III) species in atmospheric water droplets are [Fe(OH)(H2O)5]2+, [Fe(OH)2(H2O)4]+, and [Fe(SO3)(H2O)5]+; the partitioning among these complexes is a function of pH. In contrast, Cu(II), Mn(II), and Ni(II) exist almost entirely in the droplets as hexaquo complexes. (2) Within the tropospheric solar spectrum, some of the complexes of Fe(III) have large absorption cross-sections. In this work we report cross-section data for several of the complexes. Absorption of solar photons by such complexes is generally followed by cleavage, which in the same process reduces the iron (III) atom and produces a reactive free radical. This mechanism has the potential to be a significant and heretofore unappreciated source of free radicals in atmospheric droplets. (3) TMI participate in redox reactions with H2O2 and its associated species HO2· and O2-. These reactions furnish the potential for catalytic cycles involving TMI in atmospheric droplets under a variety of illumination and acidity conditions. (4) A number of organic processes in atmospheric droplets may involve TMI. Among these processes are the production and destruction of alkylhydroperoxides, the chemical chains linking RO2· radicals to stable alcohols and acids, and the oxidation of aliphatic aldehydes to organic acids.

Pulmonary toxicity and extrapulmonary tissue distribution of metals after repeated exposure to different welding fumes.

PubMed

Antonini, James M; Roberts, Jenny R; Chapman, Rebecca S; Soukup, Joleen M; Ghio, Andrew J; Sriram, Krishnan

2010-08-01

Welders are exposed to fumes with different metal profiles. The goals of this study were to compare lung responses in rats after treatment with chemically different welding fumes and to examine the extrapulmonary fate of metals after deposition in the lungs. Rats were treated by intratracheal instillation (0.5 mg/rat, once a week for 7 weeks) with gas metal arc-mild steel (GMAW-MS) or manual metal arc-hardsurfacing (MMAW-HS) welding fumes. Controls were treated with saline. At 1, 4, 35, and 105 days after the last treatment, lung injury and inflammation were measured, and elemental analysis of different organs was determined to assess metal clearance. The MMAW-HS fume was highly water-soluble and chemically more complex with higher levels of soluble Mn and Cr compared to the GMAW-MS fume. Treatments with the GMAW-MS fume had no effect on toxicity when compared with controls. The MMAW-HS fume induced significant lung damage early after treatment that remained elevated until 35 days. Metals associated with each fume sample was cleared at different rates from the lungs. Mn was cleared from the lungs at a faster rate and to a greater extent compared to the other metals over the 105-day recovery period. Mn and Cr in the MMAW-HS fume translocated from the respiratory tract and deposited in other organs. Importantly, increased deposition of Mn, but not other metals, was observed in discrete brain regions, including dopamine-rich areas (e.g., striatum and midbrain).

Bimetallic redox synergy in oxidative palladium catalysis.

PubMed

Powers, David C; Ritter, Tobias

2012-06-19

Polynuclear transition metal complexes, which are embedded in the active sites of many metalloenzymes, are responsible for effecting a diverse array of oxidation reactions in nature. The range of chemical transformations remains unparalleled in the laboratory. With few noteworthy exceptions, chemists have primarily focused on mononuclear transition metal complexes in developing homogeneous catalysis. Our group is interested in the development of carbon-heteroatom bond-forming reactions, with a particular focus on identifying reactions that can be applied to the synthesis of complex molecules. In this context, we have hypothesized that bimetallic redox chemistry, in which two metals participate synergistically, may lower the activation barriers to redox transformations relevant to catalysis. In this Account, we discuss redox chemistry of binuclear Pd complexes and examine the role of binuclear intermediates in Pd-catalyzed oxidation reactions. Stoichiometric organometallic studies of the oxidation of binuclear Pd(II) complexes to binuclear Pd(III) complexes and subsequent C-X reductive elimination from the resulting binuclear Pd(III) complexes have confirmed the viability of C-X bond-forming reactions mediated by binuclear Pd(III) complexes. Metal-metal bond formation, which proceeds concurrently with oxidation of binuclear Pd(II) complexes, can lower the activation barrier for oxidation. We also discuss experimental and theoretical work that suggests that C-X reductive elimination is also facilitated by redox cooperation of both metals during reductive elimination. The effect of ligand modification on the structure and reactivity of binuclear Pd(III) complexes will be presented in light of the impact that ligand structure can exert on the structure and reactivity of binuclear Pd(III) complexes. Historically, oxidation reactions similar to those discussed here have been proposed to proceed via mononuclear Pd(IV) intermediates, and the hypothesis of mononuclear Pd(II/IV) catalysis has guided the successful development of many reactions. Herein we discuss differences between monometallic Pd(IV) and bimetallic Pd(III) redox catalysis. We address whether appreciation of the relevance of bimetallic Pd(III) redox catalysis is of academic interest exclusively, serving to provide a more nuanced description of catalysis, or if the new insight regarding bimetallic Pd(III) chemistry can be a platform to enable future reaction development. To this end, we describe an example in which the hypothesis of bimetallic redox chemistry guided reaction development, leading to the discovery of reactivity distinct from monometallic catalysts.

Finger printing of mixed contaminants from former manufactured gas plant (MGP) site soils: Implications to bioremediation.

PubMed

Thavamani, Palanisami; Megharaj, Mallavarapu; Krishnamurti, G S R; McFarland, Ross; Naidu, Ravi

2011-01-01

Contaminants in general do not occur as single chemicals but as mixtures at any contaminated site. Gasworks sites are the typical mixed contaminated sites. These sites are not only subjected to PAH contamination but also varying degrees of heavy metal contamination. Bioremediation in these sites is often hindered by the presence of heavy metals. The co-occurrence of PAHs with heavy metals has not been systematically investigated. Metals are reported to inhibit the general soil microbiological processes. The total concentration of soluble metal in the system includes both free metal ion and complexed forms. Within bioavailable fraction, the most toxic form is the free metal species, which was not addressed well so far in gas works site characterisation. This study underpins the science and importance of metal bioavailability and speciation based site characterisation in mixed contaminated sites. In this study a detailed elemental chemistry of the gas works site soils are discussed using different methods. The PAH contamination was contributed by both low and high molecular weight PAHs. The total PAHs concentration ranged from 335 to 8645 mg/kg. Among most toxic metals Pb was found in high concentration ranging from 88 to 671 mg/kg, Cd 8 to 112 mg/kg and Zn varied from 64 to 488 mg/kg. Thermodynamic chemical equilibrium model VMINTEQ (Ver 2.52) was used to calculate the free metal species in gas works site soils. The percentage free metal species showed a different trend compared to total metal concentrations, free Zn species ranged 18-86%, free Cd was 26-87% and Pb showed lowest free metal percentage (0-17%). The bioavailable metal species and its implications to bioremediation have also been discussed. Copyright © 2010 Elsevier Ltd. All rights reserved.

Role of metal oxides in chemical evolution

NASA Astrophysics Data System (ADS)

Kamaluddin

2013-06-01

Steps of chemical evolution have been designated as formation of biomonomers followed by their polymerization and then to modify in an organized structure leading to the formation of first living cell. Formation of small molecules like amino acids, organic bases, sugar etc. could have occurred in the reducing atmosphere of the primitive Earth. Polymerization of these small molecules could have required some catalyst. In addition to clay, role of metal ions and metal complexes as prebiotic catalyst in the synthesis and polymerization of biomonomers cannot be ruled out. Metal oxides are important constituents of Earth crust and that of other planets. These oxides might have adsorbed organic molecules and catalyzed the condensation processes, which may have led to the formation of first living cell. Different studies were performed in order to investigate the role of metal oxides (especially oxides of iron and manganese) in chemical evolution. Iron oxides (goethite, akaganeite and hematite) as well as manganese oxides (MnO, Mn2O3, Mn3O4 and MnO2) were synthesized and their characterization was done using IR, powder XRD, FE-SEM and TEM. Role of above oxides was studied in the adsorption of ribose nucleotides, formation of nucleobases from formamide and oligomerization of amino acids. Above oxides of iron and manganese were found to have good adsorption affinity towards ribose nucleotides, high catalytic activity in the formation of several nucleobases from formamide and oligomerization of glycine and alanine. Characterization of products was performed using UV, IR, HPLC and ESI-MS techniques. Presence of hematite-water system on Mars has been suggested to be a positive indicator in the chemical evolution on Mars.

Characterization of the binding capacity of mercurial species in Lactobacillus strains.

PubMed

Alcántara, Cristina; Jadán-Piedra, Carlos; Vélez, Dinoraz; Devesa, Vicenta; Zúñiga, Manuel; Monedero, Vicente

2017-12-01

Metal sequestration by bacteria has been proposed as a strategy to counteract metal contamination in foodstuffs. Lactobacilli can interact with metals, although studies with important foodborne metals such as inorganic [Hg(II)] or organic (CH 3 Hg) mercury are lacking. Lactobacilli were evaluated for their potential to bind these contaminants and the nature of the interaction was assessed by the use of metal competitors, chemical and enzymatical treatments, and mutants affected in the cell wall structure. Lactobacillus strains efficiently bound Hg(II) and CH 3 Hg. Mercury binding by Lactobacillus casei BL23 was independent of cell viability. In BL23, both forms of mercury were cell wall bound. Their interaction was not inhibited by cations and it was resistant to chelating agents and protein digestion. Lactobacillus casei mutants affected in genes involved in the modulation of the negative charge of the cell wall anionic polymer lipoteichoic acid showed increased mercury biosorption. In these mutants, mercury toxicity was enhanced compared to wild-type bacteria. These data suggest that lipoteichoic acid itself or the physicochemical characteristics that it confers to the cell wall play a major role in mercury complexation. This is the first example of the biosorption of Hg(II) and CH 3 Hg in lactobacilli and it represents a first step towards their possible use as agents for diminishing mercury bioaccessibility from food at the gastrointestinal tract. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Expanding the molecular-ruler process through vapor deposition of hexadecanethiol

PubMed Central

Patron, Alexandra M; Hooker, Timothy S; Santavicca, Daniel F

2017-01-01

The development of methods to produce nanoscale features with tailored chemical functionalities is fundamental for applications such as nanoelectronics and sensor fabrication. The molecular-ruler process shows great utility for this purpose as it combines top-down lithography for the creation of complex architectures over large areas in conjunction with molecular self-assembly, which enables precise control over the physical and chemical properties of small local features. The molecular-ruler process, which most commonly uses mercaptoalkanoic acids and metal ions to generate metal-ligated multilayers, can be employed to produce registered nanogaps between metal features. Expansion of this methodology to include molecules with other chemical functionalities could greatly expand the overall versatility, and thus the utility, of this process. Herein, we explore the use of alkanethiol molecules as the terminating layer of metal-ligated multilayers. During this study, it was discovered that the solution deposition of alkanethiol molecules resulted in low overall surface coverage with features that varied in height. Because features with varied heights are not conducive to the production of uniform nanogaps via the molecular-ruler process, the vapor-phase deposition of alkanethiol molecules was explored. Unlike the solution-phase deposition, alkanethiol islands produced by vapor-phase deposition exhibited markedly higher surface coverages of uniform heights. To illustrate the applicability of this method, metal-ligated multilayers, both with and without an alkanethiol capping layer, were utilized to create nanogaps between Au features using the molecular-ruler process. PMID:29181290

Interaction of Metal Oxides with Biomolecules: Implication in Astrobiology

NASA Astrophysics Data System (ADS)

Kamaluddin; Iqubal, Md. Asif

2014-08-01

Steps of chemical evolution have been designated as formation of biomonomers followed by their polymerization and then to modify in an organized structure leading to the formation of first living cell. Polymerization of biomonomers could have required some catalyst. In addition to clay, role of metal ions and metal complexes as prebiotic catalyst in the synthesis and polymerization of biomonomers cannot be ruled out. Metal oxides are important constituents of Earth crust and that of other planets. These oxides might have adsorbed organic molecules and catalyzed the condensation processes, which may have led to the formation of first living cell. Different studies were performed in order to investigate the role of metal oxides (especially oxides of iron and manganese) in chemical evolution. Iron oxides (goethite, akaganeite and hematite) as well as manganese oxides (MnO, Mn2O3, Mn3O4 and MnO2) were synthesized and their characterization was done using IR, powder XRD, FE-SEM and TEM. Role of above oxides was studied in the adsorption of ribose nucleotides, formation of nucleobases from formamide and oligomerization of amino acids. Above oxides of iron and manganese were found to have good adsorption affinity towards ribose nucleotides, high catalytic activity in the formation of several nucleobases from formamide and oligomerization of glycine and alanine. Characterization of products was performed using UV, IR, HPLC and ESI-MS techniques. Presence of hematite-water system on Mars has been suggested to be a positive indicator in the chemical evolution on Mars.

Metallic iron for water treatment: leaving the valley of confusion

NASA Astrophysics Data System (ADS)

Makota, Susanne; Nde-Tchoupe, Arnaud I.; Mwakabona, Hezron T.; Tepong-Tsindé, Raoul; Noubactep, Chicgoua; Nassi, Achille; Njau, Karoli N.

2017-12-01

Researchers on metallic iron (Fe0) for environmental remediation and water treatment are walking in a valley of confusion for 25 years. This valley is characterized by the propagation of different beliefs that have resulted from a partial analysis of the Fe0/H2O system as (1) a reductive chemical reaction was considered an electrochemical one and (2) the mass balance of iron has not been really addressed. The partial analysis in turn has been undermining the scientific method while discouraging any real critical argumentation. This communication re-establishes the complex nature of the Fe0/H2O system while recalling that, finally, proper system analysis and chemical thermodynamics are the most confident ways to solve any conflicting situation in Fe0 environmental remediation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stair, Peter C.

The research took advantage of our capabilities to perform in-situ and operando Raman spectroscopy on complex systems along with our developing expertise in the synthesis of uniform, supported metal oxide materials to investigate relationships between the catalytically active oxide composition, atomic structure, and support and the corresponding chemical and catalytic properties. The project was organized into two efforts: 1) Synthesis of novel catalyst materials by atomic layer deposition (ALD). 2) Spectroscopic and chemical investigations of coke formation and catalyst deactivation. ALD synthesis was combined with conventional physical characterization, Raman spectroscopy, and probe molecule chemisorption to study the effect of supportedmore » metal oxide composition and atomic structure on acid-base and catalytic properties. Operando Raman spectroscopy studies of olefin polymerization leading to coke formation and catalyst deactivation clarified the mechanism of coke formation by acid catalysts.« less

NMR and TRLFS studies of Ln(iii) and An(iii) C5-BPP complexes.

PubMed

Adam, Christian; Beele, Björn B; Geist, Andreas; Müllich, Udo; Kaden, Peter; Panak, Petra J

2015-02-01

C5-BPP is a highly efficient N-donor ligand for the separation of trivalent actinides, An(iii), from trivalent lanthanides, Ln(iii). The molecular origin of the selectivity of C5-BPP and many other N-donor ligands of the BTP-type is still not entirely understood. We present here the first NMR studies on C5-BPP Ln(iii) and An(iii) complexes. C5-BPP is synthesized with 10% 15 N labeling and characterized by NMR and LIFDI-MS methods. 15 N NMR spectroscopy gives a detailed insight into the bonding of C5-BPP with lanthanides and Am(iii) as a representative for trivalent actinide cations, revealing significant differences in 15 N chemical shift for coordinating nitrogen atoms compared to Ln(iii) complexes. The temperature dependence of NMR chemical shifts observed for the Am(iii) complex indicates a weak paramagnetism. This as well as the observed large chemical shift for coordinating nitrogen atoms show that metal-ligand bonding in Am(C5-BPP) 3 has a larger share of covalence than in lanthanide complexes, confirming earlier studies. The Am(C5-BPP) 3 NMR sample is furthermore spiked with Cm(iii) and characterized by time-resolved laser fluorescence spectroscopy (TRLFS), yielding important information on the speciation of trace amounts of minor complex species.

Catalytic transformation of functionalized carboxylic acids using multifunctional rhenium complexes.

PubMed

Naruto, Masayuki; Agrawal, Santosh; Toda, Katsuaki; Saito, Susumu

2017-06-13

Carboxylic acids (CAs) are one of the most ubiquitous and important chemical feedstocks available from biorenewable resources, CO 2 , and the petrochemical industry. Unfortunately, chemoselective catalytic transformations of CH n CO 2 H (n = 1-3) groups into other functionalities remain a significant challenge. Herein, we report rhenium V complexes as extremely effective precatalysts for this purpose. Compared to previously reported heterogeneous and homogeneous catalysts derived from high- or low-valent metals, the present method involves a α-C-H bond functionalization, a hydrogenation, and a hydrogenolysis, which affords functionalized alcohols with a wide substrate scope and high chemoselectivity under relatively mild reaction conditions. The results represent an important step toward a paradigm shift from 'low-valent' to 'high-valent' metal complexes by exploring a new portfolio of selective functional group transformations of highly oxygenated organic substrates, as well as toward the exploitation of CAs as a valuable biorenewable feedstock.

FT-IR, micro-Raman and UV-vis spectroscopic and quantum chemical investigations of free 2,2'-dithiodipyridine and its metal (Co, Cu and Zn) halide complexes.

PubMed

Gökce, Halil; Bahçeli, Semiha

2013-10-01

In this study the elemental analysis results, molecular geometries, vibrational and electronic absorption spectra of free 2,2'-dithiodipyridine(C10H8N2S2), (or DTDP) (with synonym, 2,2'-dipyridyl disulfide) and M(C10H8N2S2)Cl2 (M=Co, Cu and Zn) complexes have been reported. Vibrational wavenumbers of free DTDP and its metal halide complexes have been calculated by using DFT/B3LYP calculation method with 6-31++G(d,p) and Lanl2DZ basis sets, respectively, in the ground state, for the first time. The calculated fundamental vibrational frequencies are in a good agreement with experimental data. The HOMO, LUMO and MEP analyses of all compounds are performed by DFT method. Copyright © 2013. Published by Elsevier B.V.

Plasma based formation and deposition of metal and metal oxide nanoparticles using a gas aggregation source

NASA Astrophysics Data System (ADS)

Polonskyi, Oleksandr; Ahadi, Amir Mohammad; Peter, Tilo; Fujioka, Kenji; Abraham, Jan Willem; Vasiliauskaite, Egle; Hinz, Alexander; Strunskus, Thomas; Wolf, Sebastian; Bonitz, Michael; Kersten, Holger; Faupel, Franz

2018-05-01

Metal clusters and nanoparticles (NPs) have been studied intensively due to their unique chemical, physical, electrical, and optical properties, resulting from their dimensions, which provided host of applications in nanoscience and nanotechnology. Formation of new materials by embedding NPs into various matrices (i.e. formation of nanocomposites) further expands the horizon of possible application of such nanomaterials. In the last few decades, the focus was put on the formation of metallic and metal oxide NPs via a so-called gas aggregation nanoparticle source employing magnetron sputtering (i.e. Haberland concept). In this paper, an overview is given of the recent progress in formation and deposition of NPs by the gas aggregation method. Examples range from noble metals (Ag, Au) through reactive metals (Al, Ti) to Si and the respective oxides. Emphasis is placed on the mechanism of nanoparticle growth and the resulting properties. Moreover, kinetic Monte Carlo simulations were developed to explain the growth mechanism and dynamics of nanoparticle formation depending on the experimental conditions. In addition, the role of trace amounts of reactive gases and of pulsed operation of the plasma on the nucleation process is addressed. Finally, the treatment of the NPs in the plasma environment resulting in nanoparticle charging, morphological and chemical modifications is discussed. Contribution to the Topical Issue "Fundamentals of Complex Plasmas", edited by Jürgen Meichsner, Michael Bonitz, Holger Fehske, Alexander Piel.

Simultaneous application of chemical oxidation and extraction processes is effective at remediating soil Co-contaminated with petroleum and heavy metals.

PubMed

Yoo, Jong-Chan; Lee, Chadol; Lee, Jeung-Sun; Baek, Kitae

2017-01-15

Chemical extraction and oxidation processes to clean up heavy metals and hydrocarbon from soil have a higher remediation efficiency and take less time than other remediation processes. In batch extraction/oxidation process, 3% hydrogen peroxide (H 2 O 2 ) and 0.1 M ethylenediaminetetraacetic acid (EDTA) could remove approximately 70% of the petroleum and 60% of the Cu and Pb in the soil, respectively. In particular, petroleum was effectively oxidized by H 2 O 2 without addition of any catalysts through dissolution of Fe oxides in natural soils. Furthermore, heavy metals bound to Fe-Mn oxyhydroxides could be extracted by metal-EDTA as well as Fe-EDTA complexation due to the high affinity of EDTA for metals. However, the strong binding of Fe-EDTA inhibited the oxidation of petroleum in the extraction-oxidation sequential process because Fe was removed during the extraction process with EDTA. The oxidation-extraction sequential process did not significantly enhance the extraction of heavy metals from soil, because a small portion of heavy metals remained bound to organic matter. Overall, simultaneous application of oxidation and extraction processes resulted in highly efficient removal of both contaminants; this approach can be used to remove co-contaminants from soil in a short amount of time at a reasonable cost. Copyright © 2016 Elsevier Ltd. All rights reserved.

Metal oxide nanosensors using polymeric membranes, enzymes and antibody receptors as ion and molecular recognition elements.

PubMed

Willander, Magnus; Khun, Kimleang; Ibupoto, Zafar Hussain

2014-05-16

The concept of recognition and biofunctionality has attracted increasing interest in the fields of chemistry and material sciences. Advances in the field of nanotechnology for the synthesis of desired metal oxide nanostructures have provided a solid platform for the integration of nanoelectronic devices. These nanoelectronics-based devices have the ability to recognize molecular species of living organisms, and they have created the possibility for advanced chemical sensing functionalities with low limits of detection in the nanomolar range. In this review, various metal oxides, such as ZnO-, CuO-, and NiO-based nanosensors, are described using different methods (receptors) of functionalization for molecular and ion recognition. These functionalized metal oxide surfaces with a specific receptor involve either a complex formation between the receptor and the analyte or an electrostatic interaction during the chemical sensing of analytes. Metal oxide nanostructures are considered revolutionary nanomaterials that have a specific surface for the immobilization of biomolecules with much needed orientation, good conformation and enhanced biological activity which further improve the sensing properties of nanosensors. Metal oxide nanostructures are associated with certain unique optical, electrical and molecular characteristics in addition to unique functionalities and surface charge features which shows attractive platforms for interfacing biorecognition elements with effective transducing properties for signal amplification. There is a great opportunity in the near future for metal oxide nanostructure-based miniaturization and the development of engineering sensor devices.

An Analogy Using Pennies and Dimes to Explain Chemical Kinetics Concepts

ERIC Educational Resources Information Center

Cortes-Figueroa, Jose E.; Perez, Wanda I.; Lopez, Jose R.; Moore-Russo, Deborah A.

2011-01-01

In this article, the authors present an analogy that uses coins and graphical analysis to teach kinetics concepts and resolve pseudo-first-order rate constants related to transition-metal complexes ligand-solvent exchange reactions. They describe an activity that is directed to upper-division undergraduate and graduate students. The activity…

Method and apparatus for hydrogen production from water

NASA Technical Reports Server (NTRS)

Muradov, Nazim Z. (Inventor)

2012-01-01

A method, apparatuses and chemical compositions are provided for producing high purity hydrogen from water. Metals or alloys capable of reacting with water and producing hydrogen in aqueous solutions at ambient conditions are reacted with one or more inorganic hydrides capable of releasing hydrogen in aqueous solutions at ambient conditions, one or more transition metal compounds are used to catalyze the reaction and, optionally, one or more alkali metal-based compounds. The metal or alloy is preferably aluminum. The inorganic hydride is from a family of complex inorganic hydrides; most preferably, NaBH.sub.4. The transition metal catalyst is from the groups VIII and IB; preferably, Cu and Fe. The alkali metal-based compounds are preferably NaOH, KOH, and the like. Hydrogen generated has a purity of at least 99.99 vol. % (dry basis), and is used without further purification in all types of fuel cells, including the polymer electrolyte membrane (PEM) fuel cell.

New biosorbent in removing some metals from industrial wastewater in El Mex Bay, Egypt

NASA Astrophysics Data System (ADS)

Abdallah, Maha Ahmed Mohamed; Mahmoud, Mohamed E.; Osman, Maher M.; Ahmed, Somaia B.

2017-07-01

Biosorption is an extensive technology applied for the removal of heavy metal ions and other pollutants from aqueous solutions. In the present study, the biosorption of cadmium, lead, chromium and mercury ions from polluted surface seawater in El-Max Bay was determined using hybrid active carbon sorbents. These sorbents were treated chemically by acid, base and redox reaction followed by surface loading of baker's yeast biomass for increasing their biosorption capacity and the highest metal uptake values. The surface function and morphology of the hybrid immobilized sorbents were studied by Fourier Transform Infrared analysis and scanning electron microscope imaging. Metal removal values proved that the vital role of baker's yeast as a significant high removable due to functional groups at baker's yeast cell wall surface that have the ability to forming various coordination complexes with metal ions. A noticeable increase in the removal of all studied metals was observed and reached to 100 %.

Effects of calcium, magnesium, and sodium on alleviating cadmium toxicity to Hyalella azteca

USGS Publications Warehouse

Jackson, B.P.; Lasier, P.J.; Miller, W.P.; Winger, P.V.

2000-01-01

Toxicity of trace metal ions to aquatic organisms, arising through either anthropogenic inputs or acidification of surface waters, continues to be both a regulatory and environmental problem. It is generally accepted that the free metal ion is the major toxic species (Florence et a1.,1992) and that inorganic or organic complexation renders the metal ion non-bioavailable (Meador, 1991, Galvez and Wood, 1997). However, water chemistry parameters such as alkalinity, hardness, dissolved organic carbon and pH influence metal ion toxicity either directly by lowering free metal ion concentration or indirectly through synergistic or antagonistic effects. Alkalinity and salinity can affect the speciation of metal ions by increasing ion-pair formation, thus decreasing free metal ion concentration. For example, Cu was found to be less toxic to rainbow trout in waters of high alkalinity (Miller and Mackay, 1980), due to formation of CuCO3 ion pair, and corresponding reduction in free Cu2+ concentration. The influence of salinity on the toxicity of cadmium to various organisms has been demonstrated in a number of studies (Bervoets et al., 1995, Hall et al., 1995, Lin and Dunson, 1993, Blust et al., 1992). In all these studies the apparent toxicity of cadmium was lowered as salinity was increased due to increased formation of CdC1+ and CDCl2 aqueous complexes that are non-toxic or of much lower toxicity than the free Cd2+ ion. Changes in pH exert both a biological and chemical effect on metal ion toxicity (Campbell and Stokes, 1985). Low pH favors greater metal ion solubility, and, in the absence of complexing ions, reduced speciation of the metal ion, which tends to increase toxicity compared to higher pH. However, Iow pH also enhances competition between H+ and metal ion for cell surface binding sites, which tends to decrease metal ion toxicity.

A multimodal imaging workflow to visualize metal mixtures in the human placenta and explore colocalization with biological response markers.

PubMed

Niedzwiecki, Megan M; Austin, Christine; Remark, Romain; Merad, Miriam; Gnjatic, Sacha; Estrada-Gutierrez, Guadalupe; Espejel-Nuñez, Aurora; Borboa-Olivares, Hector; Guzman-Huerta, Mario; Wright, Rosalind J; Wright, Robert O; Arora, Manish

2016-04-01

Fetal exposure to essential and toxic metals can influence life-long health trajectories. The placenta regulates chemical transmission from maternal circulation to the fetus and itself exhibits a complex response to environmental stressors. The placenta can thus be a useful matrix to monitor metal exposures and stress responses in utero, but strategies to explore the biologic effects of metal mixtures in this organ are not well-developed. In this proof-of-concept study, we used laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to measure the distributions of multiple metals in placental tissue from a low-birth-weight pregnancy, and we developed an approach to identify the components of metal mixtures that colocalized with biological response markers. Our novel workflow, which includes custom-developed software tools and algorithms for spatial outlier identification and background subtraction in multidimensional elemental image stacks, enables rapid image processing and seamless integration of data from elemental imaging and immunohistochemistry. Using quantitative spatial statistics, we identified distinct patterns of metal accumulation at sites of inflammation. Broadly, our multiplexed approach can be used to explore the mechanisms mediating complex metal exposures and biologic responses within placentae and other tissue types. Our LA-ICP-MS image processing workflow can be accessed through our interactive R Shiny application 'shinyImaging', which is available at or through our laboratory's website, .

Tailoring Thermodynamics and Kinetics for Hydrogen Storage in Complex Hydrides towards Applications.

PubMed

Liu, Yongfeng; Yang, Yaxiong; Gao, Mingxia; Pan, Hongge

2016-02-01

Solid-state hydrogen storage using various materials is expected to provide the ultimate solution for safe and efficient on-board storage. Complex hydrides have attracted increasing attention over the past two decades due to their high gravimetric and volumetric hydrogen densities. In this account, we review studies from our lab on tailoring the thermodynamics and kinetics for hydrogen storage in complex hydrides, including metal alanates, borohydrides and amides. By changing the material composition and structure, developing feasible preparation methods, doping high-performance catalysts, optimizing multifunctional additives, creating nanostructures and understanding the interaction mechanisms with hydrogen, the operating temperatures for hydrogen storage in metal amides, alanates and borohydrides are remarkably reduced. This temperature reduction is associated with enhanced reaction kinetics and improved reversibility. The examples discussed in this review are expected to provide new inspiration for the development of complex hydrides with high hydrogen capacity and appropriate thermodynamics and kinetics for hydrogen storage. © 2015 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural changes at the metal ion binding site during the phosphoglucomutase reaction.

PubMed

Ray, W J; Post, C B; Liu, Y; Rhyu, G I

1993-01-12

An electron density map of the reactive, Cd2+ form of crystalline phosphoglucomutase from X-ray diffraction studies shows that the enzymic phosphate donates a nonbridging oxygen to the ligand sphere of the bound metal ion, which appears to be tetracoordinate. 31P and 113Cd NMR spectroscopy are used to assess changes in the properties of bound Cd2+ produced by substrate/product and by substrate/product analog inhibitors. The approximately 50 ppm downfield shift of the 113Cd resonance on formation of the complex of dephosphoenzyme and glucose 1,6-bisphosphate is associated with the initial sugar-phosphate binding step and likely involves a change in the geometry of the coordinating ligands. This interpretation is supported by spectral studies involving various complexes of the active Co2+ and Ni(2+)-enzyme. In addition, there is a loss of the 31P-113Cd J coupling that characterizes the monophosphate complexes of the Cd2+ enzyme either during or immediately after the PO3- transfer step that produces the bisphosphate complex, indicating a further change at the metal binding site. The implications of these observations with respect to the PO3- transfer process in the phosphoglucomutase reaction are considered. The apparent plasticity of the ligand sphere of the active site metal ion in this system may allow a single metal ion to act as a chaperone for a nonbridging oxygen during PO3- transfer or to allow a change in metal ion coordination during catalysis. A general NMR line shape/chemical-exchange analysis for evaluating binding in protein-ligand systems when exchange is intermediate to fast on the NMR time scale is described. Its application to the present system involves multiple exchange sites that depend on a single binding rate, thereby adding further constraints to the analysis.

In situ studies of oxide nucleation, growth, and transformation using slow electrons

NASA Astrophysics Data System (ADS)

Flege, Jan Ingo; Grinter, David C.

2018-05-01

Surface processes such as metal oxidation and metal oxide growth invariably influence the physical and chemical properties of materials and determine their interaction with their surroundings and hence their functionality in many technical applications. On a fundamental level, these processes are found to be governed by a complex interplay of thermodynamic variables and kinetic constraints, resulting in a rich variety of material-specific phenomena. In this review article, we discuss recent results and insights on transition metal oxidation and rare-earth oxide growth acquired by low-energy electron microscopy and related techniques. We demonstrate that the use of in situ surface sensitive methods is a prerequisite to gaining a deeper understanding of the underlying concepts and the mechanisms responsible for the emerging oxide structure and morphology. Furthermore, examples will be provided on how structural and chemical modifications of the oxide films and nanostructures can be followed in real-time and analyzed in terms of local reactivity and cooperative effects relevant for heterogeneous model catalysis.

Complex-Morphology Metal-Based Nanostructures: Fabrication, Characterization, and Applications

PubMed Central

Gentile, Antonella; Ruffino, Francesco; Grimaldi, Maria Grazia

2016-01-01

Due to their peculiar qualities, metal-based nanostructures have been extensively used in applications such as catalysis, electronics, photography, and information storage, among others. New applications for metals in areas such as photonics, sensing, imaging, and medicine are also being developed. Significantly, most of these applications require the use of metals in the form of nanostructures with specific controlled properties. The properties of nanoscale metals are determined by a set of physical parameters that include size, shape, composition, and structure. In recent years, many research fields have focused on the synthesis of nanoscale-sized metallic materials with complex shape and composition in order to optimize the optical and electrical response of devices containing metallic nanostructures. The present paper aims to overview the most recent results—in terms of fabrication methodologies, characterization of the physico-chemical properties and applications—of complex-morphology metal-based nanostructures. The paper strongly focuses on the correlation between the complex morphology and the structures’ properties, showing how the morphological complexity (and its nanoscale control) can often give access to a wide range of innovative properties exploitable for innovative functional device production. We begin with an overview of the basic concepts on the correlation between structural and optical parameters of nanoscale metallic materials with complex shape and composition, and the possible solutions offered by nanotechnology in a large range of applications (catalysis, electronics, photonics, sensing). The aim is to assess the state of the art, and then show the innovative contributions that can be proposed in this research field. We subsequently report on innovative, versatile and low-cost synthesis techniques, suitable for providing a good control on the size, surface density, composition and geometry of the metallic nanostructures. The main purpose of this study is the fabrication of functional nanoscale-sized materials, whose properties can be tailored (in a wide range) simply by controlling the structural characteristics. The modulation of the structural parameters is required to tune the plasmonic properties of the nanostructures for applications such as biosensors, opto-electronic or photovoltaic devices and surface-enhanced Raman scattering (SERS) substrates. The structural characterization of the obtained nanoscale materials is employed in order to define how the synthesis parameters affect the structural characteristics of the resulting metallic nanostructures. Then, macroscopic measurements are used to probe their electrical and optical properties. Phenomenological growth models are drafted to explain the processes involved in the growth and evolution of such composite systems. After the synthesis and characterization of the metallic nanostructures, we study the effects of the incorporation of the complex morphologies on the optical and electrical responses of each specific device. PMID:28335236

Methylenediphosphonotetrathioate: synthesis, characterization, and chemical properties.

PubMed

Amir, Aviran; Sayer, Alon Haim; Ezra, Alon; Fischer, Bilha

2013-03-18

Metal chelators are potential therapeutic agents for treating diseases such as Wilson's and Alzheimer's where the pathology involves an excess of metal-ions (Cu(II) and Zn(II)/Cu(II)/Fe(II/III), respectively). In addition to the high affinity of the metal-ion to the chelators, metal selectivity of the chelators is essential to achieve the therapeutic goal, that is, the successful removal of excess of harmful metal-ions in a physiological extracellular medium rich in alkali and alkali earth metal-ions. For this purpose, we synthesized a novel chelator, methylenediphosphonotetrathioate (MDPT) which is the tetrathio analogue of methylenediphosphonic acid (MDP). MDPT was synthesized from bis-methylene(phosphonicdichloride) in a 3-step synthesis and a 31% overall yield. MDPT formed a stable complex with Zn(II) (log K = 10.84), which is 10(7) times more stable than the corresponding Ca(II) complex. Moreover, the MDPT-Zn(II) complex was 50-fold more stable than the MDP-Zn(II) complex. In addition, MDPT was found to inhibit the Cu(I)-catalyzed Fenton reaction (IC50 26 μM) 2.5 times more potently than a Fe(II)-catalyzed Fenton reaction, and 2.5 times more potently than EDTA (IC50 64 μM) in the Cu(I)/H2O2 system, as monitored by electron spin resonance (ESR). Furthermore, MDPT was found to be relatively stable in both acidic (pD 1.9, t(½) = 71.5 h) and basic media (pD 12.4, t(½) = 81 h) as monitored by (31)P/(1)H NMR. However, MDPT was not stable in air because of intramolecular oxidation and disulfide formation (33% oxidation after 27 h). In conclusion, MDPT was found to be a water-soluble chelator showing a clear preference to soft/borderline metal-ions and a remarkable selectivity to those metal-ions vs Ca(II) ions. The relative sensitivity of MDPT to oxidation may limit its use; however, the application of MDPT in acidic or basic media will increase its lifetime.

Syntheses, spectroscopic properties and molecular structure of silver phytate complexes - IR, UV-VIS studies and DFT calculations

NASA Astrophysics Data System (ADS)

Zając, A.; Dymińska, L.; Lorenc, J.; Ptak, M.; Hanuza, J.

2018-03-01

Silver phytate IP6, IP6Ag, IP6Ag2 and IP6Ag3 complexes in the solid state have been synthesized changing the phosphate to metal mole ratio. The obtained products have been characterized by means of chemical and spectroscopic studies. Attenuated total reflection Fourier transform infrared technique and Raman microscope were used in the measurements. These results were discussed in terms of DFT (Density Functional Theory) quantum chemical calculations using the B3LYP/6-31G(d,p) approach. The molecular structures of these compounds have been proposed on the basis of group theory and geometry optimization taking into account the shape and the number of the observed bands corresponding to the stretching and bending vibrations of the phosphate group and metal-oxygen polyhedron. The role of inter- and intra-hydrogen bonds in stabilization of the structure has been discussed. It was found that three types of hydrogen bonds appear in the studied compounds: terminal, and those engaged in the inter- and intra-molecular interactions. The Fermi resonance as a result of the strong intra-molecular Osbnd H⋯O hydrogen bonds was discovered. Electron absorption spectra have been measured to characterize the electron properties of the studied complexes and their local symmetry.

Insight into the local environment of magnesium and calcium in low-coordination-number organo-complexes using 25Mg and 43Ca solid-state NMR: a DFT study.

PubMed

Gervais, Christel; Jones, Cameron; Bonhomme, Christian; Laurencin, Danielle

2017-03-01

With the increasing number of organocalcium and organomagnesium complexes under development, there is a real need to be able to characterize in detail their local environment in order to fully rationalize their reactivity. For crystalline structures, in cases when diffraction techniques are insufficient, additional local spectroscopies like 25 Mg and 43 Ca solid-state NMR may provide valuable information to help fully establish the local environment of the metal ions. In this current work, a prospective DFT investigation on crystalline magnesium and calcium complexes involving low-coordination numbers and N-bearing organic ligands was carried out, in which the 25 Mg and 43 Ca NMR parameters [isotropic chemical shift, chemical shift anisotropy (CSA) and quadrupolar parameters] were calculated for each structure. The analysis of the calculated parameters in relation to the local environment of the metal ions revealed that they are highly sensitive to very small changes in geometry/distances, and hence that they could be used to assist in the refinement of crystal structures. Moreover, such calculations provide a guideline as to how the NMR measurements will need to be performed, revealing that these will be very challenging.

Probing Fe-V Bonding in a C3-Symmetric Heterobimetallic Complex.

PubMed

Greer, Samuel M; McKay, Johannes; Gramigna, Kathryn M; Thomas, Christine M; Stoian, Sebastian A; Hill, Stephen

2018-04-30

Direct metal-metal bonding of two distinct first-row transition metals remains relatively unexplored compared to their second- and third-row heterobimetallic counterparts. Herein, a recently reported Fe-V triply bonded species, [V( i PrNPPh 2 ) 3 FeI] (1; Kuppuswamy, S.; Powers, T. M.; Krogman, J. P.; Bezpalko, M. W.; Foxman, B. M.; Thomas, C. M. Vanadium-iron complexes featuring metal-metal multiple bonds. Chem. Sci. 2013, 4, 3557-3565), is investigated using high-frequency electron paramagnetic resonance, field- and temperature-dependent 57 Fe nuclear gamma resonance (Mössbauer) spectroscopy, and high-field electron-electron double resonance detected nuclear magnetic resonance. From the use of this suite of physical methods, we have assessed the electronic structure of 1. These studies allow us to establish the effective g̃ tensors as well as the Fe/V electro-nuclear hyperfine interaction tensors of the spin S = 1 / 2 ground state. We have rationalized these tensors in the context of ligand field theory supported by quantum chemical calculations. This theoretical analysis suggests that the S = 1 / 2 ground state originates from a single unpaired electron predominately localized on the Fe site.

A Bimetallic Nickel–Gallium Complex Catalyzes CO 2 Hydrogenation via the Intermediacy of an Anionic d 10 Nickel Hydride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cammarota, Ryan C.; Vollmer, Matthew V.; Xie, Jing

Large-scale CO2 hydrogenation could offer a renewable stream of industrially important C1 chemicals while reducing CO2 emissions. Critical to this opportunity is the requirement for inexpensive catalysts based on earth-abundant metals instead of precious metals. We report a nickel-gallium complex featuring a Ni(0)→Ga(III) bond that shows remarkable catalytic activity for hydrogenating CO2 to formate at ambient temperature (3150 turnovers, turnover frequency = 9700 h-1), compared with prior homogeneous Ni-centred catalysts. The Lewis acidic Ga(III) ion plays a pivotal role by stabilizing reactive catalytic intermediates, including a rare anionic d10 Ni hydride. The structure of this reactive intermediate shows a terminalmore » Ni-H, for which the hydride donor strength rivals those of precious metal-hydrides. Collectively, our experimental and computational results demonstrate that modulating a transition metal center via a direct interaction with a Lewis acidic support can be a powerful strategy for promoting new reactivity paradigms in base-metal catalysis. The work was supported as part of the Inorganometallic Catalysis Design Center, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences under Award DE-SC0012702. R.C.C. and M.V.V. were supported by DOE Office of Science Graduate Student Research and National Science Foundation Graduate Research Fellowship programs, respectively. J.C.L., S.A.B., and A.M.A. were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.« less

Dissolved and labile concentrations of Cd, Cu, Pb, and Zn in the South Fork Coeur d'Alene River, Idaho: Comparisons among chemical equilibrium models and implications for biotic ligand models

USGS Publications Warehouse

Balistrieri, L.S.; Blank, R.G.

2008-01-01

In order to evaluate thermodynamic speciation calculations inherent in biotic ligand models, the speciation of dissolved Cd, Cu, Pb, and Zn in aquatic systems influenced by historical mining activities is examined using equilibrium computer models and the diffusive gradients in thin films (DGT) technique. Several metal/organic-matter complexation models, including WHAM VI, NICA-Donnan, and Stockholm Humic model (SHM), are used in combination with inorganic speciation models to calculate the thermodynamic speciation of dissolved metals and concentrations of metal associated with biotic ligands (e.g., fish gills). Maximum dynamic metal concentrations, determined from total dissolved metal concentrations and thermodynamic speciation calculations, are compared with labile metal concentrations measured by DGT to assess which metal/organic-matter complexation model best describes metal speciation and, thereby, biotic ligand speciation, in the studied systems. Results indicate that the choice of model that defines metal/organic-matter interactions does not affect calculated concentrations of Cd and Zn associated with biotic ligands for geochemical conditions in the study area, whereas concentrations of Cu and Pb associated with biotic ligands depend on whether the speciation calculations use WHAM VI, NICA-Donnan, or SHM. Agreement between labile metal concentrations and dynamic metal concentrations occurs when WHAM VI is used to calculate Cu speciation and SHM is used to calculate Pb speciation. Additional work in systems that contain wide ranges in concentrations of multiple metals should incorporate analytical speciation methods, such as DGT, to constrain the speciation component of biotic ligand models. ?? 2008 Elsevier Ltd.

Assessment of essential and nonessential metals and different metal exposure biomarkers in the human placenta in a population from the south of Portugal.

PubMed

Serafim, A; Company, R; Lopes, B; Rosa, J; Cavaco, A; Castela, G; Castela, E; Olea, N; Bebianno, M J

2012-01-01

The general population is exposed to metals as trace amounts of metallic compounds are present in air, water, and food. Information on background exposures and biomarker concentrations of environmental chemicals in the general Portuguese population is limited. Therefore, the purpose of this study was to determine the levels of important nonessential metals with recognized toxicity cadmium (Cd) and lead (Pb) and essential metals copper (Cu), nickel (Ni), chromium (Cr), and zinc (Zn) in placentas of mothers living in south Portugal (Algarve). Due to the difficulty in establishing the effects of chemicals in a complex and variable environment, this study also aimed to examine the response of biomarkers, such as biochemical changes that occurs at subcellular levels in the presence of contaminants. The investigated biomarkers in placentas indicative of metal exposure or damage included the metallothioneins (MT), delta-aminolevulinic acid dehydratase (ALAD) (specific for Pb), and lipid peroxidation (LPO) as an index of oxidative stress damage. Moreover, HJ-BIPLOT was applied in order to identify and categorize mothers vulnerable to environmental contamination in this region. Metal concentrations in the placenta were not excessive but within the range found in most European studies. In general, the biomarkers MT and LPO were positively correlated with metal levels, while with ALAD the opposite occurred, indicating the selected battery of biomarkers were suitable to study the effects of metals on human placenta. Further, the application of multivariate analysis with HJ-BIPLOT showed that most significant factors contributing to maternal and fetal exposures via placenta were dietary and smoking habits.

Chemical activation of molecules by metals: Experimental studies of electron distributions and bonding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lichtenberger, D.L.

1991-10-01

The formal relationship between measured molecular ionization energies and thermodynamic bond dissociation energies has been developed into a single equation which unifies the treatment of covalent bonds, ionic bonds, and partially ionic bonds. This relationship has been used to clarify the fundamental thermodynamic information relating to metal-hydrogen, metal-alkyl, and metal-metal bond energies. We have been able to obtain a direct observation and measurement of the stabilization energy provided by the agostic interaction of the C-H bond with the metal. The ionization energies have also been used to correlate the rates of carbonyl substitution reactions of ({eta}{sup 5}-C{sub 5}H{sub 4}X)Rh(CO){sub 2}more » complexes, and to reveal the electronic factors that control the stability of the transition state. The extent that the electronic features of these bonding interactions transfer to other chemical systems is being investigated in terms of the principle of additivity of ligand electronic effects. Specific examples under study include metal- phosphines, metal-halides, and metallocenes. Especially interesting has been the recent application of these techniques to the characterization of the soccer-ball shaped C{sub 60} molecule, buckminsterfullerene, and its interaction with a metal surface. The high-resolution valence ionizations in the gas phase reveal the high symmetry of the molecule, and studies of thin films of C{sub 60} reveal weak intermolecular interactions. Scanning tunneling and atomic force microscopy reveal the arrangement of spherical molecules on gold substrates, with significant delocalization of charge from the metal surface. 21 refs.« less

Atomic contributions from spin-orbit coupling to 29Si NMR chemical shifts in metallasilatrane complexes.

PubMed

Autschbach, Jochen; Sutter, Kiplangat; Truflandier, Lionel A; Brendler, Erica; Wagler, Jörg

2012-10-01

New members of a novel class of metallasilatrane complexes [X-Si-(μ-mt)(4)-M-Y], with M=Ni, Pd, Pt, X=F, Cl, Y=Cl, Br, I, and mt=2-mercapto-1-methylimidazolide, have been synthesized and characterized structurally by X-ray diffraction and by (29)Si solid-state NMR. Spin-orbit (SO) effects on the (29)Si chemical shifts induced by the metal, by the sulfur atoms in the ligand, and by heavy halide ligands Y=Cl, Br, I were investigated with the help of relativistic density functional calculations. Operators used in the calculations were constructed such that SO coupling can selectively be switched off for certain atoms. The unexpectedly large SO effects on the (29)Si shielding in the Ni complex with X=Y=Cl reported recently originate directly from the Ni atom, not from other moderately heavy atoms in the complex. With respect to Pd, SO effects are amplified for Ni owing to its smaller ligand-field splitting, despite the smaller nuclear charge. In the X=Cl, Y=Cl, Br, I series of complexes the Y ligand strongly modulates the (29)Si shift by amplifying or suppressing the metal SO effects. The pronounced delocalization of the partially covalent M←Y bond plays an important role in modulating the (29)Si shielding. We also demonstrate an influence from the X ligand on the (29)Si SO shielding contributions originating at Y. The NMR spectra for [X-Si-(μ-mt)(4)-M-Y] must be interpreted mainly based on electronic and relativistic effects, rather than structural differences between the complexes. The results highlight the sometimes unintuitive role of SO coupling in NMR spectra of complexes containing heavy atoms. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Molecular recognition in protein modification with rhodium metallopeptides

PubMed Central

Ball, Zachary T.

2015-01-01

Chemical manipulation of natural, unengineered proteins is a daunting challenge which tests the limits of reaction design. By combining transition-metal or other catalysts with molecular recognition ideas, it is possible to achieve site-selective protein reactivity without the need for engineered recognition sequences or reactive sites. Some recent examples in this area have used ruthenium photocatalysis, pyridine organocatalysis, and rhodium(II) metallocarbene catalysis, indicating that the fundamental ideas provide opportunities for using diverse reactivity on complex protein substrates and in complex cell-like environments. PMID:25588960

Tuning of Magnetic Anisotropy in Hexairon(III) Rings by Host-Guest Interactions: An Investigation by High-Field Torque Magnetometry.

PubMed

Cornia; Affronte; Jansen; Abbati; Gatteschi

1999-08-01

Full chemical control of magnetic anisotropy in hexairon(III) rings can be achieved by varying the size of the guest alkali metal ion. Dramatically different anisotropies characterize the Li(I) and Na(I) complexes of [Fe(6)(OMe)(12)(L)(6)] (L=1,3-propanedione derivatives; a schematic representation of the Li(I) complex is shown), as revealed by high-field torque magnetometry-Iron: (g), oxygen: o, carbon: o, Li(+): plus sign in circle.

Ellipsometric study of metal-organic chemically vapor deposited III-V semiconductor structures

NASA Technical Reports Server (NTRS)

Alterovitz, Samuel A.; Sekula-Moise, Patricia A.; Sieg, Robert M.; Drotos, Mark N.; Bogner, Nancy A.

1992-01-01

An ellipsometric study of MOCVD-grown layers of AlGaAs and InGaAs in thick films and strained layer complex structures is presented. It is concluded that the ternary composition of thick nonstrained layers can be accurately determined to within experimental errors using numerical algorithms. In the case of complex structures, thickness of all layers and the alloy composition of nonstrained layers can be determined simultaneously, provided that the correlations between parameters is no higher than 0.9.

Synthesis, spectral and theoretical studies of Ni(II), Pd(II) and Pt(II) complexes of 5-mercapto-1,2,4-triazole-3-imine-2'-hydroxynaphthaline.

PubMed

Gaber, Mohamed; El-Ghamry, Hoda; Atlam, Faten; Fathalla, Shaimaa

2015-02-25

Ni(II), Pd(II) and Pt(II) complexes of 5-mercapto-1,2,4-triazole-3-imine-2'-hydroxynaphthaline have been isolated and characterized by elemental analysis, IR, (1)H NMR, EI-mass, UV-vis, molar conductance, magnetic moment measurements and thermogravimetric analysis. The molar conductance values indicated that the complexes are non-electrolytes. The magnetic moment values of the complexes displayed diamagnetic behavior for Pd(II) and Pt(II) complexes and tetrahedral geometrical structure for Ni(II) complex. From the bioinorganic applications point of view, the interaction of the ligand and its metal complexes with CT-DNA was investigated using absorption and viscosity titration techniques. The Schiff-base ligand and its metal complexes have also been screened for their antimicrobial and antitumor activities. Also, theoretical investigation of molecular and electronic structures of the studied ligand and its metal complexes has been carried out. Molecular orbital calculations were performed using DFT (density functional theory) at B3LYP level with standard 6-31G(d,p) and LANL2DZ basis sets to access reliable results to the experimental values. The calculations were performed to obtain the optimized molecular geometry, charge density distribution, extent of distortion from regular geometry, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), Mulliken atomic charges, reactivity index (ΔE), dipole moment (D), global hardness (η), softness (σ), electrophilicity index (ω), chemical potential and Mulliken electronegativity (χ). Copyright © 2014 Elsevier B.V. All rights reserved.

Tailoring the physical properties of Ni-based single-phase equiatomic alloys by modifying the chemical complexity

DOE PAGES

Jin, Ke; Sales, Brian C.; Stocks, George Malcolm; ...

2016-02-01

We discovered that equiatomic alloys (e.g. high entropy alloys) have recently attracted considerable interest due to their exceptional properties, which might be closely related to their extreme disorder induced by the chemical complexity. To understand the effects of chemical complexity on their fundamental physical properties, a family of (eight) Ni-based, face-center-cubic (FCC), equiatomic alloys, extending from elemental Ni to quinary high entropy alloys, has been synthesized, and their electrical, thermal, and magnetic properties are systematically investigated in the range of 4–300 K by combining experiments with ab initio Korring-Kohn-Rostoker coherent-potential-approximation (KKR-CPA) calculations. The scattering of electrons is significantly increased duemore » to the chemical (especially magnetic) disorder. It has weak correlation with the number of elements but strongly depends on the type of elements. Thermal conductivities of the alloys are largely lower than pure metals, primarily because the high electrical resistivity suppresses the electronic thermal conductivity. Moreover, the temperature dependence of the electrical and thermal transport properties is further discussed, and the magnetization of five alloys containing three or more elements is measured in magnetic fields up to 4 T.« less

High density hexagonal boron nitride prepared by hot isostatic pressing in refractory metal containers

DOEpatents

Hoenig, Clarence L.

1992-01-01

Boron nitride powder with less than or equal to the oxygen content of starting powder (down to 0.5% or less) is hot isostatically pressed in a refractory metal container to produce hexagonal boron nitride with a bulk density greater than 2.0 g/cc. The refractory metal container is formed of tantalum, niobium, tungsten, molybdenum or alloys thereof in the form of a canister or alternatively plasma sprayed or chemical vapor deposited onto a powder compact. Hot isostatic pressing at 1800.degree. C. and 30 KSI (206.8 MPa) argon pressure for four hours produces a bulk density of 2.21 g/cc. Complex shapes can be made.

3D highly oriented nanoparticulate and microparticulate array ofmetal oxide materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vayssieres, Lionel; Guo, Jinghua; Nordgren, Joseph

2006-09-15

Advanced nano and micro particulate thin films of 3d transition and post-transition metal oxides consisting of nanorods and microrods with parallel and perpendicular orientation with respect to the substrate normal, have been successfully grown onto various substrates by heteronucleation, without template and/or surfactant, from the aqueous condensation of solution of metal salts or metal complexes (aqueous chemical growth). Three-dimensional arrays of iron oxide nanorods and zinc oxide nanorods with parallel and perpendicular orientation are presented as well as the oxygen K-edge polarization dependent x-ray absorption spectroscopy (XAS) study of anisotropic perpendicularly oriented microrod array of ZnO performed at synchrotron radiationmore » source facility.« less

Mechanisms for trace metal enrichment at the surface microlayer in an estuarine salt marsh

USGS Publications Warehouse

Lion, Leonard W.

1982-01-01

The relative contributions of adsorption to particulate surfaces, complexation with surface-active organic ligands and uptake by micro-organisms were evaluated with respect to their importance in the surface microlayer enrichment (‘partitioning’) of Cd, Pb and Cu. The contributions of each process were inferred from field data in which partitioning of the dissolved and particulate forms of Cd, Pb and Cu, total and dissolved organic carbon, particles and total bacteria were observed. In the South San Francisco Bay estuary, particle enrichment appears to control trace metal partitioning. Trace metal association with the particulate phase and the levels of partitioning observed were in the order Pb > Cu > Cd and reflect the calculated equilibrium chemical speciation of these metals in computer-simulated seawater matrices.

Voltage-dependent cluster expansion for electrified solid-liquid interfaces: Application to the electrochemical deposition of transition metals

NASA Astrophysics Data System (ADS)

Weitzner, Stephen E.; Dabo, Ismaila

2017-11-01

The detailed atomistic modeling of electrochemically deposited metal monolayers is challenging due to the complex structure of the metal-solution interface and the critical effects of surface electrification during electrode polarization. Accurate models of interfacial electrochemical equilibria are further challenged by the need to include entropic effects to obtain accurate surface chemical potentials. We present an embedded quantum-continuum model of the interfacial environment that addresses each of these challenges and study the underpotential deposition of silver on the gold (100) surface. We leverage these results to parametrize a cluster expansion of the electrified interface and show through grand canonical Monte Carlo calculations the crucial need to account for variations in the interfacial dipole when modeling electrodeposited metals under finite-temperature electrochemical conditions.

a Baseline Study of Physico-Chemical Parameters and Trace Metals in Waters of Manakudy, South-West Coast of India

NASA Astrophysics Data System (ADS)

Subramanian, M.; Muthumanikkam, J.

2013-05-01

The transport of trace metals from the land to ocean has a number of different routes and efficiencies. The sources of toxic elements into the rivers to be debouched into the sea through estuaries are either weathered naturally from the soils and rocks or introduced anthropogenically from point or non-point sources, in labile form or in particulate form. However, recent studies indicate that the transport of trace elements to the aquatic environment is much more complex than what has been thought. The chemistry and ecology of an estuarine system are entirely different from the fluvial as well as the marine system. Estuarine environment is characterized by a constantly changing mixture of salt and freshwater. In the present study area Manakudy estuary is situated about 8 kilometres north west of Kanyakumari (Latitude N 08 05 21.8 and Longitude E 077 29 03.7). To gain a better understanding of the geochemical behavior of physico-chemical parameters and trace elements in the estuary and to examine variations in associated chemical changes, 20 water samples were collected throughout the Manakudy estuary, a minor river in south-western India. These samples, collected in typical dry season during 2012, were analyzed for physico-chemical parameters, dissolved major and trace elements. Our results show that dissolved Na, Mg, Ca and Cl behave conservatively along the salinity gradient. The concentration of nutrients is normal and they are due to the higher organic activity in soils as well as faster rates of chemical weathering reaction in the source region. The concentration of major ions is due to tidal influence and it increases with salinity and the nutrients do behave non-conservatively due to biogenic removal. The conservative behaviour of the trace metals with salinity has been strongly affected by the introduction of these metals by external sources. Even though the trace metals in the contaminated water have been removed and incorporated in sediments due to flocculation, the concentration of these metals did not decrease. S.MUTHUSAMY M.sc.,M.phil., RESEARCH SCHOLAR UNIVERSITY OF MADRAS CHENNAI,TAMILNADU INDIA

Reversible photochromic system based on rhodamine B salicylaldehyde hydrazone metal complex.

PubMed

Li, Kai; Xiang, Yu; Wang, Xiaoyan; Li, Ji; Hu, Rongrong; Tong, Aijun; Tang, Ben Zhong

2014-01-29

Photochromic molecules are widely applied in chemistry, physics, biology, and materials science. Although a few photochromic systems have been developed before, their applications are still limited by complicated synthesis, low fatigue resistance, or incomplete light conversion. Rhodamine is a class of dyes with excellent optical properties including long-wavelength absorption, large absorption coefficient, and high photostability in its ring-open form. It is an ideal chromophore for the development of new photochromic systems. However, known photochromic rhodamine derivatives, such as amides, exhibit only millisecond lifetimes in their colored ring-open forms, making their application very limited and difficult. In this work, rhodamine B salicylaldehyde hydrazone metal complex was found to undergo intramolecular ring-open reactions upon UV irradiation, which led to a distinct color and fluorescence change both in solution and in solid matrix. The complex showed good fatigue resistance for the reversible photochromism and long lifetime for the ring-open state. Interestingly, the thermal bleaching rate was tunable by using different metal ions, temperatures, solvents, and chemical substitutions. It was proposed that UV light promoted isomerization of the rhodamine B derivative from enol-form to keto-form, which induced ring-opening of the rhodamine spirolactam in the complex to generate color. The photochromic system was successfully applied for photoprinting and UV strength measurement in the solid state. As compared to other reported photochromic molecules, the system in this study has its advantages of facile synthesis and tunable thermal bleaching rate, and also provides new insights into the development of photochromic materials based on metal complex and spirolactam-containing dyes.

The effect of acidification on the bioavailability and electrochemical lability of zinc in seawater

PubMed Central

Kim, Ja-Myung; Baars, Oliver

2016-01-01

A poorly studied but potentially important consequence of the CO2-induced acidification of the surface ocean is a possible change in the bioavailability of trace metals, which play a critical role in the productivity and population dynamics of marine ecosystems. We report laboratory and field experiments designed to compare quantitatively the effects of acidification on the bioavailability of Zn, a metal essential to the growth of phytoplankton and on the extent of its complexation by model and natural ligands. We observed a good correspondence between the effects of pH on the rate of Zn uptake by a model diatom and the chemical lability of Zn measured by anodic stripping voltammetry (ASV). In model laboratory systems, the chemical lability and the bioavailability of Zn could either increase or decrease at low pH depending on the mix of complexing ligands. In a sample of coastal surface water, we observed similar increases in the ASV-labile and bioavailable Zn concentrations upon acidification, a result contrary to previous observations. These results, which can likely be generalized to other bioactive trace metals, mutatis mutandis, demonstrate the intricacy of the effects of ocean acidification on the chemistry and the ecology of surface seawater. This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’. PMID:29035261

The effect of acidification on the bioavailability and electrochemical lability of zinc in seawater.

PubMed

Kim, Ja-Myung; Baars, Oliver; Morel, François M M

2016-11-28

A poorly studied but potentially important consequence of the CO 2 -induced acidification of the surface ocean is a possible change in the bioavailability of trace metals, which play a critical role in the productivity and population dynamics of marine ecosystems. We report laboratory and field experiments designed to compare quantitatively the effects of acidification on the bioavailability of Zn, a metal essential to the growth of phytoplankton and on the extent of its complexation by model and natural ligands. We observed a good correspondence between the effects of pH on the rate of Zn uptake by a model diatom and the chemical lability of Zn measured by anodic stripping voltammetry (ASV). In model laboratory systems, the chemical lability and the bioavailability of Zn could either increase or decrease at low pH depending on the mix of complexing ligands. In a sample of coastal surface water, we observed similar increases in the ASV-labile and bioavailable Zn concentrations upon acidification, a result contrary to previous observations. These results, which can likely be generalized to other bioactive trace metals, mutatis mutandis , demonstrate the intricacy of the effects of ocean acidification on the chemistry and the ecology of surface seawater.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2016 The Author(s).

Evidence for Extended Aqueous Alteration in CR Carbonaceous Chondrites

NASA Technical Reports Server (NTRS)

Trigo-Rodriquez, J. M.; Moyano-Cambero, C. E.; Mestres, N.; Fraxedas, J.; Zolensky, M.; Nakamura, T.; Martins, Z.

2013-01-01

We are currently studying the chemical interrelationships between the main rockforming components of carbonaceous chondrites (hereafter CC), e.g. silicate chondrules, refractory inclusions and metal grains, and the surrounding meteorite matrices. It is thought that the fine-grained materials that form CC matrices are representing samples of relatively unprocessed protoplanetary disk materials [1-3]. In fact, modern non-destructive analytical techniques have shown that CC matrices host a large diversity of stellar grains from many distinguishable stellar sources [4]. Aqueous alteration has played a role in homogeneizing the isotopic content that allows the identification of presolar grains [5]. On the other hand, detailed analytical techniques have found that the aqueously-altered CR, CM and CI chondrite groups contain matrices in which the organic matter has experienced significant processing concomitant to the formation of clays and other minerals. In this sense, clays have been found to be directly associated with complex organics [6, 7]. CR chondrites are particularly relevant in this context as this chondrite group contains abundant metal grains in the interstitial matrix, and inside glassy silicate chondrules. It is important because CR are known for exhibiting a large complexity of organic compounds [8-10], and only metallic Fe is considered essential in Fischer-Tropsch catalysis of organics [11-13]. Therefore, CR chondrites can be considered primitive materials capable to provide clues on the role played by aqueous alteration in the chemical evolution of their parent asteroids.

Cytology of pollutant metals in marine invertebrates: A review of microanalytical applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nott, J.A.

1991-03-01

x-ray microanalysis (XRMA) is customized for investigations of the metabolic and detoxification strategies of heavy metals taken by marine organisms from polluted environments. Sites of uptake, intracellular accumulation, transport and excretion are visualized, analysed and quantified. Cryopreparation techniques are required to prevent the translocation or loss from specimens of soluble metal species. In marine invertebrates, metals are detoxified by systems of chemical binding and intracellular compartmentalization. XRMA investigations have concentrated on marine molluscs and crustaceans and even within these restricted groups there are marked inter-species differences in the biochemical and cytological processes which reduce metal bioavailability. Some detoxification systems alsomore » protect the carnivores which ingest the metal-laden tissues of the prey. This results in the bioreduction of metals along a food chain. These processes are investigated by XRMA which can be tuned to observe the complex interactions which operate at all levels within and between the biota and polluted environments. 90 refs.« less

Metallic Contact between MoS2 and Ni via Au Nanoglue.

PubMed

Shi, Xinying; Posysaev, Sergei; Huttula, Marko; Pankratov, Vladimir; Hoszowska, Joanna; Dousse, Jean-Claude; Zeeshan, Faisal; Niu, Yuran; Zakharov, Alexei; Li, Taohai; Miroshnichenko, Olga; Zhang, Meng; Wang, Xiao; Huang, Zhongjia; Saukko, Sami; González, Diego López; van Dijken, Sebastiaan; Alatalo, Matti; Cao, Wei

2018-05-01

A critical factor for electronics based on inorganic layered crystals stems from the electrical contact mode between the semiconducting crystals and the metal counterparts in the electric circuit. Here, a materials tailoring strategy via nanocomposite decoration is carried out to reach metallic contact between MoS 2 matrix and transition metal nanoparticles. Nickel nanoparticles (NiNPs) are successfully joined to the sides of a layered MoS 2 crystal through gold nanobuffers, forming semiconducting and magnetic NiNPs@MoS 2 complexes. The intrinsic semiconducting property of MoS 2 remains unchanged, and it can be lowered to only few layers. Chemical bonding of the Ni to the MoS 2 host is verified by synchrotron radiation based photoemission electron microscopy, and further proved by first-principles calculations. Following the system's band alignment, new electron migration channels between metal and the semiconducting side contribute to the metallic contact mechanism, while semiconductor-metal heterojunctions enhance the photocatalytic ability. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In the presence of fluoride, free Sc³⁺ is not a good predictor of Sc bioaccumulation by two unicellular algae: possible role of fluoro-complexes.

PubMed

Crémazy, Anne; Campbell, Peter G C; Fortin, Claude

2014-08-19

We investigated the effect of fluoride complexation on scandium accumulation by two unicellular algae, Chlamydomonas reinhardtii and Pseudokirchneriella subcapitata. This trivalent metal was selected for its chemical similarities with aluminum and for its convenient radioisotope (Sc-46), which can be used as a tracer in short-term bioaccumulation studies. Scandium surface-bound concentrations (Sc(ads)) and uptake fluxes (J(int)) were estimated in the two algae over short-term (<1 h) exposures at pH 5 and in the presence of 0 to 40 μM F(-). Although the computed proportion of dissolved Sc(3+) dropped from 20% to 0.01% over this [F(-)] range, Sc(ads) and J(int) values for both algae decreased only slightly, suggesting a participation of Sc fluoro-complexes in both processes. Surface adsorption and uptake of fluoride complexes with aluminum have been reported in the literature. These observations are not taken into account by current models for trace metal bioaccumulation (e.g., the biotic ligand model). Results from a previous study, where the effects of pH on Sc uptake were investigated, suggested that Sc hydroxo-complexes were internalized by C. reinhardtii. There is thus growing evidence that the free ion concentration may not be adequate to predict the accumulation of Sc (and potentially of other trivalent metals) in aquatic organisms.

Theoretical studies on the electronic structure and spectroscopic properties of transition metals bis(dipyrrinate)s

NASA Astrophysics Data System (ADS)

Ksenofontov, Alexander A.; Guseva, Galina B.; Antina, Elena V.

2016-10-01

Density functional theory (DFT) and Time-dependent density functional theory (TD- DFT) computations have been used to reveal structural, molecular, electronic and spectral-luminescent parameters and features of several homoleptic transition metals bis(dipyrrine) complexes. The influence of complexing agent and ligand nature on the regularities in geometric, spectral-luminescent properties, kinetic and thermal stability changes in the [M2L2] complexes series were studied. Special attention is paid to the influence of the solvating media (PCM/TD-B3LYP/Def2-SVP) on changing spectral-luminescent properties of d-metals bis(dipyrrinate)s. The interpretation of the dependence between spectral-luminescent properties of the complexes and HOMO-LUMO (highest occupied molecular orbital and lowest unoccupied molecular orbital) energy gap's width was given. It was shown that the regularities in changing the helicates' quantum yield depending on the nature of complexing agent, ligand and solvent properties, obtained from quantum-chemical calculations, are in the agreement with our previously obtained experimental data. Thus, structural and spectral-luminescent characteristics of new [M2L2] luminophors can be evaluated with high reliability, and good forecast prospects for their use as fluorescent dyes for optical devices can be made in terms of the results of theoretical studies (B3LYP/Def2-SVP and TD-B3LYP/Def2-SVP).

Source identification, geochemical normalization and influence factors of heavy metals in Yangtze River Estuary sediment.

PubMed

Sun, Xueshi; Fan, Dejiang; Liu, Ming; Tian, Yuan; Pang, Yue; Liao, Huijie

2018-06-18

Sediment samples, including 40 surface samples and 12 sediment cores, were collected from 52 stations of the Yangtze River Estuary (YRE) in 2015 and 2016. The 95% linear prediction intervals (LPI) and principal components analysis (PCA), were conducted to evaluate the metal sources and grain-size effect (GSE). The in situ physico-chemical properties of pH, Eh, DO, salinity, temperature and turbidity were combined to elucidate the relationships between environmental factors and the fate of heavy metals in the river-estuary-shelf system. This study indicates a decreasing trend of metals in sediments from the estuary towards the adjacent shelf and the river channel and that Zn, Cu and Cr are mainly derived from natural processes throughout the catchment, whereas Pb appears to have anthropogenic inputs via atmospheric deposition. Furthermore, considering the best fit regression lines between the concentrations of Al and heavy metals as well as the deficiencies of the conventional C elements /C Al method, we introduce an approach (Al-SN: Al-scope normalization) that can eliminate the GSE on heavy metals and be applied to other estuaries. After Al-scope normalization, the relatively constant levels of Zn, Cu and Cr that remain in sediments from the river channel to the estuary and shelf confirmed that the variation of grain size in sediments almost entirely explained the distribution patterns of sediment toxicity in the YRE, while the enrichment of Pb in estuarine sediments could be attributed to its chemical species and physico-chemical properties. The results further suggest that the relationship between grain size and spatial behavior of sediment pollutants should be given priority over the contamination assessment and provenance discrimination in estuarine or similar environments with complex sediment compositions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Assimilation of cyanide and cyano-derivatives by Pseudomonas pseudoalcaligenes CECT5344: from omic approaches to biotechnological applications

PubMed Central

Cabello, Purificación; Luque-Almagro, Víctor M; Olaya-Abril, Alfonso; Sáez, Lara P; Moreno-Vivián, Conrado; Roldán, M Dolores

2018-01-01

Abstract Mining, jewellery and metal-processing industries use cyanide for extracting gold and other valuable metals, generating large amounts of highly toxic wastewater. Biological treatments may be a clean alternative under the environmental point of view to the conventional physical or chemical processes used to remove cyanide and related compounds from these industrial effluents. Pseudomonas pseudoalcaligenes CECT5344 can grow under alkaline conditions using cyanide, cyanate or different nitriles as the sole nitrogen source, and is able to remove up to 12 mM total cyanide from a jewellery industry wastewater that contains cyanide free and complexed to metals. Complete genome sequencing of this bacterium has allowed the application of transcriptomic and proteomic techniques, providing a holistic view of the cyanide biodegradation process. The complex response to cyanide by the cyanotrophic bacterium P. pseudoalcaligenes CECT5344 and the potential biotechnological applications of this model organism in the bioremediation of cyanide-containing industrial residues are reviewed. PMID:29438505

Assimilation of cyanide and cyano-derivatives by Pseudomonas pseudoalcaligenes CECT5344: from omic approaches to biotechnological applications.

PubMed

Cabello, Purificación; Luque-Almagro, Víctor M; Olaya-Abril, Alfonso; Sáez, Lara P; Moreno-Vivián, Conrado; Roldán, M Dolores

2018-03-01

Mining, jewellery and metal-processing industries use cyanide for extracting gold and other valuable metals, generating large amounts of highly toxic wastewater. Biological treatments may be a clean alternative under the environmental point of view to the conventional physical or chemical processes used to remove cyanide and related compounds from these industrial effluents. Pseudomonas pseudoalcaligenes CECT5344 can grow under alkaline conditions using cyanide, cyanate or different nitriles as the sole nitrogen source, and is able to remove up to 12 mM total cyanide from a jewellery industry wastewater that contains cyanide free and complexed to metals. Complete genome sequencing of this bacterium has allowed the application of transcriptomic and proteomic techniques, providing a holistic view of the cyanide biodegradation process. The complex response to cyanide by the cyanotrophic bacterium P. pseudoalcaligenes CECT5344 and the potential biotechnological applications of this model organism in the bioremediation of cyanide-containing industrial residues are reviewed.

Proton and metal ion binding to natural organic polyelectrolytes-II. Preliminary investigation with a peat and a humic acid

USGS Publications Warehouse

Marinsky, J.A.; Reddy, M.M.

1984-01-01

We summarize here experimental studies of proton and metal ion binding to a peat and a humic acid. Data analysis is based on a unified physico-chemical model for reaction of simple ions with polyelectrolytes employing a modified Henderson-Hasselbalch equation. Peat exhibited an apparent intrinsic acid dissociation constant of 10-4.05, and an apparent intrinsic metal ion binding constant of: 400 for cadmium ion; 600 for zinc ion; 4000 for copper ion; 20000 for lead ion. A humic acid was found to have an apparent intrinsic proton binding constant of 10-2.6. Copper ion binding to this humic acid sample occurred at two types of sites. The first site exhibited reaction characteristics which were independent of solution pH and required the interaction of two ligands on the humic acid matrix to simultaneously complex with each copper ion. The second complex species is assumed to be a simple monodentate copper ion-carboxylate species with a stability constant of 18. ?? 1984.

Affinity of Smectite and Divalent Metal Ions (Mg(2+), Ca(2+), Cu(2+)) with L-leucine: An Experimental and Theoretical Approach Relevant to Astrobiology.

PubMed

Pandey, Pramod; Pant, Chandra Kala; Gururani, Kavita; Arora, Priyanka; Pandey, Neetu; Bhatt, Preeti; Sharma, Yogesh; Negi, Jagmohan Singh; Mehata, Mohan Singh

2015-12-01

Earth is the only known planet bestowed with life. Several attempts have been made to explore the pathways of the origin of life on planet Earth. The search for the chemistry which gave rise to life has given answers related to the formation of biomonomers, and their adsorption on solid surfaces has gained much attention for the catalysis and stabilization processes related to the abiotic chemical evolution of the complex molecules of life. In this communication, surface interactions of L-leucine (Leu) on smectite (SMT) group of clay (viz. bentonite and montmorillonite) and their divalent metal ion (Mg(2+), Ca(2+) and Cu(2+)) incorporated on SMT has been studied to find the optimal conditions of time, pH, and concentration at ambient temperature (298 K). The progress of adsorption was followed spectrophotometrically and further characterized by FTIR, SEM/EDS and XRD. Leu, a neutral/non polar amino acid, was found to have more affinity in its zwitterionic form towards Cu(2+)- exchanged SMT and minimal affinity for Mg(2+)- exchanged SMT. The vibrational frequency shifts of -NH3 (+) and -COO(-) favor Van der Waal's forces during the course of surface interaction. Quantum calculations using density functional theory (DFT) have been applied to investigate the absolute value of metal ion affinities of Leu (Leu-M(2+) complex, M = Mg(2+), Ca(2+), Cu(2+)) with the help of their physico-chemical parameters. The hydration effect on the relative stability and geometry of the individual species of Leu-M(2+) × (H2O)n, (n =2 and 4) has also been evaluated within the supermolecule approach. Evidence gathered from investigations of surface interactions, divalent metal ions affinities and hydration effects with biomolecules may be important for better understanding of chemical evolution, the stabilization of biomolecules on solid surfaces and biomolecular-metal interactions. These results may have implications for understanding the origin of life and the preservation of biomarkers.

Fate of heavy metals during municipal solid waste incineration.

PubMed

Abanades, S; Flamant, G; Gagnepain, B; Gauthier, D

2002-02-01

A thermodynamic analysis was performed to determine whether it is suitable to predict the heavy metal (HM) speciation during the Municipal Solid Waste Incineration process. The fate of several selected metals (Cd, Pb, Zn, Cr, Hg, As, Cu, Co, Ni) during incineration was theoretically investigated. The equilibrium analysis predicted the metal partitioning during incineration and determined the impact of operating conditions (temperature and gas composition) on their speciation. The study of the gas composition influence was based on the effects of the contents of oxygen (reducing or oxidising conditions) and chlorine on the HM partitioning. The theoretical HM speciation which was calculated in a complex system representing a burning sample of Municipal Solid Waste can explain the real partitioning (obtained from literature results) of all metals among the various ashes except for Pb. Then, the results of the thermodynamic study were compared with those of characterisation of real incinerator residues, using complementary techniques (chemical extraction series and X-ray micro-analyses). These analysis were performed to determine experimentally the speciation of the three representative metals Cr, Pb, and Zn. The agreement is good for Cr and Zn but not for Pb again, which mainly shows unleachable chemical speciations in the residues. Pb tends to remain in the bottom ash whereas thermodynamics often predicts its complete volatilisation under chlorides, and thus its presence exclusively in fly ash.

Fe(+) chemical ionization of peptides.

PubMed

Speir, J P; Gorman, G S; Amster, I J

1993-02-01

Laser-desorbed peptide neutral molecules were allowed to react with Fe(+) in a Fourier transform mass spectrometer, using the technique of laser desorption/chemical ionization. The Fe(+) ions are formed by laser ablation of a steel target, as well as by dissociative charge-exchange ionization of ferrocene with Ne(+). Prior to reaction with laser-desorbed peptide molecules, Fe(+) ions undergo 20-100 thermalizin collisions with xenon to reduce the population of excited-state metal ion species. The Fe(+) ions that have not experienced thermalizing collisions undergo charge exchange with peptide molecules. Iron ions that undergo thermalizing collisions before they are allowed to react with peptides are found to undergo charge exchange and to form adduct species [M + Fe(+)] and fragment ions that result from the loss of small, stable molecules, such as H2O, CO, and CO2, from the metal ion-peptide complex.

The Hydrothermal Chemistry of Gold, Arsenic, Antimony, Mercury and Silver

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bessinger, Brad; Apps, John A.

2003-03-23

A comprehensive thermodynamic database based on the Helgeson-Kirkham-Flowers (HKF) equation of state was developed for metal complexes in hydrothermal systems. Because this equation of state has been shown to accurately predict standard partial molal thermodynamic properties of aqueous species at elevated temperatures and pressures, this study provides the necessary foundation for future exploration into transport and depositional processes in polymetallic ore deposits. The HKF equation of state parameters for gold, arsenic, antimony, mercury, and silver sulfide and hydroxide complexes were derived from experimental equilibrium constants using nonlinear regression calculations. In order to ensure that the resulting parameters were internally consistent,more » those experiments utilizing incompatible thermodynamic data were re-speciated prior to regression. Because new experimental studies were used to revise the HKF parameters for H2S0 and HS-1, those metal complexes for which HKF parameters had been previously derived were also updated. It was found that predicted thermodynamic properties of metal complexes are consistent with linear correlations between standard partial molal thermodynamic properties. This result allowed assessment of several complexes for which experimental data necessary to perform regression calculations was limited. Oxygen fugacity-temperature diagrams were calculated to illustrate how thermodynamic data improves our understanding of depositional processes. Predicted thermodynamic properties were used to investigate metal transport in Carlin-type gold deposits. Assuming a linear relationship between temperature and pressure, metals are predicted to predominantly be transported as sulfide complexes at a total aqueous sulfur concentration of 0.05 m. Also, the presence of arsenic and antimony mineral phases in the deposits are shown to restrict mineralization within a limited range of chemical conditions. Finally, at a lesser aqueous sulfur concentration of 0.01 m, host rock sulfidation can explain the origin of arsenic and antimony minerals within the paragenetic sequence.« less

Modern views on the composition of anionic oxy-fluoride complexes of aluminium and their rearrangement during the electrolysis of cryolite-alumina melts

NASA Astrophysics Data System (ADS)

Khramov, A. P.; Shurov, N. I.

2014-08-01

Some consequences of the hypothesis of the absence of free F- ions in cryolite-alumina melts are observed. The melt at 1 < CR < 3 is assumed to consist of the complexes AlF{6/3-}, AlF{5/2-}, AlF{4/-}, Al2OF{6/2-}, and Al2O2F{4/2-}, and alkali metal cations. A formal-stoichiometric study of the processes occurring during electrolysis is performed on the basis of the accepted hypothesis. Judgments about some of the features of the electrode reactions and chemical reactions in the electrolyte volume are presented. The reaction schemes for the instances with and without the subsequent/preceding chemical reaction near the electrode or in the molten salt volume are given. The mass flows of various forms of ionic complexes through the electrolyte volume are given for these schemes. Definitive conclusions are not made in the study, but the range of possible variants for the electrochemical routes of the overall chemical reaction in the cell is limited.

Infrared Multiple Photon Dissociation Spectroscopy Of Metal Cluster-Adducts

NASA Astrophysics Data System (ADS)

Cox, D. M.; Kaldor, A.; Zakin, M. R.

1987-01-01

Recent development of the laser vaporization technique combined with mass-selective detection has made possible new studies of the fundamental chemical and physical properties of unsupported transition metal clusters as a function of the number of constituent atoms. A variety of experimental techniques have been developed in our laboratory to measure ionization threshold energies, magnetic moments, and gas phase reactivity of clusters. However, studies have so far been unable to determine the cluster structure or the chemical state of chemisorbed species on gas phase clusters. The application of infrared multiple photon dissociation IRMPD to obtain the IR absorption properties of metal cluster-adsorbate species in a molecular beam is described here. Specifically using a high power, pulsed CO2 laser as the infrared source, the IRMPD spectrum for methanol chemisorbed on small iron clusters is measured as a function of the number of both iron atoms and methanols in the complex for different methanol isotopes. Both the feasibility and potential utility of IRMPD for characterizing metal cluster-adsorbate interactions are demonstrated. The method is generally applicable to any cluster or cluster-adsorbate system dependent only upon the availability of appropriate high power infrared sources.

Label-free histamine detection with nanofluidic diodes through metal ion displacement mechanism.

PubMed

Ali, Mubarak; Ramirez, Patricio; Duznovic, Ivana; Nasir, Saima; Mafe, Salvador; Ensinger, Wolfgang

2017-02-01

We design and characterize a nanofluidic device for the label-free specific detection of histamine neurotransmitter based on a metal ion displacement mechanism. The sensor consists of an asymmetric polymer nanopore fabricated via ion track-etching technique. The nanopore sensor surface having metal-nitrilotriacetic (NTA-Ni 2+ ) chelates is obtained by covalent coupling of native carboxylic acid groups with N α ,N α -bis(carboxymethyl)-l-lysine (BCML), followed by exposure to Ni 2+ ion solution. The BCML immobilization and subsequent Ni 2+ ion complexation with NTA moieties change the surface charge concentration, which has a significant impact on the current-voltage (I-V) curve after chemical modification of the nanopore. The sensing mechanism is based on the displacement of the metal ion from the NTA-Ni 2+ chelates. When the modified pore is exposed to histamine solution, the Ni 2+ ion in NTA-Ni 2+ chelate recognizes histamine through a metal ion coordination displacement process and formation of stable Ni-histamine complexes, leading to the regeneration of metal-free NTA groups on the pore surface, as shown in the current-voltage characteristics. Nanomolar concentrations of the histamine in the working electrolyte can be detected. On the contrary, other neurotransmitters such as glycine, serotonin, gamma-aminobutyric acid, and dopamine do not provoke significant changes in the nanopore electronic signal due to their inability to displace the metal ion and form a stable complex with Ni 2+ ion. The nanofluidic sensor exhibits high sensitivity, specificity and reusability towards histamine detection and can then be used to monitor the concentration of biological important neurotransmitters. Copyright © 2016 Elsevier B.V. All rights reserved.

Modulation of individual steps in group I intron catalysis by a peripheral metal ion.

PubMed

Forconi, Marcello; Piccirilli, Joseph A; Herschlag, Daniel

2007-10-01

Enzymes are complex macromolecules that catalyze chemical reactions at their active sites. Important information about catalytic interactions is commonly gathered by perturbation or mutation of active site residues that directly contact substrates. However, active sites are engaged in intricate networks of interactions within the overall structure of the macromolecule, and there is a growing body of evidence about the importance of peripheral interactions in the precise structural organization of the active site. Here, we use functional studies, in conjunction with published structural information, to determine the effect of perturbation of a peripheral metal ion binding site on catalysis in a well-characterized catalytic RNA, the Tetrahymena thermophila group I ribozyme. We perturbed the metal ion binding site by site-specifically introducing a phosphorothioate substitution in the ribozyme's backbone, replacing the native ligands (the pro-R (P) oxygen atoms at positions 307 and 308) with sulfur atoms. Our data reveal that these perturbations affect several reaction steps, including the chemical step, despite the absence of direct contacts of this metal ion with the atoms involved in the chemical transformation. As structural probing with hydroxyl radicals did not reveal significant change in the three-dimensional structure upon phosphorothioate substitution, the effects are likely transmitted through local, rather subtle conformational rearrangements. Addition of Cd(2+), a thiophilic metal ion, rescues some reaction steps but has deleterious effects on other steps. These results suggest that native interactions in the active site may have been aligned by the naturally occurring peripheral residues and interactions to optimize the overall catalytic cycle.

High-resolution electron spectroscopy of lanthanide (Ce, Pr, and Nd) complexes of cyclooctatetraene: the role of 4f electrons.

PubMed

Kumari, Sudesh; Roudjane, Mourad; Hewage, Dilrukshi; Liu, Yang; Yang, Dong-Sheng

2013-04-28

Cerium, praseodymium, and neodymium complexes of 1,3,5,7-cyclooctatetraene (COT) complexes were produced in a laser-vaporization metal cluster source and studied by pulsed-field ionization zero electron kinetic energy spectroscopy and quantum chemical calculations. The computations included the second-order Møller-Plesset perturbation theory, the coupled cluster method with single, double, and perturbative triple excitations, and the state-average complete active space self-consistent field method. The spectrum of each complex exhibits multiple band systems and is assigned to ionization of several low-energy electronic states of the neutral complex. This observation is different from previous studies of M(COT) (M = Sc, Y, La, and Gd), for which a single band system was observed. The presence of the multiple low-energy electronic states is caused by the splitting of the partially filled lanthanide 4f orbitals in the ligand field, and the number of the low-energy states increases rapidly with increasing number of the metal 4f electrons. On the other hand, the 4f electrons have a small effect on the geometries and vibrational frequencies of these lanthanide complexes.

Metal Oxide Nanosensors Using Polymeric Membranes, Enzymes and Antibody Receptors as Ion and Molecular Recognition Elements

PubMed Central

Willander, Magnus; Khun, Kimleang; Ibupoto, Zafar Hussain

2014-01-01

The concept of recognition and biofunctionality has attracted increasing interest in the fields of chemistry and material sciences. Advances in the field of nanotechnology for the synthesis of desired metal oxide nanostructures have provided a solid platform for the integration of nanoelectronic devices. These nanoelectronics-based devices have the ability to recognize molecular species of living organisms, and they have created the possibility for advanced chemical sensing functionalities with low limits of detection in the nanomolar range. In this review, various metal oxides, such as ZnO-, CuO-, and NiO-based nanosensors, are described using different methods (receptors) of functionalization for molecular and ion recognition. These functionalized metal oxide surfaces with a specific receptor involve either a complex formation between the receptor and the analyte or an electrostatic interaction during the chemical sensing of analytes. Metal oxide nanostructures are considered revolutionary nanomaterials that have a specific surface for the immobilization of biomolecules with much needed orientation, good conformation and enhanced biological activity which further improve the sensing properties of nanosensors. Metal oxide nanostructures are associated with certain unique optical, electrical and molecular characteristics in addition to unique functionalities and surface charge features which shows attractive platforms for interfacing biorecognition elements with effective transducing properties for signal amplification. There is a great opportunity in the near future for metal oxide nanostructure-based miniaturization and the development of engineering sensor devices. PMID:24841244

Electrochemical Sensors for the Detection of Lead and Other Toxic Heavy Metals: The Next Generation of Personal Exposure Biomonitors

PubMed Central

Yantasee, Wassana; Lin, Yuehe; Hongsirikarn, Kitiya; Fryxell, Glen E.; Addleman, Raymond; Timchalk, Charles

2007-01-01

To support the development and implementation of biological monitoring programs, we need quantitative technologies for measuring xenobiotic exposure. Microanalytical based sensors that work with complex biomatrices such as blood, urine, or saliva are being developed and validated and will improve our ability to make definitive associations between chemical exposures and disease. Among toxic metals, lead continues to be one of the most problematic. Despite considerable efforts to identify and eliminate Pb exposure sources, this metal remains a significant health concern, particularly for young children. Ongoing research focuses on the development of portable metal analyzers that have many advantages over current available technologies, thus potentially representing the next generation of toxic metal analyzers. In this article, we highlight the development and validation of two classes of metal analyzers for the voltammetric detection of Pb, including: a) an analyzer based on flow injection analysis and anodic stripping voltammetry at a mercury-film electrode, and b) Hg-free metal analyzers employing adsorptive stripping voltammetry and novel nanostructure materials that include the self-assembled monolayers on mesoporous supports and carbon nanotubes. These sensors have been optimized to detect Pb in urine, blood, and saliva as accurately as the state-of-the-art inductively coupled plasma-mass spectrometry with high reproducibility, and sensitivity allows. These improved and portable analytical sensor platforms will facilitate our ability to conduct biological monitoring programs to understand the relationship between chemical exposure assessment and disease outcomes. PMID:18087583

Magnesiothermic reduction for direct synthesis of Ti-Nb alloy at 1073 K (800 °C)

NASA Astrophysics Data System (ADS)

Choi, Kyunsuk; Lee, Kwang Hee; Ali, Basit; Choi, Sang-Hoon; Park, Kyoung-Tae; Sohn, Il

2017-09-01

Direct fabrication of titanium (Ti) and niobium (Nb) alloys by direct magnesiothermic reduction from the respective initial metal oxides and complex oxides has been studied. TiO2, Nb2O5, and complex TiNb2O7 oxides were used as raw materials with Mg used as a reductant. To ensure a high chemical potential of the reactants to drive the spontaneous magnesiothermic reduction of the oxide mixtures, excess Mg five times higher than the required stoichiometric molar ratio was added. Samples were heated in a glove box under recycled and purified Ar atmosphere at 1073 K (800 °C) for 10 h. After the reduction of TiO2, intermediate oxide phases of Ti6O could still be observed, but reduction of Nb2O5 and TiNb2O7 showed metallic Nb and Ti-Nb to be present with negligible oxides according to the scanning electron microscope-energy dispersive spectroscopy and x ray diffraction analysis. This indicated that direct fabrication of Ti-Nb alloys through a complex TiNb2O7 oxide is possible and can be more efficient than alloying pure metallic elements of Ti and Nb.

Heterobimetallic porphyrin complexes displaying triple dynamics: coupled metal motions controlled by constitutional evolution.

PubMed

Le Gac, Stéphane; Fusaro, Luca; Roisnel, Thierry; Boitrel, Bernard

2014-05-07

A bis-strap porphyrin ligand (1), with an overhanging carboxylic acid group on each side of the macrocycle, has been investigated toward the formation of dynamic libraries of bimetallic complexes with Hg(II), Cd(II), and Pb(II). Highly heteroselective metalation processes occurred in the presence of Pb(II), with Hg(II) or Cd(II) bound out-of-plane to the N-core and "PbOAc" bound to a carboxylate group of a strap on the opposite side. The resulting complexes, 1(Hg)·PbOAc and 1(Cd)·PbOAc, display three levels of dynamics. The first is strap-level (interactional dynamics), where the PbOAc moiety swings between the left and right side of the strap owing to a second sphere of coordination with lateral amide functions. The second is ligand-level (motional dynamics), where 1(Hg)·PbOAc and 1(Cd)·PbOAc exist as two degenerate states in equilibrium controlled by a chemical effector (AcO(-)). The process corresponds to a double translocation of the metal ions according to an intramolecular migration of Hg(II) or Cd(II) through the N-core, oscillating between the two equivalent overhanging carbonyl groups, coupled to an intermolecular pathway for PbOAc exchanging between the two equivalent overhanging carboxylate groups (N-core(up) ⇆ N-core(down) coupled to strap(down) ⇆ strap(up), i.e., coupled motion #1 in the abstract graphic). The third is library-level (constitutional dynamics), where a dynamic constitutional evolution of the system was achieved by the successive addition of two chemical effectors (DMAP and then AcO(-)). It allowed shifting equilibrium forward and backward between 1(Hg)·PbOAc and the corresponding homobimetallic complexes 1(Hg2)·DMAP and 1(Pb)·PbOAc. The latter displays a different ligand-level dynamics, in the form of an intraligand coupled migration of the Pb(II) ions (N-core(up) ⇆ strap(up) coupled to strap(down) ⇆ N-core(down), i.e., coupled motion #2 in the abstract graphic). In addition, the neutral "bridged" complexes 1HgPb and 1CdPb, with the metal ions on opposite sides both bound to the N-core and to a carboxylate of a strap, were structurally characterized. These results establish an unprecedented approach in supramolecular coordination chemistry, by considering the reversible interaction of a metal ion with the porphyrin N-core as a new source of self-organization processes. This work should provide new inspirations for the design of innovative adaptative materials and devices.

Experimental and quantum chemical modeling studies of the interactions of L-phenylalanine with divalent transition metal cations.

PubMed

Mandal, Shilpi; Das, Gunajyoti; Askari, Hassan

2014-09-22

Encoded by the UUU and UUC codons of the genetic code, L-phenylalanine (LPA) serves as an important precursor for tyrosine and various other compounds that are necessary to support life on earth. Here, we report the synthesis (both in solid and solvent phases) and characterization of the Ni(2+), Cu(2+), and Zn(2+) complexes of LPA by several analytical, spectral, thermal, and electrochemical techniques. The results reveal that the products formed by following the two synthetic approaches are the same, and the metal ions bind to the LPA molecules in a 1:2 molar ratio (M(+2)/LPA). Complementary geometries of the metal complexes are modeled involving the most predominant LPA conformers predicted at the MP2/6-311++G(d,p) level. The gaseous and aqueous phase interaction enthalpies and free energies; theoretical IR and UV-vis spectra; HOMO-LUMO energy gaps; dipole moments; Wiberg bond indices as well as the partial atomic charges in LPA and its metallic complexes are calculated and evaluated using B3LYP/6-311++G(d,p) as the main computational method. This study also incorporates analyses on the efficacy of the DFT-D2 level in describing dispersion contributions, performance of the BHandHLYP functional for the open-shell Cu(2+)-LPA system, and relative metal binding affinities of the singlet versus triplet states of the Ni(2+)-LPA complex. Metal-π interactions established via the aromatic side chain of LPA add to the thermodynamic stability of the complexes, whereas metal coordination induces considerable intrinsic structural rearrangements in the molecular geometry of LPA. The LPA binding affinity order of the three Lewis acids investigated emerges as Cu(2+) > Ni(2+) > Zn(2+), paralleling the Irving-Williams series. The illustrative evidence offered by the present work suggests that the B3LYP/6-311++G(d,p) level in combination with an empirical dispersion-correction term performs well in describing the vibrational frequencies and cation-π interactions, which are undoubtedly of immense significance for natural sciences.

Environmental hazard of cadmium, copper, lead and zinc in metal-contaminated soils remediated by sulfosuccinamate formulation.

PubMed

del Carmen Hernández-Soriano, Maria; Peña, Aránzazu; Mingorance, M Dolores

2011-10-01

Accumulation of metals in soil at elevated concentrations causes risks to the environmental quality and human health for more than one hundred million people globally. The rate of metal release and the alteration of metal distribution in soil phases after soil washing with a sulfosuccinamate surfactant solution (Aerosol 22) were evaluated for four contaminated soils. Furthermore, a sequential extraction scheme was carried out using selective extractants (HAcO, NH(2)OH·HCl, H(2)O(2) + NH(4)AcO) to evaluate which metal species are extracted by A22 and the alteration in metal distribution upon surfactant-washing. Efficiency of A22 to remove metals varied among soils. The washing treatment released up to 50% of Cd, 40% of Cu, 20% of Pb and 12% of Zn, mainly from the soluble and reducible soil fractions, therefore, greatly reducing the fraction of metals readily available in soil. Metal speciation analysis for the solutions collected upon soil washing with Aerosol 22 further confirmed these results. Copper and lead in solution were mostly present as soluble complexes, while Cd and Zn were present as free ions. Besides, redistribution of metals in soil was observed upon washing. The ratios of Zn strongly retained in the soil matrix and Cd complexed with organic ligands increased. Lead was mobilized to more weakly retained forms, which indicates a high bioavailability of the remaining Pb in soil after washing. Comprehensive knowledge on chemical forms of metals present in soil allows a feasible assessment of the environmental impact of metals for a given scenario, as well as possible alteration of environmental conditions, and a valuable prediction for potential leaching and groundwater contamination.

Metal speciation in landfill leachates with a focus on the influence of organic matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Claret, Francis, E-mail: f.claret@brgm.fr; Tournassat, Christophe; Crouzet, Catherine

Highlights: > This study characterises the heavy-metal content in leachates collected from eight landfills in France. > Most of the metals are concentrated in the <30 kDa fraction, while Pb, Cu and Cd are associated with larger particles. > Metal complexation with OM is not sufficient to explain apparent supersaturation of metals with sulphide minerals. - Abstract: This study characterises the heavy-metal content in leachates collected from eight landfills in France. In order to identify heavy metal occurrence in the different size fractions of leachates, a cascade filtration protocol was applied directly in the field, under a nitrogen gas atmospheremore » to avoid metal oxidation. The results of analyses performed on the leachates suggest that most of the metals are concentrated in the <30 kDa fraction, while lead, copper and cadmium show an association with larger particles. Initial speciation calculations, without considering metal association with organic matter, suggest that leachate concentrations in lead, copper, nickel and zinc are super-saturated with respect to sulphur phases. Speciation calculations that account for metal complexation with organic matter, considered as fulvic acids based on C1(s) NEXAFS spectroscopy, show that this mechanism is not sufficient to explain such deviation from equilibrium conditions. It is therefore hypothesized that the deviation results also from the influence of biological activity on the kinetics of mineral phase precipitation and dissolution, thus providing a dynamic system. The results of chemical analyses of sampled fluids are compared with speciation calculations and some implications for the assessment of metal mobility and natural attenuation in a context of landfill risk assessment are discussed.« less

Steric modulation of coordination number and reactivity in the synthesis of lanthanoid(III) formamidinates.

PubMed

Cole, Marcus L; Deacon, Glen B; Forsyth, Craig M; Junk, Peter C; Konstas, Kristina; Wang, Jun

2007-01-01

Reactions of a range of the readily prepared and sterically tunable N,N'-bis(aryl)formamidines with lanthanoid metals and bis(pentafluorophenyl)mercury (Hg(C6F5)2) in THF have given an extensive series of tris(formamidinato)lanthanoid(III) complexes, [Ln(Form)3(thf)n], namely [La(o-TolForm)3(thf)2], [Er(o-TolForm)3(thf)], [La(XylForm)3(thf)], [Sm(XylForm)3], [Ln(MesForm)3] (Ln=La, Nd, Sm and Yb), [Ln(EtForm)3] (Ln=La, Nd, Sm, Ho and Yb), and [Ln(o-PhPhForm)3] (Ln=La, Nd, Sm and Er). [For an explanation of the N,N'-bis(aryl)formamidinate abbreviations used see Scheme 1.] Analogous attempts to prepare [Yb(o-TolForm)3] by this method invariably yielded [{Yb(o-TolForm)2(mu-OH)(thf)}2], but [Yb(o-TolForm)3] was isolated from a metathesis synthesis. X-ray crystal structures show exclusively N,N'-chelation of the Form ligands and a gradation in coordination number with Ln3+ size and with Form ligand bulk. The largest ligands, MesForm, EtForm and o-PhPhForm give solely homoleptic complexes, the first two being six-coordinate, the last having an eta1-pi-Ar--Ln interaction. Reaction of lanthanoid elements and Hg(C6F5)2 with the still bulkier DippFormH in THF resulted in C--F activation and formation of [Ln(DippForm)2F(thf)] (Ln=La, Ce, Nd, Sm and Tm) complexes, and o-HC6F4O(CH2)4DippForm in which the formamidine is functionalised by a ring-opened THF that has trapped tetrafluorobenzyne. Analogous reactions between Ln metals, Hg(o-HC6F4)2 and DippFormH yielded [Ln(DippForm)2F(thf)] (Ln=La, Sm and Nd) and 3,4,5-F3C6H2O(CH2)4DippForm. X-ray crystal structures of the heteroleptic fluorides show six-coordinate monomers with two chelating DippForm ligands and cisoid fluoride and THF ligands in a trigonal prismatic array. The organometallic species [Ln(DippForm)2(C[triple chemical bond]CPh)(thf)] (Ln=Nd or Sm) are obtained from reaction of Nd metal, bis(phenylethynyl)mercury (Hg(C[triple chemical bond]CPh)2) and DippFormH, and the oxidation of [Sm(DippForm)2(thf)2] with Hg(C[triple chemical bond]CPh)2, respectively. The monomeric, six-coordinate, cisoid [Ln(DippForm)2(C[triple chemical bond]CPh)(thf)] complexes have trigonal prismatic geometries and rare (for Ln) terminal C[triple chemical bond]CPh groups with contrasting Ln--C[triple chemical bond]C angles (Ln=Nd, 170.9(4) degrees; Ln=Sm, 142.9(7) degrees). Their formation lends support to the view that [Ln(DippForm)2F(thf)] complexes arise from oxidative formation and C--F activation of [Ln(DippForm)2(C6F5)] intermediates.

Pt–Mg, Pt–Ca, and Pt–Zn lantern complexes and metal-only donor–acceptor interactions [Pt-Mg Pt-Ca and Pt-Zn compounds with metal-only donor-acceptor interactions

DOE PAGES

Baddour, Frederick G.; Hyre, Ariel S.; Guillet, Jesse L.; ...

2016-12-12

Here, Pt-based heterobimetallic lantern complexes of the form [PtM(SOCR) 4(L)] have been shown previously to form intermolecular metallophilic interactions and engage in antiferromagnetic coupling between lanterns having M atoms with open shell configurations. In order to understand better the influence of the carboxylate bridge and terminal ligand on the electronic structure, as well as the metal–metal interactions within each lantern unit, a series of diamagnetic lantern complexes, [PtMg(SAc) 4(OH 2)] (1), [PtMg(tba) 4(OH 2)] (2), [PtCa(tba) 4(OH 2)] (3), [PtZn(tba) 4(OH 2)] (4), and a mononuclear control (Ph 4P) 2[Pt(SAc) 4] (5) have been synthesized. Crystallographic data show close Pt–Mmore » contacts enforced by the lantern structure in each dinuclear case. 195Pt-NMR spectroscopy of 1–4, (Ph 4P) 2[Pt(SAc) 4] (5), and several previously reported lanterns revealed a strong chemical shift dependence on the identity of the second metal (M), mild influence by the thiocarboxylate ligand (SOCR; R = CH 3 (thioacetate, SAc), C 6H 5 (thiobenzoate, tba)), and modest influence from the terminal ligand (L). Fluorescence spectroscopy has provided evidence for a Pt···Zn metallophilic interaction in [PtZn(SAc) 4(OH 2)], and computational studies demonstrate significant dative character. In all of 1–4, the short Pt–M distances suggest that metal-only Lewis donor (Pt)–Lewis acceptor (M) interactions could be present. DFT and NBO calculations, however, show that only the Zn examples have appreciable covalent character, whereas the Mg and Ca complexes are much more ionic.« less

Pt–Mg, Pt–Ca, and Pt–Zn lantern complexes and metal-only donor–acceptor interactions [Pt-Mg Pt-Ca and Pt-Zn compounds with metal-only donor-acceptor interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baddour, Frederick G.; Hyre, Ariel S.; Guillet, Jesse L.

Here, Pt-based heterobimetallic lantern complexes of the form [PtM(SOCR) 4(L)] have been shown previously to form intermolecular metallophilic interactions and engage in antiferromagnetic coupling between lanterns having M atoms with open shell configurations. In order to understand better the influence of the carboxylate bridge and terminal ligand on the electronic structure, as well as the metal–metal interactions within each lantern unit, a series of diamagnetic lantern complexes, [PtMg(SAc) 4(OH 2)] (1), [PtMg(tba) 4(OH 2)] (2), [PtCa(tba) 4(OH 2)] (3), [PtZn(tba) 4(OH 2)] (4), and a mononuclear control (Ph 4P) 2[Pt(SAc) 4] (5) have been synthesized. Crystallographic data show close Pt–Mmore » contacts enforced by the lantern structure in each dinuclear case. 195Pt-NMR spectroscopy of 1–4, (Ph 4P) 2[Pt(SAc) 4] (5), and several previously reported lanterns revealed a strong chemical shift dependence on the identity of the second metal (M), mild influence by the thiocarboxylate ligand (SOCR; R = CH 3 (thioacetate, SAc), C 6H 5 (thiobenzoate, tba)), and modest influence from the terminal ligand (L). Fluorescence spectroscopy has provided evidence for a Pt···Zn metallophilic interaction in [PtZn(SAc) 4(OH 2)], and computational studies demonstrate significant dative character. In all of 1–4, the short Pt–M distances suggest that metal-only Lewis donor (Pt)–Lewis acceptor (M) interactions could be present. DFT and NBO calculations, however, show that only the Zn examples have appreciable covalent character, whereas the Mg and Ca complexes are much more ionic.« less

On-bead combinatorial synthesis and imaging of europium(III)-based paraCEST agents aids in identification of chemical features that enhance CEST sensitivity.

PubMed

Singh, Jaspal; Rustagi, Vineeta; Zhang, Shanrong; Sherry, A Dean; Udugamasooriya, D Gomika

2017-08-01

The rate of water exchange between the inner sphere of a paramagnetic ion and bulk water is an important parameter in determining the magnitude of the chemical exchange saturation transfer signal from paramagnetic CEST agents (paraCEST). This is governed by various geometric, steric and ligand field factors created by macrocyclic ligands surrounding the paramagnetic metal ion. Our previous on-bead combinatorial studies of di-peptoid-europium(III)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-tetraamide complexes revealed that negatively charged groups in the immediate vicinity of the metal center strongly enhances the CEST signal. Here, we report a solid phase synthesis and on-bead imaging of 76 new DOTA derivatives that are developed by coupling with a single residue onto each of the three arms of a DOTA-tetraamide scaffold attached to resin beads. This single residue predominantly carries negatively charged groups blended with various physico-chemical characteristics. We found that non-bulky negatively charged groups are best suited at the immediate vicinity of the metal ion, while positive, bulky and halogen containing moieties suppress the CEST signal. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Chemically Designed Metallic/Insulating Hybrid Nanostructures with Silver Nanocrystals for Highly Sensitive Wearable Pressure Sensors.

PubMed

Kim, Haneun; Lee, Seung-Wook; Joh, Hyungmok; Seong, Mingi; Lee, Woo Seok; Kang, Min Su; Pyo, Jun Beom; Oh, Soong Ju

2018-01-10

With the increase in interest in wearable tactile pressure sensors for e-skin, researches to make nanostructures to achieve high sensitivity have been actively conducted. However, limitations such as complex fabrication processes using expensive equipment still exist. Herein, simple lithography-free techniques to develop pyramid-like metal/insulator hybrid nanostructures utilizing nanocrystals (NCs) are demonstrated. Ligand-exchanged and unexchanged silver NC thin films are used as metallic and insulating components, respectively. The interfaces of each NC layer are chemically engineered to create discontinuous insulating layers, i.e., spacers for improved sensitivity, and eventually to realize fully solution-processed pressure sensors. Device performance analysis with structural, chemical, and electronic characterization and conductive atomic force microscopy study reveals that hybrid nanostructure based pressure sensor shows an enhanced sensitivity of higher than 500 kPa -1 , reliability, and low power consumption with a wide range of pressure sensing. Nano-/micro-hierarchical structures are also designed by combining hybrid nanostructures with conventional microstructures, exhibiting further enhanced sensing range and achieving a record sensitivity of 2.72 × 10 4 kPa -1 . Finally, all-solution-processed pressure sensor arrays with high pixel density, capable of detecting delicate signals with high spatial selectivity much better than the human tactile threshold, are introduced.

Natural Pyrrhotite as a Catalyst in Prebiotic Chemical Evolution

PubMed Central

López Ibáñez de Aldecoa, Alejandra; Velasco Roldán, Francisco; Menor-Salván, César

2013-01-01

The idea of an autotrophic organism as the first living being on Earth leads to the hypothesis of a protometabolic, complex chemical system. In one of the main hypotheses, the first metabolic systems emerged from the interaction between sulfide minerals and/or soluble iron-sulfide complexes and fluids rich in inorganic precursors, which are reduced and derived from crustal or mantle activity. Within this context, the possible catalytic role of pyrrhotite, one of the most abundant sulfide minerals, in biomimetic redox and carbon fixation reactions was studied. Our results showed that pyrrhotite, under simulated hydrothermal conditions, could catalyze the pyruvate synthesis from lactate and that a dynamic system formed by coupling iron metal and iron-sulfur species in an electrochemical cell could promote carbon fixation from thioacetate esters. PMID:25369819

Identifying Metals as Marker for Waste Burning Aerosol Particles in New Delhi

NASA Astrophysics Data System (ADS)

Kumar, Sudhanshu

2012-07-01

{Identifying Metals as Marker for Waste Burning Aerosol Particles in New Delhi } Tracing of aerosol sources is an important task helpful for making control strategy, and for climate change study. However, it is a difficult job as aerosols have several sources, involve in complex atmospheric processing, degradation and removal processes. Several approaches have been used for this task, e.g., models, which are based on the input of chemical species; stable- and radio-isotope compositions of certain species; chemical markers in which trace metals are the better options because they persist in atmosphere until the life of a particle. For example, K and Hg are used for biomass and coal burning tracings, respectively. Open waste burning has recently been believed to be a considerable source of aerosols in several mega cities in India and China. To better understand this source contribution in New Delhi aerosols, we have conducted aerosol sampling at a landfill site (Okhla), and in proximity (within 1 km distance) of this site. Aerosol filter samples were acid digested in microwave digestion system and analyzed using inductively coupled plasma -- high resolution mass spectrometry (ICP-HRMS) for getting metal signatures in particles. The metals, e.g., Sn, Sb and As those are found almost negligible in remote aerosols, are maximized in these waste burning aerosols. Sample collected in other location of New Delhi also shows the considerable presence of these metals in particles. Preliminary studies of isotopic ratios of these metals suggested that these metals, especially Sn can be used as marker for tracing the open waste burning sources of aerosols in New Delhi.

Float processing of high-temperature complex silicate glasses and float baths used for same

NASA Technical Reports Server (NTRS)

Cooper, Reid Franklin (Inventor); Cook, Glen Bennett (Inventor)

2000-01-01

A float glass process for production of high melting temperature glasses utilizes a binary metal alloy bath having the combined properties of a low melting point, low reactivity with oxygen, low vapor pressure, and minimal reactivity with the silicate glasses being formed. The metal alloy of the float medium is exothermic with a solvent metal that does not readily form an oxide. The vapor pressure of both components in the alloy is low enough to prevent deleterious vapor deposition, and there is minimal chemical and interdiffusive interaction of either component with silicate glasses under the float processing conditions. Alloys having the desired combination of properties include compositions in which gold, silver or copper is the solvent metal and silicon, germanium or tin is the solute, preferably in eutectic or near-eutectic compositions.

Silicon micro-mold and method for fabrication

DOEpatents

Morales, Alfredo M.

2005-01-11

The present invention describes a method for rapidly fabricating a robust 3-dimensional silicon micro-mold for use in preparing complex metal micro-components. The process begins by depositing a conductive metal layer onto one surface of a silicon wafer. A thin photoresist and a standard lithographic mask are then used to transfer a trace image pattern onto the opposite surface of the wafer by exposing and developing the resist. The exposed portion of the silicon substrate is anisotropically etched through the wafer thickness down to conductive metal layer to provide an etched pattern consisting of a series of rectilinear channels and recesses in the silicon which serve as the silicon micro-mold. Microcomponents are prepared with this mold by first filling the mold channels and recesses with a metal deposit, typically by electroplating, and then removing the silicon micro-mold by chemical etching.

Silicon micro-mold

DOEpatents

Morales, Alfredo M [Livermore, CA

2006-10-24

The present invention describes a method for rapidly fabricating a robust 3-dimensional silicon-mold for use in preparing complex metal micro-components. The process begins by depositing a conductive metal layer onto one surface of a silicon wafer. A thin photoresist and a standard lithographic mask are then used to transfer a trace image pattern onto the opposite surface of the wafer by exposing and developing the resist. The exposed portion of the silicon substrate is anisotropically etched through the wafer thickness down to conductive metal layer to provide an etched pattern consisting of a series of rectilinear channels and recesses in the silicon which serve as the silicon micro-mold. Microcomponents are prepared with this mold by first filling the mold channels and recesses with a metal deposit, typically by electroplating, and then removing the silicon micro-mold by chemical etching.

Metal ion complex formation in small lakes of the Western Siberian Arctic zone

NASA Astrophysics Data System (ADS)

Kremleva, Tatiana; Dinu, Marina

2017-04-01

The paper is based on joint investigation of the Tyumen State University (Russia, Tyumen) and the Geochemistry and Analytical Chemistry Vernadsky Institute of Russian Academy of Sciences (Moscow, Russia) during 2012-2014 period. It presents the results of research of chemical composition of about 70 small lakes located in the area of tundra and northern taiga of West Siberia (Russia, Yamal-Nenets and Khanty-Mansi Autonomous Districts of the Tyumen region). The investigation includes determination of different parameters of natural water samples: • content of trace elements (Al, Fe, Mn, Cr, Cu, Ni, Zn, Cd, Co, Pb, etc., total more than 60 elements) by emission method with an inductively coupled plasma (ICP-MS) using mass spektrometrometre Element 2 equipment; • content of inorganic and total carbon (TIC and TC) by elemental analysis and the difference between the total and inorganic carbon gives the organic carbon content (TOC); • pH value by potentiometric method; • content of basic ions (Na+, Ca2+, K+, Mg2+, NH4+, Cl-, SO42-, NO3-, PO43-) by ion chromatography. Determination of the chemical composition of samples was conducted in the accredited laboratory according to standard procedures with regular quality control of results. Heavy metals in natural waters can exist in various forms: free (hydrated) ions bound in complexes with organic or inorganic ligands, as well as in the form of suspensions. The form of metal existence has a significant influence on their availability to transport in aquatic organisms. Metal ions associated in stable complexes with organic substances are considered less toxic. From the previous investigations state that the most stable complexes are ligands with organic ions Fe3+, Al3+. The main conclusion of the present research states that if the total content of aluminum, iron and manganese ions (meq/dm3) is equal to or greater than the concentration of dissolved organic carbon (TOC, mg/dm3) in lakes water other heavy metals will be predominantly in free, ionic or bound form with inorganic ligands. This state means paradox consequence that the increase of dissolved Fe content will lead to toxicity rise of other elements having less affinity to organic material. For surface waters of Western Siberian Arctic zone this situation is quite common. The total concentration of iron and aluminum ions in most lakes of tundra and northern taiga zones is approximately equal to water complexing ability. From the other side humic substances participation in inactivation of other more toxic metals (Cu, Pb, Cd, Cr, Ni et al.) will be poor. Arctic part of Western Siberia undergoes significant anthropogenic load due to extensive oil and gas recovery in this zone. Surface waters of Western Siberia are characterized by high natural content of iron, aluminum and copper ions and anthropogenic load of heavy metals makes the situation more serious.

Accounting for natural organic matter in aqueous chemical equilibrium models: a review of the theories and applications

NASA Astrophysics Data System (ADS)

Dudal, Yves; Gérard, Frédéric

2004-08-01

Soil organic matter consists of a highly complex and diversified blend of organic molecules, ranging from low molecular weight organic acids (LMWOAs), sugars, amines, alcohols, etc., to high apparent molecular weight fulvic and humic acids. The presence of a wide range of functional groups on these molecules makes them very reactive and influential in soil chemistry, in regards to acid-base chemistry, metal complexation, precipitation and dissolution of minerals and microbial reactions. Out of these functional groups, the carboxylic and phenolic ones are the most abundant and most influential in regards to metal complexation. Therefore, chemical equilibrium models have progressively dealt with organic matter in their calculations. This paper presents a review of six chemical equilibrium models, namely N ICA-Donnan, E Q3/6, G EOCHEM, M INTEQA2, P HREEQC and W HAM, in light of the account they make of natural organic matter (NOM) with the objective of helping potential users in choosing a modelling approach. The account has taken various faces, mainly by adding specific molecules within the existing model databases (E Q3/6, G EOCHEM, and P HREEQC) or by using either a discrete (W HAM) or a continuous (N ICA-Donnan and M INTEQA2) distribution of the deprotonated carboxylic and phenolic groups. The different ways in which soil organic matter has been integrated into these models are discussed in regards to the model-experiment comparisons that were found in the literature, concerning applications to either laboratory or natural systems. Much of the attention has been focused on the two most advanced models, W HAM and N ICA-Donnan, which are able to reasonably describe most of the experimental results. Nevertheless, a better knowledge of the humic substances metal-binding properties is needed to better constrain model inputs with site-specific parameter values. This represents the main axis of research that needs to be carried out to improve the models. In addition to humic substances, more non-humic compounds should also be introduced in model databases, notably the ones that readily interact with the soil microorganisms. Thermodynamic data are generally available for most of these compounds, such as low molecular-weight organic acids. However, the more complex non-humic substances, exhibiting a ratio of hydrophobic versus hydrophilic bonds lower than humic substances, need to be further characterised for a comprehensive implementation in chemical equilibrium models.

Detection of Reaction Intermediates in Mg2+-Dependent DNA Synthesis and RNA Degradation by Time-Resolved X-Ray Crystallography.

PubMed

Samara, Nadine L; Gao, Yang; Wu, Jinjun; Yang, Wei

2017-01-01

Structures of enzyme-substrate/product complexes have been studied for over four decades but have been limited to either before or after a chemical reaction. Recently using in crystallo catalysis combined with X-ray diffraction, we have discovered that many enzymatic reactions in nucleic acid metabolism require additional metal ion cofactors that are not present in the substrate or product state. By controlling metal ions essential for catalysis, the in crystallo approach has revealed unprecedented details of reaction intermediates. Here we present protocols used for successful studies of Mg 2+ -dependent DNA polymerases and ribonucleases that are applicable to analyses of a variety of metal ion-dependent reactions. © 2017 Elsevier Inc. All rights reserved.

Construction of Ligand Group Orbitals for Polyatomics and Transition-Metal Complexes Using an Intuitive Symmetry-Based Approach

ERIC Educational Resources Information Center

Johnson, Adam R.

2013-01-01

A molecular orbital (MO) diagram, especially its frontier orbitals, explains the bonding and reactivity for a chemical compound. It is therefore important for students to learn how to construct one. The traditional methods used to derive these diagrams rely on linear algebra techniques to combine ligand orbitals into symmetry-adapted linear…

Stabilization of Li Metal Anode in DMSO-Based Electrolytes via Optimization of Salt-Solvent Coordination for Li-O 2 Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Bin; Xu, Wu; Yan, Pengfei

The conventional DMSO-based electrolyte (1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in DMSO) is unstable against the Li metal anode and therefore cannot be used directly in practical Li-O2 batteries. Here, we demonstrate that a highly concentrated electrolyte based on LiTFSI in DMSO (with a molar ratio of 1:3) can greatly improve the stability of the Li metal anode against DMSO and significantly improve the cycling stability of Li-O2 batteries. This highly concentrated electrolyte contains no free DMSO solvent molecules, but only complexes of (TFSI–)a-Li+-(DMSO)b (where a + b = 4), and thus enhances their stability with Li metal anodes. In addition,more » such salt-solvent complexes have higher Gibbs activation energy barriers than the free DMSO solvent molecules, indicating improved stability of the electrolyte against the attack of superoxide radical anions. Therefore, the stability of this highly concentrated electrolyte at both Li metal anodes and carbon-based air electrodes has been greatly enhanced, resulting in improved cyclic stability of Li-O2 batteries. The fundamental stability of the electrolyte with free-solvent against the chemical and electrochemical reactions can also be used to enhance the stability of other electrochemical systems.« less

A multi-method analysis of the interaction between humic acids and heavy metal ions.

PubMed

Ke, Tao; Li, Lu; Rajavel, Krishnamoorthy; Wang, Zhenyu; Lin, Daohui

2018-03-08

Understanding of the interaction between humic acids (HAs) and heavy metal ions (HMIs) is essential for the assessment of environmental and health risks of HMIs. Multiple analyses, including fluorescence quenching of HAs; solution pH, zeta potential, and hydrodynamic size changes; and coprecipitation of HAs and HMIs, were carried out to investigate the interaction between two HAs and four HMIs (Ag + , Pb 2+ , Cd 2+ , and Cr 3+ ). The HA-HMI interaction mainly included chemical complexation, H + -HMI exchange, electrostatic attraction, and flocculation. The chemical complexation between HAs and HMIs revealed by the Stern-Volmer quenching constant was ordered as Ag < Cd < Pb < Cr. HMIs replaced protons in the acidic functional groups of HAs and thus lowered the pH of the solution. The electrostatic interaction between the negatively charged HAs and HMIs reduced the electronegativity of HAs. Interaction with HMIs, especially the high-valent ions, induced aggregation of HAs, causing precipitation of both HAs and HMIs in the sorptive solution. Cr 3+ flocculated and precipitated HAs, but at high concentrations, it reversed the surface charge of HAs and resuspended them. The HA-HMI interaction increased as the HA acidity and solution pH increased.

Heavy Metals Technogenic Pollution of Plough Lands Arable Layer in the Chelyabinsk Region

NASA Astrophysics Data System (ADS)

Mantorova, G. F.

2017-11-01

Environmental protection and rational use of natural resources in agriculture are the main directions of this scientific research. Contamination is caused by the substances of chemical, radiation and biological origin above the maximum permissible concentration (MPC). The main source of soil contamination in the arable land, hayfields and pastures is the waste of livestock complexes, agricultural chemicals (fertilizers, pesticides), motor vehicle exhausts, industrial emissions, sewage from settlements, etc. The ecological state of the soil and vegetation cover is largely determined by agricultural activities. The agricultural production technology complicating is accompanied by increase in the degree of environmental risk, especially in the chemicalization of agriculture. Pollution also enters the soil with atmospheric precipitation, surface waste. They are also introduced into the soil layer by soil and groundwater. The most dangerous for human health is considered to be contamination with heavy metals (HM)-lead, mercury and cadmium. However, the concentration of the rest elements is no less harmful. The paradox of heavy metals is that in certain quantities they are necessary to ensure the normal life of plants and organisms but their excess can lead to serious diseases and even death. A nutritional cycle causes harmful compounds to enter the human body and often cause great harm to health. The present work reveals the results of the research of a long-term experience on accumulation and distribution of heavy metals on the arable layer profile depending on the concentration in humus soil and the system of ground processing.

Characterization of metal adsorption variability in a sand and gravel aquifer, Cape Cod, Massachusetts, U.S.A

USGS Publications Warehouse

Fuller, C.C.; Davis, J.A.; Coston, J.A.; Dixon, E.

1996-01-01

Several geochemical properties of an aquifer sediment that control metal-ion adsorption were investigated to determine their potential use as indicators of the spatial variability of metal adsorption. Over the length of a 4.5-m-long core from a sand and gravel aquifer, lead (Pb2+) and zinc (Zn2+) adsorption at constant chemical conditions (pH 5.3) varied by a factor of 2 and 4, respectively. Pb2+ and Zn2+ were adsorbed primarily by Fe- and Al-oxide coatings on quartz-grain surfaces. Per unit surface area, both Pb2+ and Zn2+ adsorption were significantly correlated with the amount of Fe and Al that dissolved from the aquifer material in a partial chemical extraction. The variability in conditional binding constants for Pb2+ and Zn2+ adsorption (log KADS) derived from a simple non-electrostatic surface complexation model were also predicted by extracted Fe and Al normalized to surface area. Because the abundance of Fe- and Al-oxide coatings that dominate adsorption does not vary inversely with grain size by a simple linear relationship, only a weak, negative correlation was found between the spatial variability of Pb2+ adsorption and grain size in this aquifer. The correlation between Zn2+ adsorption and grain size was not significant. Partial chemical extractions combined with surface-area measurements have potential use for estimating metal adsorption variability in other sand and gravel aquifers of negligible carbonate and organic carbon content.

Study of the reaction of tungsten carbide in molten alkali metal nitrates. Syntheses of divalent (s and d blocks) metal tungstates

NASA Astrophysics Data System (ADS)

Deloume, Jean-Pierre; Marote, Pedro; Sigala, Catherine; Matei, Cristian

2003-08-01

WC is tested as precursor to synthesize metal tungstates by reaction in molten alkali metal nitrates. This constitutes a complex redox system with two reducing agents, W and C, and an oxidizer having several oxidation states. The mass loss due to the evolution of gases reveals the reaction steps. The infrared analyses of the gas phase show what kind of reaction develops according to the temperature. WC produces a water-soluble alkali metal tungstate. The reaction of a mixture of WC and a divalent metal chloride (Mg, Ca, Ba, Ni, Cu, Zn) leads to water-insoluble metal tungstates. As the reactivity of the cations increases in the order Zn, Ni, Cu, the reaction of WC is modified by their presence. The physico-chemical characterizations of the products show that some of them are contaminated either by WC or by metal oxide. Some others are rather pure products. These differences, in relationship with the other analyses, allow to propose first reaction pathways of the tungsten carbide in molten salts.

A multifunctional chemical sensor based on a three-dimensional lanthanide metal-organic framework

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Pei-Yao; Liao, Sheng-Yun; Gu, Wen, E-mail: guwen68@nankai.edu.cn

2016-12-15

A 3D lanthanide MOF with formula [Sm{sub 2}(abtc){sub 1.5}(H{sub 2}O){sub 3}(DMA)]·H{sub 2}O·DMA (1) has been successfully synthesized via solvothermal method. Luminescence studies reveal that 1 exhibits dual functional detection benzyl alcohol and benzaldehyde among different aromatic molecules. In addition, 1 displays a turn-on luminescence sensing with respect to ethanol among different alcohol molecules, which suggests that 1 is also a promising luminescent probe for high selective sensing of ethanol. - Highlights: • A three-dimensional lanthanide metal-organic framework has been synthesized. • Complex 1 exhibits dual functional detection benzyl alcohol and benzaldehyde among different aromatic molecules. • Complex 1 displays amore » turn-on luminescence sensing with respect to ethanol among different alcohol molecules.« less

Clean thermal decomposition of tertiary-alkyl metal thiolates to metal sulfides: environmentally-benign, non-polar inks for solution-processed chalcopyrite solar cells.

PubMed

Heo, Jungwoo; Kim, Gi-Hwan; Jeong, Jaeki; Yoon, Yung Jin; Seo, Jung Hwa; Walker, Bright; Kim, Jin Young

2016-11-09

We report the preparation of Cu 2 S, In 2 S 3 , CuInS 2 and Cu(In,Ga)S 2 semiconducting films via the spin coating and annealing of soluble tertiary-alkyl thiolate complexes. The thiolate compounds are readily prepared via the reaction of metal bases and tertiary-alkyl thiols. The thiolate complexes are soluble in common organic solvents and can be solution processed by spin coating to yield thin films. Upon thermal annealing in the range of 200-400 °C, the tertiary-alkyl thiolates decompose cleanly to yield volatile dialkyl sulfides and metal sulfide films which are free of organic residue. Analysis of the reaction byproducts strongly suggests that the decomposition proceeds via an SN 1 mechanism. The composition of the films can be controlled by adjusting the amount of each metal thiolate used in the precursor solution yielding bandgaps in the range of 1.2 to 3.3 eV. The films form functioning p-n junctions when deposited in contact with CdS films prepared by the same method. Functioning solar cells are observed when such p-n junctions are prepared on transparent conducting substrates and finished by depositing electrodes with appropriate work functions. This method enables the fabrication of metal chalcogenide films on a large scale via a simple and chemically clear process.

Clean thermal decomposition of tertiary-alkyl metal thiolates to metal sulfides: environmentally-benign, non-polar inks for solution-processed chalcopyrite solar cells

NASA Astrophysics Data System (ADS)

Heo, Jungwoo; Kim, Gi-Hwan; Jeong, Jaeki; Yoon, Yung Jin; Seo, Jung Hwa; Walker, Bright; Kim, Jin Young

2016-11-01

We report the preparation of Cu2S, In2S3, CuInS2 and Cu(In,Ga)S2 semiconducting films via the spin coating and annealing of soluble tertiary-alkyl thiolate complexes. The thiolate compounds are readily prepared via the reaction of metal bases and tertiary-alkyl thiols. The thiolate complexes are soluble in common organic solvents and can be solution processed by spin coating to yield thin films. Upon thermal annealing in the range of 200-400 °C, the tertiary-alkyl thiolates decompose cleanly to yield volatile dialkyl sulfides and metal sulfide films which are free of organic residue. Analysis of the reaction byproducts strongly suggests that the decomposition proceeds via an SN1 mechanism. The composition of the films can be controlled by adjusting the amount of each metal thiolate used in the precursor solution yielding bandgaps in the range of 1.2 to 3.3 eV. The films form functioning p-n junctions when deposited in contact with CdS films prepared by the same method. Functioning solar cells are observed when such p-n junctions are prepared on transparent conducting substrates and finished by depositing electrodes with appropriate work functions. This method enables the fabrication of metal chalcogenide films on a large scale via a simple and chemically clear process.

Metal nanoparticle-graphene oxide composites: Photophysical properties and sensing applications

NASA Astrophysics Data System (ADS)

Murphy, Sean J.

Composite nanomaterials allow for attractive properties of multiple functional components to be combined. Fundamental understanding of the interaction between different nanomaterials, their surroundings, and nearby molecular species is pertinent for implementation into devices. Metal nanoparticles have been used for their optical properties in many applications including stained glass, cancer therapy, solar steam generation, surface enhanced Raman spectroscopy (SERS), and catalysis. Carbon-based nanomaterials such as graphene and carbon nanotubes show potential for a wide variety of applications including solar energy harvesting, chemical sensors, and electronics. Combining useful and in some cases new properties of composite nanomaterials offers exciting opportunities in fundamental science and device development. In this dissertation, I aim to address understanding photoinduced interaction between porphyrin and silver nanoparticles, inter-sheet interaction between stacked graphene oxide (GO) sheets in thin films, complexation of reduced GO with Raman active target molecule in SERS applications, and efficacy of graphene-metal nanoparticle composites for sensing applications. Molecule-metal nanoparticle composite material made up of photoactive porphyrin and silver nanoparticles was studied using various spectroscopic tools. UV-visible absorption and surface enhanced Raman spectroscopic results suggest formation of a charge-transfer complex for porphyrin-silver nanoparticle composite. Ultrafast transient absorption and fluorescence upconversion spectroscopies further corroborate electronic interaction by providing evidence for excited state electron transfer between porphyrin and silver nanoparticles. Understanding electronic interaction between adsorbed photoactive molecules and metal nanoparticles may be of use for applications in photocatalysis or light-energy harvesting. Graphene oxide (GO) thin films have been prepared and studied using transient absorption microscopy (TAM). Transient absorption microscopy correlated with atomic force microscope allows for the morphological properties of GO thin film to be related to optical properties, namely dynamics of photoexcited carriers in GO. Results suggest short-timescale (ps -- ˜1 ns) dynamics of charge carriers in GO are affected very little by interaction with the glass substrate on which GO is placed. Also, the stack thickness or number of stacked GO sheets does not play a large role in the short-timescale dynamics of GO charge carriers. GO or reduced GO (RGO)-silver nanoparticles composites were produced using different methods: (1) chemical reduction of silver ion precursor and (2) photocatalytic reduction of GO and silver ion using TiO2 nanoparticles. Optical and morphological properties of composites were studied using spectroscopy and electron microscopy revealing a degree of control in metal nanoparticle growth and loading on the surface of RGO. Nanocomposites were shown to be capable of complexing with or adsorbing target molecular species. Complexation and adsorption are corroborated with demonstration that the composite nanomaterials act as effective SERRS sensors taking advantage of localized surface plasmon resonance of metal nanoparticles and the ability of RGO to interact with molecular and ionic species.

Metal-assisted etch combined with regularizing etch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yim, Joanne; Miller, Jeff; Jura, Michael

In an aspect of the disclosure, a process for forming nanostructuring on a silicon-containing substrate is provided. The process comprises (a) performing metal-assisted chemical etching on the substrate, (b) performing a clean, including partial or total removal of the metal used to assist the chemical etch, and (c) performing an isotropic or substantially isotropic chemical etch subsequently to the metal-assisted chemical etch of step (a). In an alternative aspect of the disclosure, the process comprises (a) performing metal-assisted chemical etching on the substrate, (b) cleaning the substrate, including removal of some or all of the assisting metal, and (c) performingmore » a chemical etch which results in regularized openings in the silicon substrate.« less

Unique phase identification of trimetallic copper iron manganese oxygen carrier using simultaneous differential scanning calorimetry/thermogravimetric analysis during chemical looping combustion reactions with methane

DOE PAGES

Benincosa, William; Siriwardane, Ranjani; Tian, Hanjing; ...

2017-07-05

Chemical looping combustion (CLC) is a promising combustion technology that generates heat and sequestration-ready carbon dioxide that is undiluted by nitrogen from the combustion of carbonaceous fuels with an oxygen carrier, or metal oxide. This process is highly dependent on the reactivity and stability of the oxygen carrier. The development of oxygen carriers remains one of the major barriers for commercialization of CLC. Synthetic oxygen carriers, consisting of multiple metal components, have demonstrated enhanced performance and improved CLC operation compared to single metal oxides. However, identification of the complex mixed metal oxide phases that form after calcination or during CLCmore » reactions has been challenging. Without an understanding of the dominant metal oxide phase, it is difficult to determine reaction parameters and the oxygen carrier reduction pathway, which are necessary for CLC reactor design. This is particularly challenging for complex multi-component oxygen carriers such as copper iron manganese oxide (CuFeMnO 4). This study aims to differentiate the unique phase formation of a highly reactive, complex trimetallic oxygen carrier, CuFeMnO 4, from its single and bimetallic counterparts using thermochemical and reaction data obtained from simultaneous differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) during temperature programmed reductions (TPR) with methane. DSC/TGA experiments during TPR with methane provides heat flow data and corresponding reaction rate data that can be used to determine reaction routes and mechanisms during methane reduction. Furthermore, non-isothermal TPR data provides the advantage of distinguishing reactions that may not be observable in isothermal analysis. The detailed thermochemical and reaction data, obtained during TPR with methane, distinguished a unique reduction pathway for CuFeMnO 4 that differed from its single and bimetallic counterparts. This is remarkable since X-ray diffraction (XRD) data alone could not be used to distinguish the reactive trimetallic oxide phase due to overlapping peaks from various single and mixed metal oxides. The unique reduction pathway of CuFeMnO 4 was further characterized in this study using in-situ XRD TPR with methane to determine changes in the dominant trimetallic phase that influenced the thermochemical and reaction rate data.« less

Unique phase identification of trimetallic copper iron manganese oxygen carrier using simultaneous differential scanning calorimetry/thermogravimetric analysis during chemical looping combustion reactions with methane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benincosa, William; Siriwardane, Ranjani; Tian, Hanjing

Chemical looping combustion (CLC) is a promising combustion technology that generates heat and sequestration-ready carbon dioxide that is undiluted by nitrogen from the combustion of carbonaceous fuels with an oxygen carrier, or metal oxide. This process is highly dependent on the reactivity and stability of the oxygen carrier. The development of oxygen carriers remains one of the major barriers for commercialization of CLC. Synthetic oxygen carriers, consisting of multiple metal components, have demonstrated enhanced performance and improved CLC operation compared to single metal oxides. However, identification of the complex mixed metal oxide phases that form after calcination or during CLCmore » reactions has been challenging. Without an understanding of the dominant metal oxide phase, it is difficult to determine reaction parameters and the oxygen carrier reduction pathway, which are necessary for CLC reactor design. This is particularly challenging for complex multi-component oxygen carriers such as copper iron manganese oxide (CuFeMnO 4). This study aims to differentiate the unique phase formation of a highly reactive, complex trimetallic oxygen carrier, CuFeMnO 4, from its single and bimetallic counterparts using thermochemical and reaction data obtained from simultaneous differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) during temperature programmed reductions (TPR) with methane. DSC/TGA experiments during TPR with methane provides heat flow data and corresponding reaction rate data that can be used to determine reaction routes and mechanisms during methane reduction. Furthermore, non-isothermal TPR data provides the advantage of distinguishing reactions that may not be observable in isothermal analysis. The detailed thermochemical and reaction data, obtained during TPR with methane, distinguished a unique reduction pathway for CuFeMnO 4 that differed from its single and bimetallic counterparts. This is remarkable since X-ray diffraction (XRD) data alone could not be used to distinguish the reactive trimetallic oxide phase due to overlapping peaks from various single and mixed metal oxides. The unique reduction pathway of CuFeMnO 4 was further characterized in this study using in-situ XRD TPR with methane to determine changes in the dominant trimetallic phase that influenced the thermochemical and reaction rate data.« less

Physicochemical characterization, and relaxometry studies of micro-graphite oxide, graphene nanoplatelets, and nanoribbons.

PubMed

Paratala, Bhavna S; Jacobson, Barry D; Kanakia, Shruti; Francis, Leonard Deepak; Sitharaman, Balaji

2012-01-01

The chemistry of high-performance magnetic resonance imaging contrast agents remains an active area of research. In this work, we demonstrate that the potassium permanganate-based oxidative chemical procedures used to synthesize graphite oxide or graphene nanoparticles leads to the confinement (intercalation) of trace amounts of Mn(2+) ions between the graphene sheets, and that these manganese intercalated graphitic and graphene structures show disparate structural, chemical and magnetic properties, and high relaxivity (up to 2 order) and distinctly different nuclear magnetic resonance dispersion profiles compared to paramagnetic chelate compounds. The results taken together with other published reports on confinement of paramagnetic metal ions within single-walled carbon nanotubes (a rolled up graphene sheet) show that confinement (encapsulation or intercalation) of paramagnetic metal ions within graphene sheets, and not the size, shape or architecture of the graphitic carbon particles is the key determinant for increasing relaxivity, and thus, identifies nano confinement of paramagnetic ions as novel general strategy to develop paramagnetic metal-ion graphitic-carbon complexes as high relaxivity MRI contrast agents.

Physicochemical Characterization, and Relaxometry Studies of Micro-Graphite Oxide, Graphene Nanoplatelets, and Nanoribbons

PubMed Central

Paratala, Bhavna S.; Jacobson, Barry D.; Kanakia, Shruti; Francis, Leonard Deepak; Sitharaman, Balaji

2012-01-01

The chemistry of high-performance magnetic resonance imaging contrast agents remains an active area of research. In this work, we demonstrate that the potassium permanganate-based oxidative chemical procedures used to synthesize graphite oxide or graphene nanoparticles leads to the confinement (intercalation) of trace amounts of Mn2+ ions between the graphene sheets, and that these manganese intercalated graphitic and graphene structures show disparate structural, chemical and magnetic properties, and high relaxivity (up to 2 order) and distinctly different nuclear magnetic resonance dispersion profiles compared to paramagnetic chelate compounds. The results taken together with other published reports on confinement of paramagnetic metal ions within single-walled carbon nanotubes (a rolled up graphene sheet) show that confinement (encapsulation or intercalation) of paramagnetic metal ions within graphene sheets, and not the size, shape or architecture of the graphitic carbon particles is the key determinant for increasing relaxivity, and thus, identifies nano confinement of paramagnetic ions as novel general strategy to develop paramagnetic metal-ion graphitic-carbon complexes as high relaxivity MRI contrast agents. PMID:22685555

Mechanisms and dynamics of protonation and lithiation of ferrocene.

PubMed

Sharma, Nishant; Ajay, Jayanth K; Venkatasubbaiah, Krishnan; Lourderaj, Upakarasamy

2015-09-14

By elucidating the mechanism of the simplest electrophilic substitution reaction of ferrocene, it was found that the verification of the protonation reaction has been a difficulty. In the work reported here, ab initio chemical dynamics simulations were performed at B3LYP/DZVP level of theory to understand the atomic level mechanisms of protonation and lithiation of ferrocene. Protonation of ferrocene resulted in the agostic and metal-protonated forms. Trajectory calculations revealed that protonation of ferrocene occurs by exo and endo mechanisms, with exo being the major path. H(+) was found to be mobile and hopped from the Cp ring to the metal center and vice versa after the initial attack on ferrocene, with the metal-complex having a shorter lifetime. These results remove the ambiguity surrounding the mechanism, as proposed in earlier experimental and computational studies. Lithiation of ferrocene resulted in the formation of cation-π and metal-lithiated complexes. Similar to protonation, trajectory results revealed that both exo and endo paths were followed, with the exo path being the major one. In addition, lithiated-ferrocene exhibited planetary motion. The major path (exo) followed in the protonation and lithiation of ferrocene is consistent with the observations in earlier experimental studies for other hard electrophiles.

Concentrations and chemical forms of trace metals in coastal seawater on coral reef and their seasonal variation

NASA Astrophysics Data System (ADS)

Ganaha, S.; ITOH, A.

2011-12-01

Coastal seawater on coral reef near Okinawa island in Japan, which is in oligotrophic condition, has a diverse and unique ecosystem. It is possible that nutritive sals and trace metals, classified into nutrient type, are effectively supplied to marine phytoplankton and zooxanthellae from seawater. However, the concentrations and chemical forms of trace metals in coastal seawater on coral reef have been scarcely reported so far. In the present study, the characteristics of the concentrations and chemical forms of trace metals in such a seawater were investigated with seasonal variation by analyzing the coastal seawater at every month, after an analytical method for a simple chemical speciation including on-site treatment was established. The analytical method using a chelating resin and a disposable syringe was employed for de-salt and preconcentration of trace metals in costal seawater. After that, trace metals in the concentrated solution were measured by ICP-MS. Three types of chemical forms of an ionic, a dissolved, and an acid-soluble were separated without any treatment, by filtering with membrane filter of 0.45 μm, and by filtering after adding nitric acid, respectively. Then, a monitoring investigation of the coastal seawater on coral reef, located at Sesoko island near the northern part of Okinawa island, was carried out once at every month from Sep. 2010 to Aug. 2011. As a result, 10 elements in the dissolved form in each sample could be determined. The average concentrations for all samples from Sep. 2010 to Apr. 2011 were as follows: Mo:10.7 ppb, U:3.2 ppb, V:1.5 ppb, Mn:0.17 ppb, Ni:0.16 ppb, Zn:0.13 ppb, Cu:0.070 ppb, Pb:0.024 ppb, Co:0.0022 ppb, Cd:0.0016ppb. The concentrations for most trace metals were almost close to ones in open surface seawater of the Pacific ocean. For the acid-soluble form, the concentrations of V, Mo, and U were almost same with those of the dissolved form, and ones of Mn, Co, Ni, Cu, and Cd were slightly larger than ones in the dissolved form, while ones in Zn and Pb were 3.1- and 2.5-fold larger. These results suggest that a part of trace metals in the nutrient type exists as biogenic particulate matters. For the ionic form, the concentration of Cu was 3-fold smaller than one in the dissolved form. It is considered from the result that a part of Cu in the dissolved form exists not only as the ionic form but also as the colloids and organic complexes. The seasonal variation for each chemical form is now being investigated.

New concepts for molecular magnets

NASA Astrophysics Data System (ADS)

Pilawa, Bernd

1999-03-01

Miller and Epstein (1994) define molecular magnets as magnetic materials which are prepared by the low-temperature methods of the preparative chemistry. This definition includes molecular crystals of neutral radicals, radical salts and charge transfer complexes as well as metal complexes and polymers with unpaired spins (Dormann 1995). The challenge of molecular magnets consists in tailoring magnetic properties by specific modifications of the molecular units. The combination of magnetism with mechanical or electrical properties of molecular compounds promise materials of high technical interest (Gatteschi 1994a and 1994b, Möhwald 1996) and both the chemical synthesis of new molecular materials with magnetic properties as well as the physical investigation and explanation of these properties is important, in order to achieve any progress. This work deals with the physical characterization of the magnetic properties of molecular materials. It is organized as follows. In the first part molecular crystals of neutral radicals are studied. After briefly discussing the general magnetic properties of these materials and after an overview over the physical principles of exchange interaction between organic radicals I focus on the interplay between the crystallographic structure and the magnetic properties of various derivatives of the verdazyl and nitronyl nitroxide radicals. The magnetic properties of metal complexes are the subject of the second part. After an overview over the experimental and theoretical tools which are used for the investigation of the magnetic properties I shortly discuss the exchange coupling of transition metal ions and the magnetic properties of complexes of two and three metal ions. Special emphasis is given to spin cluster compounds. Spin cluster denote complexes of many magnetic ions. They are attractive as building blocks of molecular magnets as well as magnetic model compounds for the study of spin frustration, molecular super-paramagnetism and quasi one-dimensional magnets.

On the occurrence of metallic character in the periodic table of the chemical elements.

PubMed

Hensel, Friedrich; Slocombe, Daniel R; Edwards, Peter P

2015-03-13

The classification of a chemical element as either 'metal' or 'non-metal' continues to form the basis of an instantly recognizable, universal representation of the periodic table (Mendeleeff D. 1905 The principles of chemistry, vol. II, p. 23; Poliakoff M. & Tang S. 2015 Phil. Trans. R. Soc. A 373: , 20140211). Here, we review major, pre-quantum-mechanical innovations (Goldhammer DA. 1913 Dispersion und Absorption des Lichtes; Herzfeld KF. 1927 Phys. Rev. 29: , 701-705) that allow an understanding of the metallic or non-metallic status of the chemical elements under both ambient and extreme conditions. A special emphasis will be placed on recent experimental advances that investigate how the electronic properties of chemical elements vary with temperature and density, and how this invariably relates to a changing status of the chemical elements. Thus, the prototypical non-metals, hydrogen and helium, becomes metallic at high densities; and the acknowledged metals, mercury, rubidium and caesium, transform into their non-metallic forms at low elemental densities. This reflects the fundamental fact that, at temperatures above the absolute zero of temperature, there is therefore no clear dividing line between metals and non-metals. Our conventional demarcation of chemical elements as metals or non-metals within the periodic table is of course governed by our experience of the nature of the elements under ambient conditions. Examination of these other situations helps us to examine the exact divisions of the chemical elements into metals and non-metals (Mendeleeff D. 1905 The principles of chemistry, vol. II, p. 23). © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Chemical bath deposition of II-VI compound thin films

NASA Astrophysics Data System (ADS)

Oladeji, Isaiah Olatunde

II-VI compounds are direct bandgap semiconductors with great potentials in optoelectronic applications. Solar cells, where these materials are in greater demand, require a low cost production technology that will make the final product more affordable. Chemical bath deposition (CBD) a low cost growth technique capable of producing good quality thin film semiconductors over large area and at low temperature then becomes a suitable technology of choice. Heterogeneous reaction in a basic aqueous solution that is responsible for the II-VI compound film growth in CBD requires a metal complex. We have identified the stability constant (k) of the metal complex compatible with CBD growth mechanism to be about 106.9. This value is low enough to ensure that the substrate adsorbed complex relax for subsequent reaction with the chalcogen precursor to take place. It is also high enough to minimize the metal ion concentration in the bath participating in the precipitation of the bulk compounds. Homogeneous reaction that leads to precipitation in the reaction bath takes place because the solubility products of bulk II-VI compounds are very low. This reaction quickly depletes the bath of reactants, limit the film thickness, and degrade the film quality. While ZnS thin films are still hard to grow by CBD because of lack of suitable complexing agent, the homogeneous reaction still limits quality and thickness of both US and ZnS thin films. In this study, the zinc tetraammine complex ([Zn(NH3) 4]2+) with k = 108.9 has been forced to acquire its unsaturated form [Zn(NH3)3]2+ with a moderate k = 106.6 using hydrazine and nitrilotriacetate ion as complementary complexing agents and we have successfully grown ZnS thin films. We have also, minimized or eliminated the homogeneous reaction by using ammonium salt as a buffer and chemical bath with low reactant concentrations. These have allowed us to increase the saturation thickness of ZnS thin film by about 400% and raise that of US film form 0.2 to 0.5 mum with improved quality. A novel chemical activated diffusion of Cd into ZnS thin film at temperature lower than 100°C is also developed. This in conjunction with thermal activated diffusion at 400°C has enabled us to synthesize Cd1-xZn xS thin films suitable for solar cells from CBD grown CdS/ZnS multilayer. The potential application of the new Cd1-xZnxS/CdS/CdTe solar cell structure is also demonstrated. The unoptimized structure grown on transparent conducting oxide coated soda lime glass of 3mm thickness with no antireflection coating yielded a 10% efficiency. This efficiency is the highest ever recorded in any Cd1-xZnxS film containing CdTe solar cells.

Strategies to predict metal mobility in surficial mining environments

USGS Publications Warehouse

Smith, Kathleen S.

2007-01-01

This report presents some strategies to predict metal mobility at mining sites. These strategies are based on chemical, physical, and geochemical information about metals and their interactions with the environment. An overview of conceptual models, metal sources, and relative mobility of metals under different geochemical conditions is presented, followed by a discussion of some important physical and chemical properties of metals that affect their mobility, bioavailability, and toxicity. The physical and chemical properties lead into a discussion of the importance of the chemical speciation of metals. Finally, environmental and geochemical processes and geochemical barriers that affect metal speciation are discussed. Some additional concepts and applications are briefly presented at the end of this report.

Thiolate-bridged dinuclear ruthenium and iron complexes as robust and efficient catalysts toward oxidation of molecular dihydrogen in protic solvents.

PubMed

Yuki, Masahiro; Sakata, Ken; Hirao, Yoshifumi; Nonoyama, Nobuaki; Nakajima, Kazunari; Nishibayashi, Yoshiaki

2015-04-01

Thiolate-bridged dinuclear ruthenium and iron complexes are found to work as efficient catalysts toward oxidation of molecular dihydrogen in protic solvents such as water and methanol under ambient reaction conditions. Heterolytic cleavage of the coordinated molecular dihydrogen at the dinuclear complexes and the sequential oxidation of the produced hydride complexes are involved as key steps to promote the present catalytic reaction. The catalytic activity of the dinuclear complexes toward the chemical oxidation of molecular dihydrogen achieves up to 10000 TON (turnover number), and electrooxidation of molecular dihydrogen proceeds quite rapidly. The result of the density functional theory (DFT) calculation on the reaction pathway indicates that a synergistic effect between the two ruthenium atoms plays an important role to realize the catalytic oxidation of molecular dihydrogen efficiently. The present dinuclear ruthenium complex is found to work as an efficient organometallic anode catalyst for the fuel cell. It is noteworthy that the present dinuclear complex worked not only as an effective catalyst toward chemical and electrochemical oxidation of molecular dihydrogen but also as a good anode catalyst for the fuel cell. We consider that the result described in this paper provides useful and valuable information to develop highly efficient and low-cost transition metal complexes as anode catalysts in the fuel cell.

Multifaceted Modularity: A Key for Stepwise Building of Hierarchical Complexity in Actinide Metal–Organic Frameworks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dolgopolova, Ekaterina A.; Ejegbavwo, Otega A.; Martin, Corey R.

Growing necessity for efficient nuclear waste management is a driving force for development of alternative architectures towards fundamental understanding of mechanisms involved in actinide integration inside extended structures. In this manuscript, metal-organic frameworks (MOFs) were investigated as a model system for engineering radionuclide containing materials through utilization of unprecedented MOF modularity, which cannot be replicated in any other type of materials. Through the implementation of recent synthetic advances in the MOF field, hierarchical complexity of An-materials were built stepwise, which was only feasible due to preparation of the first examples of actinide-based frameworks with “unsaturated” metal nodes. The first successfulmore » attempts of solid-state metathesis and metal node extension in An-MOFs are reported, and the results of the former approach revealed drastic differences in chemical behavior of extended structures versus molecular species. Successful utilization of MOF modularity also allowed us to structurally characterize the first example of bimetallic An-An nodes. To the best of our knowledge, through combination of solid-state metathesis, guest incorporation, and capping linker installation, we were able to achieve the highest Th wt% in mono- and bi-actinide frameworks with minimal structural density. Overall, combination of a multistep synthetic approach with homogeneous actinide distribution and moderate solvothermal conditions could make MOFs an exceptionally powerful tool to address fundamental questions responsible for chemical behavior of An-based extended structures, and therefore, shed light on possible optimization of nuclear waste administration.« less

The environmental geochemistry of Arsenic – An overview

USGS Publications Warehouse

Bowell, Robert J.; Alpers, Charles N.; Jamieson, Heather E.; Nordstrom, D. Kirk; Majzlan, Juraj

2014-01-01

Arsenic is one of the most prevalent toxic elements in the environment. The toxicity, mobility, and fate of arsenic in the environment are determined by a complex series of controls dependent on mineralogy, chemical speciation, and biological processes. The element was first described by Theophrastus in 300 B.C. and named arsenikon (also arrhenicon; Caley and Richards 1956) referring to its “potent” nature, although it was originally considered an alternative form of sulfur (Boyle and Jonasson 1973). Arsenikon is believed to be derived from the earlier Persian, zarnik (online etymology dictionary, http://www.etymonline.com/index.php?term=arsenic). It was not until the thirteenth century that an alchemist, Albertus Magnus, was able to isolate the element from orpiment, an arsenic sulfide (As2S3). The complex chemistry required to do this led to arsenic being considered a “bastard metal” or what we now call a “metalloid,” having properties of both metals and non-metals. As a chemical element, arsenic is widely distributed in nature and can be concentrated in many different ways. In the Earth’s crust, arsenic is concentrated by magmatic and hydrothermal processes and has been used as a “pathfinder” for metallic ore deposits, particularly gold, tin, copper, and tungsten (Boyle and Jonasson 1973; Cohen and Bowell 2014). It has for centuries been considered a potent toxin, is a common poison in actual and fictional crimes, and has led to significant impacts on human health in many areas of the world (Cullen 2008; Wharton 2010).

Progress and Perspective of Electrocatalytic CO2 Reduction for Renewable Carbonaceous Fuels and Chemicals.

PubMed

Zhang, Wenjun; Hu, Yi; Ma, Lianbo; Zhu, Guoyin; Wang, Yanrong; Xue, Xiaolan; Chen, Renpeng; Yang, Songyuan; Jin, Zhong

2018-01-01

The worldwide unrestrained emission of carbon dioxide (CO 2 ) has caused serious environmental pollution and climate change issues. For the sustainable development of human civilization, it is very desirable to convert CO 2 to renewable fuels through clean and economical chemical processes. Recently, electrocatalytic CO 2 conversion is regarded as a prospective pathway for the recycling of carbon resource and the generation of sustainable fuels. In this review, recent research advances in electrocatalytic CO 2 reduction are summarized from both experimental and theoretical aspects. The referred electrocatalysts are divided into different classes, including metal-organic complexes, metals, metal alloys, inorganic metal compounds and carbon-based metal-free nanomaterials. Moreover, the selective formation processes of different reductive products, such as formic acid/formate (HCOOH/HCOO - ), monoxide carbon (CO), formaldehyde (HCHO), methane (CH 4 ), ethylene (C 2 H 4 ), methanol (CH 3 OH), ethanol (CH 3 CH 2 OH), etc. are introduced in detail, respectively. Owing to the limited energy efficiency, unmanageable selectivity, low stability, and indeterminate mechanisms of electrocatalytic CO 2 reduction, there are still many tough challenges need to be addressed. In view of this, the current research trends to overcome these obstacles in CO 2 electroreduction field are summarized. We expect that this review will provide new insights into the further technique development and practical applications of CO 2 electroreduction.

Role of annealing on the structural and optical properties of nanostructured diaceto bis-benzimidazole Mn(II) complex thin films

NASA Astrophysics Data System (ADS)

Praveen, P. A.; Babu, R. Ramesh; Ramamurthi, K.

2017-02-01

A coordination complex, manganese incorporated benzimidazole, thin films were prepared by chemical bath deposition method. Structural characterization of the deposited films, carried out by Fourier transform infrared spectroscopy, Raman and electron paramagnetic resonance spectral analyses, reveals the distorted tetrahedral environment of the metal ion with bis-benzimidazole ligand. Further the molecular composition of the deposited metal complex was estimated by energy-dispersive X-ray spectroscopy. The prepared thin films were thermally treated to study the effect of annealing temperature on the surface morphology and the results showed that the surface homogeneity of the films increased for thermally treated films up to 150 °C. But distortion and voids were observed for the films annealed at 200 °C. The Raman analysis reveals the molecular hydrogen bond distortion which leads to the evaporation of the metal complex from the thin film surface with respect to annealing temperature. The linear and nonlinear optical properties of the as prepared and annealed films were studied using ultraviolet-visible transmittance spectroscopy, second harmonic generation and Z-scan analyses. Films annealed at 150 °C show a better linear transmittance in the visible region and larger SHG efficiency and third order nonlinear susceptibility when compared with the other samples. Further, the film annealed at 150 °C was subjected to optical switching analysis and demonstrated to have an inverted switching behavior.

Characterization of plastic deformation and chemical reaction in titanium-polytetrafluoroethylene mixture

NASA Astrophysics Data System (ADS)

Davis, Jeffery Jon

1998-09-01

The subject of this dissertation is the deformation process of a single metal - polymer system (titanium - polytetrafluoroethylene) and how this process leads to initiation of chemical reaction. Several different kinds of experiments were performed to characterize the behavior of this material to shock and impact. These mechanical conditions induce a rapid plastic deformation of the sample. All of the samples tested had an initial porosity which increased the plastic flow condition. It is currently believed that during the deformation process two important conditions occur: removal of the oxide layer from the metal and decomposition of the polymer. These conditions allow for rapid chemical reaction. The research from this dissertation has provided insight into the complex behavior of plastic deformation and chemical reactions in titanium - polytetrafluoroethylene (PTFE, Teflon). A hydrodynamic computational code was used to model the plastic flow for correlation with the results from the experiments. The results from this work are being used to develop an ignition and growth model for metal/polymer systems. Three sets of experiments were used to examine deformation of the 80% Ti and 20% Teflon materials: drop- weight, gas gun, and split-Hopkinson pressure bar. Recovery studies included post shot analysis of the samples using x-ray diffraction. Lagrangian hydrocode DYNA2D modeling of the drop-weight tests was performed for comparison with experiments. One of the reactions know to occur is Ti + C → TiC (s) which results in an exothermic release. However, the believed initial reactions occur between Ti and fluorine which produces TixFy gases. The thermochemical code CHEETAH was used to investigate the detonation products and concentrations possible during Ti - Teflon reaction. CHEETAH shows that the Ti - fluorine reactions are thermodynamically favorable. This research represents the most comprehensive to date study of deformation induced chemical reaction in metal/polymers.

Chemical Reaction and Flow Modeling in Fullerene and Nanotube Production

NASA Technical Reports Server (NTRS)

Scott, Carl D.; Farhat, Samir; Greendyke, Robert B.

2004-01-01

The development of processes to produce fullerenes and carbon nanotubes has largely been empirical. Fullerenes were first discovered in the soot produced by laser ablation of graphite [1]and then in the soot of electric arc evaporated carbon. Techniques and conditions for producing larger and larger quantities of fullerenes depended mainly on trial and error empirical variations of these processes, with attempts to scale them up by using larger electrodes and targets and higher power. Various concepts of how fullerenes and carbon nanotubes were formed were put forth, but very little was done based on chemical kinetics of the reactions. This was mainly due to the complex mixture of species and complex nature of conditions in the reactors. Temperatures in the reactors varied from several thousand degrees Kelvin down to near room temperature. There are hundreds of species possible, ranging from atomic carbon to large clusters of carbonaceous soot, and metallic catalyst atoms to metal clusters, to complexes of metals and carbon. Most of the chemical kinetics of the reactions and the thermodynamic properties of clusters and complexes have only been approximated. In addition, flow conditions in the reactors are transient or unsteady, and three dimensional, with steep spatial gradients of temperature and species concentrations. All these factors make computational simulations of reactors very complex and challenging. This article addresses the development of the chemical reaction involved in fullerene production and extends this to production of carbon nanotubes by the laser ablation/oven process and by the electric arc evaporation process. In addition, the high-pressure carbon monoxide (HiPco) process is discussed. The article is in several parts. The first one addresses the thermochemical aspects of modeling; and considers the development of chemical rate equations, estimates of reaction rates, and thermodynamic properties where they are available. The second part addresses modeling of the arc process for fullerene and carbon nanotube production using O-D, 1-D and 2-D fluid flow models. The third part addresses simulations of the pulsed laser ablation process using time-dependent techniques in 2-D, and a steady state 2-D simulation of a continuous laser ablation process. The fourth part addresses steady state modeling in O-D and 2-D of the HiPco process. In each of the simulations, there is a variety of simplifications that are made that enable one to concentrate on one aspect or another of the process. There are simplifications that can be made to the chemical reaction models , e.g. reduction in number of species by lumping some of them together in a representative species. Other simulations are carried out by eliminating the chemistry altogether in order to concentrate on the fluid dynamics. When solving problems with a large number of species in more than one spatial dimension, it is almost imperative that the problem be decoupled by solving for the fluid dynamics to find the fluid motion and temperature history of "particles" of fluid moving through a reactor. Then one can solve the chemical rate equations with complex chemistry following the temperature and pressure history. One difficulty is that often mixing with an ambient gas is involved. Therefore, one needs to take dilution and mixing into account. This changes the ratio of carbon species to background gas. Commercially available codes may have no provision for including dilution as part of the input. One must the write special solvers for including dilution in decoupled problems. The article addresses both ful1erene production and single-walled carbon nanotube (SWNT) production. There are at least two schemes or concepts of SWNT growth. This article will only address growth in the gas phase by carbon and catalyst cluster growth and SW T formation by the addition of carbon. There are other models that conceive of SWNT growth as a phase separation process from clusters me up carbon and metal catalyst, with the carbon precipitating from the cluster as it cools. We will not deal with that concept in this article. Further research is needed to determine the rates at which these composite clusters form, evaporate, and segregate.

Tryptophan oxidation catabolite, N-formylkynurenine, in photo degraded cell culture medium results in reduced cell culture performance.

PubMed

McElearney, Kyle; Ali, Amr; Gilbert, Alan; Kshirsagar, Rashmi; Zang, Li

2016-01-01

Chemically defined media have been widely used in the biopharmaceutical industry to enhance cell culture productivities and ensure process robustness. These media, which are quite complex, often contain a mixture of many components such as vitamins, amino acids, metals and other chemicals. Some of these components are known to be sensitive to various stress factors including photodegradation. Previous work has shown that small changes in impurity concentrations induced by these potential stresses can have a large impact on the cell culture process including growth and product quality attributes. Furthermore, it has been shown to be difficult to detect these modifications analytically due to the complexity of the cell culture media and the trace level of the degradant products. Here, we describe work performed to identify the specific chemical(s) in photodegraded medium that affect cell culture performance. First, we developed a model system capable of detecting changes in cell culture performance. Second, we used these data and applied an LC-MS analytical technique to characterize the cell culture media and identify degradant products which affect cell culture performance. Riboflavin limitation and N-formylkynurenine (NFK), a tryptophan oxidation catabolite, were identified as chemicals which results in a reduction in cell culture performance. © 2015 American Institute of Chemical Engineers.

Naval Research Reviews, Volume 32, Number 4

DTIC Science & Technology

1980-01-01

iron while (e.g., carbon, chlorine, phosphorous, sulfur, zinc other areas are still covered by an oxide . An XPS and boron). An example of the chemical...picture. Metallic bearing components, for ex- major impact on tribology. The first is the develop- ample, usually have complex oxide films on their...the composition or thickncs. IThe optical image is m,.chanisms responsible for ion beam degradation of rotated slightly withrespecttoelectronimages

Mercury Toxicity and Treatment: A Review of the Literature

PubMed Central

Bernhoft, Robin A.

2012-01-01

Mercury is a toxic heavy metal which is widely dispersed in nature. Most human exposure results from fish consumption or dental amalgam. Mercury occurs in several chemical forms, with complex pharmacokinetics. Mercury is capable of inducing a wide range of clinical presentations. Diagnosis of mercury toxicity can be challenging but can be obtained with reasonable reliability. Effective therapies for clinical toxicity have been described. PMID:22235210

REM-containing silicate concentrates

NASA Astrophysics Data System (ADS)

Pavlov, V. F.; Shabanova, O. V.; Pavlov, I. V.; Pavlov, M. V.; Shabanov, A. V.

2016-01-01

A new method of advanced complex processing of ores containing rare-earth elements (REE) is proposed to obtain porous X-ray amorphous aluminosilicate material with a stable chemical composition which concentrates oxides of rare-earth metals (REM). The ferromanganese oxide ores of Chuktukon deposit (Krasnoyarsk Region, RF) were used for the experiment. The obtained aluminosilicate material is appropriate for treatment with 5 - 15% solutions of mineral acids to leach REM.

Effect of weathering on chromated copper arsenate (CCA) treated wood : leaching of metal salts and change in water repellency

Treesearch

R. Sam Williams; Stan Lebow; Patricia Lebow

2003-01-01

Wood pressure-treated with chromated copper arsenate (CCA) wood preservative is commonly used for outdoor construction. Oxides of arsenic, copper, and chromium are bound in the wood by a complex series of chemical reactions, but a small percentage of these compounds are gradually released by leaching and weathering. Recent studies suggest that the release of these...

Predicting Metal Speciation & Bioavailability via Estimation of Metal-Organic Thermodynamic Properties

NASA Astrophysics Data System (ADS)

Prasad, A.; Howells, A. E.; Shock, E.

2017-12-01

The biological fate of any metal depends on its chemical form in the environment. Arsenic for example, is extremely toxic in the form of inorganic As+3 but completely benign in the organic form of arsenobetaine. Thus, given an exhaustive set of reactions and their equilibrium constants (logK), the bioavailability of any metal can be obtained for blood plasma, hydrothermal fluids or any system of interest. While many data exist for metal-inorganic ligands, logK data covering the temperature range of life for metal-organic complexes are sparse. Hence, we decided to estimate metal-organic logK values from correlations with the commonly available values of ligand pKa. Metal ion specific correlations were made with ligands classified according to their electron donor atoms, denticity and other chemical factors. While this approach has been employed before (Carbonaro et al. 2007, GCA 71, 3958-3968), new correlations were developed that provide estimates even when no metal-organic logK is available. In addition, we have used the same methods to make estimates of metal-organic entropy of association (ΔaS), which can provide logK for any temperature of biological relevance. Our current correlations employ logK and ΔaS data from 30 metal ions (like the biologically relevant Fe+3 & Zn+2) and 74 ligands (like formate and ethylenediamine), which can be expanded to estimate the metal-ligand reaction properties for these 30 metal ions with a possibly limitless number of ligands that may belong to our categories of ligands. With the help of such data, copper speciation was obtained for a defined growth medium for methanotrophs employed by Morton et al. (2000, AEM 66, 1730-1733) that agrees with experimental measurements showing that the free metal ion may not be the bioavailable form in all conditions. These results encourage us to keep filling the gaps in metal-organic logK data and continue finding relationships between biological responses (like metal-accumulation ratios & metal-induced toxicity) and metal speciation.

Two cases of occupational allergic contact dermatitis from a cycloaliphatic epoxy resin in a neat oil: Case Report

PubMed Central

Jensen, Charlotte D; Andersen, Klaus E

2003-01-01

Background Metal-working fluids contain complex mixtures of chemicals and metal workers constitute a potential risk group for the development of allergic contact dermatitis. Case presentation Two metal workers developed allergic contact dermatitis on the hands and lower arms from exposure to a neat oil used in metal processing. Patch testing revealed that the relevant contact allergen was a cycloaliphatic epoxy resin, 1,2-cyclohexanedicarboxylic acid, bis(oxiranylmethyl) ester, added to the oil as a stabilizer. None of the patients had positive reactions to the bisphenol A-based epoxy resin in the standard series. Conclusions These cases emphasize that well-known contact allergens may show up from unexpected sources of exposure. Further, it can be a long-lasting, laborious process to detect an occupational contact allergen and cooperation from the patient and the manufacturer of the sensitizing product is essential. PMID:12685935

High-temperature corrosion of metals in the salt and metallic melts containing rare earths

NASA Astrophysics Data System (ADS)

Karpov, V. V.; Abramov, A. V.; Zhilyakov, A. Yu.; Belikov, S. V.; Volkovich, V. A.; Polovov, I. B.; Rebrin, O. I.

2016-09-01

A complex of independent methods was employed to study the corrosion resistance of molybdenum, zirconium, tantalum and tungsten in chloride, chloride-fluoride and fluoride-oxide melts based on LiCl, CaCl2, NaCl- KCl, LiF, and containing rare earths. Tests were conducted for 30 h at 750-1050 °C. The metals showed excellent corrosion resistance in fused chlorides (the corrosion rates were below 0.0005 g/(m2 h). Despite the presence of chemically active fluoride ions in the chloride-fluoride melts, the metals studied also showed very low corrosion rates, except molybdenum, for which the rate of corrosion was 0,8 g/(m2 h). The corrosion resistance of tantalum was considerably reduced in the fluoride-oxide melts; the corrosion rate was over 1 g/(m2 h) corresponding to the 8-th grade of stability and placing tantalum to the group of "low stability" materials.

Bottom-up nanoconstruction by the welding of individual metallic nanoobjects using nanoscale solder.

PubMed

Peng, Yong; Cullis, Tony; Inkson, Beverley

2009-01-01

We report that individual metallic nanowires and nanoobjects can be assembled and welded together into complex nanostructures and conductive circuits by a new nanoscale electrical welding technique using nanovolumes of metal solder. At the weld sites, nanoscale volumes of a chosen metal are deposited using a sacrificial nanowire, which ensures that the nanoobjects to be bonded retain their structural integrity. We demonstrate by welding both similar and dissimilar materials that the use of nanoscale solder is clean, controllable, and reliable and ensures both mechanically strong and electrically conductive contacts. Nanoscale weld resistances of just 20Omega are achieved by using Sn solder. Precise engineering of nanowelds by this technique, including the chemical flexibility of the nanowire solder, and high spatial resolution of the nanowelding method, should result in research applications including fabrication of nanosensors and nanoelectronics constructed from a small number of nanoobjects, and repair of interconnects and failed nanoscale electronics.

Insight into induced charges at metal surfaces and biointerfaces using a polarizable Lennard-Jones potential.

PubMed

Geada, Isidro Lorenzo; Ramezani-Dakhel, Hadi; Jamil, Tariq; Sulpizi, Marialore; Heinz, Hendrik

2018-02-19

Metallic nanostructures have become popular for applications in therapeutics, catalysts, imaging, and gene delivery. Molecular dynamics simulations are gaining influence to predict nanostructure assembly and performance; however, instantaneous polarization effects due to induced charges in the free electron gas are not routinely included. Here we present a simple, compatible, and accurate polarizable potential for gold that consists of a Lennard-Jones potential and a harmonically coupled core-shell charge pair for every metal atom. The model reproduces the classical image potential of adsorbed ions as well as surface, bulk, and aqueous interfacial properties in excellent agreement with experiment. Induced charges affect the adsorption of ions onto gold surfaces in the gas phase at a strength similar to chemical bonds while ions and charged peptides in solution are influenced at a strength similar to intermolecular bonds. The proposed model can be applied to complex gold interfaces, electrode processes, and extended to other metals.

Charge transfer mechanism for the formation of metallic states at the KTaO3/SrTiO3 interface

NASA Astrophysics Data System (ADS)

Nazir, S.; Singh, N.; Schwingenschlögl, U.

2011-03-01

The electronic and optical properties of the KTaO3/SrTiO3 heterointerface are analyzed by the full-potential linearized augmented plane-wave approach of density functional theory. Optimization of the atomic positions points at subordinate changes in the crystal structure and chemical bonding near the interface, which is due to a minimal lattice mismatch. The creation of metallic interface states thus is not affected by structural relaxation but can be explained by charge transfer between transition metal and oxygen atoms. It is to be expected that a charge transfer is likewise important for related interfaces such as LaAlO3/SrTiO3. The KTaO3/SrTiO3 system is ideal for disentangling the complex behavior of metallic interface states, since almost no structural relaxation takes place.

CO-oxidation catalysts: Low-temperature CO oxidation over Noble-Metal Reducible Oxide (NMRO) catalysts

NASA Technical Reports Server (NTRS)

Herz, Richard K.

1990-01-01

Oxidation of CO to CO2 is an important reaction technologically and environmentally and a complex and interesting reaction scientifically. In most cases, the reaction is carried out in order to remove CO as an environmental hazard. A major application of heterogeneous catalysts is catalytic oxidation of CO in the exhaust of combustion devices. The reaction over catalysts in exhaust gas is fast and often mass-transfer-limited since exhaust gases are hot and O2/CO ratios are high. The main challenges to catalyst designers are to control thermal sintering and chemical poisoning of the active materials. The effect of the noble metal on the oxide is discussed, followed by the effect of the oxide on the noble metal, the interaction of the noble metal and oxide to form unique catalytic sites, and the possible ways in which the CO oxidation reaction is catalyzed by the NMRO materials.

Unusually Strong Long-Distance Metal-Metal Coupling in Bis(ferrocene)-Containing BOPHY: An Introduction to Organometallic BOPHYs.

PubMed

Rhoda, Hannah M; Chanawanno, Kullapa; King, Alexander J; Zatsikha, Yuriy V; Ziegler, Christopher J; Nemykin, Victor N

2015-12-07

The first organometallic BOPHY (BOPHY=bis(difluoroboron)-1,2-bis{(pyrrol-2-yl)methylene}hydrazine) containing two ferrocene substituents was prepared through a Knoevenagel condensation between tetramethyl substituted BOPHY and ferrocene carboxaldehyde. An unprecedentedly strong long-range (≈17.2 Å) metal-metal coupling in this new complex was investigated using electrochemical, spectroelectrochemical, and chemical oxidation methods. Electrochemical data is indicative of a 200 mV separation between the first and the second ferrocene-centered oxidation processes. Formation of the mixed-valence states and appearance and disappearance of two NIR bands were observed during stepwise oxidation of the first organometallic BOPHY. The electronic structure and the nature of the excited states in this new chromophore were studied by DFT and TDDFT calculations. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Acute toxicity of heavy metals to acetate-utilizing mixed cultures of sulfate-reducing bacteria: EC100 and EC50.

PubMed

Utgikar, V P; Chen, B Y; Chaudhary, N; Tabak, H H; Haines, J R; Govind, R

2001-12-01

Acid mine drainage from abandoned mines and acid mine pit lakes is an important environmental concern and usually contains appreciable concentrations of heavy metals. Because sulfate-reducing bacteria (SRB) are involved in the treatment of acid mine drainage, knowledge of acute metal toxicity levels for SRB is essential for the proper functioning of the treatment system for acid mine drainage. Quantification of heavy metal toxicity to mixed cultures of SRB is complicated by the confounding effects of metal hydroxide and sulfide precipitation, biosorption, and complexation with the constituents of the reaction matrix. The objective of this paper was to demonstrate that measurements of dissolved metal concentrations could be used to determine the toxicity parameters for mixed cultures of sulfate-reducing bacteria. The effective concentration, 100% (EC100), the lowest initial dissolved metal concentrations at which no sulfate reduction is observed, and the effective concentration, 50% (EC50), the initial dissolved metal concentrations resulting in a 50% decrease in sulfate reduction, for copper and zinc were determined in the present study by means of nondestructive, rapid physical and chemical analytical techniques. The reaction medium used in the experiments was designed specifically (in terms of pH and chemical composition) to provide the nutrients necessary for the sulfidogenic activity of the SRB and to preclude chemical precipitation of the metals under investigation. The toxicity-mitigating effects of biosorption of dissolved metals were also quantified. Anaerobic Hungate tubes were set up (at least in triplicate) and monitored for sulfate-reduction activity. The onset of SRB activity was detected by the blackening of the reaction mixture because of formation of insoluble ferrous sulfide. The EC100 values were found to be 12 mg/L for copper and 20 mg/L for zinc. The dissolved metal concentration measurements were effective as the indicators of the effect of the heavy metals at concentrations below EC100. The 7-d EC50 values obtained from the difference between the dissolved metal concentrations for the control tubes (tubes not containing copper or zinc) and tubes containing metals were found to be 10.5 mg/L for copper and 16.5 mg/L for zinc. Measurements of the turbidity and pH, bacterial population estimations by means of a most-probable number technique, and metal recovery in the sulfide precipitate were found to have only a limited applicability in these determinations.

Adsorption of poly(vinyl formamide-co-vinyl amine) (PVFA-co-PVAm) polymers on zinc, zinc oxide, iron, and iron oxide surfaces.

PubMed

Seifert, Susan; Simon, Frank; Baumann, Giesela; Hietschold, Michael; Seifert, Andreas; Spange, Stefan

2011-12-06

The adsorption of poly(vinyl formamide) (PVFA) and the statistic copolymers poly(vinyl formamide-co-vinyl amine) (PVFA-co-PVAm) onto zinc and iron metal particles as well as their oxides was investigated. The adsorbates were characterized by means of XPS, DRIFT spectroscopy, wet chemical analysis, and solvatochromic probes. Dicyano-bis-(1,10-phenanthroline)-iron(II) (1), 3-(4-amino-3-methylphenyl)-7-phenyl-benzo-[1,2-b:4,5-b']difuran-2,6-dione (2), and 4-tert-butyl-2-(dicyano-methylene)-5-[4-(diethylamino)-benzylidene]-Δ(3)-thiazoline (3) as solvatochromic probes were coadsorbed onto zinc oxide to measure various effects of surface polarity. The experimental findings showed that the adsorption mechanism of PVFA and PVFA-co-PVAm strongly depends on the degree of hydrolysis of PVFA and pH values and also on the kind of metal or metal oxide surfaces that were employed as adsorbents. The adsorption mechanism of PVFA/PVFA-co-PVAm onto zinc oxide and iron oxide surfaces is mainly affected by electrostatic interactions. Particularly in the region of pH 5, the adsorption of PVFA/PVFA-co-PVAm onto zinc and iron metal particles is additionally influenced by redox processes, dissolution, and complexation reactions. © 2011 American Chemical Society

Chemical bonding in aqueous hexacyano cobaltate from photon- and electron-detection perspectives

PubMed Central

Lalithambika, Sreeju Sreekantan Nair; Atak, Kaan; Seidel, Robert; Neubauer, Antje; Brandenburg, Tim; Xiao, Jie; Winter, Bernd; Aziz, Emad F.

2017-01-01

The electronic structure of the [Co(CN)6]3− complex dissolved in water is studied using X-ray spectroscopy techniques. By combining electron and photon detection methods from the solutions ionized or excited by soft X-rays we experimentally identify chemical bonding between the metal center and the CN ligand. Non-resonant photoelectron spectroscopy provides solute electron binding energies, and nitrogen 1 s and cobalt 2p resonant core-level photoelectron spectroscopy identifies overlap between metal and ligand orbitals. By probing resonances we are able to qualitatively determine the ligand versus metal character of the respective occupied and non-occupied orbitals, purely by experiment. For the same excitations we also detect the emitted X-rays, yielding the complementary resonant inelastic X-ray scattering spectra. For a quantitative interpretation of the spectra, we perform theoretical electronic-structure calculations. The latter provide both orbital energies and orbital character which are found to be in good agreement with experimental energies and with experimentally inferred orbital mixing. We also report calculated X-ray absorption spectra, which in conjunction with our orbital-structure analysis, enables us to quantify various bonding interactions with a particular focus on the water-solvent – ligand interaction and the strength of π-backbonding between metal and ligand. PMID:28098216

Integrated field and laboratory tests to evaluate effects of metals-impacted wetlands on amphibians: A case study from Montana

USGS Publications Warehouse

Linder, G.; ,

2003-01-01

Mining activities frequently impact wildlife habitats, and a wide range of habitats may require evaluations of the linkages between wildlife and environmental stressors common to mining activities (e.g., physical alteration of habitat, releases of chemicals such as metals and other inorganic constituents as part of the mining operation). Wetlands, for example, are frequently impacted by mining activities. Within an ecological assessment for a wetland, toxicity evaluations for representative species may be advantageous to the site evaluation, since these species could be exposed to complex chemical mixtures potentially released from the site. Amphibian species common to these transition zones between terrestrial and aquatic habitats are one key biological indicator of exposure, and integrated approaches which involve both field and laboratory methods focused on amphibians are critical to the assessment process. The laboratory and field evaluations of a wetland in western Montana illustrates the integrated approach to risk assessment and causal analysis. Here, amphibians were used to evaluate the potential toxicity associated with heavy metal-laden sediments deposited in a reservoir. Field and laboratory methods were applied to a toxicity assessment for metals characteristic of mine tailings to reduce potential "lab to field" extrapolation errors and provide adaptive management programs with critical site-specific information targeted on remediation.

Synthesis, X-ray structure and electrochemical oxidation of palladium(II) complexes of ferrocenyldiphenylphosphine.

PubMed

Bennett, Martin A; Bhargava, Suresh K; Bond, Alan M; Burgar, Iko M; Guo, Si-Xuan; Kar, Gopa; Privér, Steven H; Wagler, Jörg; Willis, Anthony C; Torriero, Angel A J

2010-10-14

Four new complexes, [PdX(κ(2)-2-C(6)R(4)PPh(2))(PPh(2)Fc)] [X = Br, R = H (1), R = F (2); X = I, R = H (3), R = F (4)], containing ferrocenyldiphenylphosphine (PPh(2)Fc) have been prepared and fully characterised. The X-ray structures of complexes trans-1, cis-2 and cis-4, and that of a decomposition product of 4, [Pd(κ(2)-2-C(6)F(4)PPh(2))(μ-I)(μ-2-C(6)F(4)PPh(2))PdI(PPh(2)Fc)] (5), have been determined. These complexes show a distorted square planar geometry about the metal atom, the bite angles of the chelate ligands being about 69°, as expected. The cis/trans ratio of 1-4 in solution is strongly dependent on solvent. The new complexes and the uncoordinated PPh(2)Fc ligand were electrochemically characterised by cyclic and rotating disk voltammetry, UV-visible spectroelectrochemistry, and bulk electrolysis in dichloromethane and acetonitrile. In both cases, oxidation occurs at both the ferrocene and phosphine centres, but the complexes oxidise at more positive potentials than uncoordinated PPh(2)Fc; subsequently, the metal-phosphorus bond is cleaved, leading to free PPh(2)Fc(+), which undergoes further chemical and electrochemical reactions.

Accelerating Chemical Discovery with Machine Learning: Simulated Evolution of Spin Crossover Complexes with an Artificial Neural Network.

PubMed

Janet, Jon Paul; Chan, Lydia; Kulik, Heather J

2018-03-01

Machine learning (ML) has emerged as a powerful complement to simulation for materials discovery by reducing time for evaluation of energies and properties at accuracy competitive with first-principles methods. We use genetic algorithm (GA) optimization to discover unconventional spin-crossover complexes in combination with efficient scoring from an artificial neural network (ANN) that predicts spin-state splitting of inorganic complexes. We explore a compound space of over 5600 candidate materials derived from eight metal/oxidation state combinations and a 32-ligand pool. We introduce a strategy for error-aware ML-driven discovery by limiting how far the GA travels away from the nearest ANN training points while maximizing property (i.e., spin-splitting) fitness, leading to discovery of 80% of the leads from full chemical space enumeration. Over a 51-complex subset, average unsigned errors (4.5 kcal/mol) are close to the ANN's baseline 3 kcal/mol error. By obtaining leads from the trained ANN within seconds rather than days from a DFT-driven GA, this strategy demonstrates the power of ML for accelerating inorganic material discovery.

Multispecies reactive tracer test in an aquifer with spatially variable chemical conditions

USGS Publications Warehouse

Davis, J.A.; Kent, D.B.; Coston, J.A.; Hess, K.M.; Joye, J.L.

2000-01-01

A field investigation of multispecies reactive transport was conducted in a well‐characterized, sand and gravel aquifer on Cape Cod, Massachusetts. The aquifer is characterized by regions of differing chemical conditions caused by the disposal of secondary sewage effluent. Ten thousand liters of groundwater with added tracers (Br, Cr(VI), and EDTA complexed with Pb, Zn, Cu, and Ni) were injected into the aquifer and distributions of the tracers were monitored for 15 months. Most of the tracers were transported more than 200 m; transport was quantified using spatial moments computed from the results of a series of synoptic samplings. Cr(VI) transport was retarded relative to Br; the retardation factor varied from 1.1 to 2.4 and was dependent on chemical conditions. At 314 days after the injection, dissolved Cr(VI) mass in the tracer cloud had decreased 85%, with the likely cause being reduction to Cr(III) in a suboxic region of the aquifer. Transport of the metal‐EDTA complexes was affected by aqueous complexation, adsorption, and dissolution‐precipitation reactions of Fe oxyhydroxide minerals in the aquifer sediments. Dissolved Pb‐EDTA complexes disappeared from the tracer cloud within 85 days, probably due to metal exchange reactions with Fe and adsorbed Zn (present prior to the injection from contamination by the sewage effluent). About 30% of the Cu‐EDTA complexes remained within the tracer cloud 314 days after injection, even though the thermodynamic stability of the Pb‐EDTA complex is greater than Cu‐EDTA. It is hypothesized that stronger adsorption of Pb2+ to the aquifer sediments causes the Pb‐EDTA complex to disassociate to a greater degree than the Cu‐EDTA complex. The mass of dissolved Zn‐EDTA increased during the first 175 days of the tracer test to 140% of the mass injected, with the increase due to desorption of sewage‐derived Zn. Dissolved Ni‐EDTA mass remained nearly constant throughout the tracer test, apparently only participating in reversible adsorption reactions. The results of the field experiment provide a chemically complex data set that can be used in the testing of reactive transport models of flow coupled with chemical reactions.

The ecotoxicity of zinc and zinc-containing substances in soil with consideration of metal-moiety approaches and organometal complexes.

PubMed

Ritchie, Ellyn; Boyd, Patrick; Lawson-Halasz, Annamaria; Hawari, Jalal; Saucier, Stacey; Scroggins, Richard; Princz, Juliska

2017-12-01

Within Canada, screening-level assessments for chemical substances are required to determine whether the substances pose a risk to human health and/or the environment, and as appropriate, risk management strategies. In response to the volume of metal and metal-containing substances, process efficiencies were introduced using a metal-moiety approach, whereby substances that contain a common metal moiety are assessed simultaneously as a group, with the moiety of concern consisting of the metal ion. However, for certain subgroups, such as organometals or organic metal salts, the organic moiety or parent substance may be of concern, rather than simply the metal ion. To further investigate the need for such additional consideration, certain substances were evaluated: zinc (Zn)-containing inorganic (Zn chloride [ZnCl2] and Zn oxide) and organic (organometal: Zn diethyldithiocarbamate [Zn(DDC) 2 ] and organic metal salts (Zn stearate [ZnSt] and 4-chloro-2-nitrobenzenediazonium tetrachlorozincate [BCNZ]). The toxicity of the substances were assessed using plant (Trifolium pratense and Elymus lanceolatus) and soil invertebrate (Folsomia candida and Eisenia andrei) tests in a sandy soil. Effect measures were determined based on total metal and total parent analyses (for organic substances). In general, the inorganic Zn substances were less toxic than the organometals and organic metal salts, with 50% effective concentrations ranging from 11 to >5194 mg Zn kg -1 dry soil. The data demonstrate the necessity for alternate approaches in the assessment of organo-metal complexes, with the organic moieties or parent substances warranting consideration rather than the metal ion alone. In this instance, the organometals and organic metal salts were significantly more toxic than other test substances despite their low total Zn content. Environ Toxicol Chem 2017;36:3324-3332. © 2017 Crown in the Right of Canada. Published by Wiley Periodicals Inc. on behalf of SETAC. © 2017 Crown in the Right of Canada. Published by Wiley Periodicals Inc. on behalf of SETAC.

Protein Stains to Detect Antigen on Membranes.

PubMed

Dsouza, Anil; Scofield, R Hal

2015-01-01

Western blotting (protein blotting/electroblotting) is the gold standard in the analysis of complex protein mixtures. Electroblotting drives protein molecules from a polyacrylamide (or less commonly, of an agarose) gel to the surface of a binding membrane, thereby facilitating an increased availability of the sites with affinity for both general and specific protein reagents. The analysis of these complex protein mixtures is achieved by the detection of specific protein bands on a membrane, which in turn is made possible by the visualization of protein bands either by chemical staining or by reaction with an antibody of a conjugated ligand. Chemical methods employ staining with organic dyes, metal chelates, autoradiography, fluorescent dyes, complexing with silver, or prelabeling with fluorophores. All of these methods have differing sensitivities and quantitative determinations vary significantly. This review will describe the various protein staining methods applied to membranes after western blotting. "Detection" precedes and is a prerequisite to obtaining qualitative and quantitative data on the proteins in a sample, as much as to comparing the protein composition of different samples. "Detection" is often synonymous to staining, i.e., the reversible or irreversible binding by the proteins of a colored organic or inorganic chemical.

Rapid onsite detection of bacterial spores of biothreat importance by paper-based colorimetric method using erbium-pyrocatechol violet complex.

PubMed

Shivakiran, M S; Venkataramana, M; Lakshmana Rao, P V

2016-01-01

Dipicolinic acid (DPA) is an important chemical marker for the detection of bacterial spores. In this study, complexes of lanthanide series elements such as erbium, europium, neodymium, and terbium were prepared with pyrocatechol violet and effectively immobilized the pyrocatechol violet (PV)-metal complex on a filter paper using polyvinyl alcohol. These filter paper strips were employed for the onsite detection of bacterial spores. The test filter papers were evaluated quantitatively with different concentrations of DPA and spores of various bacteria. Among the four lanthanide ions, erbium displayed better sensitivity than the other ions. The limit of detection of this test for DPA was 60 μM and 5 × 10(6) spores. The effect of other non-spore-forming bacteria and interfering chemicals on the test strips was also evaluated. The non-spore-forming bacteria did not have considerable effect on the test strip whereas chemicals such as EDTA had significant effects on the test results. The present test is rapid and robust, capable of providing timely results for better judgement to save resources on unnecessary decontamination procedures during false alarms.

Protein stains to detect antigen on membranes.

PubMed

D'souza, Anil; Scofield, R Hal

2009-01-01

Western blotting (protein blotting/electroblotting) is the gold standard in the analysis of complex protein mixtures. Electroblotting drives protein molecules from a polyacrylamide (or less commonly, of an agarose) gel to the surface of a binding membrane, thereby facilitating an increased availability of the sites with affinity for both general and specific protein reagents. The analysis of these complex protein mixtures is achieved by the detection of specific protein bands on a membrane, which in turn is made possible by the visualization of protein bands either by chemical staining or by reaction with an antibody of a conjugated ligand. Chemical methods employ staining with organic dyes, metal chelates, autoradiography, fluorescent dyes, complexing with silver, or prelabeling with fluorophores. All of these methods have differing sensitivities and quantitative determinations vary significantly. This review will describe the various protein staining methods applied to membranes after electrophoresis. "Detection" precedes and is a prerequisite to obtaining qualitative and quantitative data on the proteins in a sample, as much as to comparing the protein composition of different samples. Detection is often synonymous to staining, i.e., the reversible or irreversible binding by the proteins of a colored organic or inorganic chemical.

Metal transformation as a strategy for bacterial detoxification of heavy metals.

PubMed

Essa, Ashraf M M; Al Abboud, Mohamed A; Khatib, Sayeed I

2018-01-01

Microorganisms can modify the chemical and physical characters of metals leading to an alteration in their speciation, mobility, and toxicity. Aqueous heavy metals solutions (Hg, Cd, Pb, Ag, Cu, and Zn) were treated with the volatile metabolic products (VMPs) of Escherichia coli Z3 for 24 h using aerobic bioreactor. The effect of the metals treated with VMPs in comparison to the untreated metals on the growth of E. coli S1 and Staphylococcus aureus S2 (local isolates) was examined. Moreover, the toxic properties of the treated and untreated metals were monitored using minimum inhibitory concentration assay. A marked reduction of the treated metals toxicity was recorded in comparison to the untreated metals. Scanning electron microscopy and energy dispersive X-ray analysis revealed the formation of metal particles in the treated metal solutions. In addition to heavy metals at variable ratios, these particles consisted of carbon, oxygen, sulfur, nitrogen elements. The inhibition of metal toxicity was attributed to the existence of ammonia, hydrogen sulfide, and carbon dioxide in the VMPs of E. coli Z3 culture that might responsible for the transformation of soluble metal ions into metal complexes. This study clarified the capability of E. coli Z3 for indirect detoxification of heavy metals via the immobilization of metal ions into biologically unavailable species. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Online-LASIL: Laser Ablation of Solid Samples in Liquid with online-coupled ICP-OES detection for direct determination of the stoichiometry of complex metal oxide thin layers.

PubMed

Bonta, Maximilian; Frank, Johannes; Taibl, Stefanie; Fleig, Jürgen; Limbeck, Andreas

2018-02-13

Advanced materials such as complex metal oxides are used in a wide range of applications and have further promising perspectives in the form of thin films. The exact chemical composition essentially influences the electronic properties of these materials which makes correct assessment of their composition necessary. However, due to high chemical resistance and in the case of thin films low absolute analyte amounts, this procedure is in most cases not straightforward and extremely time-demanding. Commonly applied techniques either lack in ease of use (i.e., solution-based analysis with preceding sample dissolution), or adequately accurate quantification (i.e., solid sampling techniques). An analysis approach which combines the beneficial aspects of solution-based analysis as well as direct solid sampling is Laser Ablation of a Sample in Liquid (LASIL). In this work, it is shown that the analysis of major as well as minor sample constituents is possible using a novel online-LASIL setup, allowing sample analysis without manual sample handling after placing it in an ablation chamber. Strontium titanate (STO) thin layers with different compositions were analyzed in the course of this study. Precision of the newly developed online-LASIL method is comparable to conventional wet chemical approaches. With only about 15-20 min required for the analysis per sample, time demand is significantly reduced compared to often necessary fusion procedures lasting multiple hours. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis of branched metal nanostructures with controlled architecture and composition

NASA Astrophysics Data System (ADS)

Ortiz, Nancy

On account of their small size, metal nanoparticles are proven to be outstanding catalysts for numerous chemical transformations and represent promising platforms for applications in the fields of electronics, chemical sensing, medicine, and beyond. Many properties of metal nanoparticles are size-dependent and can be further manipulated through their shape and architecture (e.g., spherical vs. branched). Achieving morphology control of nanoparticles through solution-based techniques has proven challenging due to limited knowledge of morphology development in nanosyntheses. To overcome these complications, a systematic examination of the local ligand environment of metal precursors on nanostructure formation was undertaken to evaluate its contribution to nanoparticle nucleation rate and subsequent growth processes. Specifically, this thesis will provide evidence from ex situ studies---Transmission Electron Microscopy (TEM) and UV-visible spectroscopy (UV-Vis)---that support the hypothesis that strongly coordinated ligands delay burst-like nucleation to generate spherical metal nanoparticles and ligands with intermediate binding affinity regulate the gradual reduction of metal precursors to promote aggregated assembly of nanodendrites. These ex situ studies were coupled with a new in situ perspective, providing detailed understanding of metal precursor transformation, its direct relation to nanoparticle morphology development, and the ligand influence towards the formation of structurally complex metal nanostructures, using in situ synchrotron X-ray Diffraction (XRD) and Ultra Small-Angle X-ray Scattering (USAXS). The principles extracted from the study of monometallic nanostructure formation were also found to be generally applicable to the synthesis of bimetallic nanostructures, e.g., Pd-Pt architectures, with either core-shell or alloyed structures that were readily achieved by ligand selection. These outcomes provide a direct connection between fundamental principles of coordination chemistry and nanoparticle formation, with a stronger foundation for the predictive synthesis of future nanomaterials with controllable structural features.

Synthesis, characterization, molecular modeling and biological activity of metal complexes derived from (E)-N'-(furan-2-ylmethylene)morpholine-4-carbothiohydrazide

NASA Astrophysics Data System (ADS)

El-Samanody, El-Sayed A.; Emam, Sanaa M.; Emara, Esam M.

2017-10-01

A new series of some biologically active Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes was synthesized from the novel thiosemicarbazone ligand; (E)-N'-(furan-2-ylmethylene)morpholine-4-carbothiohydrazide (HL). Elemental, spectral, thermal analyses, magnetic susceptibility and molar conductivity measurements were used to elucidate the structure of separated compounds. The data prove that the ligand reacts with all metal ions in a neutral thione form. The electrolytic tetra-coordinate Cu(II); Zn(II) complexes (5, 6; 10) bind through the thione sulfur, furfural oxygen and azomethine nitrogen atoms of the ligand (NSO type) to construct fused five membered rings. However, the rest non-electrolyte octahedral complexes chelate via the furfural oxygen and azomethine nitrogen atoms of the ligand (NO type). Molecular modeling was conducted for the ligand and two representative complexes (1, 5) in order to substantiate their chemical structures. Thermal analyses are compatible with molecular modeling studies to support the proposed thermal decomposition pathways of metal complexes which start with the rupture of the long and weak N-NH bond. The thermal stability of metal complexes varies according to the number of solvents of crystallization, ionic radii and steric effect of anions. The ESR spectra of Cu(II) complexes are compatible with a primarily (dx2-y2)1 ground state with axial symmetry. The ligand and its Co(II); Cu(II); Cd(II) complexes (1; 5, 8; 11) along with their mixtures with metaldehyde were screened in vitro for their molluscicidal activity against Eobania vermiculata. Combination with metaldehyde enhances the toxicity effect of the tested compounds through reducing the period required for mortality and increasing the percentage of mortality after 24 h of treatments. The tested compounds gathered with metaldehyde are strongly affecting on the activity of ACP and ALP enzymes and TP content which are very important factors in the mucous secretion of Eobania vermiculata. These effects lead to excess mucous secretion, causing dryness and death for the snails.

The radiometal makes a difference. Synthesis and preliminary characterisation of DOTA-minigastrin analogue complexes with Ga, Lu and Y.

PubMed

Maurin, Michał; Garnuszek, Piotr; Baran, Piotr; Pawlak, Dariusz; Mikołajczak, Renata

2015-01-01

The minigastrin analogue - CP04: DOTA-(DGlu)6-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH2 has been developed for CCK2R targeting. This analogue can be radiolabelled with 111In or 68Ga for imaging, or with 90Y and 177Lu for therapy. However, affinity of the chelator-peptide conjugates to the cell membrane receptors may vary depending on the metal incorporated into the complex. So far, there are no such studies for the ligands of gastrin/cholecystokinin receptor CCK2R. It is supposed that the reason for the differentiation of receptor affinity to the respective receptors is in the changes of structure of chelating system and their influence on the bioactive conformations of the metal conjugated peptides. Herein, we report on the radiolabeling of CP04 with 90Y, 177Lu and 68Ga and synthesis of cold CP04 complexes with respective stable metals for further structural and physico-chemical and biological studies. From 200 to 600 MBq of 90Y, 177Lu or 68Ga were used for radiolabelling of 20 μg of CP04 dissolved in ascorbic acid solution (50 mg/mL, pH 4.5). Non-radioactive complexes with Lu and Ga were synthesized in milligram amounts starting from 0.5 mg up to 5 mg of CP04 dissolved in ascorbic acid solution (50 mg/mL, pH 4.5) when using 2-molar excess of the metal ions. Complex formation needed 5 min in microwave oven or 12 min in thermo-block at 95°C. RP-HPLC isocratic method (Kinetex 150/4.6 mm; 25% AcN/0.1% TFA, 1 mL/min) with UV/Vis and radiometric detection was developed for investigation of the radiolabelled and "cold" complexes. For LC-MS investigations, HPLC method was modified replacing TFA by formic acid. Yields of CP04 radiolabelling were greater than 90% for all three radionuclides. The HPLC method enabled identification of these radio-complexes based on comparison to their non-radioactive equivalents. In all cases, chromatograms revealed peaks that could be attributed to the metal-CP04 complexes and to impurities (including methionine oxidation). LC-MS analysis of Ga and Lu complexes revealed conformity of the observed molecular ions to the predicted formulas (m/z 2116 and 2220 Da for Ga and Lu, respectively). Different chromatographic behaviour observed for Ga-CP04 complex comparing to Lu- and Y- labelled peptide (relative retention to CP04: 1.08, 0.86 and 0.85, respectively) suggest different coordination of the metal ions. Therefore, further studies are planned using the non-radioactive complexes in order to assess their structural conformations.

Synthesis, spectroscopic characterization and biological activity of cis-[Ru(hesperidin)(1,10‧-phenanthroline)2](PF6) complex

NASA Astrophysics Data System (ADS)

Oliveira, Regina M. M.; de Souza Daniel, Juliana F.; Carlos, Rose M.

2013-01-01

The new complex cis-[Ru(phen)2(hesperidin)](PF6), complex 1, was synthesized and characterized by analytical (ESI-MS+, EA (C, H, N)) and spectroscopic (FTIR, UV-vis, 1H and 13C NMR) techniques and cyclic voltammetry. Complex 1 is chemically stable in the solid state and in organic solvents such as ethanol, methanol, acetone, and acetonitrile, as shown by spectrophotometric analysis. 1 is also photochemically and chemically stable (pH effects) and more hydrosoluble (518.83 ± 0.91 g mL-1) than free hesperidin (5.92 g mL-1). In accordance with this, the lipophilicity value in aqueous-octanol solution for 1 was -1.28, indicating its high hydrophilic characteristic. Although complex 1 showed to be essentially noncytotoxic, IC50 > 1.0 mmol L-1 as evaluated in the human cervical cancer cells line HeLa, it exhibited a moderate capacity of inhibiting the catalytic activity of the acetylcholinaesterase enzyme, IC50 = 63.6 mol L-1. The Lineweaver-Burk plot and the respective secondary replot indicated that the AChE inhibition was noncompetitive and reversible. These findings shows that complexation of the hesperidin improves physicochemical characteristics and increases the perspectives for development and medical applications of new bioactive-metal complexes.

Catalyst and processing effects on metal-assisted chemical etching for the production of highly porous GaN

NASA Astrophysics Data System (ADS)

Geng, Xuewen; Duan, Barrett K.; Grismer, Dane A.; Zhao, Liancheng; Bohn, Paul W.

2013-06-01

Metal-assisted chemical etching is a facile method to produce micro-/nanostructures in the near-surface region of gallium nitride (GaN) and other semiconductors. Detailed studies of the production of porous GaN (PGaN) using different metal catalysts and GaN doping conditions have been performed in order to understand the mechanism by which metal-assisted chemical etching is accomplished in GaN. Patterned catalysts show increasing metal-assisted chemical etching activity to n-GaN in the order Ag < Au < Ir < Pt. In addition, the catalytic behavior of continuous films is compared to discontinuous island films. Continuous metal films strongly shield the surface, hindering metal-assisted chemical etching, an effect which can be overcome by using discontinuous films or increasing the irradiance of the light source. With increasing etch time or irradiance, PGaN morphologies change from uniform porous structures to ridge and valley structures. The doping type plays an important role, with metal-assisted chemical etching activity increasing in the order p-GaN < intrinsic GaN < n-GaN. Both the catalyst identity and the doping type effects are explained by the work functions and the related band offsets that affect the metal-assisted chemical etching process through a combination of different barriers to hole injection and the formation of hole accumulation/depletion layers at the metal-semiconductor interface.

Syntheses and Functionalizations of Porphyrin Macrocycles

PubMed Central

Vicente, Maria da G.H.; Smith, Kevin M.

2014-01-01

Porphyrin macrocycles have been the subject of intense study in the last century because they are widely distributed in nature, usually as metal complexes of either iron or magnesium. As such, they serve as the prosthetic groups in a wide variety of primary metabolites, such as hemoglobins, myoglobins, cytochromes, catalases, peroxidases, chlorophylls, and bacteriochlorophylls; these compounds have multiple applications in materials science, biology and medicine. This article describes current methodology for preparation of simple, symmetrical model porphyrins, as well as more complex protocols for preparation of unsymmetrically substituted porphyrin macrocycles similar to those found in nature. The basic chemical reactivity of porphyrins and metalloporphyrin is also described, including electrophilic and nucleophilic reactions, oxidations, reductions, and metal-mediated cross-coupling reactions. Using the synthetic approaches and reactivity profiles presented, eventually almost any substituted porphyrin system can be prepared for applications in a variety of areas, including in catalysis, electron transport, model biological systems and therapeutics. PMID:25484638

Time-dependent local and average structural evolution of δ-phase 239Pu-Ga alloys

DOE PAGES

Smith, Alice I.; Page, Katharine L.; Siewenie, Joan E.; ...

2016-08-05

Here, plutonium metal is a very unusual element, exhibiting six allotropes at ambient pressure, between room temperature and its melting point, a complicated phase diagram, and a complex electronic structure. Many phases of plutonium metal are unstable with changes in temperature, pressure, chemical additions, or time. This strongly affects structure and properties, and becomes of high importance, particularly when considering effects on structural integrity over long periods of time [1]. This paper presents a time-dependent neutron total scattering study of the local and average structure of naturally aging δ-phase 239Pu-Ga alloys, together with preliminary results on neutron tomography characterization.

Binding characteristics of copper and cadmium by cyanobacterium Spirulina platensis.

PubMed

Fang, Linchuan; Zhou, Chen; Cai, Peng; Chen, Wenli; Rong, Xingmin; Dai, Ke; Liang, Wei; Gu, Ji-Dong; Huang, Qiaoyun

2011-06-15

Cyanobacteria are promising biosorbent for heavy metals in bioremediation. Although sequestration of metals by cyanobacteria is known, the actual mechanisms and ligands involved are not very well understood. The binding characteristics of Cu(II) and Cd(II) by the cyanobacterium Spirulina platensis were investigated using a combination of chemical modifications, batch adsorption experiments, Fourier transform infrared (FTIR) spectroscopy and X-ray absorption fine structure (XAFS) spectroscopy. A significant increase in Cu(II) and Cd(II) binding was observed in the range of pH 3.5-5.0. Dramatical decrease in adsorption of Cu(II) and Cd(II) was observed after methanol esterification of the nonliving cells demonstrating that carboxyl functional groups play an important role in the binding of metals by S. platensis. The desorption rate of Cu(II) and Cd(II) from S. platensis surface was 72.7-80.7% and 53.7-58.0% by EDTA and NH(4)NO(3), respectively, indicating that ion exchange and complexation are the dominating mechanisms for Cu(II) and Cd(II) adsorption. XAFS analysis provided further evidence on the inner-sphere complexation of Cu by carboxyl ligands and showed that Cu is complexed by two 5-membered chelate rings on S. platensis surface. Copyright © 2011 Elsevier B.V. All rights reserved.

Light-Induced Conversion of Chemical Permeability to Enhance Electron and Molecular Transfer in Nanoscale Assemblies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balgley, Renata; de Ruiter, Graham; Evmenenko, Guennadi

In this paper, we demonstrate how photochemically enhancing the permeability of metal–organic assemblies results in a significant enhancement of the electrochemical activity of metal complexes located within the assembly. The molecular assemblies consist of different layers of redox-active metal complexes ([M(mbpy-py)3][PF6]2; M = Ru or Os) that are separated by redox-inactive spacers consisting of 1,4-bis[2-(4-pyridyl)ethenyl]benzene (BPEB) and PdCl2 of variable thicknesses (0–13.4 nm). UV-irradiation (λ = 254 nm) of our assemblies induces a photochemical reaction in the redox-inactive spacer increasing the permeability of the assembly. The observed increase was evident by trapping organic (nBu4NBF4) and inorganic (NiCl2) salts inside themore » assemblies, and by evaluating the electrochemical response of quinones absorbed inside the molecular assemblies before and after UV irradiation. The increase in permeability is reflected by higher currents and a change in the directionality of electron transfer, i.e., from mono- to bidirectional, between the redox-active metal complexes and the electrode surface. The supramolecular structure of the assemblies dominates the overall electron transfer properties and overrules possible electron transfer mediated by the extensive π-conjugation of its individual organic components.« less

Large capacitance enhancement induced by metal-doping in graphene-based supercapacitors: a first-principles-based assessment.

PubMed

Paek, Eunsu; Pak, Alexander J; Hwang, Gyeong S

2014-08-13

Chemically doped graphene-based materials have recently been explored as a means to improve the performance of supercapacitors. In this work, we investigate the effects of 3d transition metals bound to vacancy sites in graphene with [BMIM][PF6] ionic liquid on the interfacial capacitance; these results are compared to the pristine graphene case with particular attention to the relative contributions of the quantum and electric double layer capacitances. Our study highlights that the presence of metal-vacancy complexes significantly increases the availability of electronic states near the charge neutrality point, thereby enhancing the quantum capacitance drastically. In addition, the use of metal-doped graphene electrodes is found to only marginally influence the microstructure and capacitance of the electric double layer. Our findings indicate that metal-doping of graphene-like electrodes can be a promising route toward increasing the interfacial capacitance of electrochemical double layer capacitors, primarily by enhancing the quantum capacitance.

UV-light assisted patterned metallization of textile fabrics

NASA Astrophysics Data System (ADS)

Bahners, Thomas; Gebert, Beate; Prager, Andrea; Hartmann, Nils; Hagemann, Ulrich; Gutmann, Jochen S.

2018-04-01

A UV-assisted process allows full-faced or local deposition of silver domains on textiles made of natural as well as synthetic fibers, which act as nuclei for subsequent galvanic metallization. SEM and XPS analyses indicate that the process generates particulate depositions - particles, aggregates - of elementary silver. Masking the UV irradiation confines silver deposition strictly to the exposed areas thus allowing patterning. Adhesion of the deposited silver is high on the studied natural fiber cotton and polyamide fibers. Adhesion on smooth and chemically inert synthethic fibers such as, e.g., poly(ethylene terephthalate) or para- and meta-aramids could be enhanced by finishing with poly(vinylamine) thus providing complex-forming amino groups. Although the process does not deposit a closed, electrically conducting layer, all studied samples could be metallized by galvanization. The resulting metal coatings exhibit high conductivity and wash stability. Following a patterned silver deposition, the subsequent galvanic metallization produced conductive patterns of identical geometry thus opening an avenue towards printed circuits on textile fabrics.

Metal organic frameworks for the catalytic detoxification of chemical warfare nerve agents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hupp, Joseph T.; Farha, Omar K.; Katz, Michael J.

A method of using a metal organic framework (MOF) comprising a metal ion and an at least bidendate organic ligand to catalytically detoxify chemical warfare nerve agents including exposing the metal-organic-framework (MOF) to the chemical warfare nerve agent and catalytically decomposing the nerve agent with the MOF.

Chemical, biochemical, and environmental fiber sensors III; Proceedings of the Meeting, Boston, MA, Sept. 4, 5, 1991

NASA Astrophysics Data System (ADS)

Lieberman, Robert A.

Various papers on chemical, biochemical, and environmental fiber sensors are presented. Individual topics addressed include: fiber optic pressure sensor for combustion monitoring and control, viologen-based fiber optic oxygen sensors, renewable-reagent fiber optic sensor for ocean pCO2, transition metal complexes as indicators for a fiber optic oxygen sensor, fiber optic pH measurements using azo indicators, simple reversible fiber optic chemical sensors using solvatochromic dyes, totally integrated optical measuring sensors, integrated optic biosensor for environmental monitoring, radiation dosimetry using planar waveguide sensors, optical and piezoelectric analysis of polymer films for chemical sensor characterization, source polarization effects in an optical fiber fluorosensor, lens-type refractometer for on-line chemical analysis, fiber optic hydrocarbon sensor system, chemical sensors for environmental monitoring, optical fibers for liquid-crystal sensing and logic devices, suitability of single-mode fluoride fibers for evanescent-wave sensing, integrated modules for fiber optic sensors, optoelectronic sensors based on narrowband A3B5 alloys, fiber Bragg grating chemical sensor.

NSR&D FY15 Final Report. Modeling Mechanical, Thermal, and Chemical Effects of Impact

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, Christopher Curtis; Ma, Xia; Zhang, Duan Zhong

2015-11-02

The main goal of this project is to develop a computer model that explains and predicts coupled mechanical, thermal and chemical responses of HE under impact and friction insults. The modeling effort is based on the LANL-developed CartaBlanca code, which is implemented with the dual domain material point (DDMP) method to calculate complex and coupled thermal, chemical and mechanical effects among fluids, solids and the transitions between the states. In FY 15, we have implemented the TEPLA material model for metal and performed preliminary can penetration simulation and begun to link with experiment. Currently, we are working on implementing amore » shock to detonation transition (SDT) model (SURF) and JWL equation of state.« less

Chemical properties of dissolved organic matter derived from sugarcane rind and the impacts on copper adsorption onto red soil.

PubMed

Hu, Sihai; Wu, Yaoguo; Yi, Na; Zhang, Shuai; Zhang, Yuanjing; Xin, Xu

2017-09-01

Dissolved organic matter (DOM), as the most active organic carbon in the soil, has a coherent affinity with heavy metals from inherent and exogenous sources. Although the important roles of DOM in the adsorption of heavy metals in soil have previously been demonstrated, the heterogeneity and variability of the chemical constitution of DOM impede the investigation of its effects on heavy metal adsorption onto soil under natural conditions. Fresh DOM (FDOM) and degraded DOM (DDOM) from sugarcane rind were prepared, and their chemical properties were measured by Fourier-transform infrared spectrometry (FTIR), excitation-emission matrix (EEM) fluorescence spectroscopes, nuclear magnetic resonance (NMR), and molecular weight distribution (MWD). They were also used in batch experiments to evaluate their effects on the adsorption of Cu(II) onto farmland red soil. Based on our results, the chemical structure and composition of DDOM greatly varied; compared with FDOM, the C/O ratio (from 24.0 to 9.6%) and fluorescence index (FI) (from 1.4 to 1.0) decreased, and high molecular weight (>10 kDa) compounds increased from 23.18 to 70.51%, while low molecular weight (<3 kDa) compounds decreased from 56.13 to 12.13%; aromaticity and humification degree were markedly enhanced. The discrepancy of FDOM and DDOM in terms of chemical properties greatly influenced Cu(II) adsorption onto red soil by affecting DOM-Cu(II) complex capacity. The FDOM inhibited the adsorption of Cu(II), while DDOM promoted adsorption, which was significantly influenced by soil pH. Maximum adsorption capacity (Q m ) was 0.92 and 5.76 mg g -1 in the presence of FDOM and DDOM, respectively. The adsorption process with DDOM could be better described by the Langmuir model, while that with FDOM was better described by the Freundlich model. The impacts caused by the dynamic changes of the chemical properties of DOM under natural conditions should therefore be considered in the risk assessment and remediation of soils contaminated with heavy metals.

Remediation technologies for heavy metal contaminated groundwater.

PubMed

Hashim, M A; Mukhopadhyay, Soumyadeep; Sahu, Jaya Narayan; Sengupta, Bhaskar

2011-10-01

The contamination of groundwater by heavy metal, originating either from natural soil sources or from anthropogenic sources is a matter of utmost concern to the public health. Remediation of contaminated groundwater is of highest priority since billions of people all over the world use it for drinking purpose. In this paper, thirty five approaches for groundwater treatment have been reviewed and classified under three large categories viz chemical, biochemical/biological/biosorption and physico-chemical treatment processes. Comparison tables have been provided at the end of each process for a better understanding of each category. Selection of a suitable technology for contamination remediation at a particular site is one of the most challenging job due to extremely complex soil chemistry and aquifer characteristics and no thumb-rule can be suggested regarding this issue. In the past decade, iron based technologies, microbial remediation, biological sulphate reduction and various adsorbents played versatile and efficient remediation roles. Keeping the sustainability issues and environmental ethics in mind, the technologies encompassing natural chemistry, bioremediation and biosorption are recommended to be adopted in appropriate cases. In many places, two or more techniques can work synergistically for better results. Processes such as chelate extraction and chemical soil washings are advisable only for recovery of valuable metals in highly contaminated industrial sites depending on economical feasibility. Copyright © 2011 Elsevier Ltd. All rights reserved.

[Role of environment in complex diseases: air pollution and food contaminants].

PubMed

Scheen, A J; Giet, D

2012-01-01

Our polluted environment exposes human beings, along their life, to various toxic compounds that could trigger and aggravate different complex diseases. Such a phenomenon is well recognized for cardiovascular diseases, respiratory diseases and cancers, but other chronic inflammatory disorders may also been implicated. The most common factors, but also the most toxic, and thereby the most extensively investigated, are air pollutants (both indoor and outdoor pollution) and various contaminants present in drinking water and food (organic compounds, chemical products, heavy metals, ...). The complex interrelationships between food and pollutants, on the one hand, and between gene and environmental pollutants, including the influence of epigenetics, on the other hand, deserve further careful studies.

Relationship between chemical composition and oxidative potential of secondary organic aerosol from polycyclic aromatic hydrocarbons

NASA Astrophysics Data System (ADS)

Wang, Shunyao; Ye, Jianhuai; Soong, Ronald; Wu, Bing; Yu, Legeng; Simpson, André J.; Chan, Arthur W. H.

2018-03-01

Owing to the complex nature and dynamic behaviors of secondary organic aerosol (SOA), its ability to cause oxidative stress (known as oxidative potential, or OP) and adverse health outcomes remains poorly understood. In this work, we probed the linkages between the chemical composition of SOA and its OP, and investigated impacts from various SOA evolution pathways, including atmospheric oligomerization, heterogeneous oxidation, and mixing with metal. SOA formed from photooxidation of the two most common polycyclic aromatic hydrocarbons (naphthalene and phenanthrene) were studied as model systems. OP was evaluated using the dithiothreitol (DTT) assay. The oligomer-rich fraction separated by liquid chromatography dominates DTT activity in both SOA systems (52 ± 10 % for naphthalene SOA (NSOA), and 56 ± 5 % for phenanthrene SOA (PSOA)). Heterogeneous ozonolysis of NSOA was found to enhance its OP, which is consistent with the trend observed in selected individual oxidation products. DTT activities from redox-active organic compounds and metals were found to be not additive. When mixing with highly redox-active metal (Cu), OP of the mixture decreased significantly for 1,2-naphthoquinone (42 ± 7 %), 2,3-dihydroxynaphthalene (35 ± 1 %), NSOA (50 ± 6 %), and PSOA (43 ± 4 %). Evidence from proton nuclear magnetic resonance (1H NMR) spectroscopy illustrates that such OP reduction upon mixing can be ascribed to metal-organic binding interactions. Our results highlight the role of aerosol chemical composition under atmospheric aging processes in determining the OP of SOA, which is needed for more accurate and explicit prediction of the toxicological impacts from particulate matter.

Geological and Chemical Factors that Impacted the Biological Utilization of Cobalt in the Archean Eon

NASA Astrophysics Data System (ADS)

Moore, Eli K.; Hao, Jihua; Prabhu, Anirudh; Zhong, Hao; Jelen, Ben I.; Meyer, Mike; Hazen, Robert M.; Falkowski, Paul G.

2018-03-01

The geosphere and biosphere coevolved and influenced Earth's biological and mineralogical diversity. Changing redox conditions influenced the availability of different transition metals, which are essential components in the active sites of oxidoreductases, proteins that catalyze electron transfer reactions across the tree of life. Despite its relatively low abundance in the environment, cobalt (Co) is a unique metal in biology due to its importance to a wide range of organisms as the metal center of vitamin B12 (aka cobalamin, Cbl). Cbl is vital to multiple methyltransferase enzymes involved in energetically favorable metabolic pathways. It is unclear how Co availability is linked to mineral evolution and weathering processes. Here we examine important biological functions of Co, as well as chemical and geological factors that may have influenced the utilization of Co early in the evolution of life. Only 66 natural minerals are known to contain Co as an essential element. However, Co is incorporated as a minor element in abundant rock-forming minerals, potentially representing a reliable source of Co as a trace element in marine systems due to weathering processes. We developed a mineral weathering model that indicates that dissolved Co was potentially more bioavailable in the Archean ocean under low S conditions than it is today. Mineral weathering, redox chemistry, Co complexation with nitrogen-containing organics, and hydrothermal environments were crucial in the incorporation of Co in primitive metabolic pathways. These chemical and geological characteristics of Co can inform the biological utilization of other trace metals in early forms of life.

DFT/TD-semiempirical study on the structural and electronic properties and absorption spectra of supramolecular fullerene-porphyrine-metalloporphyrine triads based dye-sensitized solar cells.

PubMed

Rezvani, M; Darvish Ganji, M; Jameh-Bozorghi, S; Niazi, A

2018-04-05

In the present work density functional theory (DFT) and time-dependent semiempirical ZNIDO/S (TD-ZNIDO/S) methods have been used to investigate the ground state geometries, electronic structures and excited state properties of triad systems. The influences of the type of metal in the porphyrin ring, change in bridge position and porphyrine-ZnP duplicate on the energies of frontier molecular orbital and UV-Vis spectra has been studied. Geometry optimization, the energy levels and electron density of the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO), chemical hardness (η), electrophilicity index (ω), electron accepting power (ω + ) were calculated using ZINDO/S method to predict which molecule is the most efficient with a great capability to be used as a triad molecule in solar industry. Moreover the light harvesting efficiency (LHE) was calculated by means of the oscillator strengths which are obtained by TD-ZINDO/S calculation. Theoretical studies of the electronic spectra by ZINDO/S method were helpful in interpreting the observed electronic transitions. This aspect was systematically explored in a series of C 60 -Porphyrine-Metalloporphyrine (C 60 -P-Mp) triad system with M being Fe, Co, Ni, Ti, and Zn. Generally, transition metal coordination compounds are used as effective sensitizers, due to their intense charge-transfer absorption over the whole visible range and highly efficient metal-to-ligand charge transfer. We aim to optimize the performance of the title solar cells by altering the frontier orbital energy gaps. The results reveal that cell efficiency can be enhanced by metal functionalization of the free base porphyrin. Ti-porphyrin was found to be the most efficient dye sensitizer for dye sensitized solar cells (DSSCs) based on C 60 -P-Mptriad system due to C 60 -Por-TiP complex has lower chemical hardness, gap energy and chemical potential as well as higher electron accepting power among other complexes. In addition, the performance of solar cells favors better with doubly and increasing the π conjugated of the bridge. Copyright © 2018 Elsevier B.V. All rights reserved.

DFT/TD-semiempirical study on the structural and electronic properties and absorption spectra of supramolecular fullerene-porphyrine-metalloporphyrine triads based dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Rezvani, M.; Darvish Ganji, M.; Jameh-Bozorghi, S.; Niazi, A.

2018-04-01

In the present work density functional theory (DFT) and time-dependent semiempirical ZNIDO/S (TD-ZNIDO/S) methods have been used to investigate the ground state geometries, electronic structures and excited state properties of triad systems. The influences of the type of metal in the porphyrin ring, change in bridge position and porphyrine-ZnP duplicate on the energies of frontier molecular orbital and UV-Vis spectra has been studied. Geometry optimization, the energy levels and electron density of the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO), chemical hardness (η), electrophilicity index (ω), electron accepting power (ω+) were calculated using ZINDO/S method to predict which molecule is the most efficient with a great capability to be used as a triad molecule in solar industry. Moreover the light harvesting efficiency (LHE) was calculated by means of the oscillator strengths which are obtained by TD-ZINDO/S calculation. Theoretical studies of the electronic spectra by ZINDO/S method were helpful in interpreting the observed electronic transitions. This aspect was systematically explored in a series of C60-Porphyrine-Metalloporphyrine (C60-P-Mp) triad system with M being Fe, Co, Ni, Ti, and Zn. Generally, transition metal coordination compounds are used as effective sensitizers, due to their intense charge-transfer absorption over the whole visible range and highly efficient metal-to-ligand charge transfer. We aim to optimize the performance of the title solar cells by altering the frontier orbital energy gaps. The results reveal that cell efficiency can be enhanced by metal functionalization of the free base porphyrin. Ti-porphyrin was found to be the most efficient dye sensitizer for dye sensitized solar cells (DSSCs) based on C60-P-Mptriad system due to C60-Por-TiP complex has lower chemical hardness, gap energy and chemical potential as well as higher electron accepting power among other complexes. In addition, the performance of solar cells favors better with doubly and increasing the π conjugated of the bridge.

Late metal carbene complexes generated by multiple C-H activations: examining the continuum of M=C bond reactivity.

PubMed

Whited, Matthew T; Grubbs, Robert H

2009-10-20

Unactivated C(sp(3))-H bonds are ubiquitous in organic chemicals and hydrocarbon feedstocks. However, these resources remain largely untapped, and the development of efficient homogeneous methods for hydrocarbon functionalization by C-H activation is an attractive and unresolved challenge for synthetic chemists. Transition-metal catalysis offers an attractive possible means for achieving selective, catalytic C-H functionalization given the thermodynamically favorable nature of many desirable partial oxidation schemes and the propensity of transition-metal complexes to cleave C-H bonds. Selective C-H activation, typically by a single cleavage event to produce M-C(sp(3)) products, is possible through myriad reported transition-metal species. In contrast, several recent reports have shown that late transition metals may react with certain substrates to perform multiple C-H activations, generating M=C(sp(2)) complexes for further elaboration. In light of the rich reactivity of metal-bound carbenes, such a route could open a new manifold of reactivity for catalytic C-H functionalization, and we have targeted this strategy in our studies. In this Account, we highlight several early examples of late transition-metal complexes that have been shown to generate metal-bound carbenes by multiple C-H activations and briefly examine factors leading to the selective generation of metal carbenes through this route. Using these reports as a backdrop, we focus on the double C-H activation of ethers and amines at iridium complexes supported by Ozerov's amidophosphine PNP ligand (PNP = [N(2-P(i)Pr(2)-4-Me-C(6)H(3))(2)](-)), allowing isolation of unusual square-planar iridium(I) carbenes. These species exhibit reactivity that is distinct from the archetypal Fischer and Schrock designations. We present experimental and theoretical studies showing that, like the classical square-planar iridium(I) organometallics, these complexes are best described as nucleophilic at iridium. We discuss the classification of this reactivity in the context of a scheme originally delineated by Roper. These "Roper-type" carbenes perform a number of multiple-bond metatheses leading to atom and group transfer from electrophilic heterocumulene (e.g., CO(2), CS(2), PhNCS) and diazo (e.g., N(2)O, AdN(3)) reagents. In one instance, we have extended this methodology to a process for catalytic C-H functionalization by a double C-H activation-group transfer process. Although the scope of these reactions is currently limited, these new pathways may find broader utility as the reactivity of late-metal carbenes continues to be explored. Examination of alternative transition metals and supporting ligand sets will certainly be important. Nonetheless, our findings show that carbene generation by double C-H activation is a viable strategy for C-H functionalization, leading to products not accessible through traditional C(sp(3))-H activation pathways.

Trace metal speciation in natural waters: Computational vs. analytical

USGS Publications Warehouse

Nordstrom, D. Kirk

1996-01-01

Improvements in the field sampling, preservation, and determination of trace metals in natural waters have made many analyses more reliable and less affected by contamination. The speciation of trace metals, however, remains controversial. Chemical model speciation calculations do not necessarily agree with voltammetric, ion exchange, potentiometric, or other analytical speciation techniques. When metal-organic complexes are important, model calculations are not usually helpful and on-site analytical separations are essential. Many analytical speciation techniques have serious interferences and only work well for a limited subset of water types and compositions. A combined approach to the evaluation of speciation could greatly reduce these uncertainties. The approach proposed would be to (1) compare and contrast different analytical techniques with each other and with computed speciation, (2) compare computed trace metal speciation with reliable measurements of solubility, potentiometry, and mean activity coefficients, and (3) compare different model calculations with each other for the same set of water analyses, especially where supplementary data on speciation already exist. A comparison and critique of analytical with chemical model speciation for a range of water samples would delineate the useful range and limitations of these different approaches to speciation. Both model calculations and analytical determinations have useful and different constraints on the range of possible speciation such that they can provide much better insight into speciation when used together. Major discrepancies in the thermodynamic databases of speciation models can be evaluated with the aid of analytical speciation, and when the thermodynamic models are highly consistent and reliable, the sources of error in the analytical speciation can be evaluated. Major thermodynamic discrepancies also can be evaluated by simulating solubility and activity coefficient data and testing various chemical models for their range of applicability. Until a comparative approach such as this is taken, trace metal speciation will remain highly uncertain and controversial.

Characterization of Non-Innocent Metal Complexes Using Solid-State NMR Spectroscopy: o-Dioxolene Vanadium Complexes

PubMed Central

Chatterjee, Pabitra B.; Goncharov-Zapata, Olga; Quinn, Laurence L.; Hou, Guangjin; Hamaed, Hiyam; Schurko, Robert W.; Polenova, Tatyana; Crans, Debbie C.

2012-01-01

51V solid-state NMR (SSNMR) studies of a series of non-innocent vanadium(V) catechol complexes have been conducted to evaluate the possibility that 51V NMR observables, quadrupolar and chemical shift anisotropies, and electronic structures of such compounds can be used to characterize these compounds. The vanadium(V) catechol complexes described in these studies have relatively small quadrupolar coupling constants, which cover a surprisingly small range from 3.4 to 4.2 MHz. On the other hand, isotropic 51V NMR chemical shifts cover a wide range from −200 ppm to 400 ppm in solution and from −219 to 530 ppm in the solid state. A linear correlation of 51V NMR isotropic solution and solid-state chemical shifts of complexes containing non-innocent ligands is observed. These experimental results provide the information needed for the application of 51V SSNMR spectroscopy in characterizing the electronic properties of a wide variety of vanadium-containing systems, and in particular those containing non-innocent ligands and that have chemical shifts outside the populated range of −300 ppm to −700 ppm. The studies presented in this report demonstrate that the small quadrupolar couplings covering a narrow range of values reflect the symmetric electronic charge distribution, which is also similar across these complexes. These quadrupolar interaction parameters alone are not sufficient to capture the rich electronic structure of these complexes. In contrast, the chemical shift anisotropy tensor elements accessible from 51V SSNMR experiments are a highly sensitive probe of subtle differences in electronic distribution and orbital occupancy in these compounds. Quantum chemical (DFT) calculations of NMR parameters for [VO(hshed)(Cat)] yield 51V CSA tensor in reasonable agreement with the experimental results, but surprisingly, the calculated quadrupolar coupling constant is significantly greater than the experimental value. The studies demonstrate that substitution of the catechol ligand with electron donating groups results in an increase in the HOMO-LUMO gap and can be directly followed by an upfield shift for the vanadium catechol complex. In contrast, substitution of the catechol ligand with electron withdrawing groups results in a decrease in the HOMO-LUMO gap and can directly be followed by a downfield shift for the complex. The vanadium catechol complexes were used in this work because the 51V is a half-integer quadrupolar nucleus whose NMR observables are highly sensitive to the local environment. However, the results are general and could be extended to other redox active complexes that exhibit similar coordination chemistry as the vanadium catechol complexes. PMID:21842875

New insights into micro/nanoscale combined probes (nanoAuger, μXPS) to characterize Ag/Au@SiO2 core-shell assemblies

NASA Astrophysics Data System (ADS)

Ledeuil, J. B.; Uhart, A.; Soulé, S.; Allouche, J.; Dupin, J. C.; Martinez, H.

2014-09-01

This work has examined the elemental distribution and local morphology at the nanoscale of core@shell Ag/Au@SiO2 particles. The characterization of such complex metal/insulator materials becomes more efficient when using an initial cross-section method of preparation of the core@shell nanoparticles (ion milling cross polisher). The originality of this route of preparation allows one to obtain undamaged, well-defined and planar layers of cross-cut nano-objects. Once combined with high-resolution techniques of characterization (XPS, Auger and SEM), the process appears as a powerful way to minimize charging effects and enhance the outcoming electron signal (potentially affected by the topography of the material) during analysis. SEM experiments have unambiguously revealed the hollow-morphology of the metal core, while Auger spectroscopy observations showed chemical heterogeneity within the particles (as silver and gold are randomly found in the core ring). To our knowledge, this is the first time that Auger nano probe spectroscopy has been used and successfully optimized for the study of some complex metal/inorganic interfaces at such a high degree of resolution (~12 nm). Complementarily, XPS Au 4f and Ag 3d peaks were finally detected attesting the possibility of access to the whole chemistry of such nanostructured assemblies.This work has examined the elemental distribution and local morphology at the nanoscale of core@shell Ag/Au@SiO2 particles. The characterization of such complex metal/insulator materials becomes more efficient when using an initial cross-section method of preparation of the core@shell nanoparticles (ion milling cross polisher). The originality of this route of preparation allows one to obtain undamaged, well-defined and planar layers of cross-cut nano-objects. Once combined with high-resolution techniques of characterization (XPS, Auger and SEM), the process appears as a powerful way to minimize charging effects and enhance the outcoming electron signal (potentially affected by the topography of the material) during analysis. SEM experiments have unambiguously revealed the hollow-morphology of the metal core, while Auger spectroscopy observations showed chemical heterogeneity within the particles (as silver and gold are randomly found in the core ring). To our knowledge, this is the first time that Auger nano probe spectroscopy has been used and successfully optimized for the study of some complex metal/inorganic interfaces at such a high degree of resolution (~12 nm). Complementarily, XPS Au 4f and Ag 3d peaks were finally detected attesting the possibility of access to the whole chemistry of such nanostructured assemblies. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03211j

M≡E and M=E Complexes of Iron and Cobalt that Emphasize Three-fold Symmetry (E = O, N, NR)

PubMed Central

Saouma, Caroline T.; Peters, Jonas C.

2011-01-01

Mid-to-late transition metal complexes that feature terminal, multiply bonded ligands such as oxos, imides, and nitrides have been invoked as intermediates in several catalytic transformations of synthetic and biological significance. Until about ten years ago, isolable examples of such species were virtually unknown. Over the past decade or so, numerous chemically well-defined examples of such species have been discovered. In this context, the presentreview summarizes the development of 4- and 5-coordinate Fe(E) and Co(E) species under local three-fold symmetry. PMID:21625302

TSCA Chemical Data Reporting Fact Sheet: Reporting Manufactured Chemical Substances from Metal Mining and Related Activities

EPA Pesticide Factsheets

This fact sheet provides guidance on the Chemical Data Reporting (CDR) rule requirements related to the reporting of mined metals, intermediates, and byproducts manufactured during metal mining and related activities.

Coagulation-flocculation mechanisms in wastewater treatment plants through zeta potential measurements.

PubMed

López-Maldonado, E A; Oropeza-Guzman, M T; Jurado-Baizaval, J L; Ochoa-Terán, A

2014-08-30

Based on the polyelectrolyte-contaminant physical and chemical interactions at the molecular level, this article analyzed and discussed the coagulation-flocculation and chemical precipitation processes in order to improve their efficiency. Bench experiments indicate that water pH, polyelectrolyte (PE) dosing strategy and cationic polyelectrolyte addition are key parameters for the stability of metal-PE complexes. The coagulation-flocculation mechanism is proposed based on zeta potential (ζ) measurement as the criteria to define the electrostatic interaction between pollutants and coagulant-flocculant agents. Polyelectrolyte and wastewater dispersions are exposed to an electrophoretic effect to determine ζ. Finally, zeta potential values are compared at pH 9, suggesting the optimum coagulant dose at 162mg/L polydadmac and 67mg/L of flocculant, since a complete removal of TSS and turbidity is achieved. Based on the concentration of heavy metals (0.931mg/L Sn, 0.7mg/L Fe and 0.63mg/L Pb), treated water met the Mexican maximum permissible limits. In addition, the treated water has 45mg O2/L chemical oxygen demand (COD) and 45mg C/L total organic carbon (TOC). The coagulation-flocculation mechanism is proposed taking into account both: zeta potential (ζ)-pH measurement and chemical affinity, as the criteria to define the electrostatic and chemical interaction between pollutants and polyelectrolytes. Copyright © 2014 Elsevier B.V. All rights reserved.

Metalloprotein Crystallography: More than a Structure.

PubMed

Bowman, Sarah E J; Bridwell-Rabb, Jennifer; Drennan, Catherine L

2016-04-19

Metal ions and metallocofactors play important roles in a broad range of biochemical reactions. Accordingly, it has been estimated that as much as 25-50% of the proteome uses transition metal ions to carry out a variety of essential functions. The metal ions incorporated within metalloproteins fulfill functional roles based on chemical properties, the diversity of which arises as transition metals can adopt different redox states and geometries, dictated by the identity of the metal and the protein environment. The coupling of a metal ion with an organic framework in metallocofactors, such as heme and cobalamin, further expands the chemical functionality of metals in biology. The three-dimensional visualization of metal ions and complex metallocofactors within a protein scaffold is often a starting point for enzymology, highlighting the importance of structural characterization of metalloproteins. Metalloprotein crystallography, however, presents a number of implicit challenges including correctly incorporating the relevant metal or metallocofactor, maintaining the proper environment for the protein to be purified and crystallized (including providing anaerobic, cold, or aphotic environments), and being mindful of the possibility of X-ray induced damage to the proteins or incorporated metal ions. Nevertheless, the incorporated metals or metallocofactors also present unique advantages in metalloprotein crystallography. The significant resonance that metals undergo with X-ray photons at wavelengths used for protein crystallography and the rich electronic properties of metals, which provide intense and spectroscopically unique signatures, allow a metalloprotein crystallographer to use anomalous dispersion to determine phases for structure solution and to use simultaneous or parallel spectroscopic techniques on single crystals. These properties, coupled with the improved brightness of beamlines, the ability to tune the wavelength of the X-ray beam, the availability of advanced detectors, and the incorporation of spectroscopic equipment at a number of synchrotron beamlines, have yielded exciting developments in metalloprotein structure determination. Here we will present results on the advantageous uses of metals in metalloprotein crystallography, including using metallocofactors to obtain phasing information, using K-edge X-ray absorption spectroscopy to identify metals coordinated in metalloprotein crystals, and using UV-vis spectroscopy on crystals to probe the enzymatic activity of the crystallized protein.

The alkaline earth intercalates of molybdenum disulfide

NASA Technical Reports Server (NTRS)

Somoano, R. B.; Hadek, V.; Rembaum, A.; Samson, S.; Woollam, J. A.

1975-01-01

Molybdenum disulfide has been intercalated with calcium and strontium by means of the liquid ammonia technique. Chemical, X-ray, and superconductivity data are presented. The X-ray data reveal a lowering of crystal symmetry and increase of complexity of the structure upon intercalation with the alkaline earth metals. The Ca and Sr intercalates start to superconduct at 4 and 5.6 K, respectively, and show considerable anisotropy regarding the critical magnetic field.

Mechanism of Benzene Tribopolymerization on the RuO2 (110) Surface

NASA Astrophysics Data System (ADS)

Yang, J.; Qi, Y.; Kim, H. D.; Rappe, A. M.

2018-04-01

A tribopolymer formed on the contacts of microelectromechanical and nanoelectromechanical system (MEMS-NEMS) devices is a major concern hampering their practical use in information technology. Conductive metal oxides, such as RuO2 and ReO3 , have been regarded as promising candidate materials for MEMS-NEMS contacts due to their conductivity, hardness, and relatively chemically inert surfaces. However, recent experimental works demonstrate that trace amounts of a polymer could still form on RuO2 surfaces. We demonstrate the mechanism of this class of unexpected tribopolymer formation by conducting density-functional-theory-based computational compression experiments with benzene as the contamination gas. First, mechanical force during compression changes the benzene molecules from slightly physisorbed to strongly chemisorbed. Further compression causes deformation and chemical linkage of the benzene molecules. Finally, the two contacts detach, with one having a complex organic molecule attached and the other a more reactive surface. The complex organic molecule, which has an oxabicyclic segment, can be viewed as the rudiment of a tribopolymer, and the more reactive surface can trigger the next adsorption-reaction-tribopolymer formation cycle. Based on these results, we also predict tribopolymer formation rates by using transition-state theory and the second-order rate law. We promote a deeper understanding of tribopolymer formation (especially on metal oxides) and provide strategies for suppressing tribopolymerization.

A review of combinations of electrokinetic applications.

PubMed

Moghadam, Mohamad Jamali; Moayedi, Hossein; Sadeghi, Masoud Mirmohamad; Hajiannia, Alborz

2016-12-01

Anthropogenic activities contaminate many lands and underground waters with dangerous materials. Although polluted soils occupy small parts of the land, the risk they pose to plants, animals, humans, and groundwater is too high. Remediation technologies have been used for many years in order to mitigate pollution or remove pollutants from soils. However, there are some deficiencies in the remediation in complex site conditions such as low permeability and complex composition of some clays or heterogeneous subsurface conditions. Electrokinetic is an effective method in which electrodes are embedded in polluted soil, usually vertically but in some cases horizontally, and a low direct current voltage gradient is applied between the electrodes. The electric gradient initiates movement of contaminants by electromigration (charged chemical movement), electro-osmosis (movement of fluid), electrolysis (chemical reactions due to the electric field), and diffusion. However, sites that are contaminated with heavy metals or mixed contaminants (e.g. a combination of organic compounds with heavy metals and/or radionuclides) are difficult to remediate. There is no technology that can achieve the best results, but combining electrokinetic with other remediation methods, such as bioremediation and geosynthetics, promises to be the most effective method so far. This review focuses on the factors that affect electrokinetic remediation and the state-of-the-art methods that can be combined with electrokinetic.

Excitation-Energy Transfer Paths from Tryptophans to Coordinated Copper Ions in Engineered Azurins: a Source of Observables for Monitoring Protein Structural Changes

NASA Astrophysics Data System (ADS)

Di Rocco, Giulia; Bernini, Fabrizio; Borsari, Marco; Martinelli, Ilaria; Bortolotti, Carlo Augusto; Battistuzzi, Gianantonio; Ranieri, Antonio; Caselli, Monica; Sola, Marco; Ponterini, Glauco

2016-09-01

The intrinsic fluorescence of recombinant proteins offers a powerful tool to detect and characterize structural changes induced by chemical or biological stimuli. We show that metal-ion binding to a hexahistidine tail can significantly broaden the range of such structurally sensitive fluorescence observables. Bipositive metal-ions as Cu2+, Ni2+ and Zn2+ bind 6xHis-tag azurin and its 6xHis-tagged R129W and W48A-R129W mutants with good efficiency and, thereby, quench their intrinsic fluorescence. Due to a much more favourable spectral overlap, the 6xHis-tag/Cu2+ complex(es) are the most efficient quenchers of both W48 and W129 emissions. Based on simple Förster-type dependence of energy-transfer efficiency on donor/acceptor distance, we can trace several excitation-energy transfer paths across the protein structure. Unexpected lifetime components in the azurin 6xHis-tag/Cu2+ complex emission decays reveal underneath complexity in the conformational landscape of these systems. The new tryptophan emission quenching paths provide additional signals for detecting and identifying protein structural changes.

Selective synthesis and redox sequence of a heterobimetallic nickel/copper complex of the noninnocent Siamese-twin porphyrin.

PubMed

Blusch, Lina K; Mitevski, Oliver; Martin-Diaconescu, Vlad; Pröpper, Kevin; DeBeer, Serena; Dechert, Sebastian; Meyer, Franc

2014-08-04

The Siamese-twin porphyrin (1H4) is a redox noninnocent pyrazole-expanded porphyrin with two equivalent dibasic {N4} binding sites. It is now shown that its selective monometalation can be achieved to give the nickel(II) complex 1H2Ni with the second {N4} site devoid of a metal ion. This intermediate is then cleanly converted to 1Ni2 and to the first heterobimetallic Siamese-twin porphyrin 1CuNi. Structural characterization of 1H2Ni shows that it has the same helical structure previously seen for 1Cu2, 1Ni2, and free base 1H6(2+). Titration experiments suggest that the metal-devoid pocket of 1H2Ni can accommodate two additional protons, giving [1H4Ni](2+). Both bimetallic complexes 1Ni2 and 1CuNi feature rich redox chemistry, similar to the recently reported 1Cu2, including two chemically reversible oxidations at moderate potentials between -0.3 and +0.5 V (vs Cp2Fe/Cp2Fe(+)). The locus of these oxidations, in singly oxidized [1Ni2](+) and [1CuNi](+) as well as twice oxidized [1CuNi](2+), has been experimentally derived from comparison of the electrochemical properties of the complete series of complexes 1Cu2, 1Ni2, and 1CuNi, and from electron paramagnetic resonance (EPR) spectroscopy and X-ray absorption spectroscopy (XAS) (Ni and Cu K edges). All redox events are largely ligand-based, and in heterobimetallic 1CuNi, the first oxidation takes place within its Cu-subunit, while the second oxidation then occurs in its Ni-subunit. Adding pyridine to solutions of [1Ni2](+) and [1CuNi](2+) cleanly converts them to metal-oxidized redox isomers with axial EPR spectra typical for Ni(III) having significant dz(2)(1) character, reflecting close similarity with nickel complexes of common porphyrins. The possibility of selectively synthesizing heterobimetallic complexes 1MNi from a symmetric binucleating ligand scaffold, with the unusual situation of three distinct contiguous redox sites (M, Ni, and the porphyrin-like ligand), further expands the Siamese-twin porphyrin's potential to serve as an adjustable platform for multielectron redox processes in chemical catalysis and in electronic applications.

Geochemistry of metal-rich brines from central Mississippi Salt Dome basin, U.S.A.

USGS Publications Warehouse

Kharaka, Y.K.; Maest, A.S.; Carothers, W.W.; Law, L.M.; Lamothe, P.J.; Fries, T.L.

1987-01-01

Oil-field brines are the most favored ore-forming solutions for the sediment-hosted Mississippi Valley-type ore deposits. Detailed inorganic and organic chemical and isotope analyses of water and gas samples from six oil fields in central Mississippi, one of the very few areas with high metal brines, were conducted to study the inorganic and organic complexes responsible for the high concentrations of these metals. The samples were obtained from production zones consisting of sandstone and limestone that range in depth from 1900 to 4000 m (70-120??C) and in age from Late Cretaceous to Late Jurassic. Results show that the waters are dominantly bittern brines related to the Louann Salt. The brines have extremely high salinities that range from 160,000 to 320,000 mg/l total dissolved solids and are NaCaCl-type waters with very high concentrations of Ca (up to 48,000 mg/l) and other alkaline-earth metals, but with low concentrations of aliphatic acid anions. The concentrations of metals in many water samples are very high, reaching values of 70 mg/l for Pb, 245 mg/l for Zn, 465 mg/l for Fe and 210 mg/l for Mn. The samples with high metal contents have extremely low concentrations (<0.02 mg/l) of H2S. Samples obtained from the Smackover Formation (limestone) have low metal contents that are more typical of oil-field waters, but have very high concentrations (up to 85 mg/l) of H2S. Computations with the geochemical code SOLMINEQ.87 give the following results: (1) both Pb and Zn are present predominantly as aqueous chloride complexes (mainly as PbCl42- and ZnCl42-, respectively); (2) the concentrations of metals complexed with short-chained aliphatic acid anions and reduced S species are minor; (3) organic acid anions are important in controlling the concentrations of metals because they affect the pH and buffer capacity of the waters at subsurface conditions; and (4) galena and sphalerite solubilities control the concentrations of Pb and Zn in these waters. ?? 1988.

Water soluble biocompatible vesicles based on polysaccharides and oligosaccharides inclusion complexes for carotenoid delivery.

PubMed

Polyakov, Nikolay E; Kispert, Lowell D

2015-09-05

Since carotenoids are highly hydrophobic, air- and light-sensitive hydrocarbon compounds, developing methods for increasing their bioavailability and stability towards irradiation and reactive oxygen species is an important goal. Application of inclusion complexes of "host-guest" type with polysaccharides and oligosaccharides such as arabinogalactan, cyclodextrins and glycyrrhizin minimizes the disadvantages of carotenoids when these compounds are used in food processing (colors and antioxidant capacity) as well as for production of therapeutic formulations. Cyclodextrin complexes which have been used demonstrated enhanced storage stability but suffered from poor solubility. Polysaccharide and oligosaccharide based inclusion complexes play an important role in pharmacology by providing increased solubility and stability of lipophilic drugs. In addition they are used as drug delivery systems to increase absorption rate and bioavailability of the drugs. In this review we summarize the existing data on preparation methods, analysis, and chemical reactivity of carotenoids in inclusion complexes with cyclodextrin, arabinogalactan and glycyrrhizin. It was demonstrated that incorporation of carotenoids into the "host" macromolecule results in significant changes in their physical and chemical properties. In particular, polysaccharide complexes show enhanced photostability of carotenoids in water solutions. A significant decrease in the reactivity towards metal ions and reactive oxygen species in solution was also detected. Copyright © 2015 Elsevier Ltd. All rights reserved.

40 CFR 423.11 - Specialized definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... not included. (c) The term chemical metal cleaning waste means any wastewater resulting from the cleaning of any metal process equipment with chemical compounds, including, but not limited to, boiler tube... chemical cleaning compounds] any metal process equipment including, but not limited to, boiler tube...

40 CFR 423.11 - Specialized definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... not included. (c) The term chemical metal cleaning waste means any wastewater resulting from the cleaning of any metal process equipment with chemical compounds, including, but not limited to, boiler tube... chemical cleaning compounds] any metal process equipment including, but not limited to, boiler tube...

40 CFR 423.11 - Specialized definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... air conditioning wastes are not included. (c) The term chemical metal cleaning waste means any wastewater resulting from the cleaning of any metal process equipment with chemical compounds, including, but... from cleaning [with or without chemical cleaning compounds] any metal process equipment including, but...

40 CFR 423.11 - Specialized definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... chemical metal cleaning waste means any wastewater resulting from the cleaning of any metal process equipment with chemical compounds, including, but not limited to, boiler tube cleaning. (d) The term metal cleaning waste means any wastewater resulting from cleaning [with or without chemical cleaning compounds...

40 CFR 423.11 - Specialized definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... chemical metal cleaning waste means any wastewater resulting from the cleaning of any metal process equipment with chemical compounds, including, but not limited to, boiler tube cleaning. (d) The term metal cleaning waste means any wastewater resulting from cleaning [with or without chemical cleaning compounds...

Electrifying model catalysts for understanding electrocatalytic reactions in liquid electrolytes.

PubMed

Faisal, Firas; Stumm, Corinna; Bertram, Manon; Waidhas, Fabian; Lykhach, Yaroslava; Cherevko, Serhiy; Xiang, Feifei; Ammon, Maximilian; Vorokhta, Mykhailo; Šmíd, Břetislav; Skála, Tomáš; Tsud, Nataliya; Neitzel, Armin; Beranová, Klára; Prince, Kevin C; Geiger, Simon; Kasian, Olga; Wähler, Tobias; Schuster, Ralf; Schneider, M Alexander; Matolín, Vladimír; Mayrhofer, Karl J J; Brummel, Olaf; Libuda, Jörg

2018-07-01

Electrocatalysis is at the heart of our future transition to a renewable energy system. Most energy storage and conversion technologies for renewables rely on electrocatalytic processes and, with increasing availability of cheap electrical energy from renewables, chemical production will witness electrification in the near future 1-3 . However, our fundamental understanding of electrocatalysis lags behind the field of classical heterogeneous catalysis that has been the dominating chemical technology for a long time. Here, we describe a new strategy to advance fundamental studies on electrocatalytic materials. We propose to 'electrify' complex oxide-based model catalysts made by surface science methods to explore electrocatalytic reactions in liquid electrolytes. We demonstrate the feasibility of this concept by transferring an atomically defined platinum/cobalt oxide model catalyst into the electrochemical environment while preserving its atomic surface structure. Using this approach, we explore particle size effects and identify hitherto unknown metal-support interactions that stabilize oxidized platinum at the nanoparticle interface. The metal-support interactions open a new synergistic reaction pathway that involves both metallic and oxidized platinum. Our results illustrate the potential of the concept, which makes available a systematic approach to build atomically defined model electrodes for fundamental electrocatalytic studies.

Deposition of tungsten metal by an immersion process

DOE PAGES

Small, Leo J.; Brumbach, Michael T.; Clem, Paul G.; ...

2017-03-23

A new multi-step, solution-phase method for the spontaneous deposition of tungsten from a room temperature ethereal solution is reported. This immersion process relies on the deposition of a sacrificial zinc coating which is galvanically displaced by the ether-mediated reduction of oxophilic WCl 6. Subsequent thermal treatment renders a crystalline, metallic tungsten film. The chemical evolution of the surface and formation of a complex intermediate tungsten species is characterized by X-ray diffraction, infrared spectroscopy, and X-ray photoelectron spectroscopy. Efficient metallic tungsten deposition is first characterized on a graphite substrate and then demonstrated on a functional carbon foam electrode. The resulting electrochemicalmore » performance of the modified electrode is interrogated with the canonical aqueous ferricyanide system. A tungsten-coated carbon foam electrode showed that both electrode resistance and overall electrochemical cell resistance were reduced by 50%, resulting in a concomitant decrease in redox peak separation from 1.902 V to 0.783 V. Furthermore, this process promises voltage efficiency gains in electrodes for energy storage technologies and demonstrates the viability of a new route to tungsten coating for technologies and industries where high conductivity and chemical stability are paramount.« less

Adhesion and enrichment of metals on human hands from contaminated soil at an Arctic urban brownfield.

PubMed

Siciliano, Steven D; James, K; Zhang, Guiyin; Schafer, Alexis N; Peak, J Derek

2009-08-15

Human exposure to contaminated soils drives clean up criteria at many urban brownfields. Current risk assessment guidelines assume that humans ingest some fraction of soil smaller than 4 mm but have no estimates of what fraction of soil is ingested by humans. Here, we evaluated soil adherence to human hands for 13 agricultural soils from Saskatchewan, Canada and 17 different soils from a brownfield located in Iqaluit, Nunavut, Canada. In addition, we estimated average particle size adhering to human hands for residents of a northern urban setting. Further, we estimated how metal concentrations differed between the adhered and bulk (< 4 mm) fraction of soil. The average particle size for adhered agricultural soils was 34 microm, adhered brownfield soils was 105 microm, and particles adhered to human residentswas 36 microm. Metals were significantly enriched in these adhered fractions with an average enrichment [(adhered-bulk)/bulk] in metal concentration of 184% (113% median) for 24 different elements. Enrichment was greater for key toxicological elements of concern such as chromium (140%), copper (140%), nickel (130%), lead (110%), and zinc (130%) and was highest for silver (810%), mercury (630%), selenium (500%), and arsenic (420%). Enrichment were positively correlated with carbonate complexation constants (but not bulk solubility products) and suggests that the dominant mechanism controlling metal enrichment in these samples is a precipitation of carbonate surfaces that subsequently adsorb metals. Our results suggest that metals of toxicological concern are selectively enriched in the fraction of soil that humans incidentally ingest. Investigators should likely process soil samples through a 45 microm sieve before estimating the risk associated with contaminated soils to humans. The chemical mechanisms resulting in metal enrichment likely differ between sites but at our site were linked to surface complexation with carbonates.

Protection of Metal Artifacts with the Formation of Metal–Oxalates Complexes by Beauveria bassiana

PubMed Central

Joseph, Edith; Cario, Sylvie; Simon, Anaële; Wörle, Marie; Mazzeo, Rocco; Junier, Pilar; Job, Daniel

2012-01-01

Several fungi present high tolerance to toxic metals and some are able to transform metals into metal–oxalate complexes. In this study, the ability of Beauveria bassiana to produce copper oxalates was evaluated. Growth performance was tested on various copper-containing media. B. bassiana proved highly resistant to copper, tolerating concentrations of up to 20 g L−1, and precipitating copper oxalates on all media tested. Chromatographic analyses showed that this species produced oxalic acid as sole metal chelator. The production of metal–oxalates can be used in the restoration and conservation of archeological and modern metal artifacts. The production of copper oxalates was confirmed directly using metallic pieces (both archeological and modern). The conversion of corrosion products into copper oxalates was demonstrated as well. In order to assess whether the capability of B. bassiana to produce metal–oxalates could be applied to other metals, iron and silver were tested as well. Iron appears to be directly sequestered in the wall of the fungal hyphae forming oxalates. However, the formation of a homogeneous layer on the object is not yet optimal. On silver, a co-precipitation of copper and silver oxalates occurred. As this greenish patina would not be acceptable on silver objects, silver reduction was explored as a tarnishing remediation. First experiments showed the transformation of silver nitrate into nanoparticles of elemental silver by an unknown extracellular mechanism. The production of copper oxalates is immediately applicable for the conservation of copper-based artifacts. For iron and silver this is not yet the case. However, the vast ability of B. bassiana to transform toxic metals using different immobilization mechanisms seems to offer considerable possibilities for industrial applications, such as the bioremediation of contaminated soils or the green synthesis of chemicals. PMID:22291684

Reversible Hydrogen Activation by a Pyridonate Borane Complex: Combining Frustrated Lewis Pair Reactivity with Boron-Ligand Cooperation.

PubMed

Gellrich, Urs

2018-04-16

A pyridone borane complex that liberates dihydrogen under mild conditions is described. The reverse reaction, dihydrogen activation by the formed pyridonate borane complex, is achieved under moderate H 2 pressure (2 bar) at room temperature. DFT and DLPNO-CCSD(T) computations reveal that the active form of the pyridonate borane complex is a boroxypyridine that can be described as a single component frustrated Lewis pair (FLP). Significantly, the boroxypyridine undergoes a chemical transformation to a neutral pyridone donor ligand in the course of the hydrogen activation. This unprecedented mode of action may thus, in analogy to metal-ligand cooperation, be regarded as an example of boron-ligand cooperation. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Molecular investigation on the binding of Cd(II) by the binary mixtures of montmorillonite with two bacterial species

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Huihui; Qu, ChenChen; Liu, Jing

Bacteria and phyllosilicate commonly coexist in the natural environment, producing various bacteria–clay complexes that are capable of immobilizing heavy metals, such as cadmium, via adsorption. However, the molecular binding mechanisms of heavy metals on these complex aggregates still remain poorly understood. This study investigated Cd adsorption on Gram-positive B. subtilis, Gram-negative P. putida and their binary mixtures with montmorillonite (Mont) using the Cd K-edge x-ray absorption spectroscopy (XAS) and isothermal titration calorimetry (ITC). We observed a lower adsorptive capacity for P. putida than B. subtilis, whereas P. putida–Mont and B. subtilis–Mont mixtures showed nearly identical Cd adsorption behaviors. EXAFS fitsmore » and ITC measurements demonstrated more phosphoryl binding of Cd in P. putida. The decreased coordination of C atoms around Cd and the reduced adsorption enthalpies and entropies for the binary mixtures compared to that for individual bacteria suggested that the bidentate Cd-carboxyl complexes in pure bacteria systems were probably transformed into monodentate complexes that acted as ionic bridging structure between bacteria and motmorillonite. This study clarified the binding mechanism of Cd at the bacteria–phyllosilicate interfaces from a molecular and thermodynamic view, which has an environmental significance for predicting the chemical behavior of trace elements in complex mineral–organic systems.« less

Rare‐Earth‐ and Uranium‐Mesoionic Carbenes: A New Class of f‐Block Carbene Complex Derived from an N‐Heterocyclic Olefin

PubMed Central

Seed, John A.; Gregson, Matthew; Tuna, Floriana; Chilton, Nicholas F.; Wooles, Ashley J.; McInnes, Eric J. L.

2017-01-01

Abstract Neutral mesoionic carbenes (MICs) have emerged as an important class of carbene, however they are found in the free form or ligated to only a few d‐block ions. Unprecedented f‐block MIC complexes [M(N′′)3{CN(Me)C(Me)N(Me)CH}] (M=U, Y, La, Nd; N′′=N(SiMe3)2) are reported. These complexes were prepared by a formal 1,4‐proton migration reaction when the metal triamides [M(N′′)3] were treated with the N‐heterocyclic olefin H2C=C(NMeCH)2, which constitutes a new, general way to prepare MIC complexes. Quantum chemical calculations on the 5f3 uranium(III) complex suggest the presence of a U=C donor‐acceptor bond, composed of a MIC→U σ‐component and a U(5f)→MIC(2p) π‐back‐bond, but for the d0f0 Y and La and 4f3 Nd congeners only MIC→M σ‐bonding is found. Considering the generally negligible π‐acidity of MICs, this is surprising and highlights that greater consideration should possibly be given to recognizing MICs as potential π‐acid ligands when coordinated to strongly reducing metals. PMID:28719735

Chemical speciation and mobilization of copper and zinc in naturally contaminated mine soils with citric and tartaric acids.

PubMed

Pérez-Esteban, Javier; Escolástico, Consuelo; Moliner, Ana; Masaguer, Alberto

2013-01-01

A one-step extraction procedure and a leaching column experiment were performed to assess the effects of citric and tartaric acids on Cu and Zn mobilization in naturally contaminated mine soils to facilitate assisted phytoextraction. A speciation modeling of the soil solution and the metal fractionation of soils were performed to elucidate the chemical processes that affected metal desorption by organic acids. Different extracting solutions were prepared, all of which contained 0.01 M KNO(3) and different concentrations of organic acids: control without organic acids, 0.5 mM citric, 0.5 mM tartaric, 10 mM citric, 10 mM tartaric, and 5 mM citric +5 mM tartaric. The results of the extraction procedure showed that higher concentrations of organic acids increased metal desorption, and citric acid was more effective at facilitating metal desorption than tartaric acid. Metal desorption was mainly influenced by the decreasing pH and the dissolution of Fe and Mn oxides, not by the formation of soluble metal-organic complexes as was predicted by the speciation modeling. The results of the column study reported that low concentrations of organic acids did not significantly increase metal mobilization and that higher doses were also not able to mobilize Zn. However, 5-10 mM citric acid significantly promoted Cu mobilization (from 1 mg kg(-1) in the control to 42 mg kg(-1) with 10 mM citric acid) and reduced the exchangeable (from 21 to 3 mg kg(-1)) and the Fe and Mn oxides (from 443 to 277 mg kg(-1)) fractions. Citric acid could efficiently facilitate assisted phytoextraction techniques. Copyright © 2012 Elsevier Ltd. All rights reserved.

Phytomining of heavy metals from soil by Hibiscus radiatus using phytoremediationtechnology (Part-2)

NASA Astrophysics Data System (ADS)

Panchal, K. J.; Subramanian, R. B.; Gohil, T. P.

2017-12-01

Metal ions are not only valuable intermediates in metal extraction, but also important raw materials fortechnical applications. They possess some unique but, identical physical and chemical properties, whichmake them useful probes of low temperature geochemical reactions. Heavy metals are natural constituentsof the earth's crust, but indiscriminate human activities have drastically altered their geochemical cyclesand biochemical balance. Metal concentration in soil typically ranges from less than one to as high as100,000 mg/kg. Heavy metal contaminations of land resources continue to be the focus of numerousenvironmental studies and attract a great deal of attention worldwide. This is attributed to nobiodegradabilityand persistence of heavy metals in soils. Prolonged exposure to heavy metals such ascadmium, copper, lead, nickel, and zinc can cause deleterious health effects in humans. Complexation,separation, and removal of metal ions have become increasingly attractive areas of research and have ledto new technical developments like phytoremediation that has numerous biotechnological implications ofunderstanding of plant metal accumulation. Hibiscus radiatus is newly identified as a potential heavymetal hypreaccumulator. In this study Hibiscus radiatus was subjected for in vitro heavy metalaccumulation, to explore the accumulation pattern of four heavy metals viz Cadmium, Lead, Nickel andZinc in various parts of Hibiscus radiatus plant parts. Translocation of metals in Hibiscus radiatus plant parts from soil makes this plant an eligible candidate to remove heavy metals from soil.

X-ray absorption spectral studies of copper (II) mixed ligand complexes

NASA Astrophysics Data System (ADS)

Soni, B.; Dar, Davood Ah; Shrivastava, B. D.; Prasad, J.; Srivastava, K.

2014-09-01

X-ray absorption spectra at the K-edge of copper have been studied in two copper mixed ligand complexes, one having tetramethyethylenediamine (tmen) and the other having tetraethyethylenediamine (teen) as one of the ligands. The spectra have been recorded at BL-8 dispersive extended X-ray absorption fine structure (EXAFS) beamline at the 2.5 GeV INDUS- 2 synchrotron, RRCAT, Indore, India. The data obtained has been processed using the data analysis program Athena. The energy of the K-absorption edge, chemical shift, edge-width and shift of the principal absorption maximum in the complexes have been determined and discussed. The values of these parameters have been found to be approximately the same in both the complexes indicating that the two complexes possess similar chemical environment around the copper metal atom. The chemical shift has been utilized to estimate effective nuclear charge on the absorbing atom. The normalized EXAFS spectra have been Fourier transformed. The position of the first peak in the Fourier transform gives the value of first shell bond length, which is shorter than the actual bond length because of energy dependence of the phase factors in the sine function of the EXAFS equation. This distance is thus the phase- uncorrected bond length. Bond length has also been determined by Levy's, Lytle's and Lytle, Sayers and Stern's (LSS) methods. The results obtained from LSS and the Fourier transformation methods are comparable with each other, since both are phase uncorrected bond lengths.

Metal ion binding to iron oxides

NASA Astrophysics Data System (ADS)

Ponthieu, M.; Juillot, F.; Hiemstra, T.; van Riemsdijk, W. H.; Benedetti, M. F.

2006-06-01

The biogeochemistry of trace elements (TE) is largely dependent upon their interaction with heterogeneous ligands including metal oxides and hydrous oxides of iron. The modeling of TE interactions with iron oxides has been pursued using a variety of chemical models. The objective of this work is to show that it is possible to model the adsorption of protons and TE on a crystallized oxide (i.e., goethite) and on an amorphous oxide (HFO) in an identical way. Here, we use the CD-MUSIC approach in combination with valuable and reliable surface spectroscopy information about the nature of surface complexes of the TE. The other objective of this work is to obtain generic parameters to describe the binding of the following elements (Cd, Co, Cu, Ni, Pb, and Zn) onto both iron oxides for the CD-MUSIC approach. The results show that a consistent description of proton and metal ion binding is possible for goethite and HFO with the same set of model parameters. In general a good prediction of almost all the collected experimental data sets corresponding to metal ion binding to HFO is obtained. Moreover, dominant surface species are in agreement with the recently published surface complexes derived from X-ray absorption spectroscopy (XAS) data. Until more detailed information on the structure of the two iron oxides is available, the present option seems a reasonable approximation and can be used to describe complex geochemical systems. To improve our understanding and modeling of multi-component systems we need more data obtained at much lower metal ion to iron oxide ratios in order to be able to account eventually for sites that are not always characterized in spectroscopic studies.

Synthesis, characterization and anticancer activities of two lanthanide(III) complexes with a nicotinohydrazone ligand

NASA Astrophysics Data System (ADS)

Xu, Zhou-Qin; Mao, Xian-Jie; Jia, Lei; Xu, Jun; Zhu, Tao-Feng; Cai, Hong-Xin; Bie, Hong-Yan; Chen, Ru-Hua; Ma, Tie-liang

2015-12-01

Two isostructural acylhydrazone based complexes, namely [Ce(penh)2(H2O)4](NO3)3·4H2O (1) and [Sm(penh)2(NO3)2](NO3)·C2H5OH (2) (penh = 2-acetylpyridine nicotinohydrazone), have been obtained and characterized by physico-chemical and spectroscopic methods. The ten-coordinated lanthanide metal ion in each complex is surrounded by two independent tridentate neutral acylhydrazones with two ON2 donor sets. The other four coordination oxygen atoms are from four water molecules and two bidentate nitrate anions for complexes 1 and 2, respectively, thus giving distorted bicapped square antiprism geometry. Both complexes have excellent antitumor activity towards human pancreatic cancer (PATU8988), human colorectal cancer (lovo) and human gastric cancer(SGC7901) cell line. Furthermore, the cell apoptosis of complex 1 is detected by AnnexinV/PI flow cytometry.

[Sb{sub 4}Au{sub 4}Sb{sub 4}]{sup 2−}: A designer all-metal aromatic sandwich

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Wen-Juan; You, Xue-Rui; Guo, Jin-Chang

We report on the computational design of an all-metal aromatic sandwich, [Sb{sub 4}Au{sub 4}Sb{sub 4}]{sup 2−}. The triple-layered, square-prismatic sandwich complex is the global minimum of the system from Coalescence Kick and Minima Hopping structural searches. Following a standard, qualitative chemical bonding analysis via canonical molecular orbitals, the sandwich complex can be formally described as [Sb{sub 4}]{sup +}[Au{sub 4}]{sup 4−}[Sb{sub 4}]{sup +}, showing ionic bonding characters with electron transfers in between the Sb{sub 4}/Au{sub 4}/Sb{sub 4} layers. For an in-depth understanding of the system, one needs to go beyond the above picture. Significant Sb → Au donation and Sb ←more » Au back-donation occur, redistributing electrons from the Sb{sub 4}/Au{sub 4}/Sb{sub 4} layers to the interlayer Sb–Au–Sb edges, which effectively lead to four Sb–Au–Sb three-center two-electron bonds. The complex is a system with 30 valence electrons, excluding the Sb 5s and Au 5d lone-pairs. The two [Sb{sub 4}]{sup +} ligands constitute an unusual three-fold (π and σ) aromatic system with all 22 electrons being delocalized. An energy gap of ∼1.6 eV is predicted for this all-metal sandwich. The complex is a rare example for rational design of cluster compounds and invites forth-coming synthetic efforts.« less

Role of annealing on the structural and optical properties of nanostructured diaceto bis-benzimidazole Mn(II) complex thin films.

PubMed

Praveen, P A; Babu, R Ramesh; Ramamurthi, K

2017-02-15

A coordination complex, manganese incorporated benzimidazole, thin films were prepared by chemical bath deposition method. Structural characterization of the deposited films, carried out by Fourier transform infrared spectroscopy, Raman and electron paramagnetic resonance spectral analyses, reveals the distorted tetrahedral environment of the metal ion with bis-benzimidazole ligand. Further the molecular composition of the deposited metal complex was estimated by energy-dispersive X-ray spectroscopy. The prepared thin films were thermally treated to study the effect of annealing temperature on the surface morphology and the results showed that the surface homogeneity of the films increased for thermally treated films up to 150°C. But distortion and voids were observed for the films annealed at 200°C. The Raman analysis reveals the molecular hydrogen bond distortion which leads to the evaporation of the metal complex from the thin film surface with respect to annealing temperature. The linear and nonlinear optical properties of the as prepared and annealed films were studied using ultraviolet-visible transmittance spectroscopy, second harmonic generation and Z-scan analyses. Films annealed at 150°C show a better linear transmittance in the visible region and larger SHG efficiency and third order nonlinear susceptibility when compared with the other samples. Further, the film annealed at 150°C was subjected to optical switching analysis and demonstrated to have an inverted switching behavior. Copyright © 2016 Elsevier B.V. All rights reserved.

Uptake of elements from seawater by ferromanganese crusts: Solid-phase associations and seawater speciation

USGS Publications Warehouse

Koschinsky, A.; Hein, J.R.

2003-01-01

Marine Fe-Mn oxyhydroxide crusts form by precipitation of dissolved components from seawater. Three hydrogenetic crust samples (one phosphatized) and two hydrothermal Mn-oxide samples were subjected to a sequential-leaching procedure in order to determine the host phases of 40 elements. Those host-phase associations are discussed with respect to element speciation in seawater. The partitioning of elements between the two major phases, Mn oxide and Fe oxyhydroxide, can in a first-order approximation be explained by a simple sorption model related to the inorganic speciation of the elements in seawater, as has been proposed in earlier models. Free and weakly complexed cations, such as alkali and alkaline earth metals, Mn, Co, Ni, Zn, T1(I), and partly Y, are sorbed preferentially on the negatively charged surface of the MnO2 in hydrogenetic crusts. The driving force is a strong coulombic interaction. All neutral or negatively charged chloro (Cd, Hg, T1), carbonate (Cu, Y, Pb, and U), and hydroxide (Be, Sc, Ti, Fe, Zr, Nb, In, Sn, Sb, Te, Hf, Ta, Bi, Th, and T1(III)) complexes and oxyanions (V, Cr, As, Se, Mo, and W) bind to the slightly positively charged surface of the amorphous FeOOH phase. While coulombic interaction can explain the sorption of the negatively charged species, the binding of neutral species is based on specific chemical interaction. Organic complexation of elements in deep-ocean water seems to be at most of minor importance. Surface oxidation can explain some strong metal associations, e.g. of Co and T1 with the MnO2 and Te with the FeOOH. Sorption reactions initially driven by coulombic forces are often followed by the formation of specific bonds between the adsorbate and the atoms of the oxide surface. Differences in the associations of some metals between the non-phosphatized and phosphatized hydrogenetic crusts and between the hydrogenetic and the hydrothermal samples reflect the different physico-chemical environments of formation and speciations in oxic seawater vs. less-oxic fluids, especially for the redox-sensitive metals such as Mo and V. These environmental-related differences indicate that the methodology of chemical speciation used here in combination with spectroscopic methods may allow for the detection of changes in paleoceanographic conditions recorded during the several tens of millions of years of crust growth. ?? 2003 Elsevier Science B.V. All rights reserved.