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Sample records for metal ligand anchored

  1. Photoconductivity of PbSe quantum-dot solids: dependence on ligand anchor group and length.

    PubMed

    Gao, Yunan; Aerts, Michiel; Sandeep, C S Suchand; Talgorn, Elise; Savenije, Tom J; Kinge, Sachin; Siebbeles, Laurens D A; Houtepen, Arjan J

    2012-11-27

    The assembly of quantum dots is an essential step toward many of their potential applications. To form conductive solids from colloidal quantum dots, ligand exchange is required. Here we study the influence of ligand replacement on the photoconductivity of PbSe quantum-dot solids, using the time-resolved microwave conductivity technique. Bifunctional replacing ligands with amine, thiol, or carboxylic acid anchor groups of various lengths are used to assemble quantum solids via a layer-by-layer dip-coating method. We find that when the ligand lengths are the same, the charge carrier mobility is higher in quantum-dot solids with amine ligands, while in quantum-dot solids with thiol ligands the charge carrier lifetime is longer. If the anchor group is the same, the charge carrier mobility is ligand length dependent. The results show that the diffusion length of charge carriers can reach several hundred nanometers. PMID:23078408

  2. Cobalt and nickel macrocycles anchored to nanocrystalline titanium dioxide thin films: Sensitization, catalysis, and ligand association

    NASA Astrophysics Data System (ADS)

    Achey, Darren Craig

    The global demand for renewable, clean electricity and fuel has compelled efforts to utilize the immense power incident upon the Earth from the Sun. Photovoltaic systems could power the planet's electrical demands with only moderate efficiencies. However, mitigation of fossil fuels used for transportation and night-time electricity requires the storage of photon energy, for example, in the form of chemical bonds. Mesoporous, nanocrystalline TiO2 thin films provide a manifold for anchoring molecular species that absorb and utilize photons to catalyze fuel-generating reactions. The overarching theme of this thesis is to improve understanding of the semiconductor/molecule interface utilizing earth abundant first-row transition metal coordination compounds. Chapter 2 presents the non-ideal redox behavior of cobalt porphyrins anchored to semiconductor surfaces. Additionally, CoI porphyrins were utilized as photocatalysts for the 2e- reduction of organobromides to yield a CoIII-R intermediate. The cobalt-carbon bond of CoIII-R was photodissociated with visible light to yield Co II and R·. The organic radical dimerized to form R-R. Light excitation of CoI compounds was found to result in electron transfer to TiO2, Chapter 3. Cobalt porphyrins, phthalocyanines, glyoximes, and corrins were all observed to exhibit this behavior. Electron transfer was demonstrated to primarily occur via excitation into the large extinction coefficient metal-to-ligand charge transfer absorption bands of CoI complexes. Chapter 4 focuses on the unique coordination chemistry of cobalt porphyrins anchored to a TiO2 thin film. Notably, pyridine axially ligated a CoII porphyrin following excited-state electron transfer of the CoI porphyrin to the TiO2. The rate constant for recombination of an electron in the TiO2 with CoII was observed to decrease with increasing pyridine concentration, behavior attributed primarily to a negative shift of the CoII/I potential in the presence of pyridine. Finally, Chapter 5 reports a comparative study of the kinetic and thermodynamic properties of the equilibrium between a 4-coordinate, low spin and a 6-coordinate, high spin nickel porphyrin, both in solution and anchored to TiO2. The mesoporous TiO2 thin film was found to influence the enthalpy and entropy of axial ligation while also altering the dissociative activation energy of axial ligation.

  3. Tension-compression asymmetry in the binding affinity of membrane-anchored receptors and ligands

    NASA Astrophysics Data System (ADS)

    Xu, Guang-Kui; Liu, Zishun; Feng, Xi-Qiao; Gao, Huajian

    2016-03-01

    Cell adhesion plays a crucial role in many biological processes of cells, e.g., immune responses, tissue morphogenesis, and stem cell differentiation. An essential problem in the molecular mechanism of cell adhesion is to characterize the binding affinity of membrane-anchored receptors and ligands under different physiological conditions. In this paper, a theoretical model is presented to study the binding affinity between a large number of anchored receptors and ligands under both tensile and compressive stresses, and corroborated by demonstrating excellent agreement with Monte Carlo simulations. It is shown that the binding affinity becomes lower as the magnitude of the applied stress increases, and drops to zero at a critical tensile or compressive stress. Interestingly, the critical compressive stress is found to be substantially smaller than the critical tensile stress for relatively long and flexible receptor-ligand complexes. This counterintuitive finding is explained by using the Euler instability theory of slender columns under compression. The tension-compression asymmetry in the binding affinity of anchored receptors and ligands depends subtly on the competition between the breaking and instability of their complexes. This study helps in understanding the role of mechanical forces in cell adhesion mediated by specific binding molecules.

  4. The Membrane-anchoring Domain of Epidermal Growth Factor Receptor Ligands Dictates Their Ability to Operate in Juxtacrine Mode

    SciTech Connect

    Dong, Jianying; Opresko, Lee; Chrisler, William B.; Orr, Galya; Quesenberry, Ryan D.; Lauffenburger, Douglas A.; Wiley, H S.

    2005-06-01

    All ligands of the epidermal growth factor receptor (EGFR) are synthesized as membrane-anchored precursors. Previous work has suggested that some ligands, such as EGF, must be proteolytically released to be active, whereas others, such as heparin binding EGF-like growth factor (HB-EGF) can function while still anchored to the membrane (i.e., juxtacrine signaling). To explore the structural basis for these differences in ligand activity, we engineered a series of membrane-anchored ligands in which the core, receptor-binding domain of EGF was combined with different domains of both EGF and HB-EGF. We found that ligands having the N-terminal extension of EGF could not bind to the EGFR, even when released from the membrane. Ligands lacking an N-terminal extension, but possessing the membrane-anchoring domain of EGF still required proteolytic release for activity, whereas ligands with the membrane anchoring domain of HB-EGF could elicit full biological activity while still membrane anchored. Ligands containing the HB-EGF membrane anchor, but lacking an N-terminal extension, activated EGFR during their transit through the Golgi apparatus . However, cell-mixing experiments and fluorescence resonance energy transfer (FRET) studies showed that juxtacrine signaling typically occurred in trans at the cell surface, at points of cell-cell contact. Our data suggest that the membrane-anchoring domain of ligands selectively controls their ability to participate in juxtacrine signaling and thus, only a subclass of EGFR ligands can act in a juxtacrine mode.

  5. Binding constants of membrane-anchored receptors and ligands: A general theory corroborated by Monte Carlo simulations.

    PubMed

    Xu, Guang-Kui; Hu, Jinglei; Lipowsky, Reinhard; Weikl, Thomas R

    2015-12-28

    Adhesion processes of biological membranes that enclose cells and cellular organelles are essential for immune responses, tissue formation, and signaling. These processes depend sensitively on the binding constant K2D of the membrane-anchored receptor and ligand proteins that mediate adhesion, which is difficult to measure in the "two-dimensional" (2D) membrane environment of the proteins. An important problem therefore is to relate K2D to the binding constant K3D of soluble variants of the receptors and ligands that lack the membrane anchors and are free to diffuse in three dimensions (3D). In this article, we present a general theory for the binding constants K2D and K3D of rather stiff proteins whose main degrees of freedom are translation and rotation, along membranes and around anchor points "in 2D," or unconstrained "in 3D." The theory generalizes previous results by describing how K2D depends both on the average separation and thermal nanoscale roughness of the apposing membranes, and on the length and anchoring flexibility of the receptors and ligands. Our theoretical results for the ratio K2D/K3D of the binding constants agree with detailed results from Monte Carlo simulations without any data fitting, which indicates that the theory captures the essential features of the "dimensionality reduction" due to membrane anchoring. In our Monte Carlo simulations, we consider a novel coarse-grained model of biomembrane adhesion in which the membranes are represented as discretized elastic surfaces, and the receptors and ligands as anchored molecules that diffuse continuously along the membranes and rotate at their anchor points. PMID:26723621

  6. Photodriven heterogeneous charge transfer with transition-metal compounds anchored to TiO2 semiconductor surfaces.

    PubMed

    Ardo, Shane; Meyer, Gerald J

    2009-01-01

    A critical review of light-driven interfacial charge-transfer reactions of transition-metal compounds anchored to mesoporous, nanocrystalline TiO2 (anatase) thin films is described. The review highlights molecular insights into metal-to-ligand charge transfer (MLCT) excited states, mechanisms of interfacial charge separation, inter- and intra-molecular electron transfer, and interfacial charge-recombination processes that have been garnered through various spectroscopic and electrochemical techniques. The relevance of these processes to optimization of solar-energy-conversion efficiencies is discussed (483 references). PMID:19088971

  7. Advanced Organic Ligands for Protecting Metal Nanoparticles

    NASA Astrophysics Data System (ADS)

    Yu, Jonathan Ka-Wing

    Organic monolayer protected metal nanoparticles have been utilized in many different fields such as catalysis, drug delivery, and sensor chemistry. However, these nanomaterials are prone to increase in size consequently losing its function at the nanoscale. The stability these nanoparticles have been a great interest of research. This thesis focuses on the synthesis of a novel cross-linkable ligand for the protection of metal nanoparticles. Chapter 1 reviews key concepts of nanoparticles, its usefulness in applications, some of the stabilizing strategies employed, and the scope of the thesis project. Chapter 2 describes the synthetic attempts and optimization of the novel cross-linkable ligand. In addition, its characterization data is also included. Section 2.8 also highlights another fully synthesized novel hydrophobic ligand. Chapter 3 contains the summary of the work and closing remarks. Future works is also included to describe the prospects of the synthesis of the novel ligand. Chapter 4 entails the experimental data and supplementary information.

  8. Ligand Intermediates in Metal-Catalyzed Reactions

    SciTech Connect

    Gladysz, John A.

    1999-07-31

    The longest-running goal of this project has been the synthesis, isolation, and physical chemical characterization of homogeneous transition metal complexes containing ligand types believed to be intermediates in the metal-catalyzed conversion of CO/H{sub 2}, CO{sub 2}, CH{sub 4}, and similar raw materials to organic fuels, feedstocks, etc. In the current project period, complexes that contain unusual new types of C{sub x}(carbide) and C{sub x}O{sub y} (carbon oxide) ligands have been emphasized. A new program in homogeneous fluorous phase catalysis has been launched as described in the final report.

  9. A comparison of bioabsorbable and metallic suture anchors in a dynamically loaded, intra-articular caprine model.

    PubMed

    Bottoni, Craig R; Brooks, Daniel E; DeBerardino, Thomas M; Owens, Brett D; Judson, Kurt L; Eggers, Jeffrey S; Mays, Mary Z

    2008-11-01

    Little is known about the in vivo behavior of bioabsorbable suture anchors. A goat model was used to biomechanically and histologically test bioabsorbable and metallic suture anchors in an intra-articular environment at 0, 6, and 12 weeks. Significantly greater force was required to break the bioabsorbable construct than the metallic construct at 0 and 6 weeks. Failure of the metallic anchor constructs occurred at the eyelet. Histological analysis of both bone-anchor interfaces demonstrated equally good osteointegration without evidence of osteolysis. The bioabsorbable suture anchor tested is safe for use in clinical practice without concerns for the strength of the construct or bony reaction to the material. PMID:19226088

  10. (Ligand intermediates in metal-catalyzed reactions)

    SciTech Connect

    Not Available

    1992-01-01

    This report consists of sections on sigma bond complexes of alkenes, a new carbon-hydrogen bond activation reaction of alkene complexes, carbon-hydrogen bond migrations in alkylidene complexes, carbon- hydrogen bond migrations in alkyne complexes, synthesis, structure and reactivity of C{sub x} complexes, synthesis and reactivity of alcohol and ether complexes, new catalysts for the epimerization of secondary alcohols; carbon-hydrogen bond activation in alkoxide complexes, pi/sigma equilibria in metal/O=CXX' complexes, and other hydrocarbon ligands; miscellaneous.(WET)

  11. COMPLICATIONS RESULTING FROM THE USE OF METAL ANCHORS IN SHOULDER ARTHROSCOPY

    PubMed Central

    Godinho, Glaydson Gomes; França, Flavio Oliveira; Alves Freitas, José Marcio; Aguiar, Paulo Nascimento; de Carvalho Leite, Marcelo

    2015-01-01

    To identify the complications concerning the use of metal anchors in shoulder arthroscopic procedures. Methods: 28 shoulders of 28 patients (23 male and 5 female) have been re-operated in the period between December 1997 and August 2007, at Hospital Ortopédico, Belo Horizonte Hospital and Military Police Hospital in Belo Horizonte, MG, as a result of complications such as loose anchors and prominent anchors. The primary surgeries intended to treat 20 anterior traumatic instabilities (71.5%), one posterior instability (3.5%), one slap injury (3.5%), six procedures for treating injuries on the rotator cuff (21.5%). We used the X-ray classification suggested by Samilson and Prieto and Outerbridge arthroscopic classification for assessing patients' degree of arthrosis. All patients were evaluated by the UCLA (University of California at Los Angeles) index criteria. Results: In all patients, arthroscopic reviews were made. In two cases, after anchors removal, clinical signs of instability were seen, leading to the decision of providing open stabilization by Latarjet-Patte technique. Conclusion: the complications with metallic-suture anchors result from inappropriate surgical techniques applied in arthroscopy.

  12. How to Compute Labile Metal-Ligand Equilibria

    ERIC Educational Resources Information Center

    de Levie, Robert

    2007-01-01

    The different methods used for computing labile metal-ligand complexes, which are suitable for an iterative computer solution, are illustrated. The ligand function has allowed students to relegate otherwise tedious iterations to a computer, while retaining complete control over what is calculated.

  13. Anchoring platinum on graphene using metallic adatoms: a first principles investigation

    NASA Astrophysics Data System (ADS)

    Sen, F. G.; Qi, Y.; Alpas, A. T.

    2012-06-01

    First principles calculations based on spin-polarized density functional theory were used to identify metallic adatoms that would strengthen the Pt(111)/graphene interface (with a low work of separation of 0.009 J m-2), when the adatom was placed between the Pt(111) and the graphene. It was shown that the strength of the Pt-adatom bond, which had a metallic character, increased with the amount of charge transferred from the adatom to the Pt. The carbon-adatom bond, on the other hand, had a mixed ionic and covalent character and was weaker than the Pt-adatom bond for each of the 25 elements considered. Consequently, the total Pt(111)/graphene interface strength and, hence, the anchoring effect of the adatom were controlled by the carbon-adatom bond strength. Metals with unfilled d orbitals increased the Pt/graphene interface strength to above 0.5 J m-2. The carbon-adatom bond strength was proportional to the ratio between the charge transferred from the adatom to the graphene (ΔZC) and the charge transferred to the Pt surface (ΔZPt) i.e., the ΔZC/ΔZPt ratio defined the ability of an adatom to anchor Pt to graphene. For Ir, Os, Ru, Rh and Re, ΔZC/ΔZPt > 1.0, making these elements the most effective adatoms for anchoring Pt to graphene.

  14. Ammonia formation by metal-ligand cooperative hydrogenolysis of a nitrido ligand

    NASA Astrophysics Data System (ADS)

    Askevold, Bjorn; Nieto, Jorge Torres; Tussupbayev, Samat; Diefenbach, Martin; Herdtweck, Eberhardt; Holthausen, Max C.; Schneider, Sven

    2011-07-01

    Bioinspired hydrogenation of N2 to ammonia at ambient conditions by stepwise nitrogen protonation/reduction with metal complexes in solution has experienced remarkable progress. In contrast, the highly desirable direct hydrogenation with H2 remains difficult. In analogy to the heterogeneously catalysed Haber-Bosch process, such a reaction is conceivable via metal-centred N2 splitting and unprecedented hydrogenolysis of the nitrido ligands to ammonia. We report the synthesis of a ruthenium(IV) nitrido complex. The high nucleophilicity of the nitrido ligand is demonstrated by unusual N-C coupling with π-acidic CO. Furthermore, the terminal nitrido ligand undergoes facile hydrogenolysis with H2 at ambient conditions to produce ammonia in high yield. Kinetic and quantum chemical examinations of this reaction suggest cooperative behaviour of a phosphorus-nitrogen-phosphorus pincer ligand in rate-determining heterolytic hydrogen splitting.

  15. Structure-assisted functional anchor implantation in robust metal-organic frameworks with ultralarge pores.

    PubMed

    Park, Jihye; Feng, Dawei; Zhou, Hong-Cai

    2015-02-01

    A facile functionalization assisted by the structural attributes of PCN-333 has been studied while maintaining the integrity of the parent MOF including ultralarge pores, chemical robustness, and crystallinity. Herein we thoroughly analyzed ligand exchange phenomena in PCN-333 and demonstrate that the extent of exchange can be tailored by varying the exchange conditions as potential applications may require. Through this method a variety of functional groups are incorporated into PCN-333. To further show the capabilities of this system introduction of a BODIPY fluorophore as a secondary functionality was performed to the functionalized framework via a click reaction. We anticipate the PCN-333 with functional anchor can serve as a stable platform for further chemistry to be explored in future applications. PMID:25581395

  16. Structure-Assisted Functional Anchor Implantation in Robust Metal-Organic Frameworks with Ultra large Pores

    SciTech Connect

    Park, J; Feng, DW; Zhou, HC

    2015-02-04

    A facile functionalization assisted by the structural attributes of PCN-333 has been studied while maintaining the integrity of the parent MOF including ultralarge pores, chemical robustness, and crystallinity. Herein we thoroughly analyzed ligand exchange phenomena in PCN-333 and demonstrate that the extent of exchange can be tailored by varying the exchange conditions as potential applications may require. Through this method a variety of functional groups are incorporated into PCN-333. To further show the capabilities of this system introduction of a BODIPY fluorophore as a secondary functionality was performed to the functionalized framework via a click reaction. We anticipate the PCN-333 with functional anchor can serve as a stable platform for further chemistry to be explored in future applications

  17. Chemodynamics of aquatic metal complexes: from small ligands to colloids.

    PubMed

    Van Leeuwen, Herman P; Buffle, Jacques

    2009-10-01

    Recent progress in understanding the formation/dissociation kinetics of aquatic metal complexes with complexants in different size ranges is evaluated and put in perspective, with suggestions for further studies. The elementary steps in the Eigen mechanism, i.e., diffusion and dehydration of the metal ion, are reviewed and further developed. The (de)protonation of both the ligand and the coordinating metal ion is reconsidered in terms of the consequences for dehydration rates and stabilities of the various outer-sphere complexes. In the nanoparticulate size range, special attention is given to the case of fulvic ligands, for which the impact of electrostatic interactions is especially large. In complexation with colloidal ligands (hard, soft, and combination thereof) the diffusive transport of metal ions is generally a slower step than in the case of complexation with small ligands in a homogeneous solution. The ensuing consequences for the chemodynamics of colloidal complexes are discussed in detail and placed in a generic framework, encompassing the complete range of ligand sizes. PMID:19848119

  18. Factors governing metal-ligand distances and coordination geometries of metal complexes.

    PubMed

    Kuppuraj, Gopi; Dudev, Minko; Lim, Carmay

    2009-03-01

    The metal-ligand (M-L) distances play a central role in determining the structure and reactivity of the metal complex and in metal discrimination in proteins. They reflect properties of the metal ion and the ligand during their coordination as well as the environment. However, the variation of the M-L distances as a function of the properties of the metal cation and its donor atoms had not been systematically analyzed, and no public website listing the M-L distances from metal complexes was available. Herein, the distances around 63 different types of metal ions in approximately 200,000 high-resolution crystal structures in the Cambridge Structural Database as well as their preferred coordination geometries have been determined. The dependence of these distances on (i) the donor atom's charge and charge-donating ability, (ii) the donor atom's size, (iii) the metal ion's oxidation state and charge-accepting ability, and (iv) the metal ion's size has also been determined. The concept of ligand coordination number (CN) was introduced to take into account the effect of the number of constituent ligand atoms on the M-L distances in addition to the number of metal-bound ligands. We propose grouping the M-L distances according to both the metal CN and the ligand CN. The mean M-L distance corresponding to a given metal CN and ligand CN was found to be linearly correlated with the metal's ionic radius in going down a main group or in going across the first three rows of the periodic table. The M-L distances as a function of the metal and ligand coordination numbers are available via http://bioit.ibms.sinica.edu.tw/CSD.htm PMID:19708219

  19. Anchored metal nanoparticles: effects of support and size on their energy, sintering resistance and reactivity.

    PubMed

    Campbell, Charles T; Sellers, Jason R V

    2013-01-01

    Many catalysts consist of metal nanoparticles anchored to the surfaces of oxide supports. These are key elements in technologies for the clean production and use of fuels and chemicals. We show here that the chemical reactivity of the surface metal atoms on these nanoparticles is closely related to their chemical potential: the higher their chemical potential, the more strongly they bond to small adsorbates. Controlling their chemical potential by tuning the structural details of the material can thus be used to tune their reactivity. As their chemical potential increases, this also makes the metal surface less noble, effectively pushing its behavior upwards and to the left in the periodic table. Also, when the metal atoms are in a nanoparticle with higher chemical potential, they experience a larger thermodynamic driving force to sinter. Calorimetric measurements of metal vapor adsorption energies onto clean oxide surfaces in ultrahigh vacuum show that the chemical potential increases with decreasing particle size below 6 nm, and, for a given size, decreases with the adhesion energy between the metal and its support, Eadh. The structural factors that control the metal/oxide adhesion energy are thus also keys for tuning catalytic performance. For a given oxide, Eadh increases with (deltaHsub,M--deltaHf,MOx)/OmegaM2/3 for the metal, where deltaHsub,M is its heat of sublimation, deltaHf,MOx is the standard heat of formation of that metal's most stable oxide (per mole of metal), and OmegaM is the atomic volume of the bulk solid metal. The value deltaHsub,M--deltaHf,MOx equals the heat of formation of that metal's oxide from a gaseous metal atom plus O2(g), so it reflects the strength of the chemical bonds which that metal atom can make to oxygen, and OmegaM2/3 simply normalizes this energy to the area per metal atom, since Eadh is the adhesion energy per unit area. For a given metal, Eadh to different clean oxide surfaces increases as: MgO(100) approximately TiO2(110) < or = alpha-Al2O3(0001) < CeO2-x(111) < or = Fe3O4(111). Oxygen vacancies also increase Eadh, but surface hydroxyl groups appear to decrease Eadh, even though they increase the initial heat of metal adsorption. PMID:24015573

  20. Biobased thioethers as metal-absorbing ligands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vegetable oils have been reacted with thiols (mercaptans) to form biobased thioether-functionalized vegetable oils (TFVO). TFVO were efficient in the extraction of a model heavy-metal ion (Ag+) from an aqueous solution. TFVO, prepared from corn oil, was capable of reducing Ag+ concentration from 600...

  1. Surface anchored metal-organic frameworks as stimulus responsive antifouling coatings.

    PubMed

    Sancet, Maria Pilar Arpa; Hanke, Maximilian; Wang, Zhengbang; Bauer, Stella; Azucena, Carlos; Arslan, Hasan K; Heinle, Marita; Gliemann, Hartmut; Wöll, Christof; Rosenhahn, Axel

    2013-12-01

    Surface-anchored, crystalline and oriented metal organic frameworks (SURMOFs) have huge potential for biological applications due to their well-defined and highly-porous structure. In this work we describe a MOF-based, fully autonomous system, which combines sensing, a specific response, and the release of an antimicrobial agent. The Cu-containing SURMOF, Cu-SURMOF 2, is stable in artificial seawater and shows stimulus-responsive anti-fouling properties against marine bacteria. When Cobetia marina adheres on the SURMOF, the framework's response is lethal to the adhering microorganism. A thorough analysis reveals that this response is induced by agents secreted from the microbes after adhesion to the substrate, and includes a release of Cu ions resulting from a degradation of the SURMOF. The stimulus-responsive antifouling effect of Cu-SURMOF 2 demonstrates the first application of Cu-SURMOF 2 as autonomous system with great potential for further microbiological and cell culture applications. PMID:24706148

  2. Synthesis and NMR characterization of ligand-capped metal and metal-oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Sharma, Ramesh

    Ligand-capped metal and metal-oxide nanoparticles (NPs) have some interesting and useful physical properties that are not present in their respective bulk materials. These properties are of research interest in many applications such as catalysis, drug delivery, biological imaging, and plasmonics. In such applications, it is critical to understand the surface structure of NPs and the roles played by the surface bound ligands. To characterize surface environment, ligand dynamics, and exchange kinetics, ligand-capped metal and metal-oxide NPs are synthesized and studied by multinuclear NMR. Phosphines and phosphonic acids are used to passivate metal (gold and silver) and metal-oxide (tin dioxide) NPs in different sizes (1-5 nm) by following published procedures or original synthesis methods. In both solution and solid state NMR, the 31P chemical shift of surface-bound ligands are distinctly different from those observed for free ligands. Additionally, NMR line widths in surface-bound ligands are highly broadened compared to those of free ligands. The lines are broadened due to both homogeneous and inhomogeneous broadening mechanisms, determined through hole burning NMR and spin-spin relaxation measurements. In small particles (< 2 nm), the main source of line broadening is inhomogeneous and originates due to structural heterogeneity and underlying chemical shift distributions. In large particles (> 2 nm), both inhomogeneous and homogeneous line broadening mechanisms are present. When the particles' sizes increase from small to large, the homogeneous broadening mechanism becomes dominant due to strong nuclear-electron interaction and reintroduction of residual dipolar coupling as shown by a combination of 1H, 13C and 31P NMR. Results from a series of ligand exchange experiments in silver and gold NPs further indicate the presence of Au(I) and Ag(I) on the particle surfaces.

  3. Zwitterionic Group VIII transition metal initiators supported by olefin ligands

    DOEpatents

    Bazan, Guillermo C.; Chen, Yaofeng

    2011-10-25

    A zwitterionic Group VIII transition metal complex containing the simple and relatively small 3-(arylimino)-but-1-en-2-olato ligand that catalyzes the formation of polypropylene and high molecular weight polyethylene. A novel feature of this catalyst is that the active species is stabilized by a chelated olefin adduct. The present invention also provides methods of polymerizing olefin monomers using zwitterionic catalysts, particularly polypropylene and high molecular weight polyethylene.

  4. Electrophilic Metal Alkyl Chemistry in New Ligand Environments

    SciTech Connect

    Jordan, Richard F. University of Chicago

    2013-06-30

    The goals of this project were to design new electrophilic metal alkyl complexes and to exploit these systems in fundamental studies of olefin polymerization and other important and new catalytic reactions. A key target reaction is insertion copolymerization of olefins and polar CH2=CHX vinyl monomers such as vinyl halides and vinyl ethers. During the period covered by this report we (i) investigated the properties of ortho-alkoxy-arylphosphine ligands in Ni-based olefin polymerization catalysts, (ii) studied the synthesis of double-end-capped polyethylene using group 4 metal catalysts that contain tris-pyrazolylborate ligands, (iii) explored the ethylene insertion reactivity of group 4 metal tris-pyrazolyl-borate complexes, (iv) showed that (α-diimine)PdMe{sup +} species undergo multiple insertion of silyl vinyl ethers, (v) synthesized and explored the reactivity of base-free Ni benzyl complexes that contain ortho-phosphino-arene sulfonate ligands, (vi) established the mechanism of the reaction of vinyl chloride with (α-diimine)PdMe{sup +} catalysts, (vii) explored the role of cationic polymerization and insertion chemistry in the reactions of vinyl ethers with (α-diimine)PdMe{sup +} species, (viii) discovered a new class of self-assembled tetranuclear Pd catalysts that produce high molecular weight linear polyethylene and copolymerize ethylene and vinyl fluoride, and (ix) developed model systems that enabled investigation of cis-trans isomerization of {phosphine-sulfonate}Pd(II) complexes.

  5. Metal speciation dynamics in monodisperse soft colloidal ligand suspensions.

    PubMed

    Duval, Jérôme F L; Pinheiro, José P; van Leeuwen, Herman P

    2008-08-01

    A comprehensive theory is presented for the dynamics of metal speciation in monodisperse suspensions of soft spherical particles characterized by a hard core and an ion-permeable shell layer where ligands L are localized. The heterogeneity in the binding site distribution leads to complex formation/dissociation rate constants (denoted as k a (*) and k d (*), respectively) that may substantially differ from their homogeneous solution counterparts (k a and k d). The peculiarities of metal speciation dynamics in soft colloidal ligand dispersions result from the coupling between diffusive transport of free-metal ions M within and around the soft surface layer and the kinetics of ML complex formation/dissociation within the shell component of the particle. The relationship between k a,d (*) and k a,d is derived from the numerical evaluation of the spatial, time-dependent distributions of free and bound metal. For that purpose, the corresponding diffusion equations corrected by the appropriate chemical source term are solved in spherical geometry using a Kuwabara-cell-type representation where the intercellular distance is determined by the volume fraction of soft particles. The numerical study is supported by analytical approaches valid in the short time domain. For dilute dispersions of soft ligand particles, it is shown that the balance between free-metal diffusion within and outside of the shell and the kinetic conversion of M into ML within the particular soft surface layer rapidly establishes a quasi-steady-state regime. For sufficiently long time, chemical equilibrium between the free and bound metal is reached within the reactive particle layer, which corresponds to the true steady-state regime for the system investigated. The analysis reported covers the limiting cases of rigid particles where binding sites are located at the very surface of the particle core (e.g., functionalized latex colloids) and polymeric particles that are devoid of a hard core (e.g., polysaccharide macromolecules, gel particles). For both the transient and quasi-steady-state regimes, the dependence of k a,d (*) on the thickness of the soft surface layer, the radius of the hard core of the particle, and the kinetic rate constants k a,d for homogeneous ligand solutions is thoroughly discussed within the context of dynamic features for colloidal complex systems. PMID:18636700

  6. Reactivity of halide and pseudohalide ligands in transition-metal complexes

    SciTech Connect

    Kukushkin, Yu.N.; Kukushkin, V.Yu.

    1985-10-01

    The experimental material on the reactions of coordinated halide ligands, as well as cyanide, azido, thiocyanato, and cyanato ligands, in transition-metal complexes has been generalized in this review.

  7. The emerging role of calcium-modulating cyclophilin ligand in posttranslational insertion of tail-anchored proteins into the endoplasmic reticulum membrane.

    PubMed

    Yamamoto, Yasunori; Sakisaka, Toshiaki

    2015-06-01

    Tail-anchored (TA) proteins, a class of membrane proteins having an N-terminal cytoplasmic region anchored to the membrane by a single C-terminal transmembrane domain, are posttranslationally inserted into the endoplasmic reticulum (ER) membrane. In yeasts, the posttranslational membrane insertion is mediated by the Guided Entry of TA Proteins (GET) complex. Get3, a cytosolic ATPase, targets newly synthesized TA proteins to the ER membrane, where Get2 and Get3 constitute the Get3 receptor driving the membrane insertion. While mammalian cells employ TRC40 and WRB, mammalian homologs of Get3 and Get1, respectively, they lack the gene homologous to Get2. We recently identified calcium-modulating cyclophilin ligand (CAML) as a TRC40 receptor, indicating that CAML was equivalent to Get2 in the context of the membrane insertion. On the other hand, CAML has been well characterized as a signaling molecule that regulates various biological processes, raising the question of how the two distinct actions of CAML, the membrane insertion and the signal transduction, are assembled. In this review, we summarize recent progress of the molecular mechanism of the membrane insertion of TA proteins and discuss the possibility that CAML could sense the various signals at the ER membrane, thereby controlling TA protein biogenesis. PMID:25869254

  8. Mixed-Ligand Approach to Changing the Metal Ratio in Bismuth-Transition Metal Heterometallic Precursors.

    PubMed

    Lieberman, Craig M; Wei, Zheng; Filatov, Alexander S; Dikarev, Evgeny V

    2016-04-18

    A new series of heteroleptic bismuth-transition metal β-diketonates [BiM(hfac)3(thd)2] (M = Mn (1), Co (2), and Ni (3); hfac = hexafluoroacetylacetonate, thd = tetramethylheptanedionate) with Bi:M = 1:1 ratio have been synthesized by stoichiometric reactions between homometallic reagents [Bi(III)(hfac)3] and [M(II)(thd)2]. On the basis of analysis of the metal-ligand interactions in heterometallic structures, the title compounds were formulated as ion-pair {[Bi(III)(thd)2](+)[M(II)(hfac)3](-)} complexes. The direct reaction between homometallic reagents proceeds with a full ligand exchange between main group and transition metal centers, yielding dinuclear heterometallic molecules. In heteroleptic molecules 1-3, the Lewis acidic, coordinatively unsaturated Bi(III) centers are chelated by two bulky, electron-donating thd ligands and maintain bridging interactions with three oxygen atoms of small, electron-withdrawing hfac groups that chelate the neighboring divalent transition metals. Application of the mixed-ligand approach allows one to change the connectivity pattern within the heterometallic assembly and to isolate highly volatile precursors with the proper Bi:M = 1:1 ratio. The mixed-ligand approach employed in this work opens broad opportunities for the synthesis of heterometallic (main group-transition metal) molecular precursors with specific M:M' ratio in the case when homoleptic counterparts either do not exist or afford products with an incorrect metal:metal ratio for the target materials. Heteroleptic complexes obtained in the course of this study represent prospective single-source precursors for the low-temperature preparation of multiferroic perovskite-type oxides. PMID:27054922

  9. Positional isomerism makes a difference: phosphonic acid anchoring ligands with thienyl spacers in copper(i)-based dye-sensitized solar cells.

    PubMed

    Klein, Y Maximilian; Willgert, Markus; Prescimone, Alessandro; Constable, Edwin C; Housecroft, Catherine E

    2016-03-21

    With the aim of improving the photoconversion efficiencies of heteroleptic [Cu(Lanchor)(Lancillary)](+) dyes in n-type dye-sensitized solar cells (DSCs), the previously favoured anchor ((6,6'-dimethyl-[2,2'-bipyridine]-4,4'-diyl)bis(4,1-phenylene))bis(phosphonic acid) (1) has been replaced by analogues 2 and 3 containing 2-thienyl spacers between the 2,2'-bipyridine metal-binding domain and the phosphonic acid anchoring groups. The synthesis and characterization of 2 and 3 (2-thienyl spacer with phosphonic acid in the 5- and 4-positions, respectively) are reported. A stepwise, on-surface method was used to assemble [Cu(Lanchor)(Lancillary)](+) dyes onto FTO/TiO2 electrodes with Lanchor = 1, 2 or 3, and Lancillary = 6,6'-bis(trifluoromethyl)-2,2'-bipyridine (4), 6-trifluoromethyl-2,2'-bipyridine (5), 6,6'-dimethyl-2,2'-bipyridine (6), and 6-methyl-2,2'-bipyridine (7). Changing the solvent in the dye-bath from CH2Cl2 to acetone had only a small effect on the photoconversion efficiencies of [Cu(1)(4)](+), [Cu(1)(5)](+) and [Cu(1)(6)](+); the optimal dye in this series was [Cu(1)(5)](+). Comparable DSC performances were achieved by using either anchor 1 or 2, but there is improved electron injection if the phosphonic acid group is in the 4- rather than 5-position of the thienyl ring (i.e. anchor 3 is superior to 2). Similar open-circuit voltages (VOC) are achieved on going from 1 to 3 with a given Lancillary; although there is typically a gain in short-circuit current denisty (JSC) on going from 1 or 3 to 2, there is an ≈50-60 mV drop in VOC on introducing 2 as the anchor. The best photoconversion efficiencies are obtained for the dye [Cu(3)(5)](+) (η = 2.40% relative to an N719 reference of 5.76%). The conclusions reached from plots of current-density (J) against potential (V), and external quantum efficiency spectra are supported by electrochemical impedance spectroscopic measurements. PMID:26856366

  10. The Study Of The Successive Metal-Ligand Binding Energies For Fe+, Fe-, V+ and Co+

    NASA Technical Reports Server (NTRS)

    Bauschicher, Charles W., Jr.; Ricca, Alessandra; Maitre, Philippe; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    The successive binding energies of CO and H2O to Fe(+), CO to Fe(-), and H2 to Co(+) and V(+) are presented. Overall the computed results are in good agreement with experiment. The trends in binding energies are analyzed in terms of metal to ligand donation, ligand to metal donation, ligand-ligand repulsion, and changes in the metal atom, such as hybridization, promotion, and spin multiplicity. The geometry and vibrational frequencies are also shown to be directly affected by these effects.

  11. The Study of the Successive Metal-ligand Binding Energies for Fe(+), Fe(-), V(+) and Co(+)

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Ricca, Alessandra; Maitre, Philippe; Langhoff, Stephen R. (Technical Monitor)

    1994-01-01

    The successive binding energies of CO and H2O to Fe(+), CO to Fe(-), and H2 to Co(+) and V(+) are presented. Overall the computed results are in good agreement with experiment. The trends in binding energies are analyzed in terms of metal to ligand donation, ligand to metal donation, ligand-ligand repulsion, and changes in the metal atom, such as hybridization, promotion, and spin multiplicity. The geometry and vibrational frequencies are also shown to be directly affected by these effects.

  12. New possible mode of ligand-metal cooperation in PC(sp3)P pincer complexes.

    PubMed

    Musa, Sanaa; Romm, Ronit; Azerraf, Clarite; Kozuch, Sebastian; Gelman, Dmitri

    2011-09-21

    Ligand-metal cooperation in iridium and platinum complexes bearing tricyclic dibenzobarrelene-based PC(sp(3))P pincer ligands is discussed. We demonstrated that the carbon-metal bond in these complexes may be efficiently cleaved and regenerated via 1,2-addition/elimination reactions. PMID:21431178

  13. Eugenic metal-free sensitizers with double anchors for high performance dye-sensitized solar cells.

    PubMed

    Hung, Wei-I; Liao, You-Ya; Lee, Ting-Hui; Ting, Yu-Chien; Ni, Jen-Shyang; Kao, Wei-Siang; Lin, Jiann T; Wei, Tzu-Chien; Yen, Yung-Sheng

    2015-02-01

    A series of new phenothiazine-based dyes (HL5-HL7) with double acceptors/anchors have been synthesized and used as the sensitizers for highly efficient dye-sensitized solar cells (DSSCs). Among them, the HL7-based cell exhibits the best efficiency of 8.32% exceeding the N719-based cell (7.35%) by ∼13%. PMID:25555237

  14. Phthalocyaninato complexes with peripheral alkylthio chains: disk-like adsorbate species for the vertical anchoring of ligands on gold surfaces

    PubMed Central

    Siemeling, Ulrich; Schirrmacher, Christian; Glebe, Ulrich; Bruhn, Clemens; Baio, Joe E.; Árnadóttir, Líney; Castner, David G.; Weidner, Tobias

    2011-01-01

    Thin metalorganic films were prepared on gold by self-assembly of thioether-functionalised phthalocyaninato complexes from solution. The phthalocyaninato ligands used contain eight peripheral, β-positioned, alkylthio substituents SR (1a: R = n-C8H17, 1b: R = n-C12H25), which serve as headgroups for surface binding and promote lateral assembly, while the disk-like phthalocyaninato core offers the scope for the attachment of axial ligands to the adsorbed molecules. This process was mimicked by coordination of pyridine (Py) to [Zn(1a)] and [Zn(1b)], respectively. The crystal structures of the products [Zn(1a)(Py)] and [Zn(1b)(Py)] were determined. The crystal structures of 4,5-bis(octylthio)phthalodinitrile and 4,5-bis(dodecylthio)phthalodinitrile were also determined. The films fabricated from [Mn(1a)Cl] and [Mn(1b)Cl] on gold were characterised by XPS, ToF-SIMS and NEXAFS spectroscopy, which revealed the presence of well-defined and homogeneous self-assembled monolayers (SAMs), whose constituents are bound to the substrate by thioether–gold linkages. The orientation of the macrocycles is predominantly parallel to the surface. Strong electronic interaction of the manganese(III) centre with the substrate leads to Cl loss upon adsorption and its reduction to MnII. PMID:21857743

  15. The role of metal ion-ligand interactions during divalent metal ion adsorption.

    PubMed

    Eldridge, Daniel S; Crawford, Russell J; Harding, Ian H

    2015-09-15

    A suite of seven different divalent metal ions (Ca(II), Cd(II), Cu(II), Mg(II), Ni(II), Pb(II), Zn(II)) was adsorbed from solution onto two Fe2O3 samples, quartz SiO2 and three different amphoteric polystyrene latices (containing amine and carboxyl functional groups). For the metal oxides, a high correlation was observed between the pH at which 50% of the metal was removed from solution (pH50) and the first hydrolysis constant for the metal ion (pK1). For the polystyrene latices, a much higher correlation was observed between the pH50 and pKc (equilibrium constant describing metal-carboxyl affinity) as opposed to pK1. These observations provide evidence of a strong relationship that exists between a metal's affinity for a particular ligand in solution and for that metal ion's affinity for the same ligand present as part of an adsorbing surface. The isoelectric point of the amphoteric latex surface can be increased by decreasing the carboxyl content of the latex surface. For all 7 metal ions, this resulted in a substantial decrease, for any given pH, in adsorption. We suggest that this may be partly due to the decreased carboxyl content, but is dominantly attributable to the presence of less favorable electrostatic conditions. This, in turn, demonstrates that electrostatics play a controlling role in metal ion adsorption onto amphoteric latex surfaces and, in addition to the nature of the metal ion, also controls the pH at which adsorption takes place. PMID:26001134

  16. Evaluation of Metal-Mediated DNA Binding of Benzoazole Ligands by Electrospray Ionization Mass Spectrometry

    PubMed Central

    Mazzitelli, Carolyn L.; Rodriguez, Mireya; Kerwin, Sean; Brodbelt, Jennifer S.

    2008-01-01

    The binding of a series of benzoxazole analogs with different amide- and ester-linked side chains to duplex DNA in the absence and presence of divalent metal cations is examined. All ligands were found to form complexes with Ni2+, Cu2+, and Zn2+, with 2:1 ligand/metal cation binding stoichiometries dominating for ligands containing shorter side chains (2, 6, 7, and 8), while 1:1 complexes were the most abundant for ligands with long side chains (9, 10 and 11). Ligand binding with duplex DNA in the absence of metal cations was assessed, and the long side-chain ligands were found to form low abundance complexes with 1:1 ligand/DNA binding stoichiometries. The ligands with the shorter side chains only formed DNA complexes in the presence of metal cations, most notably for 7 and 8 binding to DNA in the presence of Cu2+. The binding of long side-chain ligands was enhanced by Cu2+ and to a lesser degree by Ni2+ and Zn2+. The cytotoxicities of all of the ligands against the A549 lung cancer and MCF7 breast cancer cell lines were also examined. The ligands exhibiting the most dramatic metal-enhanced DNA binding also demonstrated the greatest cytotoxic activity. Both 7 and 8 were found to be the most cytotoxic against the A549 lung cancer cell line and 8 demonstrated moderate cytotoxicity against MCF7 breast cancer cells. Metal ions also enhanced the DNA binding of the ligands with the long side-chains, especially for 9, which also exhibited the highest level of cytotoxicity of the long side-chain compounds. PMID:17583529

  17. New Proton-Ionizable, Calixarene-Based Ligands for Selective Metal Ion Separations

    SciTech Connect

    Bartsch, Richard A.

    2012-06-04

    The project objective was the discovery of new ligands for performing metal ion separations. The research effort entailed the preparation of new metal ion complexing agents and polymers and their evaluation in metal ion separation processes of solvent extraction, synthetic liquid membrane transport, and sorption. Structural variations in acyclic, cyclic, and bicyclic organic ligands were used to probe their influence upon the efficiency and selectivity with which metal ion separations can be performed. A unifying feature of the ligand structures is the presence of one (or more) side arm with a pendent acidic function. When a metal ion is complexed within the central cavity of the ligand, ionization of the side arm(s) produces the requisite anion(s) for formation of an overall electroneutral complex. This markedly enhances extraction/transport efficiency for separations in which movement of aqueous phase anions of chloride, nitrate, or sulfate into an organic medium would be required. Through systematic structural variations, new ligands have been developed for efficient and selective separations of monovalent metal ions (e.g., alkali metal, silver, and thallium cations) and of divalent metal ion species (e.g., alkaline earth metal, lead, and mercury cations). Research results obtained in these fundamental investigations provide important insight for the design and development of ligands suitable for practical metal ion separation applications.

  18. Carbene-anchored/pendent-imidazolium species as precursors to di-N-heterocyclic carbene-bridged mixed-metal complexes.

    PubMed

    Zamora, Matthew T; Ferguson, Michael J; McDonald, Robert; Cowie, Martin

    2009-09-21

    Reaction of a series of linked diimidazolium dibromide salts with one-half equivalent of [Rh(mu-OAc)(COD)](2) under reflux conditions generates a series of carbene-anchored/pendent-imidazolium complexes, [RhBr(COD)((R)C(H)-eta(1)-C(eth))][Br] ((Me)C(H)-eta(1)-C(eth) = ethylene[(N-methyl)imidazolium][(N-methyl)imidazole-2-ylidene] and (tBu)C(H)-eta(1)-C(eth) = ethylene[(N-tert-butyl)imidazolium][(N-tert-butyl)imidazole-2-ylidene]) via deprotonation of one end of the diimidazolium salt and coordination of the resulting carbene to Rh. Reaction of these complexes with carbon monoxide or the appropriate diphosphine yields either [RhBr(CO)(2)((R)C(H)-eta(1)-C(eth))][Br] (R = Me, (t)Bu) or [RhBr(P( intersection)P)((Me)C(H)-eta(1)-C(eth))][Br] (P( intersection)P = Ph(2)PCH(2)PPh(2), Ph(2)PCH(2)CH(2)PPh(2), Et(2)PCH(2)PEt(2)), respectively. The resulting diphosphine complexes readily decompose in solution. A series of palladium complexes [PdI(3-n)(PR(3))(n)(L)][I](n) (n = 1,2) and [PdI(P( intersection)P)(L)][I](2) (L = (tBu)C(H)-eta(1)-C(meth), (tBu)C(H)-eta(1)-C(eth); (tBu)C(H)-eta(1)-C(meth) = methylene[(N-tert-butyl)imidazolium][(N-tert-butyl)imidazole-2-ylidene]), containing the linked NHC-imidazolium moiety, have also been prepared by reacting the triiodo complexes, [PdI(3)((tBu)C(H)-eta(1)-C(meth))] and [PdI(3)((tBu)C(H)-eta(1)-C(eth))] with several mono- and diphosphines. Attempts to generate mixed Rh/Pd complexes using Pd(OAc)(2) to deprotonate the pendent arm of several of the above carbene-anchored/pendent-imidazolium complexes of Rh have proven unsuccessful. However, a targeted di-NHC-bridged heterobimetallic complex [PdI(2)(PEt(3))(mu-(tBu)CC(meth))RhI(COD)] ((tBu) CC(meth) = 1,1'-methylene-3,3'-di-tert-butyldiimidazol-2,2'-diylidene) can be generated by deprotonation of the imidazolium group in [PdI(2)(PEt(3))((tBu)C(H)-eta(1)-C(meth))][I] using half an equivalent of [Rh(mu-OAc)(COD)](2). The X-ray structure determination of this Pd/Rh complex confirms the dicarbene-bridged formulation and shows a metal-metal separation of approximately 6.2 A. Reaction of this Rh/Pd complex with CO yields the corresponding dicarbonyl product [PdI(2)(PEt(3))(mu-(tBu)CC(meth))RhI(CO)(2)] via replacement of the COD ligand. The related dicarbene-bridged Ir/Rh complex [IrBr(COD)(mu-(tBu)CC(meth))RhBr(COD)] can be generated by reaction of [IrBr(COD)((tBu)C(H)-eta(1)-C(meth) )][Br] with [Rh(mu-OAc)(COD)](2), while the Pd/Ir complexes [PdI(2)(PR(3))(mu-(tBu)CC(meth))IrI(COD)] (PR(3) = PPh(3), PMe(2)Ph) can be generated by reaction of the monometallic [PdI(2)(PR(3))((tBu)C(H)-eta(1)-C(meth))][I] species with K[N(SiMe(3))(2)] in the presence of [Ir(mu-Cl)(COD)](2). The carbonyl analogues, [PdI(2)(PR(3))(mu-(tBu)CC(meth))IrI(CO)(2)], can be generated via a gentle purge of CO gas. These di-NHC-bridged heterobimetallic species represent some of the first examples of this class and are the first involving palladium. PMID:20449172

  19. Sustainable metal alkynyl chemistry: 3d metals and polyaza macrocyclic ligands.

    PubMed

    Ren, Tong

    2016-02-16

    We describe the chemistry of 3d metal alkynyls based on polyaza macrocyclic ligands, an emerging area of alkynyl chemistry that has previously been dominated by 4d and 5d metals with soft ligands. The abundance of 3d metals and low cost of tetraazacyclotetradecane ligands make these compounds more affordable, sustainable alternatives to metal alkynyls based on precious metals. Taking advantage of the rich variety of starting materials available in the literature, trans-[M(cyclam)(C2R)2]X (cyclam = 1,4,8,11-tetraazacyclotetradecane) compounds have been prepared from the reactions between [M(cyclam)X2]X (M = Cr, Fe and Co; X = Cl or OTf) and LiC2R. With [Co(cyclam)Cl2](+), both the {trans-[Co(cyclam)Cl]2(μ-(C[triple bond, length as m-dash]C)n)}(2+) and trans-[Co(cyclam)(C2R)Cl](+) compounds have been prepared by a dehydrohalogenation reaction. The latter compounds undergo the second alkynylation reaction to afford dissymmetric trans-[Co(cyclam)(C2R)(C2R')](+) compounds. Similar alkynylation chemistry with complexes of the cyclam derivatives TMC (1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) and HMC (5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) has been demonstrated in studies of [Ni(TMC)(C2R)](+) and trans-/cis-[Cr(HMC)(C2R)2](+). Me3TACN (1,4,7-N,N',N''-trimethyl-1,4,7-triazacyclononane) is also a supporting ligand that has been observed in transition metal alkynyls. The trans-[M(cyclam)(C2D)(C2A)](+) compounds (D = donor chromophore, A = acceptor chromophore) are excellent candidates for probing photoinduced electron transfer and related photophysical and photochemical processes. 3d Metal ions are often in high-spin ground states, which make these alkynyl compounds promising building blocks for magnetic materials. PMID:26779578

  20. Antimicrobial Activity of Metal & Metal Oxide Nanoparticles Interfaced With Ligand Complexes Of 8-Hydroxyquinoline And α-Amino Acids

    NASA Astrophysics Data System (ADS)

    Bhanjana, Gaurav; Kumar, Neeraj; Thakur, Rajesh; Dilbaghi, Neeraj; Kumar, Sandeep

    2011-12-01

    Antimicrobial nanotechnology is a recent addition to the fight against disease causing organisms, replacing heavy metals and toxins. In the present work, mixed ligand complexes of metals like zinc, silver etc. and metal oxide have been synthesized using 8-hydroxyquinoline (HQ) as a primary ligand and N-and/O-donor amino acids such as L-serine, L-alanine, glycine, cysteine and histidine as secondary ligands. These complexes were characterized using different spectroscopic techniques. The complexes were tested for antifungal and antibacterial activity by using agar well diffusion bioassay.

  1. 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+.

  2. Dinuclear first-row transition metal complexes with a naphthyridine-based dinucleating ligand.

    PubMed

    Davenport, T C; Tilley, T D

    2015-07-21

    A series of dinuclear and tetranuclear first-row transition metal complexes were synthesized with the dinucleating ligand 2,7-bis(di(2-pyridyl)fluoromethyl)-1,8-naphthyridine (DPFN). The coordination pocket and rigidity of the DPFN ligand enforces pseudo-octahedral geometries about the metal centers that contain chloro, hydroxo, and aqua bridging ligands forming a "diamond" shaped configuration with metal-metal distances varying from 2.7826(5) to 3.2410(11) Å. Each metal center in the dinuclear complexes has an additional open coordination site that accommodates terminal ligands in a syn geometry of particular interest in catalyst design. The complexes are characterized by electronic spectroscopy, electrochemistry and potentiometric titration methods. PMID:25420206

  3. First examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands

    SciTech Connect

    Wang Lamei; Fan Yong; Wang Yan; Xiao Lina; Hu Yangyang; Peng Yu; Wang Tiegang; Gao Zhongmin; Zheng Dafang; Cui Xiaobing; Xu Jiqing

    2012-07-15

    Two new organic-inorganic compounds based on polyoxometalates, metal halide clusters and organic ligands: [BW{sub 12}O{sub 40}]{sub 2}[Cu{sub 2}(Phen){sub 4}Cl](H{sub 2}4, 4 Prime -bpy){sub 4}{center_dot}H{sub 3}O{center_dot}5H{sub 2}O (1) and [HPW{sub 12}O{sub 40}][Cd{sub 2}(Phen){sub 4}Cl{sub 2}](4, 4 Prime -bpy) (2) (Phen=1, 10-phenanthroline, bpy=bipyridine), have been prepared and characterized by IR, UV-vis, XPS, XRD and single crystal X-ray diffraction analyses. Crystal structure analyses reveal that compound 1 is constructed from [BW{sub 12}O{sub 40}]{sup 5-}, metal halide clusters [Cu{sub 2}(Phen){sub 4}Cl]{sup +}and 4, 4 Prime -bpy ligands, while compound 2 is constructed from [PW{sub 12}O{sub 40}]{sup 3-}, metal halide cluster [Cd{sub 2}(Phen){sub 4}Cl{sub 2}]{sup 2+} and 4, 4 Prime -bpy ligands. Compound 1 and compound 2 are not common hybrids based on polyoxometalates and metal halide clusters, they also contain dissociated organic ligands, therefore, compound 1 and 2 are the first examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands. - Graphical Abstract: Two new compounds have been synthesized and characterized. Structure analyses revealed that the two compounds are the first examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands. Highlights: Black-Right-Pointing-Pointer First examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands. Black-Right-Pointing-Pointer Two different kinds of metal halide clusters. Black-Right-Pointing-Pointer Supramolecular structures based on polyoxometalates, metal halide clusters and organic ligands. Black-Right-Pointing-Pointer Hybridization of three different of building blocks.

  4. Transformations of metal species in ageing humic hydrocolloids studied by competitive ligand and metal exchange.

    PubMed

    Burba, Peter; Van den Bergh, Johan

    2004-03-01

    Transformations of metal species (particularly Al, Ca, Fe, Mg, Mn, Zn) in ageing humic hydrocolloids were studied, applying a competitive ligand and metal exchange approach. For this purpose, metal-containing hydrocolloids, freshly collected from humic-rich German bog lake waters (Hohlohsee (HO), Black Forest; Venner Moor (VM), Muensterland; Arnsberger Wald (AW), Northrhine-Westfalia) and conventionally pre-filtered through 0.45 microm membranes, were subjected on-site to an exchange with EDTA and Cu(II) ions, respectively, as a function of time. EDTA complexes gradually formed, metal fractions exchanged by Cu(II) (as well as free Cu(II) concentrations) were operationally discriminated by means of a small time-controlled tangential-flow ultrafiltration unit (nominal cutoff: 1 kDa). Metal and DOM (dissolved organic matter) fractions obtained this way were determined off-site using instrumental methods (AAS, ICP-OES, carbon analyzer). After weeks of storage, the collected hydrocolloids were studied again by this approach. The EDTA availability of colloid-bound metals (particularly Al and Fe) exhibited different ageing trends, dependent on the sample (VM: decrease of Fe availability (98-76%), HO: increase of Fe availability (76-82%)). In contrast, the Cu(II) exchange equilibria of colloid-bound metals revealed merely low availability of Al (16-38%) and Fe (5-11%) towards Cu(II) ions, also dependent on ageing effects. In particular, the conditional copper exchange constants Kex obtained from the exchange between Cu(II) ions and available metal species (such as Ca, Mg, Mn, Zn) exhibited a strong decrease (by a factor of 2-100) during sample storage, indicating considerable non-equilibria complexation of these metal ions in the original bogwaters studied on-site. PMID:15214428

  5. Conformational diversity of flexible ligand in metal-organic frameworks controlled by size-matching mixed ligands

    NASA Astrophysics Data System (ADS)

    Hua, Xiu-Ni; Qin, Lan; Yan, Xiao-Zhi; Yu, Lei; Xie, Yi-Xin; Han, Lei

    2015-12-01

    Hydrothermal reactions of N-auxiliary flexible exo-bidentate ligand 1,3-bis(4-pyridyl)propane (bpp) and carboxylates ligands naphthalene-2,6-dicarboxylic acid (2,6-H2ndc) or 4,4‧-(hydroxymethylene)dibenzoic acid (H2hmdb), in the presence of cadmium(II) salts have given rise to two novel metal-organic frameworks based on flexible ligands (FL-MOFs), namely, [Cd2(2,6-ndc)2(bpp)(DMF)]·2DMF (1) and [Cd3(hmdb)3(bpp)]·2DMF·2EtOH (2) (DMF=N,N-Dimethylformamide). Single-crystal X-ray diffraction analyses revealed that compound 1 exhibits a three-dimensional self-penetrating 6-connected framework based on dinuclear cluster second building unit. Compound 2 displays an infinite three-dimensional 'Lucky Clover' shape (2,10)-connected network based on the trinuclear cluster and V-shaped organic linkers. The flexible bpp ligand displays different conformations in 1 and 2, which are successfully controlled by size-matching mixed ligands during the self-assembly process.

  6. An application of the biotic ligand model to predict the toxic effects of metal mixtures.

    PubMed

    Kamo, Masashi; Nagai, Takashi

    2008-07-01

    The rapidly developing biotic ligand model (BLM) allows us to predict the toxicity of heavy metals in water of various chemistries; however, the current BLM predicts the toxicity of a single metal and not the toxic effects of metal mixtures. The toxic mechanisms of heavy metals are not yet completely understood, but hypocalcemia is suggested to be the most likely toxic mechanism for some metals. The BLM, which predicts the toxicity of metals by the amount of metals binding to ligand, is modified to predict the toxicity by the proportion of nonmetal binding ligand that is available for calcium uptake under the assumption that the organisms die because of hypocalcemia when so few ligands are available for calcium uptake. Because the proportion can be computed when multiple metals are present, the toxic effects of metal mixtures can be predicted. Zinc, copper, and cadmium toxicity to rainbow trout (Oncorhynchus mykiss) are considered. All data are collected from the literature, and a meta-analysis using the modified version of the BLM is conducted. The present study found that the proportion of nonmetal binding ligand is a constant value for any test condition. The proportion is not influenced by water chemistry or by metal species. Using the nature of constant proportion, toxicities of metals are well estimated. In addition, the toxic effects of metal mixtures are the simple sum of the toxicities of each metal (additive effect) corresponding to the bioavailable form of the metals. In terms of total concentration of metals in water, however, nonadditive effects, such as antagonism and synergism, are possible. PMID:18260697

  7. Narcissistic self-sorting in self-assembled cages of rare Earth metals and rigid ligands.

    PubMed

    Johnson, Amber M; Wiley, Calvin A; Young, Michael C; Zhang, Xing; Lyon, Yana; Julian, Ryan R; Hooley, Richard J

    2015-05-01

    Highly selective, narcissistic self-sorting can be achieved in the formation of self-assembled cages of rare earth metals with multianionic salicylhydrazone ligands. The assembly process is highly sensitive to the length of the ligand and the coordination geometry. Most surprisingly, high-fidelity sorting is possible between ligands of identical coordination angle and geometry, differing only in a single functional group on the ligand core, which is not involved in the coordination. Supramolecular effects allow discrimination between pendant functions as similar as carbonyl or methylene groups in a complex assembly process. PMID:25784462

  8. Design and Formation of a Large, Tetrahedral, Metal-ligand Cluster Using 1,1'-Binaphthyl Ligands

    SciTech Connect

    Biros, Shannon M.; Yeh, Robert M.; Raymond, Kenneth N.

    2008-03-13

    Many chemists have been fascinated with the development of discrete supramolecular structures that encapsulate guest molecules. These structures can be assembled through covalent or hydrogen bonds, electrostatic or metal-ligand interactions. These host structures have provided valuable insight into the forces involved in small molecule recognition. Our work has focused on the design and study of metal-ligand clusters of varying sizes. The naphthalene [M{sub 4}L{sub 6}]{sup 12-} cluster 1, shown in Figure 1, has demonstrated diastereoselective guest binding and chiral induction properties as well as the ability to catalyze reactions carried out inside the cavity in an enzyme-like manner. However, the size of the cavity (ca. 300-500 {angstrom}{sup 3}) has often limited the scope of substrates for these transformations.

  9. Metal effects on ligand non-innocence in Group 5 complexes of the redox-active [ONO] pincer ligand.

    PubMed

    Hananouchi, Steven; Krull, Brandon T; Ziller, Joseph W; Furche, Filipp; Heyduk, Alan F

    2014-12-28

    Isostructural vanadium, niobium and tantalum complexes of bis(3,5-di-tert-butyl-2-phenol)amine ([ONO]H3), were prepared and characterized to evaluate the impact of the metal ion on redox-activity of the ligand platform. New vanadium and niobium complexes with the general formula, [ONO]MCl2L (M = V, L = THF, 1-V; M = Nb, L = Et2O, 1-Nb) were prepared and structurally analysed by X-ray crystallography. The solid-state structures indicate that the niobium derivative is electronically analogous to the tantalum analog 1-Ta, containing a reduced (ONO) ligand and a niobium(V) metal ion, [ONO(cat)]Nb(V)Cl2(OEt2); whereas, the vanadium derivative is best described as a vanadium(IV) complex, [ONO(sq)]V(IV)Cl2(THF). One-electron oxidation was carried out on all three metal complexes to afford [ONO]MCl3 derivatives (3-V, 3-Nb, 3-Ta). For all three derivatives, oxidation occurs at the (ONO) ligand. In the cases of niobium and tantalum, electronically similar complexes characterized as [ONO(sq)]M(V)Cl3 were obtained and for vanadium, ligand-based oxidation led to the formation of a complex best described as [ONO(q)]V(IV)Cl3. All complexes were characterized by spectroscopic and electrochemical methods. DFT and TD-DFT calculations were used to probe the electronic structure of the complexes and help verify the different electronic structures stemming from changes to the coordinated metal ion. PMID:25352212

  10. Ligand-Free Noble Metal Nanocluster Catalysts on Carbon Supports via "Soft" Nitriding.

    PubMed

    Liu, Ben; Yao, Huiqin; Song, Wenqiao; Jin, Lei; Mosa, Islam M; Rusling, James F; Suib, Steven L; He, Jie

    2016-04-13

    We report a robust, universal "soft" nitriding method to grow in situ ligand-free ultrasmall noble metal nanocatalysts (UNMN; e.g., Au, Pd, and Pt) onto carbon. Using low-temperature urea pretreatment at 300 °C, soft nitriding enriches nitrogen-containing species on the surface of carbon supports and enhances the affinity of noble metal precursors onto these supports. We demonstrated sub-2-nm, ligand-free UNMNs grown in situ on seven different types of nitrided carbons with no organic ligands via chemical reduction or thermolysis. Ligand-free UNMNs supported on carbon showed superior electrocatalytic activity for methanol oxidation compared to counterparts with surface capping agents or larger nanocrystals on the same carbon supports. Our method is expected to provide guidelines for the preparation of ligand-free UNMNs on a variety of supports and, additionally, to broaden their applications in energy conversion and electrochemical catalysis. PMID:27014928

  11. Direct Measure of Metal-Ligand Bonding Replacing the Tolman Electronic Parameter.

    PubMed

    Setiawan, Dani; Kalescky, Robert; Kraka, Elfi; Cremer, Dieter

    2016-03-01

    The Tolman electronic parameter (TEP) derived from the A1-symmetrical CO stretching frequency of nickel-tricarbonyl complexes L-Ni(CO)3 with varying ligands L is misleading as (i) it is not based on a mode decoupled CO stretching frequency and (ii) a generally applicable and quantitatively correct or at least qualitatively reasonable relationship between the TEP and the metal-ligand bond strength does not exist. This is shown for a set of 181 nickel-tricarbonyl complexes using both experimental and calculated TEP values. Even the use of mode-mode decoupled CO stretching frequencies (L(ocal)TEPs) does not lead to a reliable description of the metal-ligand bond strength. This is obtained by introducing a new electronic parameter that is directly based on the metal-ligand local stretching force constant. For the test set of 181 nickel complexes, a direct metal-ligand electronic parameter (MLEP) in the form of a bond strength order is derived, which reveals that phosphines and related ligands (amines, arsines, stibines, bismuthines) are bonded to Ni both by σ-donation and π-back-donation. The strongest Ni-L bonds are identified for carbenes and cationic ligands. The new MLEP quantitatively assesses electronic and steric factors. PMID:26900632

  12. New avenues for ligand-mediated processes--expanding metal reactivity by the use of redox-active catechol, o-aminophenol and o-phenylenediamine ligands.

    PubMed

    Broere, Daniël L J; Plessius, Raoul; van der Vlugt, Jarl Ivar

    2015-10-01

    Redox-active ligands have evolved from being considered spectroscopic curiosities - creating ambiguity about formal oxidation states in metal complexes - to versatile and useful tools to expand on the reactivity of (transition) metals or to even go beyond what is generally perceived possible. This review focusses on metal complexes containing either catechol, o-aminophenol or o-phenylenediamine type ligands. These ligands have opened up a new area of chemistry for metals across the periodic table. The portfolio of ligand-based reactivity invoked by these redox-active entities will be discussed. This ranges from facilitating oxidative additions upon d(0) metals or cross coupling reactions with cobalt(iii) without metal oxidation state changes - by functioning as an electron reservoir - to intramolecular ligand-to-substrate single-electron transfer to create a reactive substrate-centered radical on a Pd(ii) platform. Although the current state-of-art research primarily consists of stoichiometric and exploratory reactions, several notable reports of catalysis facilitated by the redox-activity of the ligand will also be discussed. In conclusion, redox-active ligands containing catechol, o-aminophenol or o-phenylenediamine moieties show great potential to be exploited as reversible electron reservoirs, donating or accepting electrons to activate substrates and metal centers and to enable new reactivity with both early and late transition as well as main group metals. PMID:26148803

  13. Site-specific metal and ligand substitutions in a microporous Mn(2+)-based metal-organic framework.

    PubMed

    Huxley, Michael; Coghlan, Campbell J; Burgun, Alexandre; Tarzia, Andrew; Sumida, Kenji; Sumby, Christopher J; Doonan, Christian J

    2016-03-01

    The precise tuning of the structural and chemical features of microporous metal-organic frameworks (MOFs) is a crucial endeavour for developing materials with properties that are suitable for specific applications. In recent times, techniques for preparing frameworks consisting of mixed-metal or ligand compositions have emerged. However, controlled spatial organisation of the components within these structures at the molecular scale is a difficult challenge, particularly when species possessing similar geometries or chemical properties are used. Here, we describe the synthesis of mixed-metal and ligand variants possessing the Mn3L3 (Mn-MOF-1; H2L = bis(4-(4'-carboxyphenyl)-3,5-dimethylpyrazolyl)methane) structure type. In the case of mixed-ligand synthesis using a mixture of L and its trifluoromethyl-functionalised derivative (H2L' = bis(4-(4'-carboxyphenyl)-3,5-di(trifluoromethyl)pyrazolyl)methane), a mixed-ligand product in which the L' species predominanantly occupies the pillar sites lining the pores is obtained. Meanwhile, post-synthetic metal exchange of the parent Mn3L3 compound using Fe(2+) or Fe(3+) ions results in a degree of cation exchange at the trinuclear carboxylate-based clusters and metalation at the pillar bispyrazolate sites. The results demonstrate the versatility of the Mn3L3 structure type toward both metal and ligand substitutions, and the potential utility of site-specific functionalisations in achieving even greater precision in the tuning of MOFs. PMID:26902150

  14. PREDICTING SEDIMENT METAL TOXICITY USING A SEDIMENT BIOTIC LIGAND MODEL: METHODOLOGY AND INITIAL APPLICATION

    EPA Science Inventory

    An extension of the simultaneously extracted metals/acid-volatile sulfide (SEM/AVS) procedure is presented that predicts the acute and chronic sediment metals effects concentrations. A biotic ligand model (BLM) and a pore water–sediment partitioning model are used to predict the ...

  15. Unusual metal coordination chemistry from an amino-amide derivative of 4-nitrophenol, a surprising ligand.

    PubMed

    McGinley, John; McKee, Vickie; Toftlund, Hans; Walsh, John M D

    2009-10-21

    The simple ligand N-(2-aminoethyl)-2-hydroxy-5-nitrobenzamide () exhibits several coordination modes depending on the reaction conditions, acting as a zwitterion on its own or being ionic in the presence of acid and depending on the concentration of metal present in a reaction, it can coordinate to the metal in either a 1:1 or a 1:2 metal:ligand mode. Furthermore, the role of solvent plays an important role in these complexation reactions with both four and six coordinate copper complexes being obtained using water as solvent but only six coordinate copper complexes obtained using acetonitrile as solvent. PMID:19789795

  16. Isotopic studies of the metal-ligand vibrations in histamine complexes with Copper(II)

    NASA Astrophysics Data System (ADS)

    Drożdżewski, Piotr; Kordon, Ewa

    2000-06-01

    Two known copper complexes of the formulae Cu(hm) 2(ClO 4) 2, Cu(hm)Cl 2 and new, Cu(hm)Br 2 (hm=histamine) have been investigated in the 600-50 cm -1 far-infrared region. Assignments of vibrations related to metal-ligand bonds have been made based on metal isotope substitution, partial deuteration and halogen sensitivity. Copper-hm stretching vibrations have been localised at 420, 417 and 411 cm -1 for modes involving amine nitrogen and at 282, 270, 259 cm -1 for those of imidazole nitrogen. Vibrational coupling between some metal-ligand modes has been postulated.

  17. Coordination polymers of Ag(I) based on iminocarbene ligands involving metal-carbon and metal-heteroatom interactions

    NASA Astrophysics Data System (ADS)

    Netalkar, Sandeep P.; Netalkar, Priya P.; Revankar, Vidyanand K.

    2016-03-01

    The reaction of Ag2O with three novel imino-NHC ligands derived from 2-chloroacetophenone with pendant N-donor functional group incorporated by reaction with methoxyamine and 1-methyl/ethyl/n-butyl-substituted imidazoles afforded one-dimensional coordination polymers with [(-NHCarbene)Ag(NHCarbene-)PF6]n formulation involving both carbon-metal and heteroatom-metal interactions, the carbon and heteroatom involved in coordination to silver being from different molecule of the ligand. The complexes as well as the ligands were characterized by spectroscopic methods as well as the solid state structures determined in case of 2a, 3a and complex 5. The iminocarbene ligands serve as non-chelating building block for supramolecular silver assemblies.

  18. Electric transport properties of surface-anchored metal-organic frameworks and the effect of ferrocene loading.

    PubMed

    Liu, Jianxi; Wächter, Tobias; Irmler, Andreas; Weidler, Peter G; Gliemann, Hartmut; Pauly, Fabian; Mugnaini, Veronica; Zharnikov, Michael; Wöll, Christof

    2015-05-13

    Understanding of the electric transport through surface-anchored metal-organic frameworks (SURMOFs) is important both from a fundamental perspective as well as with regards to possible future applications in electronic devices. To address this mostly unexplored subject, we integrated a series of representative SURMOF thin films, formed by copper nodes and trimesic acid and known as HKUST-1, in a mercury-drop-based tunneling junction. Although the transport properties of these SURMOFs are analogous to those of hybrid metal-organic molecular wires, manifested by a very low value of the tunneling decay constant (β ≈ 0.006 Å(-1)), they are at the same time found to be consistent with a linear increase of resistance with film thickness. Upon loading of SURMOF pores with ferrocene (Fc), a noticeable increase in transport current was observed. A transport model and ab initio electronic structure calculations were used to reveal a hopping transport mechanism and to relate the changes upon Fc loading to those of the electronic and vibrational structures of the SURMOF films. PMID:25875419

  19. Synthesis and Characterization of Metal Complexes with Schiff Base Ligands

    ERIC Educational Resources Information Center

    Wilkinson, Shane M.; Sheedy, Timothy M.; New, Elizabeth J.

    2016-01-01

    In order for undergraduate laboratory experiments to reflect modern research practice, it is essential that they include a range of elements, and that synthetic tasks are accompanied by characterization and analysis. This intermediate general chemistry laboratory exercise runs over 2 weeks, and involves the preparation of a Schiff base ligand and

  20. Synthesis and Characterization of Metal Complexes with Schiff Base Ligands

    ERIC Educational Resources Information Center

    Wilkinson, Shane M.; Sheedy, Timothy M.; New, Elizabeth J.

    2016-01-01

    In order for undergraduate laboratory experiments to reflect modern research practice, it is essential that they include a range of elements, and that synthetic tasks are accompanied by characterization and analysis. This intermediate general chemistry laboratory exercise runs over 2 weeks, and involves the preparation of a Schiff base ligand and…

  1. Synthesis and isolation of cobalt hexacyanoferrate/chromate metal coordination nanopolymers stabilized by alkylamino ligand with metal elemental control.

    PubMed

    Yamada, Mami; Arai, Masaya; Kurihara, Masato; Sakamoto, Masatomi; Miyake, Mikio

    2004-08-11

    This Communication describes the novel isolation with metal elemental control of cobalt hexacyanoferrate/chromate metal coordination polymers, stabilized by stearylamine (Co-Fe/Cr-SA) as a protecting coordination ligand in a reverse micelle technique. Each Co-Fe/Cr-SA can be isolated with high uniformity of particle size and elemental composition, and the ratio of the metal component depends on the fundamental characteristics of Co-Fe/Cr-SA: the nanopolymer's shape, color, and magnetism. PMID:15291519

  2. Colloidal metal oxide nanocrystal catalysis by sustained chemically driven ligand displacement.

    PubMed

    De Roo, Jonathan; Van Driessche, Isabel; Martins, José C; Hens, Zeger

    2016-05-01

    Surface chemistry is a key enabler for colloidal nanocrystal applications. In this respect, metal oxide nanocrystals (NCs) stand out from other NCs as carboxylic acid ligands adsorb on their surface by dissociation to carboxylates and protons, the latter proving essential in electron transfer reactions. Here, we show that this binding motif sets the stage for chemically driven ligand displacement where the binding of amines or alcohols to HfO2 NCs is promoted by the conversion of a bound carboxylic acid into a non-coordinating amide or ester. Furthermore, the sustained ligand displacement, following the addition of excess carboxylic acid, provides a catalytic pathway for ester formation, whereas the addition of esters leads to NC-catalysed transesterification. Because sustained, chemically driven ligand displacement leaves the NCs-including their surface composition-unchanged and preserves colloidal stability, metal oxide nanocrystals are thus turned into effective nanocatalysts that bypass the tradeoff between colloidal stability and catalytic activity. PMID:26808460

  3. Colloidal metal oxide nanocrystal catalysis by sustained chemically driven ligand displacement

    NASA Astrophysics Data System (ADS)

    de Roo, Jonathan; van Driessche, Isabel; Martins, José C.; Hens, Zeger

    2016-05-01

    Surface chemistry is a key enabler for colloidal nanocrystal applications. In this respect, metal oxide nanocrystals (NCs) stand out from other NCs as carboxylic acid ligands adsorb on their surface by dissociation to carboxylates and protons, the latter proving essential in electron transfer reactions. Here, we show that this binding motif sets the stage for chemically driven ligand displacement where the binding of amines or alcohols to HfO2 NCs is promoted by the conversion of a bound carboxylic acid into a non-coordinating amide or ester. Furthermore, the sustained ligand displacement, following the addition of excess carboxylic acid, provides a catalytic pathway for ester formation, whereas the addition of esters leads to NC-catalysed transesterification. Because sustained, chemically driven ligand displacement leaves the NCs--including their surface composition--unchanged and preserves colloidal stability, metal oxide nanocrystals are thus turned into effective nanocatalysts that bypass the tradeoff between colloidal stability and catalytic activity.

  4. Hydrogenation and dehydrogenation iron pincer catalysts capable of metal-ligand cooperation by aromatization/dearomatization.

    PubMed

    Zell, Thomas; Milstein, David

    2015-07-21

    The substitution of expensive and potentially toxic noble-metal catalysts by cheap, abundant, environmentally benign, and less toxic metals is highly desirable and in line with green chemistry guidelines. We have recently discovered a new type of metal-ligand cooperation, which is based on the reversible dearomatization/aromatization of different heteroaromatic ligand cores caused by deprotonation/protonation of the ligand. More specifically, we have studied complexes of various transition metals (Ru, Fe, Co, Rh, Ir, Ni, Pd, Pt, and Re) bearing pyridine- and bipyridine-based PNP and PNN pincer ligands, which have slightly acidic methylene protons. In addition, we have discovered long-range metal-ligand cooperation in acridine-based pincer ligands, where the cooperation takes place at the electrophilic C-9 position of the acridine moiety leading to dearomatization of its middle ring. This type of metal-ligand cooperation was used for the activation of chemical bonds, including H-H, C-H (sp(2) and sp(3)), O-H, N-H, and B-H bonds. This unusual reactivity likely takes place in various catalytic hydrogenation, dehydrogenation, and related reactions. In this Account, we summarize our studies on novel bifunctional iron PNP and PNN pincer complexes, which were designed on the basis of their ruthenium congeners. Iron PNP pincer complexes serve as efficient (pre)catalysts for hydrogenation and dehydrogenation reactions under remarkably mild conditions. Their catalytic applications include atom-efficient and industrially important hydrogenation reactions of ketones, aldehydes, and esters to the corresponding alcohols. Moreover, they catalyze the hydrogenation of carbon dioxide to sodium formate in the presence of sodium hydroxide, the selective decomposition of formic acid to carbon dioxide and hydrogen, and the E-selective semihydrogenation of alkynes to give E-alkenes. These catalysts feature, compared to other iron-based catalysts, very high catalytic activities which in some cases can even exceed those of state-of-the-art noble-metal catalysts. For the iron PNP systems, we describe the synthesis of the pyridine- and acridine-based PNP iron complexes and their performances and limitations in catalytic reactions, and we present studies on their reactivity with relevance to their catalytic mechanisms. In the case of the bipyridine-based PNN system, we summarize the synthesis of new complexes and describe studies on the noninnocence of the methylene position, which can be reversibly deprotonated, as well as on the noninnocence of the bipyridine unit. Overall, this Account underlines that the combination of cheap and abundant iron with ligands that are capable of metal-ligand cooperation can result in the development of novel, versatile, and efficient catalysts for atom-efficient catalytic reactions. PMID:26079678

  5. Postsynthetic ligand and cation exchange in robust metal-organic frameworks.

    PubMed

    Kim, Min; Cahill, John F; Fei, Honghan; Prather, Kimberley A; Cohen, Seth M

    2012-10-31

    Postsynthetic ligand and metal ion exchange (PSE) processes are shown to readily occur in several "inert" metal-organic frameworks (MOFs), including zeolitic imidazolate frameworks (ZIFs). Ligand exchange can occur between solid samples, as was demonstrated under relatively mild conditions with two robust, topologically distinct MOFs, MIL-53(Al) and MIL-68(In). Interestingly, ligand PSE is not observed with MIL-101(Cr), which is attributed to the kinetic inertness of the Cr(III) ion. In addition to ligand exchange, metal ion (cation) PSE was also studied between intact MOF microcrystalline particles. Metal ion transfer between MIL-53(Al) and MIL-53(Fe) was readily observed. These PSE reactions were monitored and the products characterized by a number of techniques, including aerosol time-of-flight mass spectrometry, which permits single-particle compositional analysis. To show the potential synthetic utility of this approach, the PSE process was used to prepare the first Ti(IV) analogue of the robust UiO-66(Zr) framework. Finally, experiments to rule out mechanisms other than PSE (i.e., aggregation, dissolution/recrystallization) were performed. The results demonstrate that PSE, of either ligands or cations, is common even with highly robust MOFs such as UiO-66(Zr), MILs, and ZIFs. Furthermore, it is shown that PSE is useful in preparing novel materials that cannot be obtained via other synthetic methods. PMID:23039827

  6. Mild and Complete Carbonyl Ligand Scission on a Mononuclear Transition Metal Complex.

    PubMed

    Braunschweig, Holger; Celik, Mehmet Ali; Dewhurst, Rian D; Kachel, Stephanie; Wennemann, Benedikt

    2016-04-11

    The complete scission of the carbon-oxygen bond of carbon monoxide, while frequently observed on bulk metals and with bimetallic and cluster transition metal complexes, is unknown with monometallic systems. Reaction of a zerovalent iron bis(borylene) complex with a cyclic (alkyl)(amino)carbene revealed a highly selective intramolecular cleavage of the C-O bond of a carbonyl ligand at room temperature, leading to the formation of a highly unusual iron complex containing a base-stabilized (bora)alkylideneborane ligand. DFT investigation of the reaction mechanism suggested that the two Lewis acidic borylene boron atoms cooperate to cleave the C-O multiple bond. PMID:26990148

  7. The Calculation of Accurate Metal-Ligand Bond Energies

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W.; Partridge, Harry, III; Ricca, Alessandra; Arnold, James O. (Technical Monitor)

    1997-01-01

    The optimization of the geometry and calculation of zero-point energies are carried out at the B3LYP level of theory. The bond energies are determined at this level, as well as at the CCSD(T) level using very large basis sets. The successive OH bond energies to the first row transition metal cations are reported. For most systems there has been an experimental determination of the first OH. In general, the CCSD(T) values are in good agreement with experiment. The bonding changes from mostly covalent for the early metals to mostly electrostatic for the late transition metal systems.

  8. Metal Complexes of Macrocyclic Schiff-Base Ligand: Preparation, Characterisation, and Biological Activity

    PubMed Central

    Ahmed, Riyadh M.; Yousif, Enaam I.; Hasan, Hasan A.; Al-Jeboori, Mohamad J.

    2013-01-01

    A new macrocyclic multidentate Schiff-base ligand Na4L consisting of two submacrocyclic units (10,21-bis-iminomethyl-3,6,14,17-tricyclo[17.3.1.18,12]tetracosa-1(23),2,6,8,10,12(24),13,17,19,21,-decaene-23,24-disodium) and its tetranuclear metal complexes with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) are reported. Na4L was prepared via a template approach, which is based on the condensation reaction of sodium 2,4,6-triformyl phenolate with ethylenediamine in mole ratios of 2 : 3. The tetranuclear macrocyclic-based complexes were prepared from the reaction of the corresponding metal chloride with the ligand. The mode of bonding and overall geometry of the compounds were determined through physicochemical and spectroscopic methods. These studies revealed tetrahedral geometries about Mn, Co, and Zn atoms. However, square planar geometries have been suggested for NiII and CuII complexes. Biological activity of the ligand and its metal complexes against Gram positive bacterial strain Staphylococcus aureus and Gram negative bacteria Escherichia coli revealed that the metal complexes become more potentially resistive to the microbial activities as compared to the free ligand. However, these metal complexes do not exhibit any effects on the activity of Pseudomonas aeruginosa bacteria. There is therefore no inhibition zone. PMID:23935414

  9. Cage Opening of a Carborane Ligand by Metal Cluster Complexes.

    PubMed

    Adams, Richard D; Kiprotich, Joseph; Peryshkov, Dmitry V; Wong, Yuen Onn

    2016-05-01

    The reaction of Os3 (CO)10 (NCMe)2 with closo-o-C2 B10 H10 has yielded two interconvertible isomers Os3 (CO)9 (μ3 -4,5,9-C2 B10 H8 )(μ-H)2 (1 a) and Os3 (CO)9 (μ3 -3,4,8-C2 B10 H8 )(μ-H)2 (1 b) formed by the loss of the two NCMe ligands and one CO ligand from the Os3 cluster. Two BH bonds of the o-C2 B10 H10 were activated in its addition to the osmium cluster. A second triosmium cluster was added to the 1 a/1 b mixture to yield the complex Os3 (CO)9 (μ-H)2 (μ3 -4,5,9-μ3 -7,11,12-C2 B10 H7 )Os3 (CO)9 (μ-H)3 (2) that contains two triosmium triangles attached to the same carborane cage. When heated, 2 was transformed to the complex Os3 (CO)9 (μ-H)(μ3 -3,4,8-μ3 -7,11,12-C2 B10 H8 )Os3 (CO)9 (μ-H) (3) by a novel opening of the carborane cage with loss of H2 . PMID:26971388

  10. Synthesis and structures of four homochiral metal camphorates with auxiliary bipyridine ligands

    NASA Astrophysics Data System (ADS)

    Yang, E.; Lian, Ting-Ting; Lin, Shen; Chen, Shu-Mei

    2011-12-01

    Four homochiral metal camphorates with auxiliary bipyridine ligands are hydrothermally synthesized and structurally characterized. The structure of compound [Cd( D-Hcam) 2(bpa)(H 2O)] n ( 1; D-H 2cam = D-(+)-camphoric acid, bpa = 1,2-bis(4-pyridyl)-ethane) presents a rare case where the D-Hcam is not a bridging ligand, but a dangling unit attached to the infinite [Cd(bpa)] chain. Compounds [M 2( D-cam) 2(4,4'-bipy)(H 2O) 4] n (M = Co, 2; M = Cd, 3; 4,4'-bipy = 4,4'-bipyridine) are isostructural and have homochiral [M( D-cam)] n chains linked by the 4,4'-bipy ligands into a honeycomb-like 6 3 layer. Compound [Zn 2( D-cam) 2(PPE) 2] n ( 4, PPE = 1-(4-pyridyl)-2-(2-pyridyl)-ethylene) consists of the grid-like 4 4 layers with the dinuclear Zn 2(COO) 4 units and D-cam ligands, where the PPE ligands are only monodentately coordinated to the dinuclear units and act as the separators between two homochiral layers. The results demonstrate the rich coordination chemistry of the enantiopure D-camphorate ligand and the structural diversity of metal-camphorate compounds.

  11. Impact of ligand protonation on eigen-type metal complexation kinetics in aqueous systems.

    PubMed

    van Leeuwen, Herman P; Town, Raewyn M; Buffle, Jacques

    2007-03-22

    The impact of ligand protonation on metal speciation dynamics is quantitatively described. Starting from the usual situation for metal complex formation reactions in aqueous systems, i.e., exchange of water for the ligand in the inner coordination sphere as the rate-determining step (Eigen mechanism), expressions are derived for the lability of metal complexes with protonated and unprotonated ligand species being involved in formation of the precursor outer-sphere complex. A differentiated approach is developed whereby the contributions from all outer-sphere complexes are included in the rate of complex formation, to an extent weighted by their respective stabilities. The stability of the ion pair type outer-sphere complex is given particular attention, especially for the case of multidentate ligands containing several charged sites. It turns out that in such cases, the effective ligand charge can be considerably different from the formal charge. The lability of Cd(II) complexes with 1,2-diaminoethane-N,N'-diethanoic acid at a microelectrode is reasonably well predicted by the new approach. PMID:17388287

  12. Bivalent transition metal complexes of ONO donor hydrazone ligand: Synthesis, structural characterization and antimicrobial activity.

    PubMed

    Bhaskar, Ravindra; Salunkhe, Nilesh; Yaul, Amit; Aswar, Anand

    2015-12-01

    Mononuclear transition metal complexes of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with a new hydrazone ligand derived from pyrazine-2-carbohydrazide and 2-hydroxyacetophenone have been synthesized. The isolated complexes were characterized by elemental analysis, spectral and analytical methods including elemental analyses, IR, diffuse reflectance, (1)H-NMR, mass spectra, molar conductance, magnetic moment, ESR, XRD, TG and SEM analysis. From the elemental analyses data, the stoichiometry of the complexes was found to be 1:1 (metal:ligand) having the general formulae [M(HL)(Cl)(H2O)2], [M=Mn(II), Co(II), Ni(II) and Cu(II)] and [M(L)(H2O)], [M=Zn(II) and Cd(II)]. The molar conductance values indicate the nonelectrolytic nature of metal complexes. The IR spectral data suggest that the ligand behaves as tridentate moiety with ONO donor atoms sequence towards central metal ion. The Mn(II), Co(II), Ni(II) and Cu(II) complexes have been assigned a monomeric octahedral geometry whereas tetrahedral to Zn(II) and Cd(II) complexes. The antibacterial and antifungal activities of the ligand and its metal complexes were studied against bacterial species Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Enterococcus faecalis and Streptococcus pyogenes and fungi Candida albicans, Aspergillus niger and Aspergillus clavatus. The activity data show that the metal complexes have a promising biological activity comparable with the parent ligand against all bacterial and fungal species. PMID:26163785

  13. Estimating the acidity of transition metal hydride and dihydrogen complexes by adding ligand acidity constants.

    PubMed

    Morris, Robert H

    2014-02-01

    A simple equation (pKa(THF) = ∑AL + Ccharge + Cnd + Cd6) can be used to obtain an estimate of the pKa of diamagnetic transition metal hydride and dihydrogen complexes in tetrahydrofuran, and, by use of conversion equations, in other solvents. It involves adding acidity constants AL for each of the ligands in the 5-, 6-, 7-, or 8-coordinate conjugate base complex of the hydride or dihydrogen complex along with a correction for the charge (Ccharge = -15, 0 or 30 for x = +1, 0 or -1 charge, respectively) and the periodic row of the transition metal (Cnd = 0 for 3d or 4d metal, 2 for 5d metal) as well as a correction for d(6) octahedral acids (Cd6 = 6 for d(6) metal ion in the acid, 0 for others) that are not dihydrogen complexes. Constants AL are provided for 13 commonly occurring ligand types; of these, nine neutral ligands are correlated with Lever's electrochemical ligand parameters EL. This method gives good estimates of the over 170 literature pKa values that range from less than zero to 50 with a standard deviation of 3 pKa units for complexes of the metals chromium to nickel, molybdenum, ruthenium to palladium, and tungsten to platinum in the periodic table. This approach allows a quick assessment of the acidity of hydride complexes found in nature (e.g., hydrogenases) and in industry (e.g., catalysis and hydrogen energy applications). The pKa values calculated for acids that have bulky or large bite angle chelating ligands deviate the most from this correlation. The method also provides an estimate of the base strength of the deprotonated form of the complex. PMID:24410025

  14. Metal complexes of ONO donor Schiff base ligand as a new class of bioactive compounds; Synthesis, characterization and biological evolution

    NASA Astrophysics Data System (ADS)

    Kumar Naik, K. H.; Selvaraj, S.; Naik, Nagaraja

    2014-10-01

    Present work reviews that, the synthesis of (E)-N";-((7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)benzohydrazide [L] ligand and their metal complexes. The colored complexes were prepared of type [M2+L]X2, where M2+ = Mn, Co, Ni, Cu, Sr and Cd, L = (7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)benzohydrazide, X = Cl-. Ligand derived from the condensation of 8-formyl-7-hydroxy-4-methylcoumarin and benzohydrazide in the molar ratio 1:1 and in the molar ratio 1:2 for metal complexes have been prepared. The chelation of the ligand to metal ions occurs through the both oxygen groups, as well as the nitrogen atoms of the azomethine group of the ligand. Reactions of the Schiff base ligand with Manganese(II), Cobalt(II), Nickel(II), Copper(II), Strontium(II), and Cadmium(II) afforded the corresponding metal complexes. The structures of the obtained ligand and their respective metal complexes were elucidated by infra-red, elemental analysis, Double beam UV-visible spectra, conductometric measurements, magnetic susceptibility measurements and also thermochemical studies. The metal complex exhibits octahedral coordination geometrical arrangement. Schiff base ligand and their metal complexes were tested against antioxidants, antidiabetic and antimicrobial activities have been studied. The Schiff base metal complexes emerges effective α-glucosidase inhibitory activity than free Schiff base ligand.

  15. Metal complexes of ONO donor Schiff base ligand as a new class of bioactive compounds: synthesis, characterization and biological evolution.

    PubMed

    Kumar Naik, K H; Selvaraj, S; Naik, Nagaraja

    2014-10-15

    Present work reviews that, the synthesis of (E)-N'-((7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)benzohydrazide [L] ligand and their metal complexes. The colored complexes were prepared of type [M(2+)L]X2, where M(2+)=Mn, Co, Ni, Cu, Sr and Cd, L=(7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)benzohydrazide, X=Cl(-). Ligand derived from the condensation of 8-formyl-7-hydroxy-4-methylcoumarin and benzohydrazide in the molar ratio 1:1 and in the molar ratio 1:2 for metal complexes have been prepared. The chelation of the ligand to metal ions occurs through the both oxygen groups, as well as the nitrogen atoms of the azomethine group of the ligand. Reactions of the Schiff base ligand with Manganese(II), Cobalt(II), Nickel(II), Copper(II), Strontium(II), and Cadmium(II) afforded the corresponding metal complexes. The structures of the obtained ligand and their respective metal complexes were elucidated by infra-red, elemental analysis, Double beam UV-visible spectra, conductometric measurements, magnetic susceptibility measurements and also thermochemical studies. The metal complex exhibits octahedral coordination geometrical arrangement. Schiff base ligand and their metal complexes were tested against antioxidants, antidiabetic and antimicrobial activities have been studied. The Schiff base metal complexes emerges effective α-glucosidase inhibitory activity than free Schiff base ligand. PMID:24858195

  16. Theoretical dynamical studies of metal clusters and cluster-ligand systems

    SciTech Connect

    Jellinek, J.

    1995-06-01

    In what follows we use the term cluster to designate a cohesive group of like atoms (molecules), i.e., bare ({open_quotes}neet{close_quotes} {open_quotes}naked{close_quotes}) clusters. More generally, the term is also used for organo- and inorganometallic compounds, i.e., ligated clusters. Although the approaches and techniques used by the various disciplines to study metal-ligand interactions are quite different, many of the central subjects and issues are common for them. The common subjects include possible geometric structures and isomeric forms, structural (isomerization) transitions, stability, fluxionality, structure-reactivity correlation (or lack of it), role of coordination, etc. However, the precise interpretation of these issues and the details emphasized by the different disciplines are dictated by the nature of the objects studied and may not, therefore, be identical. For example, questions regarding structures, isomerization transitions, fluxionality or even melting of metal clusters refer to the state and properties of the metal network itself. The same questions, when asked in connection with organo- and inorganometallic compounds, often refer to the arrangements and rearrangements of the ligands attached to a metal framework of a fixed structure. Of course, when required, the state of and changes in the metal framework are considered as well. The fields of metal-containing molecular compounds, surface science, and physics and chemistry of clusters furnish complementary information on a broad variety of metal-ligand systems. A comprehensive understanding of the nature and properties of these systems, as defined by the type and number of metal atoms and ligands involved, can be achieved only through a mutual awareness of and continuing progress in all of these research areas.

  17. Theoretical dynamical studies of metal clusters and cluster-ligand systems

    NASA Astrophysics Data System (ADS)

    Jellinek, J.

    1995-04-01

    In what follows we use the term cluster to designate a cohesive group of like atoms (molecules), i.e., bare ('neet', 'naked')clusters.More generally, the term is also used for organo- and inorganometallic compounds, i.e., ligated clusters. Although the approaches and techniques used by the various disciplines to study metal-ligand interactions are quite different, many of the central subjects and issues are common for them. The common subjects include possible geometric structures and isomeric forms, structural (isomerization) transitions, stability, fluxionality, structure-reactivity correlation (or lack of it), role of coordination, etc. However, the precise interpretation of these issues and the details emphasized by the different disciplines are dictated by the nature of the objects studied and may not, therefore, be identical. For example, questions regarding structures, isomerization transitions, fluxionality or even melting of metal clusters refer to the state and properties of the metal network itself. The same questions, when asked in connection with organo- and inorganometallic compounds, often refer to the arrangements and rearrangements of the ligands attached to a metal framework of a fixed structure. Of course, when required, the state of and changes in the metal framework are considered as well. The fields of metal-containing molecular compounds, surface science, and physics and chemistry of clusters furnish complementary information on a broad variety of metal-ligand systems. A comprehensive understanding of the nature and properties of these systems, as defined by the type and number of metal atoms and ligands involved, can be achieved only through a mutual awareness of and continuing progress in all of these research areas.

  18. Rare Earth Metal Complexes of Bidentate Nitroxide Ligands: Synthesis and Electrochemistry.

    PubMed

    Kim, Jee Eon; Bogart, Justin A; Carroll, Patrick J; Schelter, Eric J

    2016-01-19

    We report rare earth metal complexes with tri- and bidentate ligands including strongly electron-donating nitroxide groups. The tridentate ligand 1,3,5-tris(2'-tert-butylhydroxylaminoaryl)benzene (H3arene-triNOx) was complexed to cerium(IV) in a 2:1 ligand-to-metal stoichiometry as Ce(Harene-triNOx)2 (1). Cyclic voltammetry of this compound showed stabilization of the tetravalent cerium cation with a Ce(IV/III) couple at E1/2 = -1.82 V versus Fc/Fc(+). On the basis of the uninvolvement of the third nitroxide group in the coordination chemistry with the cerium(IV) cation, the ligand system was redesigned toward a simpler bidentate mode, and a series of rare earth metal-arene-diNOx complexes were prepared with La(III), Ce(IV), Pr(III), Tb(III), and Y(III), [RE(arene-diNOx)2](-) ([2-RE](-), RE = La, Pr, Y, Tb) and Ce(IV)(arene-diNOx)2, where H2arene-diNOx = 1,3-bis(2'-tert-butylhydroxylaminoaryl)benzene. The core structures were isostructural throughout the series, with three nitroxide groups in ?(2) binding modes and one ?(1) nitroxide group coordinated to the metal center in the solid state. In all cases except Ce(IV)(arene-diNOx)2, electrochemical analysis described two subsequent, ligand-based, quasi-reversible redox waves, indicating that a stable [N-O] group was generated on the electrochemical time scale. Chemical oxidation of the terbium complex was performed, and isolation of the resulting complex, Tb(arene-diNOx)2CH2Cl2 (3CH2Cl2), confirmed the assignment of the cyclic voltammograms. Magnetic data showed no evidence of mixing between the Tb(III) states and the states of the open-shell ligand. PMID:26689656

  19. N-Heterocyclic carbenes as supporting ligands in transition metal complexes of N2.

    PubMed

    Ohki, Yasuhiro; Seino, Hidetake

    2016-01-01

    Recent developments have substantially expanded the scope of N-heterocyclic carbenes (NHCs) as ancillary ligands in coordination chemistry and homogeneous catalysis. This review provides a short overview of the emerging field of NHC-supported transition metal complexes of N2 and the possibilities to catalytically activate N2 in these complexes. PMID:26646731

  20. Synthesis, Characterization and Biological Evaluation of Transition Metal Complexes Derived from N, S Bidentate Ligands

    PubMed Central

    Md Yusof, Enis Nadia; Ravoof, Thahira Begum S. A.; Tiekink, Edward R. T.; Veerakumarasivam, Abhimanyu; Crouse, Karen Anne; Mohamed Tahir, Mohamed Ibrahim; Ahmad, Haslina

    2015-01-01

    Two bidentate NS ligands were synthesized by the condensation reaction of S-2-methylbenzyldithiocarbazate (S2MBDTC) with 2-methoxybenzaldehyde (2MB) and 3-methoxybenzaldehyde (3MB). The ligands were reacted separately with acetates of Cu(II), Ni(II) and Zn(II) yielding 1:2 (metal:ligand) complexes. The metal complexes formed were expected to have a general formula of [M(NS)2] where M = Cu2+, Ni2+, and Zn2+. These compounds were characterized by elemental analysis, molar conductivity, magnetic susceptibility and various spectroscopic techniques. The magnetic susceptibility measurements and spectral results supported the predicted coordination geometry in which the Schiff bases behaved as bidentate NS donor ligands coordinating via the azomethine nitrogen and thiolate sulfur. The molecular structures of the isomeric S2M2MBH (1) and S2M3MBH (2) were established by X-ray crystallography to have very similar l-shaped structures. The Schiff bases and their metal complexes were evaluated for their biological activities against estrogen receptor-positive (MCF-7) and estrogen receptor-negative (MDA-MB-231) breast cancer cell lines. Only the Cu(II) complexes showed marked cytotoxicity against the cancer cell lines. Both Schiff bases and other metal complexes were found to be inactive. In concordance with the cytotoxicity studies, the DNA binding studies indicated that Cu(II) complexes have a strong DNA binding affinity. PMID:25988384

  1. The second-shell metal ligands of human arginase affect coordination of the nucleophile and substrate.

    PubMed

    Stone, Everett M; Chantranupong, Lynne; Georgiou, George

    2010-12-14

    The active sites of eukaryotic arginase enzymes are strictly conserved, especially the first- and second-shell ligands that coordinate the two divalent metal cations that generate a hydroxide molecule for nucleophilic attack on the guanidinium carbon of l-arginine and the subsequent production of urea and l-ornithine. Here by using comprehensive pairwise saturation mutagenesis of the first- and second-shell metal ligands in human arginase I, we demonstrate that several metal binding ligands are actually quite tolerant to amino acid substitutions. Of >2800 double mutants of first- and second-shell residues analyzed, we found more than 80 unique amino acid substitutions, of which four were in first-shell residues. Remarkably, certain second-shell mutations could modulate the binding of both the nucleophilic water/hydroxide molecule and substrate or product ligands, resulting in activity greater than that of the wild-type enzyme. The data presented here constitute the first comprehensive saturation mutagenesis analysis of a metallohydrolase active site and reveal that the strict conservation of the second-shell metal binding residues in eukaryotic arginases does not reflect kinetic optimization of the enzyme during the course of evolution. PMID:21053939

  2. Thioether-functionalized vegetable oils: Metal-absorbing biobased ligands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vegetable oils containing thioether groups have been synthesized and used to effectively remove a heavy metal ion from an aqueous solution. The use of thioether-functionalized corn oil (TF-corn oil) and thioether-functionalized canola oil (TF-canola oil) were both effective in the extraction of Ag+ ...

  3. Excited state evolution towards ligand loss and ligand chelation at group 6 metal carbonyl centres.

    PubMed

    Manton, Jennifer C; Amirjalayer, Saeed; Coleman, Anthony C; McMahon, Suzanne; Harvey, Emma C; Greetham, Gregory M; Clark, Ian P; Buma, Wybren Jan; Woutersen, Sander; Pryce, Mary T; Long, Conor

    2014-12-21

    The photochemistry and photophysics of three model "half-sandwich" complexes (η(6)-benzophenone)Cr(CO)3, (η(6)-styrene)Cr(CO)3, and (η(6)-allylbenzene)Cr(CO)3 were investigated using pico-second time-resolved infrared spectroscopy and time-dependent density functional theory methods. The (η(6)-benzophenone)Cr(CO)3 complex was studied using two excitation wavelengths (470 and 320 nm) while the remaining complexes were irradiated using 400 nm light. Two independent excited states were detected spectroscopically for each complex, one an unreactive excited state of metal-to-arene charge-transfer character and the other with metal-to-carbonyl charge transfer character. This second excited state leads to an arrested release of CO on the pico-second time-scale. Low-energy excitation (470 nm) of (η(6)-benzophenone)Cr(CO)3 populated only the unreactive excited state which simply relaxes to the parent complex. Higher energy irradiation (320 nm) induced CO-loss. Irradiation of (η(6)-styrene)Cr(CO)3, or (η(6)-allylbenzene)Cr(CO)3 at 400 nm provided evidence for the simultaneous population of both the reactive and unreactive excited states. The efficiency at which the unreactive excited state is populated depends on the degree of conjugation of the substituent with the arene π-system and this affects the efficiency of the CO-loss process. The quantum yield of CO-loss is 0.50 for (η(6)-allylbenzene)Cr(CO)3 and 0.43 for (η(6)-styrene)Cr(CO)3. These studies provide evidence for the existence of two photophysical routes to CO loss, a minor ultrafast route and an arrested mechanism involving the intermediate population of a reactive excited state. This reactive excited state either relaxes to reform the parent species or eject CO. Thus the quantum yield of the CO-loss is strongly dependent on the excitation wavelength. Time-dependent density functional theory calculations confirm that the state responsible for ultrafast CO-loss has significant metal-centred character while the reactive state responsible for the arrested CO-loss has significant metal-to-carbonyl charge-transfer character. The CO-loss product (η(6)-allylbenzene)Cr(CO)2 formed following irradiation of (η(6)-allylbenzene)Cr(CO)3 reacts further with the pendent alkenyl group to form the chelate product (η(6),η(2)-allylbenzene)Cr(CO)2. PMID:25093429

  4. A comparative topological study of different metal-metal and metal-ligand interactions in polynuclear organometallic clusters

    SciTech Connect

    Van der Maelen, Juan F.; García-Granda, Santiago

    2015-01-22

    The existence and characterization of a bond between the Zn atoms in the recently synthesized complex [Zn{sub 2}(η{sup 5}−C{sub 5}Me{sub 5}){sub 2}] (I), as well as between two of the three Ru atoms in [Ru{sub 3}(μ−H){sub 2}(μ{sub 3}−MeImCH)(CO{sub 9}] (Me{sub 2}Im = 1,3-dimethylimidazolin-2-ylidene) (II), are firmly based on low temperature X-ray synchrotron diffraction experiments. The multipolar refinement of the experimental electron densities and their topological analyses by means of the Atoms in Molecules (AIM) theory reveal the details of the Zn-Zn and Ru-Ru bonds, such as their open-shell intermediate character. The results are consistent with a typical metal-metal single σ bond for the former, whereas a delocalized kind of bond involving 5c-6e is present in the latter. In addition, experimental results are compared with theoretical ab initio calculations of the DFT (density functional theory) and MP2 (Mo/ller-Plesset perturbation theory) electron densities, giving a coherent view of the bonding in both complexes. Many other topological properties of both compounds are also studied, in particular the different metal-ligand interactions.

  5. Metal coordination architectures of triazole-based ligands: Effect of the backbone of bridging ligands on the construction of polymers

    NASA Astrophysics Data System (ADS)

    Du, Jian-Long; Hu, Tong-Liang; Bu, Xian-He

    2012-04-01

    In our efforts to investigate the influence of the backbone of different triazole-based bridging ligands on the structure of their metal complexes, four new coordination polymers, {[Cu(L1)2(H2O)2]Cl2}n (1), [Cu(L2)2Cl2]n (2), [Co(L2)2(SCN)2]n (3), and [Cu(L3)2(NO3)2]n (4), (L1 = 1,2-bis(triazol-1-ylmethyl)benzene, L2 = 1,3-bis(triazol-1-ylmethyl)benzene, L3 = 1,4-bis(triazol-1-ylmethyl)benzene), have been synthesized. All the complexes have been structurally characterized by IR, elemental analysis and single-crystal X-ray diffraction. Structural analyses show that 1 and 4 possess 2D coordination networks with (4,4) topology, and 1 shows a diagonal-diagonal inclined interpenetration. 2 and 3 are isostructural and feature 1D double chain, which further connected by C-H···Cl or π···π weak interactions to form 2D supramolecular frameworks. The results show that the structures of ligands (with different non-coordination backbone spacers) play important roles in the formation of such coordination architectures. Furthermore, EPR (Electron Paramagnetic Resonance) spectra of CuII complexes (1, 2, and 4) have been investigated in the solid state at room temperature.

  6. Tuning of the spin distribution between ligand- and metal-based spin: electron paramagnetic resonance of mixed-ligand molybdenum tris(dithiolene) complex anions.

    PubMed

    Fekl, Ulrich; Sarkar, Biprajit; Kaim, Wolfgang; Zimmer-De Iuliis, Marco; Nguyen, Neilson

    2011-09-19

    Electron paramagnetic resonance spectra of homoleptic and mixed-ligand molybdenum tris(dithiolene) complex anions [Mo(tfd)(m)(bdt)(n)](-) (n + m = 3; bdt = S(2)C(6)H(4); tfd = S(2)C(2)(CF(3))(2)) reveal that the spin density has mixed metal-ligand character with more ligand-based spin for [Mo(tfd)(3)](-) and a higher degree of metal-based spin for [Mo(bdt)(3)](-): the magnitude of the isotropic (95,97)Mo hyperfine interaction increases continuously, by a factor of 2.5, on going from the former to the latter. The mixed complexes fall in between, and the metal character of the spin increases with the bdt content. The experiments were corroborated by density functional theory computations, which reproduce this steady increase in metal-based character. PMID:21853970

  7. Production of Cisplatin-Incorporating Hyaluronan Nanogels via Chelating Ligand-Metal Coordination.

    PubMed

    Ohta, Seiichi; Hiramoto, Syota; Amano, Yuki; Sato, Mayu; Suzuki, Yukimitsu; Shinohara, Marie; Emoto, Shigenobu; Yamaguchi, Hironori; Ishigami, Hironori; Sakai, Yasuyuki; Kitayama, Joji; Ito, Taichi

    2016-03-16

    Hyaluronan (HA) is a promising drug carrier for cancer therapy because of its CD44 targeting ability, good biocompatibility, and biodegradability. In this study, cisplatin (CDDP)-incorporating HA nanogels were fabricated through a chelating ligand-metal coordination cross-linking reaction. We conjugated chelating ligands, iminodiacetic acid or malonic acid, to HA and used them as a precursor polymer. By mixing the ligand-conjugated HA with CDDP, cross-linking occurred via coordination of the ligands with the platinum in CDDP, resulting in the spontaneous formation of CDDP-loaded HA nanogels. The nanogels showed pH-responsive release of CDDP, because the stability of the ligand-platinum complex decreases in an acidic environment. Cell viability assays for MKN45P human gastric cancer cells and Met-5A human mesothelial cells revealed that the HA nanogels selectively inhibited the growth of gastric cancer cells. In vivo experiments using a mouse model of peritoneal dissemination of gastric cancer demonstrated that HA nanogels specifically localized in peritoneal nodules after the intraperitoneal administration. Moreover, penetration assays using multicellular tumor spheroids indicated that HA nanogels had a significantly higher ability to penetrate tumors than conventional, linear HA. These results suggest that chelating-ligand conjugated HA nanogels will be useful for targeted cancer therapy. PMID:26781684

  8. Functional and computational studies of the ligand-associated metal binding site of beta3 integrins.

    PubMed

    Murcia, Marta; Jirouskova, Marketa; Li, Jihong; Coller, Barry S; Filizola, Marta

    2008-06-01

    A combination of experimental and computational approaches was used to provide a structural context for the role of the beta3 integrin subunit ligand-associated metal binding site (LIMBS) in the binding of physiological ligands to beta3 integrins. Specifically, we have carried out (1) adhesion assays on cells expressing normal alphaIIbeta3, normal alphaVbeta3, or the corresponding beta3 D217A LIMBS mutants; and (2) equilibrium and nonequilibrium (steered) molecular dynamics (MD) simulations of eptifibatide in complex with either a fully hydrated normal alphaIIbeta3 integrin fragment (alphaIIb beta-propeller and the beta3 betaA (I-like), hybrid, and PSI domains) or the equivalent beta3 D217A mutant. Normal alphaIIbeta3 expressing cells adhered to immobilized fibrinogen and echistatin, whereas cells expressing the alphaIIbeta3 D217A LIMBS mutant failed to adhere to either ligand. Similarly, the equivalent alphaVbeta3 mutant was unable to support adhesion to vitronectin or fibrinogen. The alphaIIbeta3 D217A mutation increased the binding of mAb AP5, which recognizes a ligand-induced binding site (LIBS) in the beta3 PSI domain, indicating that this mutation induced allosteric changes in the protein. Steered MD simulating the unbinding of eptifibatide from either normal alphaIIbeta3 or the equivalent beta3 D217A mutant suggested that the reduction in ligand binding caused by the LIMBS mutant required the loss of both the LIMBS and the metal ion-dependent adhesion site (MIDAS) metal ions. Our computational results indicate that the LIMBS plays a crucial role in ligand binding to alphaIIbeta3 by virtue of its effects on the coordination of the MIDAS. PMID:18175315

  9. Metal-Ligand Cooperativity in a Methandiide-Derived Iridium Carbene Complex.

    PubMed

    Weismann, Julia; Waterman, Rory; Gessner, Viktoria H

    2016-03-01

    The synthesis, electronic structure, and reactivity of the first Group 9 carbene complex, [Cp*IrL] [L=C(Ph2 PS)(SO2 Ph)] (2), based on a dilithio methandiide are reported. Spectroscopic as well as computational studies have shown that, despite using a late transition-metal precursor, sufficient charge transfer occurred from the methandiide to the metal, resulting in a stable, nucleophilic carbene species with pronounced metal-carbon double-bond character. The potential of this iridium complex in the activation of a series of E-H bonds by means of metal-ligand cooperation has been tested. These studies have revealed distinct differences in the reactivity of 2 compared to a previously reported ruthenium analogue. Whereas attempts to activate the O-H bond in different phenol derivatives resulted in ligand cleavage, H-H and Si-H activation as well as dehydrogenation of isopropanol have been accomplished. These reactions are driven by the transformation of the carbene to an alkyl ligand. Contrary to a previously reported ruthenium carbene system, the dihydrogen activation has been found to proceed by a stepwise mechanism, with the activation first taking place solely at the metal. The activated products further reacted to afford a cyclometalated complex through liberation of the activated substrates. In the case of triphenylsilane, cyclometalation could thus be induced by a substoichiometric (i.e., catalytic) amount of silane. PMID:26748420

  10. Anchoring strategies for bimetallic species in zeolites

    SciTech Connect

    Bein, T.

    1993-03-01

    We explore a new approach by introducing heterobinuclear organometallic compounds for linking catalytic functions to zeolite frameworks. With two different metals present, the complexes are being anchored to the support via one oxophilic metal, ligand exchange and catalytic reactions may proceed at the second metal center. Anchoring chemistry, thermal stability and reactivity of Me[sub 3]SnMn(CO)[sub 5] in zeolite NaY and acid forms of zeolite Y was studied with X-ray absorption spectroscopy (Sn, Mn edge EXAFS) and in-situ FTIR/TPD-MS techniques. Subsequently, the tin-cobalt complex Me[sub 3]SnCo(CO)[sub 4] has been a focus of detailed synthetic and spectroscopic studies. The reactivity of tricarbonyl (cyclopentadienyl) (trimethylstannyl) molybdenum in new mesoporous hosts has been explored. A recent development is the design of vanadium oxo species in different micro- and mesoporous hosts. These are of great interest for the selective reduction of nitrogen oxides by ammonia, and selective oxidation of different hydrocarbons, such as xylenes, olefines and alkanes. Combination analytical techniques used to probe local structural changes at the molecular level, include EXAFS (Extended X-Ray Absorption Fine Structure) spectroscopy utilizing synchrotron radiation, in situ FT-IR coupled to thermodesorption/MS, UV-NIR, and CCD Raman.

  11. Synthesis and characterization of novel nitrogen-containing ligands for metal ion separations

    NASA Astrophysics Data System (ADS)

    Hoch, Cortney Leigh

    A serious limiting factor in the continued development of nuclear power is the disposal of high-level radioactive waste from spent nuclear fuel. The PUREX process can be used for the recovery of U and Pu, but it does not separate the products of fission which are potentially useful, but currently cause most of our problems with radioactive waste. An important complicating factor is the presence of large amounts of lanthanides in dissolved spent nuclear fuel. The separation of lanthanides (Ln) from actinides (An) is therefore critical to the future of nuclear power. One approach to recovering these materials and decreasing the volume of the radioactive waste is the development of novel, highly selective organic ligands for the lanthanide and actinide ions. The focus of this dissertation is to design and synthesize new tridentate polyaza-ligands expected to exhibit affinity for first-row transition metals, lanthanides and actinides. In general, these chelating agents are structurally and functionally related to the pyridine and bipyridine bis-triazinyl compounds that have been investigated for potential application as separations agents for radioactive materials. Selected 1,2,3-triazoles have been synthesized using Sharpless' "Click Chemistry". Variation of the backbone and substituents on the triazole ring allows for facile modification of the cation binding pocket and phase compatibility properties of the new compounds. Characterization of the new ligands was performed using conventional analytical methods. Overall, the studies with three different ligands revealed useful information about the continuing effort of ligand design for actinide (III)/lanthanide (III) separations. Crystal structures established the purity of the organic molecules by showing that the PTMP and BDTP ligands are able to bind transition metals. Also, it was shown that the BDTB ligand was able to bind to Nd 3+ as observed from the spectrophotometric titrations and the calculated binding constant. To increase the lipophilicity of the ligand, the addition of an alkyl chain on the 4-position of the pyridine ring could be made. This confirms that scientists are advancing in the area of ligand design and hopefully one day the ligand with all of the desired characteristics will be used to close the nuclear fuel cycle.

  12. Voltage clustering in redox-active ligand complexes: mitigating electronic communication through choice of metal ion

    DOE PAGESBeta

    Zarkesh, Ryan A.; Ichimura, Andrew S.; Monson, Todd C.; Tomson, Neil C.; Anstey, Mitchell R.

    2016-02-01

    We used the redox-active bis(imino)acenapthene (BIAN) ligand to synthesize homoleptic aluminum, chromium, and gallium complexes of the general formula (BIAN)3M. The resulting compounds were characterized using X-ray crystallography, NMR, EPR, magnetic susceptibility and cyclic voltammetry measurements and modeled using both DFT and ab initio wavefunction calculations to compare the orbital contributions of main group elements and transition metals in ligand-based redox events. Ultimately, complexes of this type have the potential to improve the energy density and electrolyte stability of grid-scale energy storage technologies, such as redox flow batteries, through thermodynamically-clustered redox events.

  13. Metallo-β-lactamases withstand low Zn(II) conditions by tuning metal-ligand interactions.

    PubMed

    González, Javier M; Meini, María-Rocío; Tomatis, Pablo E; Medrano Martín, Francisco J; Cricco, Julia A; Vila, Alejandro J

    2012-08-01

    A number of multiresistant bacterial pathogens inactivate antibiotics by producing Zn(II)-dependent β-lactamases. We show that metal uptake leading to an active dinuclear enzyme in the periplasmic space of Gram-negative bacteria is ensured by a cysteine residue, an unusual metal ligand in oxidizing environments. Kinetic, structural and affinity data show that such Zn(II)-cysteine interaction is an adaptive trait that tunes the metal binding affinity, thus enabling antibiotic resistance at restrictive Zn(II) concentrations. PMID:22729148

  14. Metallo-β-lactamases withstand low ZnII conditions by tuning metal-ligand interactions

    PubMed Central

    González, Javier M.; Meini, María-Rocío; Tomatis, Pablo E.; Medrano Martín, Francisco J.; Cricco, Julia A.; Vila, Alejandro J.

    2012-01-01

    A number of multiresistant bacterial pathogens inactivate antibiotics by producing ZnII-dependent β-lactamases. We show that metal uptake leading to an active dinuclear enzyme in the periplasmic space of Gram-negative bacteria is ensured by a cysteine residue, an unusual metal ligand in oxidizing environments. Kinetic, structural and affinity data show that such ZnII-Cys interaction is an adaptive trait tuning the metal binding affinity, thus enabling antibiotic resistance at restrictive ZnII concentrations. PMID:22729148

  15. Advances in Homogeneous Catalysis Using Secondary Phosphine Oxides (SPOs): Pre-ligands for Metal Complexes.

    PubMed

    Achard, Thierry

    2016-01-01

    The secondary phosphine oxides are known to exist in equilibrium between the pentavalent phosphine oxides (SPO) and the trivalent phosphinous acids (PA). This equilibrium can be displaced in favour of the trivalent tautomeric form upon coordination to late transition metals. This tutorial review provides the state of the art of the use of secondary phosphine oxides as pre-ligands in transition metal-catalysed reactions. Using a combination of SPOs and several metals such as Pd, Pt, Ru, Rh and Au, a series of effective and original transformations have been obtained and will be discussed here. PMID:26931212

  16. High performance ion chromatography of transition metal chelate complexes and aminopolycarboxylate ligands.

    PubMed

    Tófalvi, Renáta; Horváth, Krisztián; Hajós, Péter

    2013-01-11

    A simple ion chromatographic method was developed for the separation of transition metal chelates (CuEDTA, CuDCTA, ZnEDTA, ZnDCTA) and free anionic complexing ligands (EDTA, DCTA) using alkaline carbonate eluents and conductivity detection. The complex equilibria and kinetic process of separations were studied in order to understand major factors in the control of selectivity and retention order of complex anions. A systematic study was applied to identify the additional peaks of the system as NaEDTA(3-), NaHEDTA(2-), Na(2)EDTA(2-), EDTA(4-)/HEDTA(3-), DCTA(4-)/HDCTA(-3). On the basis of microequilibrium considerations of chelating ligand, it was shown that one should expect the peaks of sodium chelates when the ligand is in excess in the sample solution. The probability density function was introduced for calculation of complex chromatograms, because complexing ligands can exist in at least two different interconvertible forms in the presence of metal ion. The chromatogram of interconverting chelate species can be given as the sum of probability density functions (P) weighed by the molar fractions of complexed (Φ(ML)) and dissociated (Φ(L)) forms. The influences of kinetic rate of complex formation and dissociation on the distribution of components between eluents and ion exchange stationary phases were quantitatively described and demonstrated by elution profiles. The applicability of the developed method is represented by the simultaneous analysis of transition metal chelates and inorganic anions. ICP-AES analysis and FTIR-ATR technique were used for confirmation of IC results for metals and ligands, respectively. Collection protocols for the heart-cutting procedure of chromatograms were applied in the analysis of target components. The limit of detection and linearity of the method in the range of 0.01-0.25 mM sample concentration were also presented. PMID:23253118

  17. Actuated transitory metal--ligand bond as tunable electromechanical switch.

    PubMed

    Ohmann, Robin; Vitali, Lucia; Kern, Klaus

    2010-08-11

    Electrically tunable molecules are highly attractive for the construction of molecular devices, such as switches, transistors, or machines. Here, we present a novel nanomechanical element triggered by an electrical bias as external stimulus. We demonstrate that a transitory chemical bond between a copper atom and coordinating organic molecules adsorbed on a metal surface acts as variable frequency switch, which can be actuated and probed by means of low-temperature scanning tunneling microscopy. Whereas below a threshold bias voltage the bond is permanently either formed or broken the bonding state continuously oscillates at higher voltages. The switching rate of the bistable molecular system can be widely tuned from below 1 Hz up to the kilohertz regime. The quantum yield per tunneling electron to trigger a transition between the two states varies spatially and is related to the local density of states of the bonded and nonbonded configuration. PMID:20597466

  18. Stretchable Self-Healing Polymeric Dielectrics Cross-Linked Through Metal-Ligand Coordination.

    PubMed

    Rao, Ying-Li; Chortos, Alex; Pfattner, Raphael; Lissel, Franziska; Chiu, Yu-Cheng; Feig, Vivian; Xu, Jie; Kurosawa, Tadanori; Gu, Xiaodan; Wang, Chao; He, Mingqian; Chung, Jong Won; Bao, Zhenan

    2016-05-11

    A self-healing dielectric elastomer is achieved by the incorporation of metal-ligand coordination as cross-linking sites in nonpolar polydimethylsiloxane (PDMS) polymers. The ligand is 2,2'-bipyridine-5,5'-dicarboxylic amide, while the metal salts investigated here are Fe(2+) and Zn(2+) with various counteranions. The kinetically labile coordination between Zn(2+) and bipyridine endows the polymer fast self-healing ability at ambient condition. When integrated into organic field-effect transistors (OFETs) as gate dielectrics, transistors with FeCl2 and ZnCl2 salts cross-linked PDMS exhibited increased dielectric constants compared to PDMS and demonstrated hysteresis-free transfer characteristics, owing to the low ion conductivity in PDMS and the strong columbic interaction between metal cations and the small Cl(-) anions which can prevent mobile anions drifting under gate bias. Fully stretchable transistors with FeCl2-PDMS dielectrics were fabricated and exhibited ideal transfer characteristics. The gate leakage current remained low even after 1000 cycles at 100% strain. The mechanical robustness and stable electrical performance proved its suitability for applications in stretchable electronics. On the other hand, transistors with gate dielectrics containing large-sized anions (BF4(-), ClO4(-), CF3SO3(-)) displayed prominent hysteresis due to mobile anions drifting under gate bias voltage. This work provides insights on future design of self-healing stretchable dielectric materials based on metal-ligand cross-linked polymers. PMID:27099162

  19. Identification of an altered peptide ligand based on the endogenously presented, rheumatoid arthritis-associated, human cartilage glycoprotein-39(263–275) epitope: an MHC anchor variant peptide for immune modulation

    PubMed Central

    Boots, Annemieke MH; Hubers, Henk; Kouwijzer, Milou; den Hoed-van Zandbrink, Leontien; Westrek-Esselink, Bernice M; van Doorn, Cindy; Stenger, Rachel; Bos, Ebo S; van Lierop, Marie-jose C; Verheijden, Gijs F; Timmers, Cornelis M; van Staveren, Catharina J

    2007-01-01

    We sought to identify an altered peptide ligand (APL) based on the endogenously expressed synovial auto-epitope of human cartilage glycoprotein-39 (HC gp-39) for modulation of cognate, HLA-DR4-restricted T cells. For this purpose we employed a panel of well-characterized T cell hybridomas generated from HC gp-39-immunized HLA-DR4 transgenic mice. The hybridomas all respond to the HC gp-39(263–275) epitope when bound to HLA-DR4(B1*0401) but differ in their fine specificities. First, the major histocompatibility complex (MHC) and T-cell receptor (TCR) contact residues were identified by analysis of single site substituted analogue peptides for HLA-DR4 binding and cognate T cell recognition using both T hybridomas and polyclonal T cells from peptide-immunized HLA-DR4 transgenic mice. Analysis of single site substituted APL by cognate T cells led to identification of Phe265 as the dominant MHC anchor. The amino acids Ala268, Ser269, Glu271 and Thr272 constituted the major TCR contact residues, as substitution at these positions did not affect HLA-DR4(B1*0401) binding but abrogated T cell responses. A structural model for visualisation of TCR recognition was derived. Second, a set of non-classical APLs, modified at the MHC key anchor position but with unaltered TCR contacts, was developed. When these APLs were analysed, a partial TCR agonist was identified and found to modulate the HC gp-39(263–275)-specific, pro-inflammatory response in HLA-DR4 transgenic mice. We identified a non-classical APL by modification of the p1 MHC anchor in a synovial auto-epitope. This APL may qualify for rheumatoid arthritis immunotherapy. PMID:17645792

  20. Coupled metal partitioning dynamics and toxicodynamics at biointerfaces: a theory beyond the biotic ligand model framework.

    PubMed

    Duval, Jérôme F L

    2016-04-14

    A mechanistic understanding of the processes governing metal toxicity to microorganisms (bacteria, algae) calls for an adequate formulation of metal partitioning at biointerfaces during cell exposure. This includes the account of metal transport dynamics from bulk solution to biomembrane and the kinetics of metal internalisation, both potentially controlling the intracellular and surface metal fractions that originate cell growth inhibition. A theoretical rationale is developed here for such coupled toxicodynamics and interfacial metal partitioning dynamics under non-complexing medium conditions with integration of the defining cell electrostatic properties. The formalism explicitly considers intertwined metal adsorption at the biointerface, intracellular metal excretion, cell growth and metal depletion from bulk solution. The theory is derived under relevant steady-state metal transport conditions on the basis of coupled Nernst-Planck equation and continuous logistic equation modified to include metal-induced cell growth inhibition and cell size changes. Computational examples are discussed to identify limitations of the classical Biotic Ligand Model (BLM) in evaluating metal toxicity over time. In particular, BLM is shown to severely underestimate metal toxicity depending on cell exposure time, metal internalisation kinetics, cell surface electrostatics and initial cell density. Analytical expressions are provided for the interfacial metal concentration profiles in the limit where cell-growth is completely inhibited. A rigorous relationship between time-dependent cell density and metal concentrations at the biosurface and in bulk solution is further provided, which unifies previous equations formulated by Best and Duval under constant cell density and cell size conditions. The theory is sufficiently flexible to adapt to toxicity scenarios with involved cell survival-death processes. PMID:26980542

  1. Atomically Precise Alkynyl-Protected Metal Nanoclusters as a Model Catalyst: Observation of Promoting Effect of Surface Ligands on Catalysis by Metal Nanoparticles.

    PubMed

    Wang, Yu; Wan, Xian-Kai; Ren, Liting; Su, Haifeng; Li, Gang; Malola, Sami; Lin, Shuichao; Tang, Zichao; Häkkinen, Hannu; Teo, Boon K; Wang, Quan-Ming; Zheng, Nanfeng

    2016-03-16

    Metal nanoclusters whose surface ligands are removable while keeping their metal framework structures intact are an ideal system for investigating the influence of surface ligands on catalysis of metal nanoparticles. We report in this work an intermetallic nanocluster containing 62 metal atoms, Au34Ag28(PhC≡C)34, and its use as a model catalyst to explore the importance of surface ligands in promoting catalysis. As revealed by single-crystal diffraction, the 62 metal atoms in the cluster are arranged as a four-concentric-shell Ag@Au17@Ag27@Au17 structure. All phenylalkynyl (PA) ligands are linearly coordinated to the surface Au atoms with staple "PhC≡C-Au-C≡CPh" motif. Compared with reported thiolated metal nanoclusters, the surface PA ligands on Au34Ag28(PhC≡C)34 are readily removed at relatively low temperatures, while the metal core remains intact. The clusters before and after removal of surface ligands are used as catalysts for the hydrolytic oxidation of organosilanes to silanols. It is, for the first time, demonstrated that the organic-capped metal nanoclusters work as active catalysts much better than those with surface ligands partially or completely removed. PMID:26922997

  2. Anchor Modeling

    NASA Astrophysics Data System (ADS)

    Regardt, Olle; Rönnbäck, Lars; Bergholtz, Maria; Johannesson, Paul; Wohed, Petia

    Maintaining and evolving data warehouses is a complex, error prone, and time consuming activity. The main reason for this state of affairs is that the environment of a data warehouse is in constant change, while the warehouse itself needs to provide a stable and consistent interface to information spanning extended periods of time. In this paper, we propose a modeling technique for data warehousing, called anchor modeling, that offers non-destructive extensibility mechanisms, thereby enabling robust and flexible management of changes in source systems. A key benefit of anchor modeling is that changes in a data warehouse environment only require extensions, not modifications, to the data warehouse. This ensures that existing data warehouse applications will remain unaffected by the evolution of the data warehouse, i.e. existing views and functions will not have to be modified as a result of changes in the warehouse model.

  3. Extraction of metals using supercritical fluid and chelate forming ligand

    DOEpatents

    Wai, C.M.; Laintz, K.E.

    1998-03-24

    A method of extracting metalloid and metal species from a solid or liquid material by exposing the material to a supercritical fluid solvent containing a chelating agent is described. The chelating agent forms chelates that are soluble in the supercritical fluid to allow removal of the species from the material. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is a fluorinated {beta}-diketone. In especially preferred embodiments the extraction solvent is supercritical carbon dioxide, and the chelating agent comprises a fluorinated {beta}-diketone and a trialkyl phosphate, or a fluorinated {beta}-diketone and a trialkylphosphine oxide. Although a trialkyl phosphate can extract lanthanides and actinides from acidic solutions, a binary mixture comprising a fluorinated {beta}-diketone and a trialkyl phosphate or a trialkylphosphine oxide tends to enhance the extraction efficiencies for actinides and lanthanides. The method provides an environmentally benign process for removing contaminants from industrial waste without using acids or biologically harmful solvents. The method is particularly useful for extracting actinides and lanthanides from acidic solutions. The chelate and supercritical fluid can be regenerated, and the contaminant species recovered, to provide an economic, efficient process. 7 figs.

  4. De Novo Design of Ligands for Metal Separation - Final Report - 09/15/1996 - 09/14/2000

    SciTech Connect

    Marshall, Garland, R.

    2001-09-14

    This application focuses on the development of appropriate computation tools and parameters for the de novo design of selective metal ligands. We have developed a successful suite of tools for computer-aided design of ligands for receptors of known three-dimensional structure (structure-based design), including the prediction of affinity. Adaptation of the algorithms to place donor atoms at appropriate geometrical locations surrounding the metal of interest, rather than filling up a cavity with donor/acceptor atoms placed optimally to interact with a protein active site, is straightforward. Appropriate geometrical parameters for metals can be derived from crystal structures and force constants adapted from recent advances in theories of metal-ligand interactions. The practical goal is computer-aided design of ligands which would be selective for one metal over another with a predicted selectivity ratio and affinity.

  5. Quantitative structure-property relationships for predicting metal binding by organic ligands.

    PubMed

    Cabaniss, Stephen E

    2008-07-15

    Quantitative structure-property relationships (QSPRs) are developed to predict the complexation of Al(III), Ca(II), Cd(II), Cu(II), Ni(II), Pb(II), and Zn(II) by organic ligands containing carboxylate, phenol, amine, ether, and alcoholfunctional groups. These QSPRs predict conditional stability constants (K(M') at pH 7.0 and I = 0.1) over a range of ligand types with consistent uncertainties of approximately 1 log unit without requiring any steric or connectivity information. Calibration and validation data sets were constructed using 1:1 complex formation constants from the NIST Critical Stability Constants database (version 8.0). The descriptor variables are intuitive quantities conceptually related to metal binding, such as the numbers of various ligand groups, charge density, etc. The resulting calibrations have r2 = 0.87 to 0.93 and Spred = 0.67 to 1.05 log units, with positive values for all ligand count descriptor variables. The QSPRs account for 75-95% of the variability in the validation data set with RMSE of 0.74 to 1.30 log units. These QSPRs improve upon previous work by providing a tested and mechanistically reasonable method for log K(M') prediction with uncertainties comparable to or betterthan other QSPRs calibrated with groups of diverse ligands. PMID:18754371

  6. Distortions of a flexible metal-organic framework from substituted pendant ligands.

    PubMed

    Munn, Alexis S; Clarkson, Guy J; Walton, Richard I

    2014-02-01

    Four new variants of the 1,4-benzenedicarboxylate MIL-53 structure have been prepared for Co(II) under solvothermal conditions and their structures solved and refined from single-crystal X-ray data. All materials contain pendant pyridine-N-oxide ligands that bridge pairs of Co(II) atoms in the inorganic backbone of the structure via O. By the use of the ligands 3-bromopyridine-N-oxide, 4-methoxypyridine-N-oxide, isoquinoline-N-oxide and 4-phenylpyridine-N-oxide, materials are prepared with the same topology but distinct structures. These illustrate how the MIL-53 structure is able to distort to accommodate the bulk of the various substituents on the pyridine ring. The bulkiest pendant ligand, 4-phenylpyridine-N-oxide, results in a distortion of the diamond-shaped channels in an opposite sense to that seen previously in expanded forms of the parent MIL-53 structure. By comparison with published crystal structures for MIL-53 with various occluded guests, the structural distortions that take place to accommodate the pendant ligands are quantified and it is shown how a twisting of the 1,4-benzenedicarboxylate ligand, instead of a hinging about the μ(2)-carboxylate-metal connection, allows the new structures that are observed. PMID:24441123

  7. Four transition metal complexes with a semicarbazone ligand bearing pyrazine unit

    NASA Astrophysics Data System (ADS)

    Chen, Hong; Ma, Xiu-qin; Lv, Yan-yun; Jia, Lei; Xu, Jun; Wang, Yuan; Ge, Zhi-jun

    2016-04-01

    Four new complexes based on L (where L = 3-ethyl-2-acetylpyrazine semicarbazone), namely [CoL2]Cl2·0.5H2O (1), [CoL2](NO3)2 (2), [CdL(H2O)2(NO3)](NO3)·H2O (3) and [CuL(CH3OH)Cl2]·[CuLCl2] (4) have been synthesized and characterized by X-ray diffraction analyses. The results show that the semicarbazone acts as a tridentate neutral ligand in all complexes. Each of complex 1 and 2 reveals a distorted octahedral geometry around the metal ion provided by two units of the ligand, while the ratio of the ligand and metal is 1:1 in complexes 3 and 4. The effect of complexes 1-4 on cell proliferation, apoptosis of human pancreatic cancer (Patu8988), human gastric cancer (SGC7901) and human hepatic cancer (SMMC7721) cell lines have been detected by MTT assay, Annexin V/PI double staining flow cytometry and TUNEL assay. The results show that complexes 1-4 can inhibit cell proliferation of Patu8988, SGC7901 and SMMC7721 cells, significantly higher than the effect of the ligand. However, the complex 4 reveals higher apoptosis rate, and displays up-regulated expression level of caspase 3, detected by western blotting, which also indicates the complex 4 can induce caspase-dependent cell apoptosis in SMMC7721.

  8. Functional Identification of Ligands for a Catalytic Metal Ion in Group I Introns†

    PubMed Central

    Forconi, Marcello; Lee, Jihee; Lee, Jungjoon K.; Piccirilli, Joseph A.; Herschlag, Daniel

    2009-01-01

    Many enzymes use metal ions within their active sites to achieve enormous rate acceleration. Understanding how metal ions mediate catalysis requires elucidation of metal ion interactions with both the enzyme and the substrate(s). The three-dimensional arrangement determined by X-ray crystallography provides a powerful starting point for identifying ground state interactions, but only functional studies can establish and interrogate transition state interactions. The Tetrahymena group I ribozyme is a paradigm for the study of RNA catalysis, and previous work using atomic mutagenesis and quantitative analysis of metal ion rescue behavior identified catalytic metal ions making five contacts with the substrate atoms. Here, we have combined atomic mutagenesis with site-specific phosphorothioate substitutions in the ribozyme backbone to establish transition state ligands on the ribozyme for one of the catalytic metal ions, referred to as MA. We identified the pro-S P oxygen atoms at nucleotides C208, A304, and A306 as ground state ligands for Ma, verifying interactions suggested by the Azoarcus crystal structures. We further established that these interactions are present in the chemical transition state, a conclusion that requires functional studies, such as those carried out herein. Elucidating these active site connections is a crucial step toward an in-depth understanding of how specific structural features of the group I intron lead to catalysis. PMID:18517225

  9. Functional identification of ligands for a catalytic metal ion in group I introns.

    PubMed

    Forconi, Marcello; Lee, Jihee; Lee, Jungjoon K; Piccirilli, Joseph A; Herschlag, Daniel

    2008-07-01

    Many enzymes use metal ions within their active sites to achieve enormous rate acceleration. Understanding how metal ions mediate catalysis requires elucidation of metal ion interactions with both the enzyme and the substrate(s). The three-dimensional arrangement determined by X-ray crystallography provides a powerful starting point for identifying ground state interactions, but only functional studies can establish and interrogate transition state interactions. The Tetrahymena group I ribozyme is a paradigm for the study of RNA catalysis, and previous work using atomic mutagenesis and quantitative analysis of metal ion rescue behavior identified catalytic metal ions making five contacts with the substrate atoms. Here, we have combined atomic mutagenesis with site-specific phosphorothioate substitutions in the ribozyme backbone to establish transition state ligands on the ribozyme for one of the catalytic metal ions, referred to as M A. We identified the pro-S P oxygen atoms at nucleotides C208, A304, and A306 as ground state ligands for M A, verifying interactions suggested by the Azoarcus crystal structures. We further established that these interactions are present in the chemical transition state, a conclusion that requires functional studies, such as those carried out herein. Elucidating these active site connections is a crucial step toward an in-depth understanding of how specific structural features of the group I intron lead to catalysis. PMID:18517225

  10. Solid State Structures of Alkali Metal Ion Complexes Formed by Low-Molecular-Weight Ligands of Biological Relevance.

    PubMed

    Aoki, Katsuyuki; Murayama, Kazutaka; Hu, Ning-Hai

    2016-01-01

    This chapter provides structural data, mainly metal binding sites/modes, observed in crystal structures of alkali metal ion complexes containing low-molecular-weight ligands of biological relevance, mostly obtained from the Cambridge Structural Database (the CSD version 5.35 updated to February 2014). These ligands include (i) amino acids and small peptides, (ii) nucleic acid constituents (excluding quadruplexes and other oligonucleotides), (iii) simple carbohydrates, and (iv) naturally occurring antibiotic ionophores. For some representative complexes of these ligands, some details on the environment of the metal coordination and structural characteristics are described. PMID:26860299

  11. Synthesis of new microbial pesticide metal complexes derived from coumarin-imine ligand.

    PubMed

    Elhusseiny, Amel F; Aazam, Elham S; Al-Amri, Huda M

    2014-07-15

    A series of metal complexes of zinc(II), cadmium(II), copper(II), nickel(II) and palladium(II) have been synthesized from coumarin-imine ligand, 8-[(1E)-1-(2-aminophenyliminio)ethyl]-2-oxo-2H-chromen-7-olate, [HL]. The structures of the complexes were proposed in the light of their spectroscopic, molar conductance, magnetic and thermal studies. The ligand coordinated in a tridentate manner through the azomethine nitrogen, the phenolic oxygen and the amine nitrogen and all complexes were non-electrolytes with different geometrical arrangements around the central metal ion. Photoluminescence data unambiguously showed remarkable fluorescence enhancement to Zn(2+) over other cations. The antimicrobial screening tests revealed that copper(II) complex exhibited the highest potency and its minimum inhibitory concentration on the enzymatic activities of the tested microbial species was determined. No toxin productivity was detected for all tested toxigenic species upon the exposure of copper complex. PMID:24704603

  12. Synthesis of new microbial pesticide metal complexes derived from coumarin-imine ligand

    NASA Astrophysics Data System (ADS)

    Elhusseiny, Amel F.; Aazam, Elham S.; Al-Amri, Huda M.

    2014-07-01

    A series of metal complexes of zinc(II), cadmium(II), copper(II), nickel(II) and palladium(II) have been synthesized from coumarin-imine ligand, 8-[(1E)-1-(2-aminophenyliminio)ethyl]-2-oxo-2H-chromen-7-olate, [HL]. The structures of the complexes were proposed in the light of their spectroscopic, molar conductance, magnetic and thermal studies. The ligand coordinated in a tridentate manner through the azomethine nitrogen, the phenolic oxygen and the amine nitrogen and all complexes were non-electrolytes with different geometrical arrangements around the central metal ion. Photoluminescence data unambiguously showed remarkable fluorescence enhancement to Zn2+ over other cations. The antimicrobial screening tests revealed that copper(II) complex exhibited the highest potency and its minimum inhibitory concentration on the enzymatic activities of the tested microbial species was determined. No toxin productivity was detected for all tested toxigenic species upon the exposure of copper complex.

  13. An evolutionarily conserved alternate metal ligand is important for activity in ?-isopropylmalate synthase from Mycobacterium tuberculosis.

    PubMed

    Frantom, Patrick A; Birman, Yuliya; Hays, Brittani N; Casey, Ashley K

    2014-10-01

    Members of the DRE-TIM metallolyase superfamily rely on an active-site divalent cation to catalyze various reactions involving the making and breaking of carbon-carbon bonds. While the identity of the metal varies, the binding site is well-conserved at the superfamily level with an aspartic acid and two histidine residues acting as ligands to the metal. Previous structural and bioinformatics results indicate that the metal can adopt an alternate architecture through the addition of an asparagine residue as a fourth ligand. This asparagine residue is strictly conserved in all members of the DRE-TIM metallolyase superfamily except fungal homocitrate synthase (HCS-lys) where it is replaced with isoleucine. The role of this additional metal ligand in ?-isopropylmalate synthase from Mycobacterium tuberculosis (MtIPMS) has been investigated using site-directed mutagenesis. Substitution of the asparagine ligand with alanine or isoleucine results in inactive enzymes with respect to ?-isopropylmalate formation. Control experiments suggest that the substitutions have not drastically affected the enzyme's structure indicating that the asparagine residue is essential for catalysis. Interestingly, all enzyme variants retained acetyl CoA hydrolysis activity in the absence of ?-ketoisovalerate, similar to the wild-type enzyme. In contrast to the requirement of magnesium for ?-isopropylmalate formation, hydrolytic activity could be inhibited by the addition of magnesium chloride in wild-type, D81E, and N321A MtIPMS, but not in the other variants studied. Attempts to rescue loss of activity in N321I MtIPMS by mimicking the fungal HCS active site through the D81E/N321I double variant were unsuccessful. This suggests epistatic constraints in evolution of function in IPMS and HCS-lys enzymes. PMID:25064783

  14. Highly Fluorescent Group 13 Metal Complexes with Cyclic, Aromatic Hydroxamic Acid Ligands

    SciTech Connect

    Seitz, Michael; Moore, Evan G.; Raymond, Kenneth N.

    2008-02-11

    The neutral complexes of two ligands based on the 1-oxo-2-hydroxy-isoquinoline (1,2-HOIQO) motif with group 13 metals (Al, Ga, In) show bright blue-violet luminescence in organic solvents. The corresponding transition can be attributed to ligand-centered singlet emission, characterized by a small Stokes shifts of only a few nm combined with lifetimes in the range between 1-3 ns. The fluorescence efficiency is high, with quantum yields of up to 37% in benzene solution. The crystal structure of one of the indium(III) complexes (trigonal space group R-3, a = b = 13.0384(15) {angstrom}, c = 32.870(8) {angstrom}, ? = {beta} = 90{sup o}, {gamma} = 120{sup o}, V = 4839.3(14) {angstrom}{sup 3}, Z = 6) shows a six-coordinate geometry around the indium center which is close to trigonal-prismatic, with a twist angle between the two trigonal faces of 20.7{sup o}. Time-dependent density functional theory (TD-DFT) calculations (Al and Ga: B3LYP/6-31G(d)); In: B3LYP/LANL2DZ of the fac and mer isomers with one of the two ligands indicate that there is no clear preference for either one of the isomeric forms of the metal complexes. In addition, the metal centers do not have a significant influence on the electronic structure, and as a consequence, on the predominant intraligand optical transitions.

  15. A QICAR approach for quantifying binding constants for metal-ligand complexes.

    PubMed

    Zhou, Dong-Mei; Li, Lian-Zhen; Peijnenburg, Willie J G M; Ownby, David R; Hendriks, A Jan; Wang, Peng; Li, Dan-Dan

    2011-05-01

    Relative metal-ligand complex stability is predicted by evaluating the relationships between physicochemical properties of metal ions and their experimental biotic and abiotic binding constants, K. Linear regression analysis showed that the softness index (σ(p)) and the covalent index (χ(2)(m) r) were especially useful in model construction for rainbow trout (Oncorhynchus mykiss), fathead minnows (Pimephales promelas) and crustaceansaquatic (Daphnia magna) based on RMSE and F-ratio criterion (F(observed)/F(critical) of ≥4). The absolute value of the log of the first hydrolysis constant |logK(OH)| correlated best with logK values for barley (R(2)=0.74, p=0.02) and earthworm (R(2)=0.82, p=0.01). In contrast, the ionic index Z(2)/r explained most of the variability of logK values for the two clays kaolinite and montmorillonite, while |logK(OH)| was a better predictor of the generic NICA-Donnan parameters for HA and FA (0.67ligands and the different binding mechanisms between metal and ligands. PMID:21377206

  16. Synthesis, characterization and antimicrobial activities of mixed ligand transition metal complexes with isatin monohydrazone Schiff base ligands and heterocyclic nitrogen base

    NASA Astrophysics Data System (ADS)

    Devi, Jai; Batra, Nisha

    2015-01-01

    Mixed ligand complexes of Co(II), Ni(II), Cu(II) and Zn(II) with various uninegative tridentate ligands derived from isatin monohydrazone with 2-hydroxynapthaldehyde/substituted salicylaldehyde and heterocyclic nitrogen base 8-hydroxyquinoline have been synthesized and characterized by elemental analysis, conductometric studies, magnetic susceptibility and spectroscopic techniques (IR, UV-VIS, NMR, mass and ESR). On the basis of these characterizations, it was revealed that Schiff base ligands existed as monobasic tridentate ONO bonded to metal ion through oxygen of carbonyl group, azomethine nitrogen and deprotonated hydroxyl oxygen and heterocyclic nitrogen base 8-hydroxyquinoline existed as monobasic bidentate ON bonded through oxygen of hydroxyl group and nitrogen of quinoline ring with octahedral or distorted octahedral geometry around metal ion. All the compounds have been tested in vitro against various pathogenic Gram positive bacteria, Gram negative bacteria and fungi using different concentrations (25, 50, 100, 200 μg/mL) of ligands and their complexes. Comparative study of antimicrobial activity of ligands, and their mixed complexes indicated that complexes exhibit enhanced activity as compared to free ligands and copper(II) Cu(LIV)(Q)ṡH2O complex was found to be most potent antimicrobial agent.

  17. Electrophilic metal alkyl chemistry in new ligand environments. Annual report, January 1, 1992--September 15, 1992

    SciTech Connect

    Jordan, R.F.

    1992-12-31

    Methods have been worked out for efficient synthesis of various N{sub 4}{sup 2{minus}} macrocyclic ligands, neutral group 4 metal (e.g., Zr) (N{sub 4})MR{sub 2} complexes, and cationic mono-alkyl (N{sub 4})M(R){sup +} species. Intital indications are that the latter will be highly reactive in base-free form. Objective is to develop new types of electrophilic metal alkyl complexes for study of olefin polymerization and C-H activation catalysis.

  18. Four homochiral coordination polymers contain N-acetyl-L-tyrosine and different N-donor ligand: Influence of metal cations, ancillary ligands and coordination modes

    SciTech Connect

    Li, Meng-Li; Song, Hui-Hua

    2013-10-15

    Using the chiral ligand N-acetyl-L-tyrosine (Hacty) and maintaining identical reaction conditions, Zn(II), Co(II), and Cd(II) salts provided four novel homochiral coordination polymers ([Zn(acty)(bipy){sub 2}(H{sub 2}O){sub 2}]·NO{sub 3}·2H{sub 2}O){sub n}1, ([Co(acty)(bipy){sub 2}(H{sub 2}O){sub 2}]·NO{sub 3}·2H{sub 2}O){sub n}2, ([Cd(acty){sub 2}(bipy)H{sub 2}O]·H{sub 2}O){sub n}3, and ([Cd(acty)(bpe){sub 2}(Ac)]·6H{sub 2}O){sub n}4 (bipy=4,4′-bipyridine; bpe=1,2-di(4-pyridyl)ethane) in the presence of ancillary ligands. Compounds 1 and 2 are isostructural 1D chain structures. The neighboring chains are further linked into a 3D supramolecular structure via π⋯π stacking and hydrogen bond interactions. Compound 3 shows a 2D network and 4 generates 1D infinite chains along the c-axis. Compounds 3 and 4 are further connected into 3D supramolecular network by hydrogen bond interactions. More importantly, coordination in acyl oxygen atoms and ancillary ligands (bpe) as monodentate decorating ligands in 4 are rarely reported. Ancillary ligands and metal cations significantly influence the structure of the complexes. The photoluminescence properties of 1, 3, and 4 were studied at room temperature. Circular dichroism (CD) of the complexes have been investigated. - Graphical abstract: Four new homochiral coordination polymers were prepared and structurally characterized, which investigate the influence of the ancillary ligands and metal ions on the design and synthesis of coordination polymers. Display Omitted - Highlights: • It is rarely reported that the chiral coordination polymers prepared with N-acetyl-L-tyrosine ligands. • The alkalescent acetyl oxygen atom is difficult to participate in coordination but it is happened in the N-acetyl-L-tyrosine ligands. • The ancillary ligands (4,4′-bipy and bpe) are present in an unusual coordination modes, monodentate decorating ligands in 1, 2 and 4. • Structure comparative analyses results indicate that the secondary ligands and metal ions influence the fabrication of these inorganic–organic arrangements.

  19. Anchor connector

    SciTech Connect

    Quigg, D.F.; Bell, J.L. Jr.; Jones, D.L.; McFerron, R.G.

    1984-03-27

    An anchor connector incorporating a flexible joint for securing the tension legs of a tensioned leg platform. A latch dog head engages a first recess on the fixed member of the flexible joint and a template recess to prevent disconnection when the dog heads and latch carrier are in a lower position. With the latch carrier (40) in an upper position the latch dog heads fit within a second recess (44) in the fixed member with the dog heads clearing shoulder of template recess, whereby the connector may be released.

  20. The influence of the enantiomeric ratio of an organic ligand on the structure and chirality of Metal-Organic Frameworks

    PubMed Central

    Burneo, Iván; Stylianou, Kyriakos C.; Imaz, Inhar; Maspoch, Daniel

    2016-01-01

    We have prepared three distinct polyamino acid-based metal-organic frameworks (MOFs) with different chirality and porosity using the same chemistry, by simply modifying the enantiomeric ratio of the chiral organic ligand used. PMID:25253285

  1. Homoleptic Transition Metal Complexes of the 7-Azaindolide Ligand Featuring κ1-N1 Coordination

    PubMed Central

    Fillman, Kathlyn L.; Arman, Hadi D.; Tonzetich, Zachary J.

    2015-01-01

    Homoleptic complexes of the anion of 7-azaindole (AzaIn) have been synthesized and characterized for a series of 3d transition metals. For Mn(II), Fe(II), and Co(II), complexes of formula Na2[M(AzaIn)4]·2L (L = THF, 2-MeTHF, toluene, or benzene) have been isolated by treatment of the corresponding metal chloride salts with 7-azaindole in the presence of sodium hexamethyldisilazide. The complexes adopt tetrahedral geometries with exclusive coordination to the transition metal ion through the pyrrolic N1 nitrogen atoms of the AzaIn ligands. Solid-state structures of the complexes demonstrate that the sodium cations remain tightly associated to the coordination entities through interaction with both the pyrrolic and pyridine nitrogen atoms of the azaindolide ligands. For Fe(II), replacement of the sodium cations by other alkali metal ions (Li or K) generates new complexes that demonstrate similar coordination geometries to the sodium salts. As a means of comparison, the Fe(II) complex of 4-azaindolide was also investigated. Na2[Fe(4-AzaIn)4]·2L adopts a similar solution structure to the 7-azaindolide complexes as judged by NMR spectroscopy and cyclic voltammetry. DFT calculations have been performed to investigate the bonding in the 7-azaindolide complexes. Results demonstrate that 7-azaindolide-κ1-N1 is a nearly pure sigma donor ligand that features a high degree of ionic character in its bonding to mid 3d transition metal ions. PMID:26378471

  2. Homoleptic transition metal complexes of the 7-azaindolide ligand featuring κ(1)-N1 coordination.

    PubMed

    Przyojski, Jacob A; Kiewit, Monica L; Fillman, Kathlyn L; Arman, Hadi D; Tonzetich, Zachary J

    2015-10-01

    Homoleptic complexes of the anion of 7-azaindole (AzaIn) were synthesized and characterized for a series of 3d transition metals. For Mn(II), Fe(II), and Co(II), complexes of formula Na2[M(AzaIn)4]·2L (L = tetrahydrofuran (THF), 2-MeTHF, toluene, or benzene) were isolated by treatment of the corresponding metal chloride salts with 7-azaindole in the presence of sodium hexamethyldisilazide. The complexes adopt tetrahedral geometries with exclusive coordination to the transition metal ion through the pyrrolic N1 nitrogen atoms of the AzaIn ligands. Solid-state structures of the complexes demonstrate that the sodium cations remain tightly associated with the coordination entities through interaction with both the pyrrolic and pyridine nitrogen atoms of the azaindolide ligands. For Fe(II), replacement of the sodium cations by other alkali metal ions (Li or K) generates new complexes that demonstrate similar coordination geometries to the sodium salts. As a means of comparison, the Fe(II) complex of 4-azaindolide was also investigated. Na2[Fe(4-AzaIn)4]·2L adopts a similar solution structure to the 7-azaindolide complexes as judged by NMR spectroscopy and cyclic voltammetry. Density functional theory calculations were performed to investigate the bonding in the 7-azaindolide complexes. Results demonstrate that 7-azaindolide-κ(1)-N1 is a nearly pure sigma donor ligand that features a high degree of ionic character in its bonding to mid 3d transition metal ions. PMID:26378471

  3. Redox, thermodynamic and spectroscopic of some transition metal complexes containing heterocyclic Schiff base ligands

    NASA Astrophysics Data System (ADS)

    Abu-Hussen, Azza A. A.; Linert, Wolfgang

    2009-09-01

    Complexes of two series of Schiff base ligands, H 2L a and H 2L b derived from the reaction of 2,6-diacetyl pyridine with semicarbazide, H 2L a and thiosemicarbazide, H 2L b, with the metal ions, Co(II), Ni(II), Cu(II), VO(IV) and UO 2(VI) have been prepared. The ligands are characterized by elemental analysis, IR, UV-vis and 1H NMR. The structures of the complexes are investigated with the IR, UV-vis, X-band ESR spectra, 1H NMR and thermal gravimetric analysis as well as conductivity and magnetic moment measurements. The IR-spectra reveal the presence of variable modes of chelation for the investigated ligands. A variety of binuclear or mononuclear complexes were obtained with the two ligands in tri-, tetra or pentadentate forms. The bonding sites are the pyridine nitrogen, two azomethine nitrogen atoms and ketonic oxygen in case of H 2L a or sulphur atoms in case of H 2L b. The Coats-Redfern equation has been used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition steps of some complexes. Cyclic voltammograms of Co(II) and Ni(II) show quasi-reversible peaks. The redox properties and the nature of the electro-active species of the complexes have been characterized.

  4. Aspects of C-H Activation in Metal Complexes Containing Sulfur Ligands

    SciTech Connect

    Rakowski-DuBois, Mary C.

    2004-10-08

    The research project proposed to synthesize new metal complexes with sulfido, disulfido and other types of reactive sulfur ligands, and to explore the joint reactivity of metal and sulfur ligands with hydrogen and organic molecules. The overall objective was to investigate reaction pathways relevant to those observed for the heterogeneous metal sulfide catalysts which promote hydrogen activation, hydrogenation-dehydrogenation of organic substrates, and hydrogenolysis of carbon-heteroatom bonds. Particular emphasis was placed on CpRe derivatives (where Cp might be C5H5 or alkylated versions) so that comparisons could be made with the previously studied CpMo complexes, which showed extensive reactivity at the sulfur ligands. Heterogeneous rhenium sulfides generally show higher catalytic activity than molybdenum sulfides, and this is attributed, in part, to the weaker Re-S bond strength, relative to the moybdenum-sulfur bond. In our studies of discrete Re-sulfide complexes, we have also observed evidence for weaker Re-S bonds relative to the molybdenum systems. In addition we have characterized novel hydrogen activation by rhenium sulfido complexes, as well as carbon-hydrogen, carbon-sulfur and metal sulfur bond cleavage reactions. Hydrogen Activation. The complex Cp{prime}ReCl2S3 was synthesized in ca 70% yield and characterized by an X-ray diffraction study which confirms that the complex contains a {eta}2-trisulfide ligand. The cyclic voltammogram of Cp{prime}ReCl2S3 shows a wide window of redox stability with an irreversible reduction wave at -0.97 V and an irreversible oxidation at +1.03 V vs Fc. Nevertheless, the complex undergoes a facile reaction with hydrogen at 50 C to form H2S and a new dinuclear sulfido bridged rhenium complex. This reaction is of interest because it is the first example of the hydrogenolysis of a discrete metal polysulfide complex to produce H2S, a reaction also observed for heterogeneous rhenium sulfides. The reaction contrasts with those of related Cp-molybdenum complexes with sulfide ligands, which also activate hydrogen, but generally form hydrosulfido products without H2S elimination. C-H and C-S Cleavage Reactions. New mononuclear Cp{prime}Re(dithiolate) complexes such as Cp{prime}ReCl2(SC2H4S), 1, have been prepared and characterized and have been found to display a very interesting range of reactions. The thermal reaction of 1 involves the dehydrogenation of the alkanedithiolate ligand to form Cp{prime}ReCl2(SCH=CHS), 2 as well as a competing elimination of olefin from the dithiolate ligand in 1. On the basic of kinetic and related studies, the mechanism is proposed to involve a sequential series of reactions. In the first reaction, the olefin extrusion is proposed to produce a reactive Re-disulfide or Re-bis(sulfido) intermediate, CpReCl2S2 which serves as an oxidant for the dithiolate complex 1. The ability of the bis sulfido complex to dehydrogenate hydrocarbons is a unique feature and several additional dehydrogenation reactions with this system have been characterized, including the oxidation of other dithiolate complexes, of tetrahydro-naphthalene and of cyclohexadiene. Precedents for the role of metal sulfides in dehydrogenation reactions have been reported for heterogeneous metal sulfide surfaces. This work has begun to provide information about the electronic and structural features necessary for such reactivity. Carbon Sulfur Bond Formation. When the thermal reaction of 1 was carried out in the presence of excess dry ethene a new reaction was observed in which the dithiolate ligand is displaced by incoming olefin to form the cyclic organic product, 1,4-dithiane. The Re product is identified as Cp{prime}Re(alkene)Cl2 on the basis of NMR and mass spectroscopic data. Similar reactions with alkynes have been found to form unsaturated 6-membered rings and reactions with 1,3 dithiolate complexes form the organic 7-membered rings. To our knowledge the formation of cyclic bis-thioethers by the reactions of an alkene or alkyne with a discrete dithiolate metal complex has not been reported previously. Conclusions. A series of new rhenium complexes with sulfido, disulfido, and thiolate ligands have been synthesized and characterized. The complexes have shown novel patterns of reactivity at the sulfur ligands that include hydrogen activation and addition, dehydrogenations, and carbon-sulfur bond formation. Systematic studies of sulfur ligand reactivity as the coligands in these rhenium complexes were varied have established electronic features that favor the novel ligand based reactivity. This series of complexes provides a model system for aspects of rhenium-sulfide surface reactivity, and have led to the suggestion of new mechanistic possibilities.

  5. TIM-4 structures identify a Metal Ion-dependent Ligand Binding Site where phosphatidylserine binds

    PubMed Central

    Santiago, Cesar; Ballesteros, Angela; Martinez-Muñoz, Laura; Mellado, Mario; Kaplan, Gerardo G.; Freeman, Gordon J.; Casasnovas, José M.

    2008-01-01

    The T-cell immunoglobulin and mucin domain (TIM) proteins are important regulators of T cell responses. They have been linked to autoimmunity and cancer. Structures of the murine TIM-4 identified a Metal Ion-dependent Ligand Binding Site (MILIBS) in the immunoglobulin (Ig) domain of the TIM family. The characteristic CC’ loop of the TIM domain and the hydrophobic FG loop shaped a narrow cavity where acidic compounds penetrate and coordinate to a metal ion bound to conserved residues in the TIM proteins. The structure of phosphatidylserine bound to the Ig domain showed that the hydrophilic head penetrates into the MILIBS and coordinates with the metal ion, while the aromatic residues on the tip of the FG loop interacted with the fatty acid chains and could insert into the lipid bilayer. Our results also revealed a significant role of the MILIBS in trafficking of TIM-1 to the cell surface. PMID:18083575

  6. Phase stability of transition metal dichalcogenide by competing ligand field stabilization and charge density wave

    NASA Astrophysics Data System (ADS)

    C, Santosh K.; Zhang, Chenxi; Hong, Suklyun; Wallace, Robert M.; Cho, Kyeongjae

    2015-09-01

    Transition metal dichalcogenides (TMDs) have been investigated extensively for potential application as device materials in recent years. TMDs are found to be stable in trigonal prismatic (H), octahedral (T), or distorted octahedral (Td) coordination of the transition metal. However, the detailed understanding of stabilities of TMDs in a particular phase is lacking. In this work, the detailed TMD phase stability using first-principles calculations based on density functional theory (DFT) has been investigated to clarify the mechanism of phase stabilities of TMDs, consistent with the experimental observation. Our results indicate that the phase stability of TMDs can be explained considering the relative strength of two competing mechanisms: ligand field stabilization of d-orbitals corresponding to transition metal coordination geometry, and charge density wave (CDW) instability accompanied by a periodic lattice distortion (PLD) causing the phase transition in particular TMDs.

  7. Determination of the metal complexation capacity of natural waters by ligand titration in the presence of complexing resins

    NASA Astrophysics Data System (ADS)

    Pesavento, M.; Biesuz, R.; Alberti, G.

    2003-05-01

    The complexation properties of some drinking waters for U(VI), Al(III) and Cu(II) are determined by ligand titration (LT) with the metal ions, using a new method for monitoring, i.e. the sorpion of metal ion on complexing resins. The concentration of the free metal ion in solution is evaluated from the concentration of sorbed metal ion and from the quantity K^*, which is the ratio of the concentration of the metal ion sorbed on the resin to the concentration of free metal ion in solution, and can be independently evaluated. The concentration of the ligands in solution (c_I) and the conditional stability constant (K_M(I)) are obtained by the Ruzic linearization. Different resins, i.e. the iminodiacetic resin Chelex 100, the carboxylic resin Amberlite CG 50 and the anion exchange resin AGIX8 were used for monitoring the titration, since they have different sorbing properties, and in principe they allow the detection of different ligands. Ligands at low concentration and with very high complexation constants were detected in the considered samples. Particularly in the case of U(VI), they are able to complex the metal ion much more strongly than the ligands that are usually considered in aqueous solution, i.e. carbonate and hydroxyl.

  8. Mononuclear and three-dimensional metal complexes based on a multidentate hydrazone ligand.

    PubMed

    Liu, Yan-Fei; Liu, Ya-Ping; Zhang, Ke-Ke; Ren, Qing-Ling; Qin, Jie

    2015-02-01

    A potentially pentadentate hydrazone ligand, N'-[1-(pyrazin-2-yl)ethylidene]nicotinohydrazide (HL), was prepared from the condensation reaction of nicotinohydrazide and acetylpyrazine. Reactions of HL with MnCl2, Mn(CH3COO)2 and Cd(CH3COO)2 afforded three metal complexes, namely dichlorido{N'-[1-(pyrazin-2-yl-κN(1))ethylidene]nicotinohydrazide-κ(2)N',O}manganese(II), [MnCl2(C12H11N5O)], (I), bis{N'-[1-(pyrazin-2-yl-κN(1))ethylidene]nicotinohydrazidato-κ(2)N',O]manganese(II), [Mn(C12H10N5O)2], (II), and poly[[(acetato-κ(2)O,O'){μ3-N'-[1-(pyrazin-2-yl-κ(2)N(1):N(4))ethylidene]nicotinohydrazidato-κ(3)N',O:N(1)}cadmium(II)] chloroform disolvate], {[Cd(C12H10N5O)(CH3COO)]·2CHCl3}n, (III), respectively. Complex (I) has a mononuclear structure, the Mn(II) centre adopting a distorted square-pyramidal coordination. Complex (II) also has a mononuclear structure, with the Mn(II) centre occupying a special position (C2 symmetry) and adopting a distorted octahedral coordination environment, which is defined by two O atoms and four N atoms from two N'-[1-(pyrazin-2-yl)ethylidene]nicotinohydrazidate (L(-)) ligands related via a crystallographic twofold axis. Complex (III) features a unique three-dimensional network with rectangular channels, and the L(-) ligand also serves as a counter-anion. The coordination geometry of the Cd(II) centre is pentagonal bipyramidal. This study demonstrates that HL, which can act as either a neutral or a mono-anionic ligand, is useful in the construction of interesting metal-organic compounds. PMID:25652278

  9. The use of polymer-ligands vs bioindicators in heavy metal monitoring

    SciTech Connect

    Wu, R.S.S.; Lau, T.C.

    1995-12-31

    Major problems involved in using bio-indicators to monitor heavy metals in the marine environment include standardizing a great variety of physical and biological factors which have a significant effect on metal accumulation. The fact that different species may have different accumulation strategies for different metals; and also limits of natural distribution of indicator species often prevent comparison between monitoring results in different geographic areas and hydrographic conditions. Environmental effects on the uptake and deputation of the metals in the biological indicators are generally poorly understood. In the present study, uptake of Cd, Cr, Cu, Ni, Pb and Zn by four polymer-ligands (i.e. Chelex 100, poly(4-vinylpyridine), Sephadex Sp C-J5 and Amberlite IR-122) were studied. Laboratory results showed that Chelex 100 was most effective in taking up the soluble fractions of these three metals at low ambient concentrations (0.1 to 10 mg/L). Equilibrium at low concentrations was reached at about 21 days. Concentration factors after 21 days` exposure ranged from 2,500 to 5,500, depending upon the metal species and ambient concentration. Both uptake and release of metals by Chelex are directly responsive to ambient concentrations and exposure time. Results of field transplantation of Chelex and mussels (P. virvidis) also showed that Chelex accumulated significantly higher levels of Cd, Cr and Pb; similar levels of Cu, and a lower level of Zn than those of mussels under natural field conditions. Coefficients of variations of metal uptake of Chelex were also much smaller. The suitability of using Chelex 100 as a novel chemical device for monitoring metal pollution in the aquatic environment is evaluated against selection criteria established for metal bioindicators.

  10. C-H functionalization: thoroughly tuning ligands at a metal ion, a chemist can greatly enhance catalyst's activity and selectivity.

    PubMed

    Shul'pin, Georgiy B

    2013-09-28

    This brief essay consists of a few "exciting stories" devoted to relations within a metal-complex catalyst between a metal ion and a coordinated ligand. When, as in the case of a human couple, the rapport of the partners is cordial and a love cements these relations, a chemist finds an ideal married couple, in other words he obtains a catalyst of choice which allows him to functionalize C-H bonds very efficiently and selectively. Examples of such lucky marriages in the catalytic world of ions and ligands are discussed here. Activity of the catalyst is characterized by turnover number (TON) or turnover frequency (TOF) as well as by yield of a target product. Introducing a chelating N,N- or N,O-ligand to the catalyst molecule (this can be an iron or manganese derivative) sharply enhances its activity. However, the activity of vanadium derivatives (with additionally added to the solution pyrazinecarboxylic acid, PCA) as well as of various osmium complexes does not dramatically depend on the nature of ligands surrounding metal ions. Complexes of these metals are very efficient catalysts in oxidations with H2O2. Osmium derivatives are record-holders exhibiting extremely high TONs whereas vanadium complexes are on the second position. Finally, elegant examples of alkane functionalization on the ions of non-transition metals (aluminium, gallium etc.) are described when one ligand within the metal complex (namely, hydroperoxyl ligand HOO(-)) helps other ligand of this complex (H2O2 molecule coordinated to the metal) to disintegrate into two species, generating very reactive hydroxyl radical. Hydrogen peroxide molecule, even ligated to the metal ion, is perfectly stable without the assistance of the neighboring HOO(-) ligand. This ligand can be easily oxidized donating an electron to its partner ligand (H2O2). In an analogous case, when the central ion in the catalyst is a transition metal, this ion changing its oxidation state can donate an electron to the coordinated H2O2 fragment. This provokes the O-O bond rupture in the hydrogen peroxide molecule as is assumed for the role of Fe(2+) ions in the Fenton system. PMID:23873447

  11. Heavy metal complexation with naturally occurring organic ligands in wetland ecosystems

    SciTech Connect

    Tuschall, J.R. Jr.

    1981-01-01

    The mode, rate, and extent of heavy metal uptake by freshwater wetlands were investigated as well as heavy metal complexation by a variety of soluble organics. One study involved adding Cd, Cu, Mn, and Zn to septage from Waldo, Florida, and pumping the wastewater through a 10 x 40-m corridor in a cypress swamp. Soluble concentrations of all four metals decreased within the corridor to levels close to those considered acceptable for discharge to surface water. Rates of immobilization were calculated to be a minimum of 7.2, 36, and 72, and 72 g metal/ha.day/sup -1/ for Cd, Cu, Mn, and Zn, respectively. In addition, microcosms (model ecosystems that simulated a swamp) were constructed for a laboratory investigation of factors that control metal immobilization rates. Of the factors - dissolved organic carbon, iron, calcium, sulfide, and pH - the latter two most greatly affected metal immobilization rates. Heavy metal interactions with naturally occurring organics and model compounds were examined by complexometric titrations using five separate techniques. Three of the techniques used (anodic stripping voltammetry (ASV) ion-selective electrode, and fluorescence quenching) were previously published methods, and the other two methods (continuous flow ultrafiltration and competing ligand/differential spectroscopy) were developed for this study. Each procedure was used to determine the available metal binding ability of the organic solutions and the conditional stability constants of the metal-organic complexes. For each solution, agreement among the procedures was good except for the ASV method, which produced results lower than the others. Additionally, the ASV method yielded a conditional stability constant for copper with ethylenedinitrilotetraacetic acid that was five orders of magnitude lower than other published values. The low ASV results for copper with swamp-water organics were found to be caused by the reducible nature of organically complexed copper.

  12. [Ligand intermediates in metal-catalyzed reactions]. Progress report, July 1, 1989--June 30, 1992

    SciTech Connect

    Not Available

    1992-08-01

    This report consists of sections on sigma bond complexes of alkenes, a new carbon-hydrogen bond activation reaction of alkene complexes, carbon-hydrogen bond migrations in alkylidene complexes, carbon- hydrogen bond migrations in alkyne complexes, synthesis, structure and reactivity of C{sub x} complexes, synthesis and reactivity of alcohol and ether complexes, new catalysts for the epimerization of secondary alcohols; carbon-hydrogen bond activation in alkoxide complexes, pi/sigma equilibria in metal/O=CXX` complexes, and other hydrocarbon ligands; miscellaneous.(WET)

  13. Neutral N-donor ligand based flexible metal-organic frameworks.

    PubMed

    Manna, Biplab; Desai, Aamod V; Ghosh, Sujit K

    2016-03-01

    This short review gives a focussed discussion on metal-organic frameworks (MOFs) made of neutral N-donor ligands which show structural flexibility under various exogenous stimuli. Chemical stimuli such as presence of anions, free guests, coordinated guests and physical stimuli (light, heat and so on) render structural flexibility in MOFs. Single-crystal-to-single-crystal transformation studies have attracted a lot of attention for the understanding of such flexible MOF materials. Such a dynamic structural behavior with proper host-guest interactions gives very interesting functions such as chemical separation, sensing and magnetic properties and so on. PMID:26508411

  14. Unsymmetrical Schiff bases functionalize as bibasic tetradentate (ONNO) and monobasic tridentate (NNO) ligands on complexation with some transition metal ions

    NASA Astrophysics Data System (ADS)

    Rabie, U. M.; Assran, A. S. A.; Abou-El-Wafa, M. H. M.

    2008-01-01

    Three dissymmetrical Schiff bases have been prepared by the condensation of 2-hydroxyacetophenone, ethylenediamine and several aldehydes. The electronic transitions within these Schiff bases molecules and the effect of solvents of different polarities on these transitions have been investigated by UV/vis spectroscopy. Schiff bases complexes, binary 1:1 (metal:ligand) and ternary 1:1:1 (metal:ligand:Lewis base, where Lewis base = imidazole or pyridine), with transition metals, Co(II), Ni(II), Cu(II), and Zn(II) have been synthesized and characterized by elemental analysis, molar conductivity and electronic absorption and IR spectra. Further, the stoichiometric ratios of the complexes in solutions and the formation constants of the interaction of Schiff base ligands with metal ions have been determined.

  15. Spectroscopic, Structural, and Computational Characterization of Three Bispidinone Derivatives, as Ligands for Enantioselective Metal Catalyzed Reactions.

    PubMed

    Castellano, Carlo; Sacchetti, Alessandro; Meneghetti, Fiorella

    2016-04-01

    Three chiral derivatives of the alkaloid sparteine (bispidines), characterized by the 3,7-diazabicyclo[3.3.1]nonane moiety, were designed as efficient ligands in a number of enantioselective reactions due to their metal coordination properties. A full evaluation of the 3D properties of the compounds was carried out, as the geometrical features of the bicyclic framework are strictly related to the efficiency of the ligands in the asymmetric catalysis. The selected molecules have different molecular complexity for investigating the effects of different chiral groups on the bicycle conformation. We report here a thorough analysis of their molecular arrangement, by NMR spectroscopy, single crystal X-ray crystallography, and computational techniques, which put in evidence their conformational preferences and the parameters needed for the design of more efficient ligands in asymmetric synthetic routes. The results confirmed the high molecular flexibility of the compounds, and indicated how to achieve a control of the chair-chair/boat-chair conformational ratio, by adjusting the relative size of the substituents on the piperidine nitrogens. Chirality 28:332-339, 2016. © 2016 Wiley Periodicals, Inc. PMID:26899470

  16. Porous coordination polymers with ubiquitous and biocompatible metals and a neutral bridging ligand

    NASA Astrophysics Data System (ADS)

    Noro, Shin-Ichiro; Mizutani, Junya; Hijikata, Yuh; Matsuda, Ryotaro; Sato, Hiroshi; Kitagawa, Susumu; Sugimoto, Kunihisa; Inubushi, Yasutaka; Kubo, Kazuya; Nakamura, Takayoshi

    2015-01-01

    The design of inexpensive and less toxic porous coordination polymers (PCPs) that show selective adsorption or high adsorption capacity is a critical issue in research on applicable porous materials. Although use of Group II magnesium(II) and calcium(II) ions as building blocks could provide cheaper materials and lead to enhanced biocompatibility, examples of magnesium(II) and calcium(II) PCPs are extremely limited compared with commonly used transition metal ones, because neutral bridging ligands have not been available for magnesium(II) and calcium(II) ions. Here we report a rationally designed neutral and charge-polarized bridging ligand as a new partner for magnesium(II) and calcium(II) ions. The three-dimensional magnesium(II) and calcium(II) PCPs synthesized using such a neutral ligand are stable and show selective adsorption and separation of carbon dioxide over methane at ambient temperature. This synthetic approach allows the structural diversification of Group II magnesium(II) and calcium(II) PCPs.

  17. Porous coordination polymers with ubiquitous and biocompatible metals and a neutral bridging ligand

    PubMed Central

    Noro, Shin-ichiro; Mizutani, Junya; Hijikata, Yuh; Matsuda, Ryotaro; Sato, Hiroshi; Kitagawa, Susumu; Sugimoto, Kunihisa; Inubushi, Yasutaka; Kubo, Kazuya; Nakamura, Takayoshi

    2015-01-01

    The design of inexpensive and less toxic porous coordination polymers (PCPs) that show selective adsorption or high adsorption capacity is a critical issue in research on applicable porous materials. Although use of Group II magnesium(II) and calcium(II) ions as building blocks could provide cheaper materials and lead to enhanced biocompatibility, examples of magnesium(II) and calcium(II) PCPs are extremely limited compared with commonly used transition metal ones, because neutral bridging ligands have not been available for magnesium(II) and calcium(II) ions. Here we report a rationally designed neutral and charge-polarized bridging ligand as a new partner for magnesium(II) and calcium(II) ions. The three-dimensional magnesium(II) and calcium(II) PCPs synthesized using such a neutral ligand are stable and show selective adsorption and separation of carbon dioxide over methane at ambient temperature. This synthetic approach allows the structural diversification of Group II magnesium(II) and calcium(II) PCPs. PMID:25592677

  18. Utilizing Metal to Ligand Charge Transfer States of MM Quadruply Bonded Complexes for Photovoltaic Applications

    NASA Astrophysics Data System (ADS)

    Lewis, Sharlene A.; Brown-Xu, Samantha E.; Chisholm, Malcolm H.; Epstein, Arthur J.

    2013-06-01

    In this contribution, we report two examples of our efforts to develop MM quadruply bonded complexes for photovoltaic applications. In the first example, evidence, based on femtosecond transient absorption and time resolved infrared spectroscopy, is presented for photoinduced charge transfer from the Mo_{2}δ orbital of the quadruply bonded molecule trans-Mo_{2}(TiPB)_{2}BTh)_{2}, where TiPB = 2,4,6-triisopropyl benzoate and BTh = 2,2'-bithienylcarboxylate, to di-n-octyl perylene diimide and di-n-hexylheptyl perylene diimide in thin films and solutions of the mixtures. In the second example, the structural and photophysical properties of the new compounds trans-M_{2}(TiPB)_{2}(L)_{2} and trans-M_{2}(TiPB)_{2}(L')_{2}, where M=Mo or W and L and L' are triphenylamine-cyanoacrylate ligands are presented. These ligands promote intense metal to ligand charge transfer transitions that span the range 550 to 1100 nm. The excited states have been studied by transient absorption and time resolved infrared spectroscopy

  19. Distinct roles of beta1 metal ion-dependent adhesion site (MIDAS), adjacent to MIDAS (ADMIDAS), and ligand-associated metal-binding site (LIMBS) cation-binding sites in ligand recognition by integrin alpha2beta1.

    PubMed

    Valdramidou, Dimitra; Humphries, Martin J; Mould, A Paul

    2008-11-21

    Integrin-ligand interactions are regulated in a complex manner by divalent cations, and previous studies have identified ligand-competent, stimulatory, and inhibitory cation-binding sites. In collagen-binding integrins, such as alpha2beta1, ligand recognition takes place exclusively at the alpha subunit I domain. However, activation of the alphaI domain depends on its interaction with a structurally similar domain in the beta subunit known as the I-like or betaI domain. The top face of the betaI domain contains three cation-binding sites: the metal-ion dependent adhesion site (MIDAS), the ADMIDAS (adjacent to MIDAS), and LIMBS (ligand-associated metal-binding site). The role of these sites in controlling ligand binding to the alphaI domain has yet to be elucidated. Mutation of the MIDAS or LIMBS completely blocked collagen binding to alpha2beta1; in contrast mutation of the ADMIDAS reduced ligand recognition but this effect could be overcome by the activating monoclonal antibody TS2/16. Hence, the MIDAS and LIMBS appear to be essential for the interaction between alphaI and betaI, whereas occupancy of the ADMIDAS has an allosteric effect on the conformation of betaI. An activating mutation in the alpha2 I domain partially restored ligand binding to the MIDAS and LIMBS mutants. Analysis of the effects of Ca(2+), Mg(2+), and Mn(2+) on ligand binding to these mutants showed that the MIDAS is a ligand-competent site through which Mn(2+) stimulates ligand binding, whereas the LIMBS is a stimulatory Ca(2+)-binding site, occupancy of which increases the affinity of Mg(2+) for the MIDAS. PMID:18820259

  20. Labeling of fatty acid ligands with the strong electrophilic metal fragment [99mTc(N)(PNP)]2+ (PNP=diphosphane ligand).

    PubMed

    Cazzola, Emiliano; Benini, Elisa; Pasquali, Micol; Mirtschink, Peter; Walther, Martin; Pietzsch, Hans-Jurgen; Uccelli, Licia; Boschi, Alessandra; Bolzati, Cristina; Duatti, Adriano

    2008-02-01

    The electrophilic metal fragment [(99m)Tc(N)(PNP)](2+) (PNP=diphosphane ligand) has been employed for the labeling of fatty acid chains of different lengths. To provide a site-specific group for the attachment of the metallic moiety, the fatty acid derivatives were functionalized by appending a bis-mercapto or, alternatively, a dithiocarbamato pi-donor chelating systems to one terminus of the carbon chain to yield both dianionic and monoanionic bifunctional ligands (L). The resulting complexes, [(99m)Tc(N)(PNP)(L)] (0/+), exhibited the usual asymmetrical structure in which a Tc(triple bond)N group was surrounded by two different bidentate chelating ligands. Dianionic ligands gave rise to neutral complexes, while monoanionic ligands afforded monocationic species. Biodistribution studies were carried out in rats. An isolated perfused rat heart model was employed to assess how structural changes in the radiolabeled fatty acid compound affect the myocardial first pass extraction. Results showed that only monocationic complexes accumulated in myocardium to a significant extent. Conversely, neutral complexes were not efficiently retained into the heart region and rapidly washed out. In isolated perfused rat heart experiments, monocationic complexes exhibited a behavior similar to that of the monocationic flow tracers (99m)Tc-MIBI and (99m)Tc-DBODC with almost identical extraction values, a result that could be attributed to the presence of the monopositive charge. Instead, a slightly lower myocardial extraction was found for neutral complexes. Comparison of the observed kinetic behavior of neutral complexes in the isolated perfused rat heart model with that of the myocardial metabolic tracer [(123)I]IPPA revealed that the introduction of the metallic moiety partially hampers recognition of the labeled fatty acids by cardiac enzymes, and consequently, their behavior did not completely reflect myocardial metabolism. PMID:18205326

  1. Copper acetylacetonate anchored onto amine-functionalised clays.

    PubMed

    Pereira, Clara; Patrício, Sónia; Silva, Ana Rosa; Magalhães, Alexandre L; Carvalho, Ana Paula; Pires, João; Freire, Cristina

    2007-12-15

    Copper (II) acetylacetonate was immobilised directly onto two clays, laponite (Lap) and K10-montmorillonite (K10), and after their amine functionalisation with (3-aminopropyl)triethoxysilane (APTES). All the materials were characterised by nitrogen adsorption isotherms at -196 degrees C, elemental analysis, TG-DSC, XRD, and IR spectroscopy. The K10-based materials were also characterised by XPS. The APTES-functionalised K10 showed higher copper loading than K10, indicating that the clay functionalisation enhanced the complex immobilisation; on the contrary, in Lap-based materials higher metal content was obtained by direct complex anchoring, probably due to the delaminated nature of Lap which induced the particles aggregation on functionalisation with APTES. All the results pointed out that the Cu complex was anchored onto the amine-functionalised clays by Schiff condensation between the amine groups of anchored APTES and the carbonyl groups of the acetylacetonate ligand, whereas direct immobilisation proceeded mostly through interaction between the metal centre and the clay surface hydroxyl groups. PMID:17727870

  2. Metal complexes containing allenylidene and higher cumulenylidene ligands: a theoretical perspective.

    PubMed

    Coletti, Cecilia; Marrone, Alessandro; Re, Nazzareno

    2012-02-21

    Transition metal complexes containing unsaturated carbenes have enjoyed a recent surge in research interest. In addition to showing potential as molecular wires and as components of opto-electronic materials, they provide multifaceted reactive sites for organic synthesis. In this Account, we describe results of recent theoretical studies that delineate the main features of electronic structure and bonding in allenylidenes and higher cumulenylidene complexes, [L(m)M]═C(═C)(n)═CR(1)R(2) (where L represents the ligand, M the metal, and n ≥ 1). Although free cumulenylidene ligands, :C(═C)(n)═CR(1)R(2), are extremely unstable and reactive species, they can be stabilized by coordination to a transition metal. The σ-donation of the electron lone pair on the terminal carbon atom to an empty metal d-orbital, together with the simultaneous π back-donation from filled metal d(π)-orbitals to empty cumulene π* system orbitals, leads to the formation of a strong M═C bond with multiple character. Density functional theory studies on the model systems [(CO)(5)Cr(═C)(n)CH(2)] and [trans-Cl(PH(3))(4)Ru(═C)(n)CH(2)](+) (where n = 1-9) have been useful in interpreting the structural and spectroscopic properties and the reactivity of this class of complexes. Geometry optimizations significantly contributed to the generalization of the sparse structural data available for allenylidene, butatrienylidene, and pentatetraenylidene complexes to higher cumulenylidene complexes (with up to eight carbon atoms in the chain), which show a clear structural trend. In particular, the geometries of all even-chain cumulenes are consistent with an almost purely cumulenic structure, whereas the geometries of odd-chain cumulenes present a significant polyyne-like carbon-carbon bond length alternation. The calculated bond dissociation energies (BDEs) of the cumulenylidene ligand remain almost constant on lengthening the cumulene chain. These BDEs indicate that there is no thermodynamic upper limit to the cumulene chain length and suggest that the synthetic difficulties in preparing higher cumulenylidenes are due to an increase in reactivity. The calculated charges on the carbon atoms show no significant polarization along the cumulene chain, indicating that charge distribution is not important in determining the regioselectivity of either electrophilic or nucleophilic attack, which is instead determined by frontier orbital factors. The breakdown of the contributions from the metal and the carbon atoms along the chain to the HOMO and LUMO shows that the HOMO has contributions mainly from the metal and the carbon atoms in even positions along the chain (C(2), C(4), C(6), and higher). In contrast, the LUMO has contributions mainly from the carbon atoms in odd positions along the chain (C(1), C(3), C(5), and higher), thus explaining the experimentally observed regioselectivity of electrophilic and nucleophilic attacks, which are directed, respectively, to even and odd positions of the cumulenylidene chain. The study of the electronic structure of cumulenylidenes has allowed us not only to give a consistent rationale for the main structural and spectroscopic properties and for the reactivity of this emerging class of compounds but also to predict the effect of ancillary ligands on the metal center or substituents on the carbon end. The result is a useful guide to new developments in the still-underexplored fields of this fascinating class of compounds. PMID:21899273

  3. New metal complexes of N3 tridentate ligand: Synthesis, spectral studies and biological activity

    NASA Astrophysics Data System (ADS)

    Al-Hamdani, Abbas Ali Salih; Al Zoubi, Wail

    2015-02-01

    New tridentate ligand 3-amino-4-{1,5-dimethyl-3-[2-(5-methyl-1H-indol-3-yl)-ethylimino]-2phenyl-2,3-dihydro-1H-pyrazol-4-ylazo}-phenol L was synthesized from the reaction of 1,5-dimethyl-3-[2-(5-methyl-1H-indol-3-yl)-ethylimino]-2-phenyl-2,3-dihydro-1H-pyrazol-4-ylamine and 3.4-amino phenol. A complexes of these ligand [Ni(II)(L)(H2O)2 Cl]Cl, [pt(IV)(L)Cl3]Cl and [M(II)(L)Cl]Cl (M = Pd (II), Zn (II), Cd (II) and Hg (II) were synthesized. The complexes were characterized by spectroscopic methods and magnetic moment measurements, elemental analysis, metal content, Chloride containing and conductance. These studies revealed octahedral geometries for the Ni (II), pt (IV) complexes, square planar for Pd (II) complex and tetrahedral for the Zn (II), Cd(II) and Hg (II) complexes. The study of complexes formation via molar ratio and job method in DMF solution has been investigated and results were consistent to those found in the solid complexes with a ratio of (M:L) as (1:1). The thermodynamic parameters, such as ΔE*, ΔH*, ΔS* ΔG* and K are calculated from the TGA curve using Coats-Redfern method. Hyper Chem-8 program has been used to predict structural geometries of compounds in gas phase. The synthesized ligand and its metal complexes were screened for their biological activity against bacterial species, two Gram positive bacteria (Bacillus subtilis and Staphylococcus aureus) and two Gram negative bacteria (Escherichia coli and Pseudomonasaeruginosa).

  4. Assembly of new polyoxometalate-templated metal-organic frameworks based on flexible ligands

    NASA Astrophysics Data System (ADS)

    Li, Na; Mu, Bao; Lv, Lei; Huang, Rudan

    2015-03-01

    Four new polyoxometalate(POM)-templated metal-organic frameworks based on flexible ligands, namely, [Cu6(bip)12(PMoVI12O40)2(PMoVMoVI11O40O2)]·8H2O(1), [CuI3CuII3(bip)12(PMoVI12O40)2(PMoV12O34)]·8H2O(2), [Ni6(bip)12(PMoVI12O40)(PMoVI11MoVO40)2]Cl·6H2O(3), [CoII3CoIII2(H2bib)2(Hbib)2(PW9O34)2(H2O)6]·6H2O(4) (bip=1,3-bis(imidazolyl)propane, bib=1,4-bis(imidazolyl)butane) have been obtained under hydrothermal condition and characterized by single-crystal X-ray diffraction analyses, elemental analyses, and thermogravimetric (TG) analyses. The studies of single crystal X-ray indicate that compounds 1-3 crystallize in the trigonal space group P-3, and compound 4 crystallizes in the triclinic space group P-1. Compounds 1 and 3 represent 3D frameworks, and POMs as the guest molecules are incorporated into the cages which are composed of the ligands and metals, while compounds 2 and 4 show 3D frameworks by hydrogen bonds. This compounds provide new examples of host-guest compounds based on flexible bis(imidazole) ligands. In addition, the electrochemical property and the catalytic property of compound 1 have also been investigated.

  5. Hydrothermal synthesis and structural characterization of metal-organic frameworks based on new tetradentate ligands.

    PubMed

    Liang, Yue; Yuan, Wei-Guan; Zhang, Shu-Fang; He, Zhan; Xue, Junru; Zhang, Xia; Jing, Lin-Hai; Qin, Da-Bin

    2016-01-28

    The hydrothermal reaction of two new tetradentate ligands with different metal salts of cadmium nitrate, zinc chloride, cobalt nitrate and deprotonated terephthalic acid (H2tp), isophthalic acid (H2ip), 4,4'-oxybisbenzoic acid (H2obba) in H2O/DMF or H2O/methanol gave three metal-organic frameworks (MOFs): {[Zn2(L1)(tp)(formate)2]·H2O}n (), {[Cd2(L2)(ip)2]·2H2O}n (), {[Co2(L2)(obba)2]}n () (L1 = 1,2-bis {2,6-bis [(1H-imidazol-1-yl) methyl]-4-methylphenoxy} ethane, L2 = 1,3-bis {2,6-bis [(1H-imidazol-1-yl) methyl]-4-methylphenoxy} propane). The structures of the frameworks are established by single-crystal X-ray diffraction. Compound is a three-dimensional (3D) framework with a 2-fold interpenetrated form, which exhibits a 2-nodal (3,4)-connected fsh-3,4-P21/c net with a {8(3)}2{8(5)·10} topology. Compound has a 2-nodal (4,8)-connected 3D framework where the dinuclear cadmium cluster secondary building units (SBUs) assemble with isophthalate and ligand L2 to construct a rare topological type sqc22 net with a {3(2)·5(4)}{3(4)·4(4)·5(10)·6(10)} topology. Whereas, Compound can be extended to a 2D interlocked (4,4)-connected 4,4 L28 net with the point symbol {4·6(4)·8}2{4(2)·6(4)}. L1 and L2 are tetradentate ligands with diverse linkers and display different coordination modes. In addition, the thermal stability and photochemical properties of the frameworks are also investigated. PMID:26674324

  6. Complex-forming organic ligands in cloud-point extraction of metal ions: a review.

    PubMed

    Pytlakowska, K; Kozik, V; Dabioch, M

    2013-06-15

    Cloud-point extraction (CPE), an easy, safe, environmentally friendly, rapid and inexpensive methodology for preconcentration and separation of trace metals from aqueous solutions has recently become an attractive area of research and an alternative to liquid-liquid extraction. Moreover, it provides results comparable to those obtained with other separation techniques and has a greater potential to be explored in improving detection limits and other analytical characteristics over other methods. A few reviews have been published covering different aspects of the CPE procedure and its relevant applications, such as the phenomenon of clouding, the application in the extraction of trace inorganic and organic materials, as well as pesticides and protein substrates from different sources, or incorporation of CPE into an FIA system. This review focuses on general properties of the most frequently used organic ligands in cloud-point extraction and on literature data (from 2000 to 2012) concerning the use of modern techniques in determination of metal ions' content in various materials. The article is divided according to the class of organic ligands to be used in CPE. PMID:23618195

  7. Supported Molecular Iridium Catalysts: Resolving Effects of Metal Nuclearity and Supports as Ligands

    SciTech Connect

    Lu, Jing; Serna, Pedro; Aydin, Cerem; Browning, Nigel D.; Gates, Bruce C.

    2012-02-07

    The performance of a supported catalyst is influenced by the size and structure of the metal species, the ligands bonded to the metal, and the support. Resolution of these effects has been lacking because of the lack of investigations of catalysts with uniform and systematically varied catalytic sites. We now demonstrate that the performance for ethene hydrogenation of isostructural iridium species on supports with contrasting properties as ligands (electron-donating MgO and electron-withdrawing HY zeolite) can be elucidated on the basis of molecular concepts. Spectra of the working catalysts show that the catalytic reaction rate is determined by the dissociation of H{sub 2} when the iridium, either as mono- or tetra-nuclear species, is supported on MgO and is not when the support is the zeolite. The neighboring iridium sites in clusters are crucial for activation of both H{sub 2} and C{sub 2}H{sub 4} when the support is MgO but not when it is the zeolite, because the electron-withdrawing properties of the zeolite support enable even single site-isolated Ir atoms to bond to both C{sub 2}H{sub 4} and H{sub 2} and facilitate the catalysis.

  8. Metal flux through consuming interfaces in ligand mixtures: boundary conditions do not influence the lability and relative contributions of metal species.

    PubMed

    Zhang, Zeshi; Alemani, Davide; Buffle, Jacques; Town, Raewyn M; Wilkinson, Kevin J

    2011-10-21

    In a mixture of metal ions and complexes, it is difficult to predict ecological risk without understanding the contribution of each metal species to biouptake. For microorganisms, the rate of uptake (internalization flux) has not only a major influence on the total metal flux but also on the bioavailability of the various metal species and their relative contributions to the total flux. In this paper, the microorganism is considered as a consuming interface, which interacts with the metal ion, M, via the Michaelis-Menten boundary conditions. The contribution of each metal complex to the overall metal flux, in relation to its lability, is examined for a number of important boundary parameters (the equilibrium constant K(a) of metal with transport sites, internalization rate constant k(int) and total transport sites concentration {R}(t)). Computations were performed for Cu(II) complexes, in a multicomponent culture medium for microoganisms. For a one-ligand system, results were acquired using rigorous mathematical expressions, whereas approximate expressions, based on the reaction layer approximation (RLA) and rigorous numerical computations (computer codes MHEDYN and FLUXY), were employed for ligand mixtures. Under the condition of ligand excess, as often found in the natural environment, the relative contribution of each metal species to the total flux is shown to be independent of the boundary conditions. This finding has important implications, including an improved basis for relating the analytical signals of dynamic metal speciation sensors to metal bioavailability. PMID:21897934

  9. Anchoring of Cu(II) onto surface of porous metal-organic framework through post-synthesis modification for the synthesis of benzimidazoles and benzothiazoles

    NASA Astrophysics Data System (ADS)

    Kardanpour, Reihaneh; Tangestaninejad, Shahram; Mirkhani, Valiollah; Moghadam, Majid; Mohammadpoor-Baltork, Iraj; Zadehahmadi, Farnaz

    2016-03-01

    Efficient synthesis of various benzimidazoles and benzothiazoles under mild conditions catalyzed by Cu(II) anchored onto UiO-66-NH2 metal organic framework is reported. In this manner, first, the aminated UiO-66 was modified with thiophene-2-carbaldehyde and then the prepared Schiff base was reacted with CuCl2. The prepared catalyst was characterized by FT-IR, UV-vis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption, inductively coupled plasma atomic emission spectroscopy (ICP-AES) and field emission scanning electron microscopy (FE-SEM). The UiO-66-NH2-TC-Cu was applied as a highly efficient catalyst for synthesis of benzimidazole and benzothiazole derivatives by the reaction of aldehydes with 1,2-diaminobenzene or 2-aminothiophenol. The Cu(II)-containing MOF was reused several times without any appreciable loss of its efficiency.

  10. Using a Combination of Experimental and Computational Methods to Explore the Impact of Metal Identity and Ligand Field Strength on the Electronic Structure of Metal Ions

    ERIC Educational Resources Information Center

    Pernicone, Naomi C.; Geri, Jacob B.; York, John T.

    2011-01-01

    In this exercise, students apply a combination of techniques to investigate the impact of metal identity and ligand field strength on the spin states of three d[superscript 5] transition-metal complexes: Fe(acac)[subscript 3], K[subscript 3][Fe(CN)[subscript 6

  11. XAFS studies of metal-ligand interactions at organic surfaces and in solution

    NASA Astrophysics Data System (ADS)

    Boyanov, Maxim I.

    X-ray absorption fine structure spectroscopy (XAFS) was used as a structural probe to determine the mechanism of metal adsorption to organic surfaces. Two specific systems were investigated, Pb adsorption to heneicosanoic acid Langmuir monolayers (CH3(CH2)19COOH), and Cd adsorption to isolated cell walls of the Bacillus subtilis bacterium. Although the study of these systems is important for quite different reasons, the goal in both is metal binding site speciation and structural characterization of the surface complex. The adsorption of aqueous Cd to B. subtilis was studied as a function of pH by fluorescence mode bulk XAFS. Samples were prepared at six pH values in the range 3.4 to 7.8, and the bacterial functional groups responsible for the adsorption were identified under each condition. Under the experimental Cd and bacterial concentrations, the spectroscopy results indicate that Cd binds predominantly to protonated phosphoryl ligands below pH 4.4, while at higher pH adsorption to carboxyl groups becomes increasingly important. At pH 7.8 we observe the activation of an additional binding site, which we tentatively ascribe to deprotonated phosphoryl ligands. A quantitative Cd speciation diagram for the pH range is presented. Grazing-incidence Pb L3 edge XAFS was used in situ to determine the adsorption complex structure in the Pb-Langmuir monolayer study. The results indicate covalent binding of the Pb cations to the carboxyl headgroups, and the observed Pb-Pb coordination suggests that the metal is adsorbed as a hydrolysis polymer, rather than as individual Pb 2+ ions. The data suggest a bidentate binding mechanism and a one Pb atom to one carboxyl headgroup binding stoichiometry. We discuss how this adsorption model can explain the peculiarities observed with Pb in previous metal-Langmuir monolayer studies. A systematic study of the metal local environment in aqueous solutions was conducted and used in the above analyses. Perchlorate and acetate salt solutions of Cd, Pb, Mn, Cr, and Cu were characterized as standards of hydrated ions and metal-carboxyl complexes. The utility of XAFS in differentiating between the ionic, monodentate, bridging-bidentate, and bidentate metal-carboxyl complexes through C-C multiple scattering effects and XANES features is demonstrated.

  12. Ultrasonic/Sonic Anchor

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Sherrit, Stewart

    2009-01-01

    The ultrasonic/sonic anchor (U/S anchor) is an anchoring device that drills a hole for itself in rock, concrete, or other similar material. The U/S anchor is a recent addition to a series of related devices, the first of which were reported in "Ultrasonic/Sonic Drill/Corers With Integrated Sensors"

  13. Electric relaxation processes in chemodynamics of aqueous metal complexes: from simple ligands to soft nanoparticulate complexants.

    PubMed

    van Leeuwen, Herman P; Buffle, Jacques; Town, Raewyn M

    2012-01-10

    The chemodynamics of metal complexes with nanoparticulate complexants can differ significantly from that for simple ligands. The spatial confinement of charged sites and binding sites to the nanoparticulate body impacts on the time scales of various steps in the overall complex formation process. The greater the charge carried by the nanoparticle, the longer it takes to set up the counterion distribution equilibrium with the medium. A z+ metal ion (z > 1) in a 1:1 background electrolyte will accumulate in the counterionic atmosphere around negatively charged simple ions, as well as within/around the body of a soft nanoparticle with negative structural charge. The rate of accumulation is often governed by diffusion and proceeds until Boltzmann partition equilibrium between the charged entity and the ions in the medium is attained. The electrostatic accumulation proceeds simultaneously with outer-sphere and inner-sphere complex formation. The rate of the eventual inner-sphere complex formation is generally controlled by the rate constant of dehydration of the metal ion, k(w). For common transition metal ions with moderate to fast dehydration rates, e.g., Cu(2+), Pb(2+), and Cd(2+), it is shown that the ionic equilibration with the medium may be the slower step and thus rate-limiting in their overall complexation with nanoparticles. PMID:22126743

  14. Synthesis, crystal structures and properties of three new mixed-ligand d{sup 10} metal complexes constructed from pyridinecarboxylate and in situ generated amino-tetrazole ligand

    SciTech Connect

    Liu Dongsheng; Huang, Xihe; Huang Changcang; Huang Gansheng; Chen Jianzhong

    2009-07-15

    Three new metal-organic frameworks, [Zn(atz)(nic)]{sub n}(1), [Zn(atz)(isonic)]{sub n}.nHisonic(2) and [Cd(atz)(isonic)]{sub n}(3) (Hnic=nicotinic acid, Hisonic=isonicotinic acid), have been firstly synthesized by employing mixed-ligand of pyridinecarboxylate with the in situ generated ligand of 5-amino-tetrazolate(atz{sup -}), and characterized by elemental analysis, IR spectroscopy, TGA and single crystal X-ray diffraction. The results revealed that 1 presents a two-dimensional (2D) 'sql' topological network constructed from the linear chain subunit of Zn(nic){sub 2} and atz{sup -} ligand. A remarkable feature of 2 is a 2-fold interpenetrated diamondoid network with free Hisonic molecules locating in the channels formed by the zigzag chain subunits of Zn(isonic){sub 2}. Complex 3 is a 3D non-interpenetrated pillared framework constructed from the double chain subunits of Cd-COO{sup -}Cd. It possesses a rarely observed (4,6)-connected 'fsc' topology. The thermal stabilities and fluorescent properties of the complexes were investigated. All of these complexes exhibited intense fluorescent emissions in the solid state at room temperature. - Graphical abstract: Three new mixed-ligand d{sup 10} metal complexes have been synthesized by employing mixed-ligand synthetic approach. Complex 1 presents a 2D 'sql' topological network. Complex 2 is a 2-fold interpenetrated diamondoid network with microporous channels. Rarely observed (4,6)-connected 'fsc' topological network was found in complex 3.

  15. Antioxidant, electrochemical, thermal, antimicrobial and alkane oxidation properties of tridentate Schiff base ligands and their metal complexes

    NASA Astrophysics Data System (ADS)

    Ceyhan, Gökhan; Çelik, Cumali; Uruş, Serhan; Demirtaş, İbrahim; Elmastaş, Mahfuz; Tümer, Mehmet

    2011-10-01

    In this study, two Schiff base ligands (HL 1 and HL 2) and their Cu(II), Co(II), Ni(II), Pd(II) and Ru(III) metal complexes were synthesized and characterized by the analytical and spectroscopic methods. Alkane oxidation activities of the metal complexes were studied on cyclohexane as substrate. The ligands and their metal complexes were evaluated for their antimicrobial activity against Corynebacterium xerosis, Bacillus brevis, Bacillus megaterium, Bacillus cereus, Mycobacterium smegmatis, Staphylococcus aureus, Micrococcus luteus and Enterococcus faecalis (as Gram-positive bacteria) and Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Yersinia enterocolitica, Klebsiella fragilis, Saccharomyces cerevisiae, and Candida albicans (as Gram-negative bacteria). The antioxidant properties of the Schiff base ligands were evaluated in a series of in vitro tests: 1,1-diphenyl-2-picrylhydrazyl (DPPH rad ) free radical scavenging and reducing power activity of superoxide anion radical generated non-enzymatic systems. Electrochemical and thermal properties of the compounds were investigated.

  16. Evaluation of donor and steric properties of anionic ligands on high valent transition metals.

    PubMed

    DiFranco, Stephen A; Maciulis, Nicholas A; Staples, Richard J; Batrice, Rami J; Odom, Aaron L

    2012-01-16

    Synthetic protocols and characterization data for a variety of chromium(VI) nitrido compounds of the general formula NCr(NPr(i)(2))(2)X are reported, where X = NPr(i)(2) (1), I (2), Cl (3), Br (4), OTf (5), 1-adamantoxide (6), OSiPh(3) (7), O(2)CPh (8), OBu(t)(F6) (9), OPh (10), O-p-(OMe)C(6)H(4) (11), O-p-(SMe)C(6)H(4) (12), O-p-(Bu(t))C(6)H(4) (13), O-p-(F)C(6)H(4) (14), O-p-(Cl)C(6)H(4) (15), O-p-(CF(3))C(6)H(4) (16), OC(6)F(5) (17), κ(O)-N-oxy-phthalimide (18), SPh (19), OCH(2)Ph (20), NO(3) (21), pyrrolyl (22), 3-C(6)F(5)-pyrrolyl (23), 3-[3,5-(CF(3))(2)C(6)H(3)]pyrrolyl (24), indolyl (25), carbazolyl (26), N(Me)Ph (27), κ(N)-NCO (28), κ(N)-NCS (29), CN (30), NMe(2) (31), F (33). Several different techniques were employed in the syntheses, including nitrogen-atom transfer for the formation of 1. A cationic chromium complex [NCr(NPr(i)(2))(2)(DMAP)]BF(4) (32) was used as an intermediate for the production of 33, which was produced by tin-catalyzed degredation of the salt. Using spin saturation transfer or line shape analysis, the free energy barriers for diisopropylamido rotation were studied. It is proposed that the estimated enthalpic barriers, Ligand Donor Parameters (LDPs), for amido rotation can be used to parametrize the donor abilities of this diverse set of anionic ligands toward transition metal centers in low d-electron counts. The new LDPs do not correlate well to the pK(a) value of X. Conversely, the LDP values of phenoxide ligands do correlate with Hammett parameters for the para-substituents. Literature data for (13)C NMR chemical shifts for a tungsten-based system with various X ligands plotted versus LDP provided a linear fit. In addition, the angular overlap model derived e(σ) + e(π) values for chromium(III) ammine complexes correlate with LDP values. Also discussed is the correlation with XTiCp*(2) spectroscopic data. X-ray diffraction has been used used to characterize 31 of the compounds. From the X-ray diffraction data, steric parameters for the ligands using the Percent Buried Volume and Solid Angle techniques were found. PMID:22200335

  17. A new model for predicting time course toxicity of heavy metals based on Biotic Ligand Model (BLM).

    PubMed

    Hatano, Ayumi; Shoji, Ryo

    2010-01-01

    A new model for predicting time course toxicity of heavy metals was developed by extending the effective ratio of biotic ligand binding with toxic heavy metals to the total biotic ligand for 50% of test organisms (f(50)) derived by the Biotic Ligand Model (BLM). BLM has been well-known as a useful model for prediction of heavy metal toxicity. BLM can consider the effect of exposure conditions such as pH and Ca(2+) on heavy metal toxicity. In addition to the exposure conditions, heavy metal toxicity is strongly dependent on exposure time. In this study, BLM is extended to predict time dependency of heavy metal toxicity by connecting with the concept of primary reaction. The model developed in this study also generates the estimation of the 50% effect concentration (EC(50)) for toxicologically unknown organisms and heavy metals. Two toxicological and kinetic constants, f(50,0) and k, were derived from the initial value of f(50) (f(50,0)) and a time constant (k) independent of time. The model developed in this study enables us to acquire information on the toxicity of heavy metals such as Cu, Cd and Co easily. PMID:19689929

  18. Metal-Ligand Misfits: Facile Access to Rhenium-Oxo Corroles by Oxidative Metalation.

    PubMed

    Einrem, Rune F; Gagnon, Kevin J; Alemayehu, Abraham B; Ghosh, Abhik

    2016-01-11

    With the exception of a single accidental synthesis, rhenium corroles are unknown, but of great interest as catalysts and potential radiopharmaceuticals. Oxidative metalation of meso-triarylcorroles with [Re2 (CO)10 ] in refluxing decalin has provided a facile and relatively high-yielding route to rhenium(V)-oxo corroles. The complexes synthesized could all be fully characterized by single-crystal X-ray structure analyses. PMID:26639951

  19. Testing an application of a biotic ligand model to predict acute toxicity of metal mixtures to rainbow trout.

    PubMed

    Iwasaki, Yuichi; Kamo, Masashi; Naito, Wataru

    2015-04-01

    The authors tested the applicability of a previously developed biotic ligand model (BLM) to predict acute toxicity of single metals and metal mixtures (cadmium, lead, and zinc) to rainbow trout fry (Oncorhynchus mykiss) from a single available dataset. The BLM used in the present study hypothesizes that metals inhibit an essential cation (calcium) and organisms die as a result of its deficiency, leading to an assumption that the proportion of metal-binding ligand (f) is responsible for the toxic effects of metals on the survival of rainbow trout. The f value is a function of free-ion concentrations of metals computed by a chemical speciation model, and the function has affinity constants as model parameters. First, the survival effects of single metals were statistically modeled separately (i.e., f-survival relationship) by using the generalized linear mixed model with binomial distribution. The modeled responses of survival rates to f overlapped reasonably irrespective of metals tested, supporting the theoretical prediction from the BLM that f-survival relationships are comparable regardless of metal species. The authors thus developed the generalized linear mixed model based on all data pooled across the single-metal tests. The best-fitted model well predicted the survival responses observed in mixture tests (r = 0.97), providing support for the applicability of the BLM to predict effects of metal mixtures. PMID:25323464

  20. Synthesis of metal complexes involving Schiff base ligand with methylenedioxy moiety: Spectral, thermal, XRD and antimicrobial studies

    NASA Astrophysics Data System (ADS)

    Sundararajan, M. L.; Jeyakumar, T.; Anandakumaran, J.; Karpanai Selvan, B.

    2014-10-01

    Metal complexes of Zn(II), Cd(II), Ni(II), Cu(II), Fe(III), Co(II), Mn(II) Hg(II), and Ag(I) have been synthesized from Schiff base ligand, prepared by the condensation of 3,4-(methylenedioxy)aniline and 5-bromo salicylaldehyde. All the compounds have been characterized by using elemental analysis, molar conductance, FT-IR, UV-Vis, 1H NMR, 13C NMR, mass spectra, powder XRD and thermal analysis (TG/DTA) technique. The elemental analysis suggests the stoichiometry to be 1:1 (metal:ligand). The FT-IR, 1H NMR, 13C NMR and UV-Vis spectral data suggest that the ligand coordinate to the metal atom by imino nitrogen and phenolic oxygen as bidentate manner. Mass spectral data further support the molecular mass of the compounds and their structure. Powder XRD indicates the crystalline state and morphology of the ligand and its metal complexes. The thermal behaviors of the complexes prove the presence of lattice as well as coordinated water molecules in the complexes. Melting point supports the thermal stability of all the compounds. The in vitro antimicrobial effects of the synthesized compounds were tested against five bacterial and three fungal species by well diffusion method. Antioxidant activities have also been performed for all the compounds. Metal complexes show more biological activity than the Schiff base.

  1. Synthesis of metal complexes involving Schiff base ligand with methylenedioxy moiety: spectral, thermal, XRD and antimicrobial studies.

    PubMed

    Sundararajan, M L; Jeyakumar, T; Anandakumaran, J; Karpanai Selvan, B

    2014-10-15

    Metal complexes of Zn(II), Cd(II), Ni(II), Cu(II), Fe(III), Co(II), Mn(II) Hg(II), and Ag(I) have been synthesized from Schiff base ligand, prepared by the condensation of 3,4-(methylenedioxy)aniline and 5-bromo salicylaldehyde. All the compounds have been characterized by using elemental analysis, molar conductance, FT-IR, UV-Vis, (1)H NMR, (13)C NMR, mass spectra, powder XRD and thermal analysis (TG/DTA) technique. The elemental analysis suggests the stoichiometry to be 1:1 (metal:ligand). The FT-IR, (1)H NMR, (13)C NMR and UV-Vis spectral data suggest that the ligand coordinate to the metal atom by imino nitrogen and phenolic oxygen as bidentate manner. Mass spectral data further support the molecular mass of the compounds and their structure. Powder XRD indicates the crystalline state and morphology of the ligand and its metal complexes. The thermal behaviors of the complexes prove the presence of lattice as well as coordinated water molecules in the complexes. Melting point supports the thermal stability of all the compounds. The in vitro antimicrobial effects of the synthesized compounds were tested against five bacterial and three fungal species by well diffusion method. Antioxidant activities have also been performed for all the compounds. Metal complexes show more biological activity than the Schiff base. PMID:24820326

  2. Multicomponent assembly of fluorescent-tag functionalized ligands in metal-organic frameworks for sensing explosives.

    PubMed

    Gole, Bappaditya; Bar, Arun Kumar; Mukherjee, Partha Sarathi

    2014-10-01

    Detection of trace amounts of explosive materials is significantly important for security concerns and pollution control. Four multicomponent metal-organic frameworks (MOFs-12, 13, 23, and 123) have been synthesized by employing ligands embedded with fluorescent tags. The multicomponent assembly of the ligands was utilized to acquire a diverse electronic behavior of the MOFs and the fluorescent tags were strategically chosen to enhance the electron density in the MOFs. The phase purity of the MOFs was established by PXRD, NMR spectroscopy, and finally by single-crystal XRD. Single-crystal structures of the MOFs-12 and 13 showed the formation of three-dimensional porous networks with the aromatic tags projecting inwardly into the pores. These electron-rich MOFs were utilized for detection of explosive nitroaromatic compounds (NACs) through fluorescence quenching with high selectivity and sensitivity. The rate of fluorescence quenching for all the MOFs follows the order of electron deficiency of the NACs. We also showed the detection of picric acid (PA) by luminescent MOFs is not always reliable and can be misleading. This attracts our attention to explore these MOFs for sensing picryl chloride (PC), which is as explosive as picric acid and used widely to prepare more stable explosives like 2,4,6-trinitroaniline from PA. Moreover, the recyclability and sensitivity studies indicated that these MOFs can be reused several times with parts per billion (ppb) levels of sensitivity towards PC and 2,4,6-trinitrotoluene (TNT). PMID:25164426

  3. The ligand-promoted mobilisation of metal ions from mineral surfaces

    NASA Astrophysics Data System (ADS)

    Putnis, C. V.

    2003-04-01

    Many metals such as Fe, Mo, Cu, Zn etc have been identified as essential micronutrients for plants and microorganisms. These metals have to be mobilised from mineral surfaces in contact with crustal fluids in order to be available to living cells. Many studies have shown the importance of chelation in the mobilisation of metal ions into these fluids. The ligand-promoted dissolution of minerals enables elements essential to life to be accessible. Organic acids with chelating properties are widely present on the surface of the earth (both anthropogenic and those produced naturally such as siderophores) and as well as releasing metal ions into solution for bioavailability, they control processes such as metal ion transport and adsorption and thereby are important in the understanding of toxicity and contamination. In this study we have compared mineral dissolution using a strong industrial chelator (DTPA -- diethylene triamine penta-acetic acid) and dissoluton using a synthetically produced naturally occurring siderophore, 2,3-dihydroxybenzoic acid produced by Azotobacter vinelandii. The dissolution kinetics of a number of minerals (barite, chalcopyrite, malachite) by DTPA solution has been studied as a function of DTPA concentration in the range 0.001--0.5 M. Batch experiments were carried out at pH 12 where the DTPA is effectively de-protonated and over a range of temperatures (22--90C^o) to investigate the factors controlling the dissolution rate.. Although the dissolution mechanism involves the chelation of one metal ion by each molecule of DTPA, the dissolution rate was found to be inversely related to the DTPA concentration in solution and not dependent on the initial grain size of the mineral. The high activation energy for the dissolution process suggests that the rate is controlled by a surface desorption process rather than diffusion in the solution. The inverse dependence on the DTPA concentration suggests steric hindrance associated with the metal-DTPA surface complex formation. Dissolution kinetics of the natural siderophore, known to be specfic to Fe chelation, was observed under similar conditions and comparisons made with the strong industrial chelator in an attempt to understand the dissolution process. The results have important applications to many aspects of mineral dissolution and therefore metal ion mobility as well as raising fundamental questions regarding the nature of the crystal-solution interface at an atomic level.

  4. Cationic heterocycles as ligands: synthesis and reactivity with anionic nucleophiles of cationic triruthenium clusters containing C-metalated N-methylquinoxalinium or N-methylpyrazinium ligands.

    PubMed

    Cabeza, Javier A; del Río, Ignacio; Goite, María C; Pérez-Carreño, Enrique; Pruneda, Vanessa

    2009-07-27

    The cationic cluster complexes [Ru3(CO)10(mu-H)(mu-kappa2N,C-L1Me)]+ (3+; HL1=quinoxaline) and [Ru3(CO)10(mu-H)(mu-kappa2N,C-L2Me)]+ (5+; HL2=pyrazine) have been prepared as triflate salts by treatment of their neutral precursors [Ru3(CO)10(mu-H)(mu-kappa2N,C-Ln)] with methyl triflate. The cationic character of their heterocyclic ligands is responsible for their enhanced tendency to react with anionic nucleophiles relative to that of hydrido triruthenium carbonyl clusters that have neutral N-heterocyclic ligands. These clusters react instantaneously with methyl lithium and potassium tris-sec-butylborohydride (K-selectride) to give neutral products that contain novel nonaromatic N-heterocyclic ligands. The following are the products that have been isolated: [Ru3(CO)9(mu-H)(mu3-kappa2N,C-L1Me2)] (6; from 3+ and methyl lithium), [Ru3(CO)9(mu-H)(mu3-kappa2N,C-L1HMe)] (7; from 3+ and K-selectride), [Ru3(CO)9(mu-H)(mu3-kappa2N,C-L2Me2)] (8; from 5+ and methyl lithium), and [Ru3(CO)9(mu-H)(mu3-kappa2N,C-L2HMe)] (11; from 5+ and K-selectride). Whereas the reactions of 3+ lead to products that arise from the attack of the corresponding nucleophile at the C atom of the only CH group adjacent to the N-methyl group, the reactions of 5+ give mixtures of two products that arise from the attack of the nucleophile at one of the C atoms located on either side of the N-methyl group. The LUMOs and the atomic charges of 3+ and 5+ confirm that the reactions of these clusters with anionic nucleophiles are orbital-controlled rather than charge-controlled processes. The N-heterocyclic ligands of all of these neutral products are attached to the metal atoms in nonconventional face-capping modes. Those of compounds 6-8 have the atoms of a ligand C=N fragment sigma-bonded to two Ru atoms and pi-bonded to the other Ru atom, whereas the ligand of compound 11 has a C-N fragment attached to a Ru atom through the N atom and to the remaining two Ru atoms through the C atom. A variable-temperature 1H NMR spectroscopic study showed that the ligand of compound 7 is involved in a fluxional process at temperatures above -93 degrees C, the mechanism of which has been satisfactorily modeled with the help of DFT calculations and involves the interconversion of the two enantiomers of this cluster through a conformational change of the ligand CH(2) group, which moves from one side of the plane of the heterocyclic ligand to the other, and a 180 degrees rotation of the entire organic ligand over a face of the metal triangle. PMID:19544502

  5. On the dielectric and optical properties of surface-anchored metal-organic frameworks: A study on epitaxially grown thin films

    NASA Astrophysics Data System (ADS)

    Redel, Engelbert; Wang, Zhengbang; Walheim, Stefan; Liu, Jinxuan; Gliemann, Hartmut; Wöll, Christof

    2013-08-01

    We determine the optical constants of two highly porous, crystalline metal-organic frameworks (MOFs). Since it is problematic to determine the optical constants for the standard powder modification of these porous solids, we instead use surface-anchored metal-organic frameworks (SURMOFs). These MOF thin films are grown using liquid phase epitaxy (LPE) on modified silicon substrates. The produced SURMOF thin films exhibit good optical properties; these porous coatings are smooth as well as crack-free, they do not scatter visible light, and they have a homogenous interference color over the entire sample. Therefore, spectroscopic ellipsometry (SE) can be used in a straightforward fashion to determine the corresponding SURMOF optical properties. After careful removal of the solvent molecules used in the fabrication process as well as the residual water adsorbed in the voids of this highly porous solid, we determine an optical constant of n = 1.39 at a wavelength of 750 nm for HKUST-1 (stands for Hong Kong University of Science and Technology-1; and was first discovered there) or [Cu3(BTC)2]. After exposing these SURMOF thin films to moisture/EtOH atmosphere, the refractive index (n) increases to n = 1.55-1.6. This dependence of the optical properties on water/EtOH adsorption demonstrates the potential of such SURMOF materials for optical sensing.

  6. The Study of the Successive Metal-Ligand Binding Energies for Fe(sup +), Fe(sup -), V(sup +) and Co(sup +)

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Ricca, Alessandra; Maitre, Philippe; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    The successive binding energies of CO and H2O to Fe(sup +), CO to Fe(sup -), and H2 to Co(sup +) and V(sup +) are presented. Overall the computed results are in good agreement with experiment. The trends in binding energies are analyzed in terms of metal to ligand donation, ligand to metal donation, ligand-ligand repulsion, and changes in the metal atom, such as hybridization, promotion, and spin multiplicity. The geometry and vibrational frequencies are also shown to be directly affected by these effects.

  7. Carbonyl substitution chemistry of some trimetallic transition metal cluster complexes with polyfunctional ligands

    SciTech Connect

    Byrne, Lindsay T.; Hondow, Nicole S.; Koutsantonis, George A.; Skelton, Brian W.; Torabi, A. Asgar; White, Allan H.; Wild, S. Bruce

    2008-11-03

    The trimetallic clusters [Ru{sub 3}(CO){sub 10}(dppm)], [Ru{sub 3}(CO){sub 12}] and [RuCo{sub 2}(CO){sub 11}] react with a number of multifunctional secondary phosphine and tertiary arsine ligands to give products consequent on carbonyl substitution and, in the case of the secondary phosphines, PH activation. The reaction with the unresolved mixed P/S donor, 1-phenylphosphino-2-thio(ethane), HSCH{sub 2}CH{sub 2}PHPh ({double_bond}LH{sub 2}), gave two products under various conditions which have been characterized by spectroscopic and crystallographic means. These two complexes [Ru{sub 3}({mu}dppm)(H)(CO){sub 7}(LH)] and [Ru{sub 3}({mu}-dppm)(H)(CO){sub 8}(LH)Ru{sub 3}({mu}-dppm)(CO){sub 9}], show the versatility of the ligand, with it chelating in the former and bridging two Ru{sub 3} units in the latter. The stereogenic centres in the molecules gave rise to complicated spectroscopic data which are consistent with the presence of diastereoisomers. In the case of [Ru{sub 3}(CO){sub 12}] the reaction with LH{sub 2} gave a poor yield of a tetranuclear butterfly cluster, [Ru{sub 4}(CO){sub 10}(L){sub 2}], in which two of the ligands bridge opposite hinge wingtip bonds of the cluster. A related ligand, HSCH{sub 2}CH{sub 2}AsMe(C{sub 6}H{sub 4}CH{sub 2}OMe), reacted with [RuCo{sub 2}(CO){sub 11}] to give a low yield of the heterobimetallic Ru-Co adduct, [RuCo(CO){sub 6}(SCH{sub 2}CH{sub 2}AsMe(C{sub 6}H{sub 4}CH{sub 2}OMe))], which appears to be the only one of its type so far structurally characterized. The secondary phosphine, HPMe(C{sub 6}H{sub 4}(CH{sub 2}OMe)) and its oxide HP(O)Me(C{sub 6}H{sub 4}(CH{sub 2}OMe)) also react with the cluster [Ru{sub 3}(CO){sub 10}(dppm)] to give carbonyl substitution products, [Ru{sub 3}(CO){sub 5}(dppm)({mu}{sub 2}-PMe(C{sub 6}H{sub 4}CH{sub 2}OMe)){sub 4}], and [Ru{sub 3}H(CO){sub 7}(dppm)({mu}{sub 2},{eta}{sup 1}P({double_bond}O)Me(C{sub 6}H{sub 4}CH{sub 2}OMe))]. The former consists of an open Ru{sub 3} triangle with four phosphide ligands bridging the metal-metal bonds; the latter has the O atom symmetrically bridging one Ru-Ru bond, the P atom being attached to a non-bridged Ru atom.

  8. Linear free energy relationships for metal-ligand complexation: Bidentate binding to negatively-charged oxygen donor atoms

    NASA Astrophysics Data System (ADS)

    Carbonaro, Richard F.; Atalay, Yasemin B.; Di Toro, Dominic M.

    2011-05-01

    Stability constants for metal complexation to bidentate ligands containing negatively-charged oxygen donor atoms can be estimated from the following linear free energy relationship (LFER): log KML = χOO( αO log KHL,1 + αO log KHL,2) where KML is the metal-ligand stability constant for a 1:1 complex, KHL,1 and KHL,2 are the proton-ligand stability constants (the ligand p Ka values), and αO is the Irving-Rossotti slope. The parameter χOO is metal specific and has slightly different values for five and six membered chelate rings. LFERs are presented for 21 different metal ions and are accurate to within approximately 0.30 log units in predictions of log KML values. Ligands selected for use in LFER development include dicarboxylic acids, carboxyphenols, and ortho-diphenols. For ortho-hydroxybenzaldehydes, α-hydroxycarboxylic acids, and α-ketocarboxylic acids, a modification of the LFER where log KHL,2 is set equal to zero is required. The chemical interpretation of χOO is that it accounts for the extra stability afforded to metal complexes by the chelate effect. Cu-NOM binding constants calculated from the bidentate LFERs are similar in magnitude to those used in WHAM 6. This LFER can be used to make log KML predictions for small organic molecules. Since natural organic matter (NOM) contains many of the same functional groups (i.e. carboxylic acids, phenols, alcohols), the LFER log KML predictions shed light on the range of appropriate values for use in modeling metal partitioning in natural systems.

  9. Linear Free Energy Relationships for Metal-Ligand Complexation: Bidentate Binding to Negatively-Charged Oxygen Donor Atoms

    PubMed Central

    Carbonaro, Richard F.; Atalay, Yasemin B.; Di Toro, Dominic M.

    2011-01-01

    Stability constants for metal complexation to bidentate ligands containing negatively-charged oxygen donor atoms can be estimated from the following linear free energy relationship (LFER): log KML = χOO(αO log KHL,1 + αO log KHL,2) where KML is the metal-ligand stability constant for a 1:1 complex, KHL,1 and KHL,2 are the proton-ligand stability constants (the ligand pKa values), and αO is the Irving-Rossotti slope. The parameter χOO is metal specific and has slightly different values for 5 and 6 membered chelate rings. LFERs are presented for 21 different metal ions and are accurate to within approximately 0.30 log units in predictions of log KML values. Ligands selected for use in LFER development include dicarboxylic acids, carboxyphenols, and ortho-diphenols. For ortho-hydroxybenzaldehydes, α-hydroxycarboxylic acids, and α-ketocarboxylic acids, a modification of the LFER where log KHL,2 is set equal to zero is required. The chemical interpretation of χOO is that it accounts for the extra stability afforded to metal complexes by the chelate effect. Cu-NOM binding constants calculated from the bidentate LFERs are similar in magnitude to those used in WHAM 6. This LFER can be used to make log KML predictions for small organic molecules. Since natural organic matter (NOM) contains many of the same functional groups (i.e. carboxylic acids, phenols, alcohols), the LFER log KML predictions shed light on the range of appropriate values for use in modeling metal partitioning in natural systems. PMID:21833149

  10. Structural diversity through ligand flexibility: two novel metal-organic nets via ligand-to-ligand cross-linking of "paddlewheels".

    PubMed

    Qiu, Wenge; Perman, Jason A; Wojtas, Łukasz; Eddaoudi, Mohamed; Zaworotko, Michael J

    2010-12-14

    Solvothermal reaction of a partially flexible ligand, H(4)L, and Cu(NO(3))(2)·2.5H(2)O afforded two cross-linked Kagomé lattices of formula [Cu(2)(L)](n): an acs net sustained by novel trigonal prismatic supermolecular building blocks (SBBs) and the first example of a partially pillared Kagomé net. PMID:20967349

  11. Synthesis, characterization, biological activity and equilibrium studies of metal(II) ion complexes with tridentate hydrazone ligand derived from hydralazine

    NASA Astrophysics Data System (ADS)

    El-Sherif, Ahmed A.; Shoukry, Mohamed M.; Abd-Elgawad, Mohamed M. A.

    2012-12-01

    In the present study, a new hydrazone ligand (2-((2-phthalazin-1-yl)hydrazono)methyl)phenol) prepared by condensation of hydralazine (1-Hydralazinophthalazine) with salicylaldehyde (SAH). The synthesized SAH-hydrazone and its metal complexes have been characterized by elemental analyses, IR, 1H NMR, solid reflectance, magnetic moment, molar conductance, mass spectra, UV-vis and thermal analysis (TGA). The analytical data of the complexes show the formation of 1:1 [M:L] ratio, where M represents Ni(II), Co(II) and Cu(II) ions, while L represents the deprotonated hydrazone ligand. IR spectra show that SAH is coordinated to the metal ions in a tridentate manner through phthalazine-N, azomethine-N and phenolic-oxygen groups. The ligand and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria and fungi. Proton-ligand association constants of (SAH) and the stepwise stability constants of its metal complexes are determined potentiometrically in 0.1 M NaNO3 at different temperatures and the corresponding thermodynamic parameters were derived and discussed. The order of -ΔG° and -ΔH° were found to obey Mn2+ < Co2+ < Ni2+ < Cu2+, in accordance with the Irving-Williams order. The complexes were stabilized by enthalpy changes and the results suggest that the complexation is an enthalpy-driven process. The concentration distribution diagrams of the complexes are evaluated.

  12. Tandem isomerization-decarboxylation of unsaturated fatty acids to olefins via ruthenium metal-as-ligand catalysts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new facile Ru-catalyzed route to bio-olefins3 from unsaturated fatty acids via readily accessible metal-as-ligand type catalyst precursors, [Ru(CO)2RCO2]n and Ru3(CO)12, will be described. The catalyst apparently functions in a tandem mode by dynamically isomerizing the positions of double bonds i...

  13. Preparation, spectral and biological investigation of formaldehyde-based ligand containing piperazine moiety and its various polymer metal complexes

    NASA Astrophysics Data System (ADS)

    Khan, Shamim Ahmad; Nishat, Nahid; Parveen, Shadma; Rasool, Raza

    2011-10-01

    A novel tetradentate salicylic acid-formaldehyde ligand containing piperazine moiety (SFP) was synthesized by condensation of salicylic acid, formaldehyde and piperazine in presence of base catalyst, which was subjected for the preparation of coordination polymers with metal ions like manganese(II), cobalt(II), copper(II), nickel(II) and zinc(II). All the synthesized polymeric compounds were characterized by elemental analysis, IR, 1H NMR and electronic spectral studies. The thermal stability was determined by thermogravimetric analysis and thermal data revealed that all the polymer metal complexes show good thermal stability than their parent ligand. Electronic spectral data and magnetic moment values revealed that polymer metal complexes of Mn(II), Co(II) and Ni(II) show an octahedral geometry while Cu(II) and Zn(II) show distorted octahedral and tetrahedral geometry respectively. The antimicrobial screening of the ligand and coordination polymers was done by using Agar well diffusion method against various bacteria and fungi. It was evident from the data that antibacterial and antifungal activity increased on chelation and all the polymer metal complexes show excellent antimicrobial activity than their parent ligand.

  14. One-pot assembly of metal/organic-acid sites on amine-functionalized ligands of MOFs for photocatalytic hydrogen peroxide splitting.

    PubMed

    Qin, Lei; Li, Zhaowen; Hu, Qiong; Xu, Zehai; Guo, Xinwen; Zhang, Guoliang

    2016-06-01

    A one-pot organic-acid-directed post-synthetic modification allows molecular iron/citric acid complexes to be anchored into amine-functionalized MOFs by a simple and rapid liquid spraying method. Amidation between organic acid and -NH2 groups of ligands can lead to more small nanoparticles (NPs) that are well-dispersed into MOFs and exhibit high activity for photocatalytic H2O2 splitting. PMID:27166081

  15. Anchoring strategies for bimetallic species in zeolites. Progress report

    SciTech Connect

    Bein, T.

    1993-03-01

    We explore a new approach by introducing heterobinuclear organometallic compounds for linking catalytic functions to zeolite frameworks. With two different metals present, the complexes are being anchored to the support via one oxophilic metal, ligand exchange and catalytic reactions may proceed at the second metal center. Anchoring chemistry, thermal stability and reactivity of Me{sub 3}SnMn(CO){sub 5} in zeolite NaY and acid forms of zeolite Y was studied with X-ray absorption spectroscopy (Sn, Mn edge EXAFS) and in-situ FTIR/TPD-MS techniques. Subsequently, the tin-cobalt complex Me{sub 3}SnCo(CO){sub 4} has been a focus of detailed synthetic and spectroscopic studies. The reactivity of tricarbonyl (cyclopentadienyl) (trimethylstannyl) molybdenum in new mesoporous hosts has been explored. A recent development is the design of vanadium oxo species in different micro- and mesoporous hosts. These are of great interest for the selective reduction of nitrogen oxides by ammonia, and selective oxidation of different hydrocarbons, such as xylenes, olefines and alkanes. Combination analytical techniques used to probe local structural changes at the molecular level, include EXAFS (Extended X-Ray Absorption Fine Structure) spectroscopy utilizing synchrotron radiation, in situ FT-IR coupled to thermodesorption/MS, UV-NIR, and CCD Raman.

  16. A flexible ligand-based wavy layered metal-organic framework for lithium-ion storage.

    PubMed

    An, Tiance; Wang, Yuhang; Tang, Jing; Wang, Yang; Zhang, Lijuan; Zheng, Gengfeng

    2015-05-01

    A substantial challenge for direct utilization of metal-organic frameworks (MOFs) as lithium-ion battery anodes is to maintain the rigid MOF structure during lithiation/delithiation cycles. In this work, we developed a flexible, wavy layered nickel-based MOF (C20H24Cl2N8Ni, designated as Ni-Me4bpz) by a solvothermal approach of 3,3',5,5'-tetramethyl-4,4'-bipyrazole (H2Me4bpz) with nickel(II) chloride hexahydrate. The obtained MOF materials (Ni-Me4bpz) with metal azolate coordination mode provide 2-dimensional layered structure for Li(+) intercalation/extraction, and the H2Me4bpz ligands allow for flexible rotation feature and structural stability. Lithium-ion battery anodes made of the Ni-Me4bpz material demonstrate excellent specific capacity and cycling performance, and the crystal structure is well preserved after the electrochemical tests, suggesting the potential of developing flexible layered MOFs for efficient and stable electrochemical storage. PMID:25638743

  17. Rational design, characterization and catalytic application of metal clusters functionalized with hydrophilic, chiral ligands: a proof of principle study.

    PubMed

    Kunz, Sebastian; Schreiber, Patrick; Ludwig, Martin; Maturi, Mark M; Ackermann, Olaf; Tschurl, Martin; Heiz, Ueli

    2013-11-28

    A proof of principle is presented for the rational design of metal clusters functionalized with hydrophilic, chiral ligands. A colloidal method is used to prepare "unprotected" metal clusters of well-defined size that are subsequently functionalized in a separate step with hydrophilic, chiral ligands. As clusters from the same batch are functionalized with different organic molecules while the cluster size is maintained, the approach allows for systematic investigations and the differences in the observed properties to be related to the influence of the functionalizing ligand. Within this work cysteine and two cysteine derivatives (glutathione and N-acetyl-cysteine) are used as functionalizing ligands for Pt clusters. The materials are characterized using various methods allowing for the determination of ligand coverage, binding mode and chiro-optical properties. Finally, 2-butanone hydrogenation is used as a simple model reaction to demonstrate that these systems exhibit the potential to be used as asymmetric, heterogeneous catalysts. The observed differences in selectivity and reactivity are discussed based on the knowledge gained from the characterization. PMID:24113576

  18. Coordination stability between metal/ligands interaction by modern spectroscopic studies: IR, electronic, EPR and cyclic voltammetry of cobalt(II) complexes with organic skeleton containing cyclic ligands

    NASA Astrophysics Data System (ADS)

    Chandra, Sulekh; Kumar, Rajiv; Singh, Rajeev; Jain, Akash Kr.

    2006-11-01

    A comparative investigation of the interaction of two pyrrole-substituted, mixed oxygen and nitrogen donor, macrocycles ligands have been designed and their coordination interaction with cobalt(II) is studied. Cobalt(II) salts combine with a tetradentate and hexadentate macrocyclic nitrogen/oxygen donor ligands and formed novel cobalt(II) complexes which are characterized by elemental analysis, molar conductance, magnetic moments, mass, 1H NMR, IR, electronic and EPR spectral studies. At the room temperature magnetic moment for cobalt(II) complexes lie in the range 4.70-5.01 BM, which is higher than the spin-only value. All the complexes are high-spin type and have three unpaired electrons. Therefore, the electronic confutation and the splitting of the orbital will be t2g5eg. The electrochemical behaviour of the cobalt(II) complexes, the Co(III)/Co(II) couple are observed. Their positive potential indicates that metal in lower oxidation state is strongly bound to these ligands. The difference between the potential of the anodic peak and cathodic peak remains constant in all complexes. Also, the ratio between the cathodic peak current and square root of the scan rate is practically constant for the studied complexes.

  19. Photoelectric conversion at a [Ru(bpy)3](2+)-based metallic triad anchored on ITO surface.

    PubMed

    Farran, Rajaa; Jouvenot, Damien; Loiseau, Frédérique; Chauvin, Jérôme; Deronzier, Alain

    2014-08-28

    A tri-metallic triad based on a [Ru(bpy)3](2+) moiety connected to Fe(ii) and Co(iii) bisterpyridine has been grafted on an ITO electrode by a stepwise procedure. Under visible light, in the presence of a sacrificial electron donor, the system produces electric current. The photo-current magnitude is compared to the one generated from a Co(iii)-Ru(ii) dyad and shows an increase of 40%. PMID:25002098

  20. The different catalytic roles of the metal-binding ligands in human 4-hydroxyphenylpyruvate dioxygenase.

    PubMed

    Huang, Chih-Wei; Liu, Hsiu-Chen; Shen, Chia-Pei; Chen, Yi-Tong; Lee, Sung-Jai; Lloyd, Matthew D; Lee, Hwei-Jen

    2016-05-01

    4-Hydroxyphenylpyruvate dioxygenase (HPPD) is a non-haem iron(II)-dependent oxygenase that catalyses the conversion of 4-hydroxyphenylpyruvate (HPP) to homogentisate (HG). In the active site, a strictly conserved 2-His-1-Glu facial triad co-ordinates the iron ready for catalysis. Substitution of these residues resulted in about a 10-fold decrease in the metal binding affinity, as measured by isothermal titration calorimetry, and a large reduction in enzyme catalytic efficiencies. The present study revealed the vital role of the ligand Glu(349) in enzyme function. Replacing this residue with alanine resulted in loss of activity. The E349G variant retained 5% activity for the coupled reaction, suggesting that co-ordinating water may be able to support activation of the trans-bound dioxygen upon substrate binding. The reaction catalysed by the H183A variant was fully uncoupled. H183A variant catalytic activity resulted in protein cleavage between Ile(267) and Ala(268) and the production of an N-terminal fragment. The H266A variant was able to produce 4-hydroxyphenylacetate (HPA), demonstrating that decarboxylation had occurred but that there was no subsequent product formation. Structural modelling of the variant enzyme with bound dioxygen revealed the rearrangement of the co-ordination environment and the dynamic behaviour of bound dioxygen in the H266A and H183A variants respectively. These models suggest that the residues regulate the geometry of the reactive oxygen intermediate during the oxidation reaction. The mutagenesis and structural simulation studies demonstrate the critical and unique role of each ligand in the function of HPPD, and which correlates with their respective co-ordination position. PMID:26936969

  1. New advances in homoleptic organotransition-metal compounds: the case of perhalophenyl ligands.

    PubMed

    García-Monforte, M Angeles; Alonso, Pablo J; Forniés, Juan; Menjón, Babil

    2007-08-21

    Homoleptic derivatives of formula [M(C(6)X(5))(n)](z-) (X = F, Cl) have been prepared and isolated for every first-row transition metal as well as for several of the heavier ones. The stoichiometry attained in each case (n ranging between 2 and 6) can be understood considering the tendency of a given metal ion to compensate its coordinative and electronic unsaturation, while not incurring severe interligand repulsive effects. The molecular structures associated with each stoichiometry seem, in turn, to be governed by electronic rather than steric factors. Most of these [M(C(6)X(5))(n)](z-) compounds are unsaturated, open-shell organometallic species, not fulfilling the 18-electron (or Effective Atomic Number) rule. This behaviour can be attributed to the absence of pi stabilising ligands (such as CO, phosphines, alkenes, alkynes, a variety of substituted aromatic rings, and so on) which are otherwise ubiquitous in organotransition-metal chemistry. The magnetic properties of the [M(C(6)X(5))(n)](z-) species have been determined by EPR spectroscopy and/or bulk magnetisation measurements. Excellent correlation between molecular geometry and magnetic properties (whether diamagnetic or paramagnetic) has been observed. Many of these compounds undergo chemically- or electrochemically-induced electron exchange processes. These redox reactions proceed without alteration in the stoichiometry of the [M(C(6)X(5))(n)](z-) compound, but usually involve a sharp change in the molecular geometry according to the different electron configuration of the interrelated species. PMID:17664969

  2. Coinage metal complexes with bridging hybrid phosphine-NHC ligands: synthesis of di- and tetra-nuclear complexes.

    PubMed

    Simler, Thomas; Braunstein, Pierre; Danopoulos, Andreas A

    2016-03-15

    A series of P-NHC-type hybrid ligands containing both PR2 and N-heterocyclic carbene (NHC) donors on meta-bis-substituted phenylene backbones, , and (R = Cy, tBu, Ph, respectively), was accessed through a modular synthesis from a common precursor, and their coordination chemistry with coinage metals was explored and compared. Metallation of ·n(HBr) (n = 1, 2) with Ag2O gave the pseudo-cubane [Ag4Br4()2], isostructural to [Ag4Br4()2] (R = Cy, tBu) (T. Simler, P. Braunstein and A. A. Danopoulos, Angew. Chem., Int. Ed., 2015, 54, 13691), whereas metallation of ·HBF4 (R = Ph, tBu) led to the dinuclear complexes [Ag2()2](BF4)2 which, in the solid state, feature heteroleptic Ag centres and a 'head-to-tail' (HT) arrangement of the bridging ligands. In solution, interconversion with the homoleptic 'head-to-head' (HH) isomers is facilitated by ligand fluxionality. 'Head-to-tail' [Cu2Br2()2] (R = Cy, tBu) dinuclear complexes were obtained from ·HBr and [Cu5(Mes)5], Mes = 2,4,6-trimethylphenyl, which also feature bridging ligands and heteroleptic Cu centres. Although the various ligands led to structurally analogous complexes for R = Cy, tBu and Ph, the rates of dynamic processes occurring in solution are dependent on R, with faster rates for R = Ph. Transmetallation of both NHC and P donor groups from [Ag4Br4()2] to Au(I) by reaction with [AuCl(THT)] (THT = tetrahydrothiophene) led to transfer and to the dinuclear complex [Au2Cl2] with one ligand bridging the two Au centres. Except for the silver pseudo-cubanes, all other complexes do not exhibit metallophilic interactions. PMID:26886084

  3. Metal-organic coordination polymers based on dicarboxylate and a flexible bispyridyl ligand: Synthesis, structures, and photoluminescence

    NASA Astrophysics Data System (ADS)

    Lin, Jian-Li; Zhu, Hong-Lin; Zhang, Jie; Zhao, Jun-Ming; Zheng, Yue-Qing

    2011-05-01

    Three new transition metal-organic coordination polymers [Zn(bpp)(C 4H 4O 4)]·1.2H 2O 1, [Cd(bpp) 2(H 2O) 2](C 4O 4)·8H 2O 2 and [Cd(bpp) 2(C 4O 4)]·H 2O 3 have been synthesized from the reaction of d 10 block metal, dicarboxylic acid with 1,3-bis(4-pyridyl)-propane (bpp). Structural analysis reveal that the Zn atoms in 1 are bridged by the succinate anions to generate helical chains, which are interlinked by bpp ligands to a 3D framework with Sra (4 2 · 6 3 · 8) topology. The CdN 4O 2 octahedras in 2 are bridged by a pair of bpp ligands to form 1D repeated rhomboid chains, which are assembled into 2D layer via the hydrogen bonds. The six-coordinated Cd 2+ ions in 3 are bridged by the acetylenedicarboxylato ligand to form 1D zigzag chains, which are interconnected by bpp ligands to construct 3D metal-organic framework with a (4 8 · 6 7) topology. The fluorescent spectra of 1- 3 indicate intraligand fluorescence emission upon irradiation.

  4. How a redox-innocent metal promotes the formal reductive elimination of biphenyl using redox-active ligands.

    PubMed

    Ashley, Daniel Charles; Baik, Mu-Hyun

    2015-03-01

    One of the most compelling strategies for utilizing redox-active ligands is to perform redox events at the ligands to avoid accessing prohibitively high energy oxidation states at the metal center. This has been demonstrated experimentally in many systems, yet there is little understanding of the fundamental electronic structures involved with these transformations or how to control them. Here, the reductive elimination of biphenyl from [M(isq)2Ph2] (M = Ti, Zr, and Hf and isq = 2,4-di-tert-butyl-6-tert-butyliminosemiquinone) was studied computationally. It was found that the metal remains in the +IV oxidation state and all redox chemistry was mediated by the redox-active ligands. Two types of electron-transfer mechanisms were identified, an asymmetric unpaired electron transfer (UET) and a symmetric pairwise electron transfer (PET), the former always being lower in energy. The energetic differences between these two mechanisms were explained through simple molecular orbital theory arguments. Despite the metal's redox-inactivity, it still has a marked influence on the calculated energetics of the reaction, with the Ti systems being much more reactive than the Zr/Hf systems. This primarily originates from the shorter Ti-Ph bond, which leads to a stronger filled-filled interaction between these ligands at the reactant state. This greater reactant destabilization leads to the lower activation energies. PMID:25653096

  5. Synthesis, spectral, thermal and antimicrobial studies of transition metal complexes of 14-membered tetraaza[N4] macrocyclic ligand

    NASA Astrophysics Data System (ADS)

    Shankarwar, Sunil G.; Nagolkar, Bhagwat B.; Shelke, Vinod A.; Chondhekar, Trimbak K.

    2015-06-01

    A series of metal complexes of Mn(II), Co(II), Ni(II), Cu(II), have been synthesized with newly synthesized biologically active macrocyclic ligand. The ligand was synthesized by condensation of β-diketone 1-(4-chlorophenyl)-3-(2-hydroxyphenyl)propane-1,3-dione and o-phenylene diamine. All the complexes were characterized by elemental analysis, molar conductivity, magnetic susceptibility, thermal analysis, X-ray diffraction, IR, 1H-NMR, UV-Vis spectroscopy and mass spectroscopy. From the analytical data, stoichiometry of the complexes was found to be 1:2 (metal:ligand). Thermal behavior (TG/DTA) and kinetic parameters suggest more ordered activated state in complex formation. All the complexes are of high spin type and six coordinated. On the basis of IR, electronic spectral studies and magnetic behavior, an octahedral geometry has been assigned to these complexes. The antibacterial and antifungal activities of the ligand and its metal complexes, has been screened in vitro against Staphylococcus aureus, Escherichia coli and Aspergillus niger, Trichoderma respectively.

  6. Synthesis, spectral, thermal and antimicrobial studies of transition metal complexes of 14-membered tetraaza[N₄] macrocyclic ligand.

    PubMed

    Shankarwar, Sunil G; Nagolkar, Bhagwat B; Shelke, Vinod A; Chondhekar, Trimbak K

    2015-06-15

    A series of metal complexes of Mn(II), Co(II), Ni(II), Cu(II), have been synthesized with newly synthesized biologically active macrocyclic ligand. The ligand was synthesized by condensation of β-diketone 1-(4-chlorophenyl)-3-(2-hydroxyphenyl)propane-1,3-dione and o-phenylene diamine. All the complexes were characterized by elemental analysis, molar conductivity, magnetic susceptibility, thermal analysis, X-ray diffraction, IR, (1)H-NMR, UV-Vis spectroscopy and mass spectroscopy. From the analytical data, stoichiometry of the complexes was found to be 1:2 (metal:ligand). Thermal behavior (TG/DTA) and kinetic parameters suggest more ordered activated state in complex formation. All the complexes are of high spin type and six coordinated. On the basis of IR, electronic spectral studies and magnetic behavior, an octahedral geometry has been assigned to these complexes. The antibacterial and antifungal activities of the ligand and its metal complexes, has been screened in vitro against Staphylococcus aureus, Escherichia coli and Aspergillus niger, Trichoderma respectively. PMID:25775943

  7. "Third-Generation"-Type Functional Tris(2-pyridyl)borate Ligands and Their Transition-Metal Complexes.

    PubMed

    Jeong, So Yi; Lalancette, Roger A; Lin, Huina; Lupinska, Patrycja; Shipman, Patrick O; John, Alexandra; Sheridan, John B; Jäkle, Frieder

    2016-04-01

    Phenyltris(2-pyridyl)borates (Tpyb) are a promising class of tripodal "scorpionate"-type ligands with potential utility in the development of transition-metal complexes with interesting optical, electronic, or magnetic properties and as building blocks to metallosupramolecular polymers. We report here a new class of "third-generation"-type Tpyb ligands that contain different functional groups attached to the boron-bound aryl moiety. The synthesis, characterization, and metal-ion complexation behavior of ligands with iodo and trimethylsilyl groups are discussed. The electrochemical and absorption characteristics of the corresponding low-spin iron(II) and ruthenium(II) complexes are compared. We demonstrate the further elaboration of iodo derivatives with alkynes via Sonogashira-Hagihara coupling, a process that proceeds with high yield for the iron(II) and ruthenium(II) complexes but not for the free ligand. Borylation of the silyl-substituted ruthenium(II) complex with BBr3 was also investigated. In addition to the expected borylation product Ru(Tpyb-Bpin)2, the replacement of one (major product) or two phenyl groups is observed, suggesting that electrophilic borylation occurs at both the C(Ph)-Si and the C(Ph)-B aromatic carbon atoms. The successful attachment of a range of different functional groups at the periphery of the Tpyb metal complexes is expected to provide opportunities to access new polymeric materials via C-C coupling or click-type reactions. PMID:26991520

  8. Oriented circular dichroism analysis of chiral surface-anchored metal-organic frameworks grown by liquid-phase epitaxy and upon loading with chiral guest compounds.

    PubMed

    Gu, Zhi-Gang; Bürck, Jochen; Bihlmeier, Angela; Liu, Jinxuan; Shekhah, Osama; Weidler, Peter G; Azucena, Carlos; Wang, Zhengbang; Heissler, Stefan; Gliemann, Hartmut; Klopper, Wim; Ulrich, Anne S; Wöll, Christof

    2014-08-01

    Oriented circular dichroism (OCD) is explored and successfully applied to investigate chiral surface-anchored metal-organic frameworks (SURMOFs) based on camphoric acid (D- and Lcam) with the composition [Cu2(Dcam)(2x)(Lcam)(2-2x)(dabco)]n (dabco = 1,4-diazabicyclo-[2.2.2]-octane). The three-dimensional chiral SURMOFs with high-quality orientation were grown on quartz glass plates by using a layer-by-layer liquid-phase epitaxy method. The growth orientation, as determined by X-ray diffraction (XRD), could be switched between the [001] and [110] direction by using either OH- or COOH-terminated substrates. These SURMOFs were characterized by using OCD, which confirmed the ratio as well as the orientation of the enantiomeric linker molecules. Theoretical computations demonstrate that the OCD band intensities of the enantiopure [Cu2(Dcam)2(dabco)]n grown in different orientations are a direct result of the anisotropic nature of the chiral SURMOFs. Finally, the enantiopure [Cu2(Dcam)2(dabco)]n and [Cu2(Lcam)2(dabco)]n SURMOFs were loaded with the two chiral forms of ethyl lactate [(+)-ethyl-D-lactate and (-)-ethyl-L-lactate)]. An enantioselective enrichment of >60 % was observed by OCD when the chiral host scaffold was loaded from the racemic mixture. PMID:24938623

  9. Switching and redox isomerism in first-row transition metal complexes containing redox active Schiff base ligands.

    PubMed

    Sasmal, Ashok; Garribba, Eugenio; Gómez-García, Carlos J; Desplanches, Cédric; Mitra, Samiran

    2014-11-14

    The reversible redox isomerisms in first row transition metal complexes of the type ML2 were studied. The six ML2 complexes (M = Mn(III) (), Fe(II) (), Co(III) (), Ni(II) (), Cu(II) () and Zn(II) ()) were synthesized with a redox active Schiff base ligand [2-(3,5-di-tert-butyl-2-hydroxyphenylamino)-4-chlorophenol] (H3L) presenting different oxidation states from -2 to 0 (L(2-), L(-) and L(0)). EPR spectra and magnetic susceptibility measurements indicate the presence of complexes of the type [Mn(III)(L(2-))(L(-))] () with S = 1/2, [Fe(II)(L(-))2] () with S = 2, [Co(III)(L(2-))(L(-))] () with S = 1/2, [Ni(II)(L(-))2] () with S = 1, [Cu(II)(L(-))2] () with S = 1/2 and [Zn(II)(L(-))2] () with S = 0 at high temperatures. Temperature and solvents influence the electronic structures of the species and give several valence tautomers. At low temperatures these complexes present thermally induced metal-to-ligand (, , ) or ligand-to-ligand (in , ) electron transfer (partial or total), resulting in compounds of the type [Mn(IV)(L(2-))2] () with S = 1/2, [Fe(III)(L(-))(L(2-))] () with S = 1, [Ni(III)(L(2-))(L(-))] () with S = 0, [Cu(II)(L(2-))(L(0))] () with S = 1/2 and [Zn(II)(L(2-))(L(0))] () with S = 1. This electron transfer is in agreement with the general trend in the redox potentials of the first row transition metal ions from Mn(ii) to Zn(ii), and it allows us to prepare and stabilize reversibly switchable tautomeric forms in transition metal complexes with redox-active ligands. PMID:25233051

  10. Metal chelates anchored to poly-l-peptides and linear d,l-α-peptides with promising nanotechnological applications

    NASA Astrophysics Data System (ADS)

    Punzi, P.; Giordano, C.; Marino, F.; Morosetti, S.; De Santis, P.; Scipioni, A.

    2012-10-01

    Regular configurationally alternating amino acid sequences generate cyclic and linear helical peptides with a local β-conformation able to self-assemble in nanowires and nanoscaffolds directed and stabilized by hydrogen bonds. The possibility of modulating the chemical profile of the various amino acid residues containing reactive side chains means that peptides could be flexible templates for creating various building blocks. A method for the design of molecules with potential spintronic properties is described. Peptides containing lysine residues, the side chains of which are bridged through the formation of metal chelates via Schiff bases, could provide stable molecular channels. When metal chelates with high electron spin states are used, their coupling could generate materials that are interesting due to their magnetic properties as well as for the patterning of nanometric lattices driven by their orientation under a magnetic field. With this aim, three alternating d- and l-lysine-containing octapeptides are synthesized and the formation of their bis(pyridoxalaldimine) copper(II) chelate derivatives is shown by absorption and circular dichroism spectroscopies.

  11. Increased Diversity of the HLA-B40 Ligandome by the Presentation of Peptides Phosphorylated at Their Main Anchor Residue*

    PubMed Central

    Marcilla, Miguel; Alpízar, Adán; Lombardía, Manuel; Ramos-Fernandez, Antonio; Ramos, Manuel; Albar, Juan Pablo

    2014-01-01

    Human leukocyte antigen (HLA) class I molecules bind peptides derived from the intracellular degradation of endogenous proteins and present them to cytotoxic T lymphocytes, allowing the immune system to detect transformed or virally infected cells. It is known that HLA class I–associated peptides may harbor posttranslational modifications. In particular, phosphorylated ligands have raised much interest as potential targets for cancer immunotherapy. By combining affinity purification with high-resolution mass spectrometry, we identified more than 2000 unique ligands bound to HLA-B40. Sequence analysis revealed two major anchor motifs: aspartic or glutamic acid at peptide position 2 (P2) and methionine, phenylalanine, or aliphatic residues at the C terminus. The use of immobilized metal ion and TiO2 affinity chromatography allowed the characterization of 85 phosphorylated ligands. We further confirmed every sequence belonging to this subset by comparing its experimental MS2 spectrum with that obtained upon fragmentation of the corresponding synthetic peptide. Remarkably, three phospholigands lacked a canonical anchor residue at P2, containing phosphoserine instead. Binding assays showed that these peptides bound to HLA-B40 with high affinity. Together, our data demonstrate that the peptidome of a given HLA allotype can be broadened by the presentation of peptides with posttranslational modifications at major anchor positions. We suggest that ligands with phosphorylated residues at P2 might be optimal targets for T-cell-based cancer immunotherapy. PMID:24366607

  12. Bioabsorbable anchors in glenohumeral shoulder surgery.

    PubMed

    Nho, Shane J; Provencher, Matthew T; Seroyer, Shane T; Romeo, Anthony A

    2009-07-01

    The use of implants to provide glenohumeral soft tissue fixation has changed dramatically over the past few decades, from point tack fixation to metallic suture anchors to bioabsorbable suture anchors. Bioabsorbable suture anchors have largely replaced metallic anchors because of concerns of implant loosening, migration, and chondral injury. Although the safety and efficacy of bioabsorbable anchors has been well documented, there are numerous reports regarding the early failure related to implant bioabsorbable implant breakage or premature degradation. Patients with anchor-related complications generally present with pain and/or stiffness, and the surgeon should have a high index of suspicion if a patient does not progress as expected. Glenohumeral synovitis, glenoid osteolysis, loose bodies, and chondral injury are some of the notable complications that have been reported. Careful attention to proper anchor insertion techniques can limit the potential for complications. Newer materials, such as polyetheretherketone and other composites, have recently been introduced. These materials may address concerns of biocompatibility and material strength, but additional rigorous in vitro and in vivo trials need to be conducted before their use becomes widespread. PMID:19560644

  13. Photoemission mechanism of water-soluble silver nanoclusters: ligand-to-metal-metal charge transfer vs strong coupling between surface plasmon and emitters.

    PubMed

    Chen, Yuting; Yang, Taiqun; Pan, Haifeng; Yuan, Yufeng; Chen, Li; Liu, Mengwei; Zhang, Kun; Zhang, Sanjun; Wu, Peng; Xu, Jianhua

    2014-02-01

    Using carboxylate-protected silver nanoclusters (Ag-carboxylate NCs) as a model, we separately investigated the contribution of the ligand shell and the metal core to understand the nature of photoluminescence of Ag NCs. A new Ag(0)NCs@Ag(I)-carboxylate complex core-shell structural model has been proposed. The emission from the Ag-carboxylate NCs could be attributed to ligand-to-metal-metal charge transfer from Ag(I)-carboxylate complexes (the oxygen atom in the carboxylate ligands to the Ag(I) ions) to the Ag atoms and subsequent radiative relaxation. Additionally, we found that the emission wavelength of the Ag NCs depends on the excitation wavelength implying a strong coupling between surface plasmon and emitter in Ag NCs. The strong coupling between the surface plasmon and the emitter determines the quantum yield and lifetime. The emission mechanism of Ag NCs and its relation to the organic templates and metal cores were clearly clarified. The results should stimulate additional experimental and theoretical research on the molecular-level design of luminescent metal probes for optoelectronics and other applications. PMID:24437963

  14. Novel bio-essential metal based complexes linked by heterocyclic ligand: Synthesis, structural elucidation, biological investigation and docking analysis.

    PubMed

    Arun, T; Subramanian, R; Raman, N

    2016-01-01

    New series of bio-essential metal based complexes linked by Schiff base ligand (L) and 2,2'-bipyridine (bpy) have been synthesized and characterized by diverse spectral techniques such as elemental analysis, magnetic susceptibility, molar conductivity measurements, FT-IR, UV-Vis., (1)H NMR, (13)C NMR, EPR and Mass. The spectral data suggest that the metal complexes espouse octahedral geometry around the metal ions. Interactions of the complexes with CT DNA have been explored by electronic absorption, ethidium bromide displacement assay, viscosity measurements, cyclic voltammetry and differential pulse voltammetry in order to evaluate the possible DNA-binding mode and to calculate the corresponding DNA-binding constants. The DNA interaction studies propose that the intercalative mode of interaction and the complexes exhibit oxidative cleavage of pUC19 DNA in the presence of hydrogen peroxide as activator. The synthesized Schiff base ligand and its metal complexes have been screened for anti-microbial activity by micro dilution method against two Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), two Gram-negative bacteria (Escherichia coli and Salmonella typhi) and three fungi strains (Fusarium solani, Aspergillus niger and Candida albicans) revealing that the complexes are good anti-pathogenic agents than the ligand. Moreover, molecular docking analysis has been performed to confirm the nature of binding of the complexes with DNA. PMID:26690017

  15. Anchored nanostructure materials and method of fabrication

    DOEpatents

    Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei

    2012-11-27

    Anchored nanostructure materials and methods for their fabrication are described. The anchored nanostructure materials may utilize nano-catalysts that include powder-based or solid-based support materials. The support material may comprise metal, such as NiAl, ceramic, a cermet, or silicon or other metalloid. Typically, nanoparticles are disposed adjacent a surface of the support material. Nanostructures may be formed as anchored to nanoparticles that are adjacent the surface of the support material by heating the nano-catalysts and then exposing the nano-catalysts to an organic vapor. The nanostructures are typically single wall or multi-wall carbon nanotubes.

  16. Ligand Noninnocence in Coinage Metal Corroles: A Silver Knife-Edge.

    PubMed

    Thomas, Kolle E; Vazquez-Lima, Hugo; Fang, Yuanyuan; Song, Yang; Gagnon, Kevin J; Beavers, Christine M; Kadish, Karl M; Ghosh, Abhik

    2015-11-16

    A silver β-octabromo-meso-triarylcorrole has been found to exhibit a strongly saddled geometry, providing the first instance of a strongly saddled corrole complex involving a metal other than copper. The Soret maxima of the Ag octabromocorroles also redshift markedly in response to increasingly electron-donating para substituents on the meso-aryl groups. In both these respects, the Ag octabromocorroles differ from simple Ag triarylcorrole derivatives, which exhibit only mild saddling and substituent-insensitive Soret maxima. These results have been rationalized in terms of an innocent M(III)-corrole(3-) description for the simple Ag corroles and a noninnocent M(II)-corrole(·2-) description for the Ag octabromocorroles. In contrast, all copper corroles are thought to be noninnocent, while all gold corroles are innocent. Uniquely among metallocorroles, silver corroles thus seem poised on a knife-edge, so to speak, between innocent and noninnocent electronic structures and may tip either way, depending on the exact nature of the corrole ligand. PMID:26345592

  17. Aqueous Hydricity of Late Metal Catalysts as a Continuum Tuned by Ligands and the Medium

    PubMed Central

    2016-01-01

    Aqueous hydride transfer is a fundamental step in emerging alternative energy transformations such as H2 evolution and CO2 reduction. “Hydricity,” the hydride donor ability of a species, is a key metric for understanding transition metal hydride reactivity, but comprehensive studies of aqueous hydricity are scarce. An extensive and self-consistent aqueous hydricity scale is constructed for a family of Ru and Ir hydrides that are key intermediates in aqueous catalysis. A reference hydricity is determined using redox potentiometry and spectrophotometric titration for a particularly water-soluble species. Then, relative hydricity values for a range of species are measured using hydride transfer equilibria, taking advantage of expedient new synthetic procedures for Ru and Ir hydrides. This large collection of hydricity values provides the most comprehensive picture so far of how ligands impact hydricity in water. Strikingly, we also find that hydricity can be viewed as a continuum in water: the free energy of hydride transfer changes with pH, buffer composition, and salts present in solution. PMID:26777267

  18. Flexible Organic Phototransistor Array with Enhanced Responsivity via Metal-Ligand Charge Transfer.

    PubMed

    Liu, Xien; Lee, Eun Kwang; Kim, Dong Yeong; Yu, Hojeong; Oh, Joon Hak

    2016-03-23

    Phototransistors based on organic photoactive materials combine tunable light absorption in the spectral region from ultraviolet to near-infrared with low-temperature processability over large areas on flexible substrates. However, they often exhibit low photoresponsivity because of low molar extinction coefficient of photoactive components. We report a simple, yet highly efficient solution method for enhancing the performance of organic phototransistors using ruthenium complex 1 (Ru-complex 1). An air-stable n-type organic semiconductor, N,N'-bis(2-phenylethyl)-perylene-3,4:9,10-tetracarboxylic diimide (BPE-PTCDI), has been deposited on a silicon wafer and a transparent polyimide (PI) substrate via thermal evaporation under vacuum. The BPE-PTCDI phototransistors functionalized with Ru-complex 1 exhibit ∼5000 times higher external quantum efficiency (EQE) than that of pristine BPE-PTCDI phototransistors, owing to the metal-ligand charge transfer (MLCT) from Ru-complex 1 to the active component of the device. In addition, a large 10 × 10 phototransistor array (2.5 × 2.5 cm(2)) has been prepared on a transparent PI substrate, showing distinct light mapping. The fabricated phototransistor array is highly flexible and twistable and works well under tensile and compressive strains. We believe that our simple method will pave a viable way for improvements in the photoresponsivity of organic semiconductors for applications in wearable organic optoelectronic devices. PMID:26926464

  19. Suture anchor strength revisited.

    PubMed

    Barber, F A; Herbert, M A; Click, J N

    1996-02-01

    The rapid proliferation of suture anchors continues. Our prior report on the pullout strength of 14 different anchors is supplemented by a similar test conducted on 8 additional anchors. Comparative data on modes of failure and failure strengths (ultimate loads to failure) for these new devices are compared statistically with the previously tested anchors. In a fresh never-frozen porcine femur model, 10 samples of each of the additional anchors tested were threaded with stainless steel sutures and inserted into three different test areas (diaphyseal cortex, metaphyseal cortex, and a cancellous trough). Tensile stress parallel to the axis of insertion was applied at a rate of 12.5 mm/s by an Instron 1321 testing machine (Instron Corp, Canton, MA) until failure and mean anchor failure strengths calculated. The anchors tested were the Mitek G2 as a control, miniMitek, Mitek Superanchor, Mitek Rotator Cuff anchor (Mitek Products, Westwood, MA), Innovasive Devices Radial Osteal Compression device (Innovasive Devices, Hopkinton, MA), Arthrex Fastak (Arthrex Inc, Naples, FL), Arthrotek miniHarpoon (Arthrotek, Warsaw, IN), Orthopedic Biosystems PeBA 3 and PeBA 5 (Orthopedic Biosystems, Scottsdale, AZ), and AME 5.5 screw (American Medical Electronics, Richardson, TX). Failure mode (anchor pullout, suture eyelet cut out, or wire breakage) was generally consistent for each anchor type. The size of insertion hole is clinically important and each anchor's performance was evaluated as a function of its minor diameter or drill hole. For screw anchors, the larger the minor diameter of the screw, the higher the mean failure strengths in all three test areas (P = .001). However, larger drill holes for non-screw anchors resulted in lower mean failure strengths in cancellous bone (P = .03) and diaphyseal cortex (P < .005). PMID:8838726

  20. One pot synthesis of metal ion anchored alginate-gelatin binary biocomposite for efficient Cr(VI) removal.

    PubMed

    Gopalakannan, Venkatrajan; Viswanathan, Natrayasamy

    2016-02-01

    Biopolymers are widely used for the removal of chromium from aqueous medium but it possesses limitations like poor sorption capacity and low stability. To overcome the limitations of biopolymers and to improve their properties, the present study was designed in such a way to develop a novel sorbent with enhanced chromium sorption capacity and better stability by synthesizing metal ion cross-linked binary biocomposites using biopolymers like alginate and gelatin cross-linked with Ca(2+), Ce(3+) and Zr(4+) ions namely Ca@AlgGel, Ce@AlgGel and Zr@AlgGel composites. The functional groups, agglomeration, surface area, surface morphology, elemental analysis and thermal stability of the composites were investigated by FTIR, TEM, BET, SEM with EDAX and TGA analysis. The chromium removal studies of the biocomposites were carried out in batch mode. The sorption process was optimized by varying the influencing aspects like contact time, dosage, presence of common ions, pH, initial chromium concentration and temperature. The maximum sorption capacity of Ca@AlgGel, Ce@AlgGel and Zr@AlgGel composites were found to be 19.40, 24.50 and 25.40mg/g, respectively. The sorption data was fitted by using Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. Thermodynamic parameters indicate the nature of chromium sorption. The suitability of the composite materials was also tested under the field conditions. PMID:26456290

  1. Synthesis and thermal studies of tetraaza macrocylic ligand and its transition metal complexes. DNA binding affinity of copper complex

    NASA Astrophysics Data System (ADS)

    Saif, M.; Mashaly, Mahmoud M.; Eid, Mohamed F.; Fouad, R.

    2011-09-01

    A Tetraaza Macrocylic Ligand (H 2L) and its complexes, [Cd(H 2L)(OH 2) 2](NO 3) 2·1/2OH 2 (I), [Co(H 2L)(OH 2)](NO 3) 2·1/2OH 2 (II), [Cu(H 2L)(NO 3) 2]·3/2OH 2 (III) and [Ni(H 2L)(NO 3)(OH 2)]NO 3·OH 2 (IV), have been synthesized and characterized on the basis of elemental analysis, molar conductivity, 1H NMR, UV-vis, FT-IR and mass spectroscopy. All results confirm that the prepared compounds have 1:1 metal-to-ligand stoichiometry, octahedral configuration and the ligand behaves as a neutral tetradendate towards the metal ions. [CdL(OH 2) 2] (V), [CoL(OH 2) 2] (VI), [CuL(OH 2) 2] (VII) and [Ni(H 2L)(NO 3) 2] (VIII) were synthesized pyrolytically in solid state from corresponding compounds (I-IV). Analytical results of complexes (V-VIII) show that the ligand behaves either as a neutral tetradendate or dianionic tetradentate ligand towards the metal ions. The binding of H 2L and its copper complex (III) to DNA has been investigated by ultraviolet absorption spectroscopy. The experiments indicate that H 2L and its copper complex (III) can bind to DNA through an intercalative mode. The H 2L and its copper complex (III) exhibited anti-tumor activity against Ehrlich Acites Carcinoma (E.A.C) at the concentration of 100 μg/ml.

  2. Chirality at metal and helical ligand folding in optical isomers of chiral bis(naphthaldiminato)nickel(II) complexes.

    PubMed

    Enamullah, Mohammed; Quddus, Mohammad Abdul; Hasan, Mohammad Rezabul; Pescitelli, Gennaro; Berardozzi, Roberto; Makhloufi, Gamall; Vasylyeva, Vera; Janiak, Christoph

    2016-01-14

    Enantiopure bis[{(R or S)-N-1-(Ar)ethyl-2-oxo-1-naphthaldiminato-κ(2)N,O}]nickel(ii) complexes {Ar = C6H5 ( or ), p-OMeC6H4 ( or ), and p-BrC6H4 ( or )} are synthesized from the reactions between (R or S)-N-1-(Ar)ethyl-2-oxo-1-naphthaldimine and nickel(ii) acetate. Circular-dichroism spectra and their density-functional theoretical simulation reveal the expected mirror image relationship between the enantiomeric pairs / and / in solution. CD spectra are dominated by the metal-centered Λ- or Δ-chirality of non-planar four-coordinated nickel, this latter being in turn dictated by the ligand chirality. Single crystal structure determination for and shows that there are two symmetry-independent molecules (A and B) in each asymmetric unit that give a Z' = 2 structure. Two asymmetric and chiral bidentate N^O-chelate Schiff base ligands coordinate to the nickel atom in a distorted square planar N2O2-coordination sphere. The conformational difference between the symmetry-independent molecules arises from the "up-or-down" folding of the naphthaldiminato ligand with respect to the coordination plane, which creates right- (P) or left-handed (M) helical conformations. Overall, the combination of ligand chirality, chirality at the metal and ligand folding gives rise to discrete metal helicates of preferred helicity in a selective way. Cyclic voltammograms (CV) show an oxidation wave at ca. 1.30 V for the [Ni(L)2]/[Ni(L)2](+) couple, and a reduction wave at ca. -0.35 V for the [Ni(L)2]/[Ni(L)2](-) couple in acetonitrile. PMID:26619269

  3. Microwave Assisted Synthesis, Spectral and Antifungal Studies of 2-Phenyl-N,N′-bis(pyridin-4-ylcarbonyl)butanediamide Ligand and Its Metal Complexes

    PubMed Central

    Shiekh, Rayees Ahmad; Malik, Maqsood Ahmad; Al-Thabaiti, Shaeel Ahmed; Nabi, Arshid

    2014-01-01

    2-Phenyl-N,N′-bis(pyridin-4-ylcarbonyl)butanediamide ligand with a series of transition metal complexes has been synthesized via two routes: microwave irradiation and conventional heating method. Microwave irritation method happened to be the efficient and versatile route for the synthesis of these metal complexes. These complexes were found to have the general composition M(L)Cl2/M(L)(CH3COO)2 (where M = Cu(II), Co(II), Ni(II), and L = ligand). Different physical and spectroscopic techniques were used to investigate the structural features of the synthesized compounds, which supported an octahedral geometry for these complexes. In vitro antifungal activity of the ligand and its metal complexes revealed that the metal complexes are highly active compared to the standard drug. Metal complexes showed enhanced activity compared to the ligand, which is an important step towards the designing of antifungal drug candidates. PMID:24772018

  4. Nano-diamond particles functionalized with single/double-arm amide-thiourea ligands for adsorption of metal ions.

    PubMed

    Zhao, Xiaosheng; Zhang, Shuang; Bai, Chiyao; Li, Bo; Li, Yang; Wang, Lei; Wen, Rui; Zhang, Meicheng; Ma, Lijian; Li, Shoujian

    2016-05-01

    Separation efficiency of solid-phase extractant is greatly subjected to the spatial configurations of functional ligands attached to the matrix, which has not been studied efficiently till now. In order to further understand the relationship between spatial configurations of the attached functional ligand and the adsorption ability of the extractant, two novel molecules (single-armed ligand, SA and double-armed ligand, DA) with identical coordination unit (amide-thiourea) but different spatial configurations (single/double arms) were designed and synthesized. The corresponding extractants, ND-SA and ND-DA were obtained by modification of nanodiamond (ND) with SA and DA and both the extractants displayed good chemical and thermal stabilities. The batch adsorption experiments showed that ND-SA and ND-DA possess large adsorption capacities (∼200mgg(-1)), very fast adsorption kinetics (reaching equilibrium within 2min) and excellent selectivities (up to 82% and 72%, respectively) for uranium. The study of the possible mechanism indicated that ND-DA tends to utilize its tweezer-like double arms to "clamp" metal ions and the stronger chelate interaction could to some extent weaken the coordination selectivity of attached DA ligand. In contrast, single-armed adsorbent ND-SA unexpectedly exhibited better adsorption selectivity for uranium than ND-DA owing to its more flexible spatial configuration and moderate complexing ability. PMID:26874273

  5. Transition metal complexes of a new 15-membered [N5] penta-azamacrocyclic ligand with their spectral and anticancer studies

    NASA Astrophysics Data System (ADS)

    El-Boraey, Hanaa A.; Serag El-Din, Azza A.

    2014-11-01

    Novel penta-azamacrocyclic 15-membered [N5] ligand [L] i.e. 1,5,8,12-tetetraaza-3,4: 9,10-dibenzo-6-ethyl-7-methyl-1,12-(2,6-pyrido)cyclopentadecan-5,7 diene-2,11-dione and its transition metal complexes with Co(II), Ni(II), Cu(II), Ru(III) and Pd(II) have been synthesized and structurally characterized by elemental analysis, spectral, thermal as well as magnetic and molar conductivity measurements. On basis of IR, MS, UV-Vis 1H NMR and EPR spectral studies an octahedral geometry has been proposed for all complexes except Co(II), Cu(II) nitrate complexes and Pd(II) chloride complex that adopt tetrahedral, square pyramidal and square planar geometries, respectively. The antitumor activity of the synthesized ligand and some complexes against human breast cancer cell lines (MCF-7) and human hepatocarcinoma cell lines (HepG2) has been studied. The complexes (IC50 = 2.04-9.7, 2.5-3.7 μg/mL) showed potent antitumor activity comparable with their ligand (IC50 = 11.7, 3.45 μg/mL) against the above mentioned cell lines, respectively. The results evidently show that the activity of the ligand becomes more pronounced and significant when coordinated to the metal ion.

  6. Transition metal complexes of a new 15-membered [N5] penta-azamacrocyclic ligand with their spectral and anticancer studies.

    PubMed

    El-Boraey, Hanaa A; Serag El-Din, Azza A

    2014-11-11

    Novel penta-azamacrocyclic 15-membered [N5] ligand [L] i.e. 1,5,8,12-tetetraaza-3,4: 9,10-dibenzo-6-ethyl-7-methyl-1,12-(2,6-pyrido)cyclopentadecan-5,7 diene-2,11-dione and its transition metal complexes with Co(II), Ni(II), Cu(II), Ru(III) and Pd(II) have been synthesized and structurally characterized by elemental analysis, spectral, thermal as well as magnetic and molar conductivity measurements. On basis of IR, MS, UV-Vis 1H NMR and EPR spectral studies an octahedral geometry has been proposed for all complexes except Co(II), Cu(II) nitrate complexes and Pd(II) chloride complex that adopt tetrahedral, square pyramidal and square planar geometries, respectively. The antitumor activity of the synthesized ligand and some complexes against human breast cancer cell lines (MCF-7) and human hepatocarcinoma cell lines (HepG2) has been studied. The complexes (IC50=2.04-9.7, 2.5-3.7 μg/mL) showed potent antitumor activity comparable with their ligand (IC50=11.7, 3.45 μg/mL) against the above mentioned cell lines, respectively. The results evidently show that the activity of the ligand becomes more pronounced and significant when coordinated to the metal ion. PMID:24892547

  7. Syntheses, structures and tunable luminescence of lanthanide metal-organic frameworks based on azole-containing carboxylic acid ligand

    SciTech Connect

    Zhao, Dian; Rao, Xingtang; Yu, Jiancan; Cui, Yuanjing Yang, Yu; Qian, Guodong

    2015-10-15

    Design and synthesis of a series of isostructural lanthanide metal-organic frameworks (LnMOFs) serving as phosphors by coordinate the H{sub 2}TIPA (5-(1H-tetrazol-5-yl)isophthalic acid) ligands and lanthanide ions is reported. The color of the luminescence can be tuned by adjusting the relative concentration of the lanthanide ions in the host framework GdTIPA, and near-pure-white light emission can be achieved. - Graphical abstract: Lanthanide metal-organic frameworks (LnMOFs) with tunable luminescence were synthesized using an azole-containing carboxylic acid as ligand. - Highlights: • A series of isostructural LnMOFs serving as phosphor is reported. • We model the GdTIPA: Tb{sup 3+}, Eu{sup 3+} which can tune color and emit white light. • The scheme and mechanism of luminescent LnMOFs are also presented and discussed.

  8. Bandgap Engineering of Titanium-Oxo Clusters: Labile Surface Sites Used for Ligand Substitution and Metal Incorporation.

    PubMed

    Liu, Jin-Xiu; Gao, Mei-Yan; Fang, Wei-Hui; Zhang, Lei; Zhang, Jian

    2016-04-18

    Through the labile coordination sites of a robust phosphonate-stabilized titanium-oxo cluster, 14 O-donor ligands have been successfully introduced without changing the cluster core. The increasing electron-withdrawing effect of the organic species allows the gradual reduction of the bandgaps of the {Ti6 } complexes. Transition-metal ions are then incorporated by the use of bifunctional O/N-donor ligands, organizing these {Ti6 } clusters into polymeric structures. The coordination environments of the applied metal ions show significant influence on their visible-light adsorption. Both the above structural functionalizations also tune the photocatalytic H2 production activities of these clusters. This work provides a systematic bandgap engineering study of titanium-oxo clusters, which is important not only for their future photocatalytic applications, also for the better understanding of the structure-property relationships. PMID:26959286

  9. Structural Investigations of Silica Polyamine Composites: Surface Coverage, Metal Ion Coordination, and Ligand Modification

    SciTech Connect

    Hughes, Mark; Nielsen, Daniel; Rosenberg, Edward; Gobetto, Roberto; Viale, Alessandra; Burton, Sarah D.; Ferel, Joseph

    2006-09-13

    Silanization of the silica gel surface in the synthesis of silica gel polyamine composites uses (chloropropyl)-trichlorosilane (CPTCS). It is possible to substitute a molar fraction of reagent CPTCS with methyltrichlorosilane (MTCS), creating a mixed silane surface layer. Two types of silica gels were modified with a series of MTCS:CPTCS molar ratios. Solid-state CP/MAS 29Si and 13C NMR spectroscopies were used to evaluate the surface silane composition. Surface silane coverage was markedly improved for the resulting gels. When polyamines were grafted to the resultant MTCS:CPTCS silane layers, it was shown that the decrease in the number of propyl attachments to the polyamine resulted in increased quantities of ''free amines''. Optimum MTCS:CPTCS ratios were determined for three polyamines grafted onto one silica gel. A substantial free amine increase was observed for poly(allylamine) (PAA). Metal uptake studies show increases in Cu(II) capacity and/or an improvement in Cu(II) mass-transfer kinetics. The effect of polymer molecular weight upon Cu(II) capacity was investigated for each polyamine. Substantial differences in Cu(II) capacity between 50,000 MW poly(vinylamine) (PVA) and >1000 MW PVA were evident. Similar differences between 25,000 MW poly(ethyleneimine) (PEI) and 1200 MW PEI were found. The mass-transfer kinetics was shown to be improved for composites prepared using a large fraction of MTCS in the reagent silane mixture. This resulted in substantial improvements in the 10% breakthrough Cu(II) capacity for PVA (50 000 MW). PEI composites were further modified to form an amino-acetate ligand. The impact of the MTCS:CPTCS silane ratio on the acetate ligand loading and ultimately on the Cu(II) capacity at pH 2 was investigated. A ratio of 12.5:1 was shown to result in an acetate modified PEI composite with a Cu(II) capacity 140% of the Cu(II) capacity of the same composite prepared with ''CPTCS only''.

  10. Breaking the dogma of the metal-coordinating carboxylate group in integrin ligands: introducing hydroxamic acids to the MIDAS to tune potency and selectivity.

    PubMed

    Heckmann, Dominik; Laufer, Burkhardt; Marinelli, Luciana; Limongelli, Vittorio; Novellino, Ettore; Zahn, Grit; Stragies, Roland; Kessler, Horst

    2009-01-01

    A suitable substitute: All integrin receptors bind their ligands, which contain an aspartate residue, in the metal-ion- dependent adhesion site (MIDAS). So far all attempts to replace the carboxyl group of aspartate with other, pharmacologically favorable isosteric groups have failed. Now it has been shown that a hydroxamic acid group can replace the carboxyl group; the resulting ligand retains its high binding activity. The picture shows one such ligand in the binding site of alphavbeta3. PMID:19343753

  11. Synthesis of Imine-Naphthol Tripodal Ligand and Study of Its Coordination Behaviour towards Fe(III), Al(III), and Cr(III) Metal Ions

    PubMed Central

    Kaur, Kirandeep

    2014-01-01

    A hexadentate Schiff base tripodal ligand is synthesized by the condensation of tris (2-aminoethyl) amine with 2-hydroxy-1-naphthaldehyde and characterized by various spectroscopic techniques like UV-VIS, IR, NMR, MASS, and elemental analysis. The solution studies by potentiometric and spectrophotometric methods are done at 25 ± 1°C, µ = 0.1 M KCl, to calculate the protonation constants of the ligand and formation constants of metal complexes formed by the ligand with Fe(III), Al(III), and Cr(III) metal ions. The affinity of the ligand towards Fe(III) is compared with deferiprone (a drug applied for iron intoxication) and transferrin (the main Fe(III) binding protein in plasma). Structural analysis of the ligand and the metal complexes was done using semiempirical PM6 method. Electronic and IR spectra are calculated by semiempirical methods and compared with experimental one. PMID:25294978

  12. GPI-anchor and GPI-anchored protein expression in PMM2-CDG patients

    PubMed Central

    2013-01-01

    Background Mutations in PMM2 impair phosphomannomutase-2 activity and cause the most frequent congenital disorder of glycosylation, PMM2-CDG. Mannose-1-phosphate, that is deficient in this disorder, is also implicated in the biosynthesis of glycosylphosphatidyl inositol (GPI) anchors. Objective To evaluate whether GPI-anchor and GPI-anchored proteins are defective in PMM2-CDG patients. Methods The expression of GPI-anchor and seven GPI-anchored proteins was evaluated by flow cytometry in different cell types from twelve PMM2-CDG patients. Additionally, neutrophil CD16 and plasma hepatic proteins were studied by Western blot. Transferrin glycoforms were evaluated by HPLC. Results Patients and controls had similar surface expression of GPI-anchor and most GPI-anchored proteins. Nevertheless, patients displayed a significantly diminished binding of two anti-CD16 antibodies (3G8 and KD1) to neutrophils and also of anti-CD14 (61D3) to monocytes. Interestingly, CD16 immunostaining and asialotransferrin levels significantly correlated with patients’ age. Analysis by flow cytometry of CD14 with MΦP9, and CD16 expression in neutrophils by Western blot using H-80 ruled out deficiencies of these antigens. Conclusions PMM2 mutations do not impair GPI-anchor or GPI-anchored protein expression. However, the glycosylation anomalies caused by PMM2 mutations might affect the immunoreactivity of monoclonal antibodies and lead to incorrect conclusions about the expression of different proteins, including GPI-anchored proteins. Neutrophils and monocytes are sensitive to PMM2 mutations, leading to abnormal glycosylation in immune receptors, which might potentially affect their affinity to their ligands, and contribute to infection. This study also confirms less severe hypoglycosylation defects in older PMM2-CDG patients. PMID:24139637

  13. A novel supramolecular polymer gel constructed by crosslinking pillar[5]arene-based supramolecular polymers through metal-ligand interactions.

    PubMed

    Wang, Pi; Xing, Hao; Xia, Danyu; Ji, Xiaofan

    2015-12-21

    A novel heteroditopic A-B monomer was synthesized and used to construct linear supramolecular polymers utilizing pillar[5]arene-based host-guest interactions. Specifically, upon addition of Cu(2+) ions, the supramolecular polymer chains are crosslinked through metal-ligand interactions, resulting in the formation of a supramolecular polymer gel. Interestingly, this self-organized supramolecular polymer can be used as a novel fluorescent sensor for detecting Cu(2+) ions. PMID:26466511

  14. Metal-ligand cooperation on a diruthenium platform: selective imine formation through acceptorless dehydrogenative coupling of alcohols with amines.

    PubMed

    Saha, Biswajit; Rahaman, S M Wahidur; Daw, Prosenjit; Sengupta, Gargi; Bera, Jitendra K

    2014-05-19

    Metal-metal singly-bonded diruthenium complexes, bridged by naphthyridine-functionalized N-heterocyclic carbene (NHC) ligands featuring a hydroxy appendage on the naphthyridine unit, are obtained in a single-pot reaction of [Ru2(CH3COO)2(CO)4] with 1-benzyl-3-(5,7-dimethyl-1,8-naphthyrid-2-yl)imidazolium bromide (BIN⋅HBr) or 1-isopropyl-3-(5,7-dimethyl-1,8-naphthyrid-2-yl)imidazolium bromide (PIN⋅HBr), TlBF4, and substituted benzaldehyde containing an electron-withdrawing group. The modified NHC-naphthyridine-hydroxy ligand spans the diruthenium unit in which the NHC carbon and hydroxy oxygen occupy the axial sites. All the synthesized compounds catalyze acceptorless dehydrogenation of alcohols to the corresponding aldehydes in the presence of a catalytic amount of weak base 1,4-diazabicyclo[2.2.2]octane (DABCO). Further, acceptorless dehydrogenative coupling (ADHC) of the alcohol with amines affords the corresponding imine as the sole product. The substrate scope is examined with 1 (BIN, p-nitrobenzaldehyde). A similar complex [Ru2(CO)4(CH3COO)(3-PhBIN)][Br], that is devoid of a hydroxy arm, is significantly less effective for the same reaction. Neutral complex 1 a, obtained by deprotonation of the hydroxy arm in 1, is found to be active for the ADHC of alcohols and amines under base-free conditions. A combination of control experiments, deuterium labeling, kinetic Hammett studies, and DFT calculations support metal-hydroxyl/hydroxide and metal-metal cooperation for alcohol activation and dehydrogenation. The bridging acetate plays a crucial role in allowing β-hydride elimination to occur. The ligand architecture on the diruthenium core causes rapid aldehyde extrusion from the metal coordination sphere, which is responsible for exclusive imine formation. PMID:24715433

  15. Essentially Molecular Metal Complexes Anchored to Zeolite: Synthesis and Characterization of Rhodium Complexes and Ruthenium Complexes Prepared from Rh(acac)(2-C2H4)2 and cis-Ru(acac)2( -C2H4)2

    SciTech Connect

    Ogino, I.; Gates, B

    2010-01-01

    Mononuclear complexes of rhodium and of ruthenium, Rh(acac)({eta}{sup 2}-C{sub 2}H{sub 4}){sub 2} and cis-Ru(acac)2({eta}{sup 2}-C{sub 2}H{sub 4}){sub 2} (acac = C{sub 5}H{sub 7}O{sub 2}{sup -}), were used as precursors to synthesize metal complexes bonded to zeolite {beta}. Infrared (IR) and extended X-ray absorption fine structure (EXAFS) spectra show that the species formed from Rh(acac)({eta}{sup 2}-C{sub 2}H{sub 4}){sub 2} was Rh({eta}{sup 2}-C{sub 2}H{sub 4}){sub 2}{sup +}, which was bonded to the zeolite at aluminum sites via two Rh-O bonds. Reaction of this supported rhodium complex with CO gave the supported rhodium gem-dicarbonyl Rh(CO){sub 2}{sup +}, which was characterized by two {nu}{sub CO} bands in the IR spectrum, at 2048 and 2115 cm{sup -1}, that were sharp (fwhm of 2115-cm{sup -1} band = 5 cm{sup -1}), indicating a high degree of uniformity of the supported species. Nearly the same result was observed (Liang, A. et al. J. Am. Chem. Soc. 2009, 131, 8460) for the isostructural rhodium complex supported on dealuminated HY zeolite, which was characterized by frequencies of the {nu}{sub CO} bands that were 4 and 2 cm{sup -1}, respectively, greater than those characterizing the zeolite {beta}-supported complex. This comparison indicates that the Rh atoms in Rh({eta}{sup 2}-C{sub 2}H{sub 4}){sub 2}{sup +} anchored on zeolite {beta} were slightly more electron-rich than those on zeolite Y. This inference is supported by EXAFS results showing shorter Rh-C bonds in the zeolite {beta}-supported rhodium ethene complex than in the zeolite Y-supported rhodium ethene complex. In contrast to these supported rhodium complexes, the zeolite {beta}-supported ruthenium samples were shown by IR and EXAFS spectroscopies to consist of mixtures of mononuclear ruthenium complexes with various numbers of acac ligands; when CO reacted with the supported ruthenium complexes, the resultant ruthenium carbonyls were characterized by {nu}{sub CO} spectra characteristic of both ruthenium dicarbonyls and ruthenium tricarbonyls.

  16. Synthesis and spectral studies on metal complexes of s-triazine based ligand and non linear optical properties

    NASA Astrophysics Data System (ADS)

    Shanmugakala, R.; Tharmaraj, P.; Sheela, C. D.

    2014-11-01

    A series of transition metal complexes of type [ML] and [ML2]Cl2 (where M = Cu(II), Ni(II), Co(II) have synthesized from 2-phenylamino-4,6-dichloro-s-triazine and 3,5-dimethyl pyrazole; their characteristics have been investigated by means of elemental analyses, magnetic susceptibility, molar conductance, IR, UV-Vis, Mass, NMR and ESR spectra. The electrochemical behavior of copper(II) complexes we have studied, by using cyclic voltammetry. The ESR spectra of copper(II) complexes are recorded at 300 K and 77 K and their salient features are appropriately reported. Spectral datas, we found, show that the ligand acts as a neutral tridentate, and coordinates through the triazine ring nitrogen and pyrazolyl ring nitrogen atoms to the metal ion. Evident from our findings, the metal(II) complexes of [ML] type exhibit square pyramidal geometry, and that of [ML2]Cl2 exhibit octahedral geometry. The in vitro antimicrobial activities of the ligand and its complexes are evaluated against Bacillus subtilis, Micrococcus luteus, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus mutans, Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae, Proteus vulgaris, Cryptococcus neoformans, Pseudomonas aeruginosa, Salmonella typhi, Serratia marcescens, Shigella flexneri, Vibrio cholera, Vibris parahaemolyticus, Aspergillus niger, Candida albicans and Penicillium oxalicum by well-diffusion method. The second harmonic generation efficiency of the ligand and its complexes are determined and compared with urea and KDP.

  17. Review: Formation of Peptide Radical Ions Through Dissociative Electron Transfer in Ternary Metal-Ligand-Peptide Complexes

    SciTech Connect

    Chu, Ivan K.; Laskin, Julia

    2011-12-31

    The formation and fragmentation of odd-electron ions of peptides and proteins is of interest to applications in biological mass spectrometry. Gas-phase redox chemistry occurring during collision-induced dissociation of ternary metal-ligand-peptide complexes enables the formation of a variety of peptide radicals including the canonical radical cations, M{sup +{sm_bullet}}, radical dications, [M{sup +}H]{sup 2+{sm_bullet}}, radical anions, [M-2H]{sup -{sm_bullet}}. In addition, odd-electron peptide ions with well-defined initial location of the radical site are produced through side chain losses from the radical ions. Subsequent fragmentation of these species provides information on the role of charge and the location of the radical site on the competition between radical-induced and proton-driven fragmentation of odd-electron peptide ions. This account summarizes current understanding of the factors that control the efficiency of the intramolecular electron transfer (ET) in ternary metal-ligand-peptide complexes resulting in formation of odd-electron peptide ions. Specifically, we discuss the effect of the metal center, the ligand and the peptide structure on the competition between the ET, proton transfer (PT), and loss of neutral peptide and neutral peptide fragments from the complex. Fundamental studies of the structures, stabilities, and the energetics and dynamics of fragmentation of such complexes are also important for detailed molecular-level understanding of photosynthesis and respiration in biological systems.

  18. 30 CFR 57.7032 - Anchoring.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Anchoring. 57.7032 Section 57.7032 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Drilling and Rotary Jet...

  19. 30 CFR 57.7032 - Anchoring.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Anchoring. 57.7032 Section 57.7032 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Drilling and Rotary Jet...

  20. 30 CFR 57.7032 - Anchoring.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Anchoring. 57.7032 Section 57.7032 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Drilling and Rotary Jet...

  1. 30 CFR 57.7032 - Anchoring.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Anchoring. 57.7032 Section 57.7032 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Drilling and Rotary Jet...

  2. 30 CFR 57.7032 - Anchoring.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Anchoring. 57.7032 Section 57.7032 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Drilling and Rotary Jet...

  3. Metal-ligand ``multiple`` bonding: Revelations in the electronic structure of complexes of high-valent f-elements

    SciTech Connect

    Burns, C.J.; Arney, D.S.J.; Schnabel, R.C.; Warner, B.P.; Bursten, B.E.; Green, J.C.; Marks, T.J.

    1997-07-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal of this project has been to extend the understanding of the nature of interactions between f-metals and first row elements (important both in natural systems and in ceramics), as well as providing important new information regarding basic differences in the chemical nature of d- and f-metals. By developing preparative routes to novel classes of early actinide and lanthanide complexes in which metal-ligand bonding is formally unsaturated, this project has provided the means to study orbital interactions and charge distribution in these species by physical, chemical, and theoretical means. Evaluation of the physical and chemical characteristics of these species is providing dramatic evidence for the involvement of valence metal orbitals [nf and (n+1)d] in bonding, and is yielding new insights into the factors influencing stability of related species.

  4. Synthesis, characterisation, spectral, thermal, XRD, molecular modelling and potential antibacterial study of metal complexes containing octadentate azodye ligands

    NASA Astrophysics Data System (ADS)

    Mahapatra, Bipin Bihari; Chaulia, Satyanarayan; Sarangi, Ashish Kumar; Dehury, Satyanarayan; Panda, Jnyanaranjan

    2015-05-01

    Twelve tetrametallic complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) with two new octadentate azodye ligands, 4,4‧-bis(2‧,4‧-dihydroxy-5‧carboxyphenylazo) diphenylether (LH6) and 4,4‧-bis(2‧,4‧-dihydroxy-5‧-acylphenylazo) diphenylether (L‧H4) have been synthesised. The structural elucidation of the complexes was made basing upon analytical, conductance, magnetic susceptibility, IR, electronic spectra, ESR, NMR, ESI-MS, TG, DTG, DTA and X-ray diffraction (powder pattern) data. The cobalt (II) and nickel (II) complexes are found to be octahedral, copper (II) complexes are distorted octahedral and a tetrahedral stereochemistry has been suggested to zinc (II), cadmium (II) and mercury (II) complexes. The thermal analysis data provided the kinetic parameters as order of decomposition reaction, activation energy and frequency factor. The geometry of the ligands and their Co(II), Ni(II), Cu(II) and Zn(II) complexes were optimised and their physicochemical properties were calculated by using molecular modelling procedure. The ESI-MS determination supports the molecular formula and molecular weight of the ligands and the complexes. The Ni(II) complex is found to have a triclinic crystal system. The potential antibacterial study of the two ligands and eight metal complexes was made by cup-plate method against one gram positive and one gram negative bacteria. The results showed increase in the activity of some metal complexes as compare with azodye ligands.

  5. Synergistic assembly of heavy metal clusters and luminescent organic bridging ligands in metal-organic frameworks for highly efficient X-ray scintillation.

    PubMed

    Wang, Cheng; Volotskova, Olga; Lu, Kuangda; Ahmad, Moiz; Sun, Conroy; Xing, Lei; Lin, Wenbin

    2014-04-30

    We have designed two metal-organic frameworks (MOFs) to efficiently convert X-ray to visible-light luminescence. The MOFs are constructed from M6(μ3-O)4(μ3-OH)4(carboxylate)12 (M = Hf or Zr) secondary building units (SBUs) and anthracene-based dicarboxylate bridging ligands. The high atomic number of Zr and Hf in the SBUs serves as effective X-ray antenna by absorbing X-ray photons and converting them to fast electrons through the photoelectric effect. The generated electrons then excite multiple anthracene-based emitters in the MOF through inelastic scattering, leading to efficient generation of detectable photons in the visible spectrum. The MOF materials thus serve as efficient X-ray scintillators via synergistic X-ray absorption by the metal-cluster SBUs and optical emission by the bridging ligands. PMID:24730683

  6. Rare-earth-metal methyl, amide, and imide complexes supported by a superbulky scorpionate ligand.

    PubMed

    Schädle, Dorothea; Maichle-Mössmer, Cäcilia; Schädle, Christoph; Anwander, Reiner

    2015-01-01

    The reaction of monomeric [(Tp(tBu,Me) )LuMe2 ] (Tp(tBu,Me) =tris(3-Me-5-tBu-pyrazolyl)borate) with primary aliphatic amines H2 NR (R=tBu, Ad=adamantyl) led to lutetium methyl primary amide complexes [(Tp(tBu,Me) )LuMe(NHR)], the solid-state structures of which were determined by XRD analyses. The mixed methyl/tetramethylaluminate compounds [(Tp(tBu,Me) )LnMe({μ2 -Me}AlMe3 )] (Ln=Y, Ho) reacted selectively and in high yield with H2 NR, according to methane elimination, to afford heterobimetallic complexes: [(Tp(tBu,Me) )Ln({μ2 -Me}AlMe2 )(μ2 -NR)] (Ln=Y, Ho). X-ray structure analyses revealed that the monomeric alkylaluminum-supported imide complexes were isostructural, featuring bridging methyl and imido ligands. Deeper insight into the fluxional behavior in solution was gained by (1) H and (13) C NMR spectroscopic studies at variable temperatures and (1) H-(89) Y HSQC NMR spectroscopy. Treatment of [(Tp(tBu,Me) )LnMe(AlMe4 )] with H2 NtBu gave dimethyl compounds [(Tp(tBu,Me) )LnMe2 ] as minor side products for the mid-sized metals yttrium and holmium and in high yield for the smaller lutetium. Preparative-scale amounts of complexes [(Tp(tBu,Me) )LnMe2 ] (Ln=Y, Ho, Lu) were made accessible through aluminate cleavage of [(Tp(tBu,Me) )LnMe(AlMe4 )] with N,N,N',N'-tetramethylethylenediamine (tmeda). The solid-state structures of [(Tp(tBu,Me) )HoMe(AlMe4 )] and [(Tp(tBu,Me) )HoMe2 ] were analyzed by XRD. PMID:25392940

  7. Anchors for Education Reforms

    ERIC Educational Resources Information Center

    Alok, Kumar

    2012-01-01

    Education reforms, considering their significance, deserve better methods than mere "trial and error." This article conceptualizes a network of six anchors for education reforms: education policy, education system, curriculum, pedagogy, assessment, and teacher education. It establishes the futility to reform anchors in isolation and anticipates

  8. Anchors for Education Reforms

    ERIC Educational Resources Information Center

    Alok, Kumar

    2012-01-01

    Education reforms, considering their significance, deserve better methods than mere "trial and error." This article conceptualizes a network of six anchors for education reforms: education policy, education system, curriculum, pedagogy, assessment, and teacher education. It establishes the futility to reform anchors in isolation and anticipates…

  9. "Ligands-with-Benefits": Naphthalene-Substituted Schiff Bases Yielding New Ni(II) Metal Clusters with Ferromagnetic and Emissive Properties and Undergoing Exciting Transformations.

    PubMed

    Perlepe, Panagiota S; Cunha-Silva, Luís; Gagnon, Kevin J; Teat, Simon J; Lampropoulos, Christos; Escuer, Albert; Stamatatos, Theocharis C

    2016-02-01

    The initial employment of the fluorescent bridging ligand N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2) in metal cluster chemistry has led to new Ni12 (1) and Ni5 (2) clusters with wheel-like and molecular-chain topologies, respectively. The doubly-deprotonated nacb(2-) ligands were found to adopt four different coordination modes within 1 and 2. The nature of the ligand has also allowed unexpected organic transformations to occur and ferromagnetic and emission behaviors to emerge. The combined work demonstrates the ability of some "ligands-with-benefits" to yield beautiful structures with exciting topologies and interesting physicochemical properties. PMID:26788587

  10. Humic Acid Complexation of Th, Hf and Zr in Ligand Competition Experiments: Metal Loading and Ph Effects

    NASA Technical Reports Server (NTRS)

    Stern, Jennifer C.; Foustoukos, Dionysis I.; Sonke, Jeroen E.; Salters, Vincent J. M.

    2014-01-01

    The mobility of metals in soils and subsurface aquifers is strongly affected by sorption and complexation with dissolved organic matter, oxyhydroxides, clay minerals, and inorganic ligands. Humic substances (HS) are organic macromolecules with functional groups that have a strong affinity for binding metals, such as actinides. Thorium, often studied as an analog for tetravalent actinides, has also been shown to strongly associate with dissolved and colloidal HS in natural waters. The effects of HS on the mobilization dynamics of actinides are of particular interest in risk assessment of nuclear waste repositories. Here, we present conditional equilibrium binding constants (Kc, MHA) of thorium, hafnium, and zirconium-humic acid complexes from ligand competition experiments using capillary electrophoresis coupled with ICP-MS (CE- ICP-MS). Equilibrium dialysis ligand exchange (EDLE) experiments using size exclusion via a 1000 Damembrane were also performed to validate the CE-ICP-MS analysis. Experiments were performed at pH 3.5-7 with solutions containing one tetravalent metal (Th, Hf, or Zr), Elliot soil humic acid (EHA) or Pahokee peat humic acid (PHA), and EDTA. CE-ICP-MS and EDLE experiments yielded nearly identical binding constants for the metal- humic acid complexes, indicating that both methods are appropriate for examining metal speciation at conditions lower than neutral pH. We find that tetravalent metals form strong complexes with humic acids, with Kc, MHA several orders of magnitude above REE-humic complexes. Experiments were conducted at a range of dissolved HA concentrations to examine the effect of [HA]/[Th] molar ratio on Kc, MHA. At low metal loading conditions (i.e. elevated [HA]/[Th] ratios) the ThHA binding constant reached values that were not affected by the relative abundance of humic acid and thorium. The importance of [HA]/[Th] molar ratios on constraining the equilibrium of MHA complexation is apparent when our estimated Kc, MHA values attained at very low metal loading conditions are compared to existing literature data. Overall, experimental data suggest that the tetravalent transition metal/-actinide-humic acid complexation is important over a wide range of pH values, including mildly acidic conditions, and thus, these complexes should be included in speciation models.

  11. Synthesis, spectra and DNA interactions of certain mononuclear transition metal(II) complexes of macrocyclic tetraaza diacetyl curcumin ligand

    NASA Astrophysics Data System (ADS)

    Rajesh, Jegathalaprathaban; Gubendran, Ammavasi; Rajagopal, Gurusamy; Athappan, Periyakaruppan

    2012-02-01

    A series of mononuclear transition metal(II) complexes of type [M(LL)]2+ (LL = the template condensate of orthophenylene diamine and benzilidene diacetyl curcumin (ben-diacecur) and M = Cu(II) (1) or Co(II) (2) or Ni(II) (3) or Mn(II) (4)), have been isolated and the spectral behaviors are discussed. The ligand and complexes have also been characterized by the analytical and spectral methods like UV-Visible, FT-IR, NMR and EPR. Further, the interaction of the transition metal complexes with Calf thymus (CT) DNA have also been studied by the use of physical methods like UV-Visible, emission and CD spectroscopic techniques. The electrochemical responses of these metal complexes both in presence and absence of DNA have also been demonstrated. All these findings support the hypothesis of DNA interactions of all these metal complexes through the grooves with a higher degree of interaction by complex 1 (Kb = 1.4 × 105) possibly through the interposition of the aromatic rings of the ligand compared to complexes, 2-4. The complex 1 display significant oxidative cleavage of circular plasmid pUC18 DNA in the presence of H2O2 using the singlet oxygen as a reactive species. The spectral and electrochemical response of these complexes designate that the square-planar Cu(II), Ni(II) and Co(II) complexes interact much better than the axially coordinated octahedral Mn(II) complex.

  12. SOD activity and DNA binding properties of a new symmetric porphyrin Schiff base ligand and its metal complexes.

    PubMed

    Çay, Sevim; Köse, Muhammet; Tümer, Ferhan; Gölcü, Ayşegül; Tümer, Mehmet

    2015-12-01

    4-Methoxy-2,6-bis(hydroxymethyl)phenol (1) was prepared from the reaction of 4-methoxyphenol and formaldehyde. The compound (1) was then oxidized to the 4-methoxy-2,6-diformylphenol (2) compound. Molecular structure of compound (2) was determined by X-ray diffraction method. A new symmetric porphyrin Schiff base ligand 4-methoxy-2,6-bis[5-(4-iminophenyl)-10,15,20-triphenylporphyrin]phenol (L) was prepared from the reaction of the 5-(4-aminophenyl)-10,15,20-triphenylporphyrin (TTP-NH2) and the compound (2) in the toluene solution. The metal complexes (Cu(II), Fe(III), Mn(III), Pt(II) and Zn(II)) of the ligand (L) were synthesized and characterized by the spectroscopic and analytical methods. The DNA (fish sperm FSdsDNA) binding studies of the ligand and its complexes were performed using UV-vis spectroscopy. Additionally, superoxide dismutase activities of the porphyrin Schiff base metal complexes were investigated. Additionally, electrochemical, photoluminescence and thermal properties of the compounds were investigated. PMID:26172470

  13. Biotic ligand modeling approach: Synthesis of the effect of major cations on the toxicity of metals to soil and aquatic organisms.

    PubMed

    Ardestani, Masoud M; van Straalen, Nico M; van Gestel, Cornelis A M

    2015-10-01

    The biotic ligand model (BLM) approach is used to assess metal toxicity, taking into account the competition of other cations with the free metal ions for binding to the biotic ligand sites of aquatic and soil organisms. The bioavailable fraction of metals, represented by the free metal ion, is a better measure than the total concentration for assessing their potential risk to the environment. Because BLMs are relating toxicity to the fraction of biotic ligands occupied by the metal, they can be useful for investigating factors affecting metal bioaccumulation and toxicity. In the present review, the effects of major cations on the toxicity of metals to soil and aquatic organisms were comprehensively studied by performing a meta-analysis of BLM literature data. Interactions at the binding sites were shown to be species- and metal-specific. The main factors affecting the relationships between toxicity and conditional binding constants for metal binding at the biotic ligand appeared to be Ca(2+) , Mg(2+) , and protons. Other important characteristics of the exposure medium, such as levels of dissolved organic carbon and concentrations of other cations, should also be considered to obtain a proper assessment of metal toxicity to soil and aquatic organisms. PMID:25953362

  14. Kinetic Studies of the Coordination of Mono- and Ditopic Ligands with First Row Transition Metal Ions.

    PubMed

    Munzert, Stefanie Martina; Schwarz, Guntram; Kurth, Dirk G

    2016-03-01

    The reactions of the ditopic ligand 1,4-bis(2,2':6',2?-terpyridin-4'-yl)benzene (1) as well as the monotopic ligands 4'-phenyl-2,2':6',2?-terpyridine (2) and 2,2':6',2?-terpyridine (3) with Fe(2+), Co(2+), and Ni(2+) in solution are studied. While the reaction of 1 with Fe(2+), Co(2+), and Ni(2+) results in metallo-supramolecular coordination polyelectrolytes (MEPEs), ligands 2 and 3 give mononuclear complexes. All compounds are analyzed by UV/vis and fluorescence spectroscopy. Fluorescence spectroscopy indicates that protonation as well as coordination to Zn(2+) leads to an enhanced fluorescence of the terpyridine ligands. In contrast, Fe(2+), Co(2+), or Ni(2+) quench the fluorescence of the ligands. The kinetics of the reactions are studied by stopped-flow fluorescence spectroscopy. Analysis of the measured data is presented and the full kinetic rate laws for the coordination of the terpyridine ligands 1, 2, and 3 to Fe(2+), Co(2+), and Ni(2+) are presented. The coordination occurs within a few seconds, and the rate constant increases in the order Ni(2+) < Co(2+) < Fe(2+). With the rate constants at hand, the polymer growth of Ni-MEPE is computed. PMID:26908136

  15. Axial ligand effects on the diradical characters and second hyperpolarizabilities of open-shell singlet transition-metal dinuclear complexes

    NASA Astrophysics Data System (ADS)

    Yamada, Taishi; Takamuku, Shota; Matsui, Hiroshi; Champagne, Benoît; Nakano, Masayoshi

    2014-07-01

    We investigate the axial ligand effects on the diradical character (y) dependences of the second hyperpolarizabilities (γ) of transition-metal dinuclear complexes, Mo(I)2(CO)2, with different bond lengths (R) using the spin-unrestricted coupled-cluster method. Mo(I)2(CO)2 exhibits intrinsic y-γ correlation and dominant dσ-electron contribution to the maximum γ (γmax), which are also observed in the bare dinuclear analogs. The axial-ligand coordination to Mo(I)2 is found to cause the increase of the diradical character of the dσ orbital, the emergence of large negative γ for small R, and an enhancement of |γmax| by a factor of ∼30 as compared to the bare analogs.

  16. Synthesis and characterization of metal complexes of Schiff base ligand derived from imidazole-2-carboxaldehyde and 4-aminoantipyrine

    NASA Astrophysics Data System (ADS)

    Selwin Joseyphus, R.; Shiju, C.; Joseph, J.; Justin Dhanaraj, C.; Arish, D.

    2014-12-01

    The Co(II), Ni(II), Cu(II) and Zn(II) complexes of the Schiff base derived from imidazole-2-carboxaldehyde and 4-aminoantipyrine were synthesized. These compounds were characterized by elemental analysis, IR, mass, 1H NMR, electronic spectra, magnetic moment, molar conductance, thermal analysis, powder XRD and SEM. The analytical data show that the metal to ligand ratio is 1:1. The IR results show that the ligand acts as a bidentate donor coordinating through the azomethine nitrogen and imidazole nitrogen atoms. From the electronic spectra and magnetic moment value predicts the geometry of the complexes. The surface morphology of the compounds was studied by SEM. The compounds were screened for their antibacterial activity and antifungal activity using Kirby Bayer disc diffusion method. The DNA cleavage and superoxide dismutase activities of the compounds were investigated. The anticancer activities of the complexes have been carried out towards HeLa and HCT116 cancer cells.

  17. New sterically-hindered o-quinones annelated with metal-dithiolates: regiospecificity in oxidative addition reactions of a bifacial ligand to the Pd and Pt complexes.

    PubMed

    Martyanov, K A; Cherkasov, V K; Abakumov, G A; Samsonov, M A; Khrizanforova, V V; Budnikova, Y H; Kuropatov, V A

    2016-04-25

    An unusual reactivity of sterically hindered o-quinones with an annelated dithiete ring towards coordination at a dithiolene site has been discovered. New Pd and Pt dithiolate complexes have been synthesized. The reaction proceeds regioselectively, and the quinone site of the parent ligand is not affected even while using an excess of the metal complex. Both Pt and Pd complexes display a square planar surrounding for the metal ion and have very similar NMR, IR and UV/Vis spectra. Surprisingly, being coordinated at the dithiolene site to the metal, the ligand exhibits activity like an o-quinone, it could be reduced with different metals resulting in the corresponding o-semiquinonates which were confirmed by EPR spectroscopy. It was shown that an unpaired electron exhibits HFC with the phosphorus nuclei of phosphine ligands coordinated to the metal ions at the dithiolene site of the molecule. PMID:27040038

  18. Synthesis and characterization of mixed ligand complexes of lomefloxacin drug and glycine with transition metals. Antibacterial, antifungal and cytotoxicity studies

    NASA Astrophysics Data System (ADS)

    Mohamed, Gehad G.; Abd El-Halim, Hanan F.; El-Dessouky, Maher M. I.; Mahmoud, Walaa H.

    2011-07-01

    Mixed ligand complexes derived from lomefloxacin (LFX, L 1) as primary ligand and glycine (L 2) as secondary ligand have been prepared and characterized by conventional techniques including elemental analyses, XRD, infrared, electronic spectra, molar conductivity and thermal analyses. The elemental analyses data display the formation of 1:1:1 [M:L 1:L 2] complexes. The diffused reflectance and magnetic moment measurements reveal the presence of the complexes in an octahedral geometry. The infrared spectral data show that the chelation behavior of the ligands toward transition metal ions is through carbonyl O, and carboxylate O of LFX whereas the amino acid coordinate through the carboxylate oxygen and the amino nitrogen. The electronic spectral results display the existence of π-π∗ (phenyl rings), n-π∗ (NH 2 and sbnd C dbnd N) and confirm the mentioned structure. The molar conductivity reveals an electrolytic nature of all chelates. The thermogravimetric analysis data of the complexes displays the existence of hydrated and coordinated water molecules. The effect of LFX, glycine and their complexes on the inhibition of bacteria or fungi growth were evaluated. The prepared complexes were found to exhibit enhanced activity on bacteria or fungi growth compared to LFX and glycine ligands. LFX, [Mn(LFX)(Gly)(H 2O) 2]·Cl, [Co(LFX)(Gly)(H 2O) 2]·Cl and [Zn(LFX)(Gly)(H 2O) 2]·Cl were found to be very active against breast cancer cells with IC50 values 14, 11.2, 13 and 16.8, respectively, while glycine and other complexes had been shown to be inactive at lower concentration than 100 μg/ml.

  19. The Resolution of Chiral, Tetrahedral M4L6 Metal-LigandHosts

    SciTech Connect

    Davis, Anna V.; Fiedler, Dorothea; Ziegler, Marco; Terpin,Andreas; Raymond, Kenneth N.

    2007-08-28

    The supramolecular metal-ligand assemblies of M{sub 4}1{sub 6} stoichiometry are chiral (M = Ga{sup III}, Al{sup III}, In{sup III}, Fe{sup III}, Ti{sup IV}, or Ge{sup IV}, H{sub 4}1 = N,N'-bis(2,3-dihydroxybenzoyl)-1,5-diaminonaphthalene). The resolution process of {Delta}{Delta}{Delta}{Delta}- and {Lambda}{Lambda}{Lambda}{Lambda}-[M{sub 4}1{sub 6}]{sup 12-} by the chiral cation s-nicotinium (S-nic{sup +}) is described for the Ga{sup III}, Al{sup III}, and Fe{sup III} assemblies, and the resolution is shown to be proton dependent. From a methanol solution of M(acac){sub 3}, H{sub 4}1, S-nicI, and KOH, the {Delta}{Delta}{Delta}{Delta}-KH{sub 3}(S-nic){sub 7}[(S-nic) {contained_in}M{sub 4}1{sub 6}] complexes precipitate, and the {Lambda}{Lambda}{Lambda}{Lambda}-K{sub 6}(S-nic){sub 5}[(S-nic) {contained_in} M{sub 4}1{sub 6}] complexes subsequently can be isolated from the supernatant. Ion exchange enables the isolation of the (NEt{sub 4}{sup +}){sub 12}, (NMe{sub 4}{sup +}){sub 12} and K{sub 12}{sup +} salts of the resolved structures, which have been characterized by CD and NMR spectroscopies. Resolution can also be accomplished with one equivalent of NEt{sub 4}{sup +} blocking the cavity interior, demonstrating that external binding sites are responsible for the difference in S-nic{sup +} enantiomer interactions. Circular dichroism data demonstrate that the (NMe{sub 4}{sup +}){sub 12} and (NEt{sub 4}{sup +}){sub 12} salts of the resolved [Ga{sub 4}1{sub 6}]{sup 12-} and [Al{sub 4}1{sub 6}]{sup 12-} structures retain their chirality over extended periods of time (>20 d) at room temperature; heating the (NEt{sub 4}{sup +}){sub 12}[Ga{sub 4}1{sub 6}] assembly to 75 C also had no effect on its CD spectrum. Finally, experiments with the resolved K{sub 12}[Ga{sub 4}1{sub 6}] assemblies point to the role of a guest in stabilizing the resolved framework.

  20. Measurement of complexation properties of metal ions in natural conditions by ultrafiltration: measurement of equilibrium constants for complexation of zinc by synthetic and natural ligands

    SciTech Connect

    Buffle, J.; Staub, C.

    1984-12-01

    A new ultrafiltration method is described to measure complexation properties (stability constants) of trace metal ions with natural aquatic ligands. The determination of stability constants is described theoretically and the best operational conditions are discussed theoretically and experimentally. Theory is tested with Zn, known synthetic ligands, and pedogenic fulvic acids of natural waters. The results obtained by this method compare well with the literature data. In particular, for natural mixture of complexing sites like fulvic acids, this method permits the determination of the detailed equilibrium function to be carried out instead of its average value, over a given range of metal to ligand ratio. The most important advantages of this method are the fact that there is no limitation with regard to the nature of metal ions and little for that of the ligands.

  1. Interfacial metal flux in ligand mixtures. 1. The revisited reaction layer approximation: theory and examples of applications.

    PubMed

    Zhang, Zeshi; Buffle, Jacques

    2009-06-18

    Understanding the physical chemical behaviors of each metal species in a solution containing a mixture of ligands is a prerequisite, e.g., for studying metal bioavailability or making predictions on dynamic risk assessment in ecotoxicology. For many years, the reaction layer concept has been used fruitfully due to its simplicity for understanding and making predictions on diffusion/reaction processes. Until now, it has been applied mainly to solutions containing one ligand. Here, we reconsider the fundamentals of this approach and extend it to multiligand systems. It is shown that each metal complex has its own reaction layer (so-called composite reaction layer), which results from the interplay of this particular complex with all the other complexes. Moreover, it is shown that the overall metal flux can be computed by assuming the existence of one single fictitious equivalent reaction layer thickness for the whole of the complexes. This equivalent reaction layer is a mathematical combination of all the composite reaction layers. Simple analytical equations are obtained, which make it possible to readily interpret the role of the various types of metal species in a mixture. The revisited reaction layer approach, denoted as the reaction layer approximation (RLA), is validated by comparing the total metal flux, the individual fluxes of each metal species, and their concentration profiles computed by the RLA with those obtained by a rigorous mathematical approach. The examples of Pb(II) in a modified Aquil medium and of Cu(II) in solutions of nitrilotriacetic acid and N-(2-carboxyphenyl)glycine are treated in detail. In particular, an original result is obtained with the Cu/NTA/N-(2-carboxyphenyl)glycine system, namely an unexpected flux enhancement is observed, which is specific to solutions with ligand mixtures. The corresponding physicochemical mechanism is not readily understood by the rigorous mathematical (either numerical or analytical) solutions due to their involved combination of parameters. On the other hand, we show that, due to the simplicity of the RLA concept, the RLA facilitates elucidation of the physicochemical mechanism underlying complicated processes. PMID:19459606

  2. Low-Coordinate First Row Early Transition Metal Complexes Stabilized by Modified Terphenyl Ligands

    NASA Astrophysics Data System (ADS)

    Boynton, Jessica Nicole

    The research in this dissertation is focused on the synthesis, structural, and magnetic characterization of two-coordinate open shell (d1-d4) transition metal complexes. Background information on this field of endeavor is provided in Chapter 1. In Chapter 2 I describe the synthesis and characterization of the mononuclear chromium (II) terphenyl substituted primary amido complexes and a Lewis base adduct. These studies suggest that the two-coordinate chromium complexes have significant spin-orbit coupling effects which lead to moments lower than the spin only value of 4.90 muB owing to the fact that lambda (the spin orbit coupling parameter) is positive. The three-coordinated complex 2.3 had a magnetic moment of 3.77 muB. The synthesis and characterization of the first stable two-coordinate vanadium complexes are described in Chapter 3. The values suggest a significant spin orbital angular momentum contribution that leads to a magnetic moment that is lower than their spin only value of 3.87 muB. DFT calculations showed that the major absorptions in their UV-Vis spectra were due to ligand to metal charge transfer transitions. The titanium synthesis and characterization of the bisamido complex along with its three-coordinate titanium(III) precursor are described in Chapter 4. Compound 4.1 was obtained via the stoichiometric reaction of LiN(H)AriPr 6 with the Ti(III) complex TiCl3 *2NMe 3 in trimethylamine. The precursor 4.1 has trigonal pyramidal coordination at the titanium atom, with bonding to two amido nitrogens and a chlorine as well as a secondary interaction to a flanking aryl ring of a terphenyl substituent. Compound 4.2 displays a very distorted four-coordinate metal environment in which the titanium atom is bound to two amido nitrogens and to two carbons from a terphenyl aryl ring. This structure is in sharp contrast to the two-coordinate linear structure that was observed in its first row metal (V-Ni) analogs. The synthesis and characterization of mononuclear chromium(II) terphenyl primary substituted thiolate complexes are described in Chapter 5. Reaction of the terphenyl primary thiolate lithium derivatives LiSAriPr4 and LiSArMe6 with CrCl2THF2 in a 2:1 ratio afforded complexes 5.1 and 5.2, which are the very rare examples of chromium(II) thiolates with quasi-two-coordination at the metal center. Both deviate from linearity and have S-Cr-S angles of 111.02(3)° and 107.86(3) ° with secondary Cr-C(aryl ring) interactions of ca. 2.115 A and 1.971 A respectively. The initial work on titanium and vanadium terphenyl thiolates is described in Appendix I and II. In Chapter 6 I show that the reaction of K2COT (COT= 1,3,5,7-cyclooctatetraene, C8H8) with an aryl chromium(II) halide gave (CrAriPr 4)2(mu2-n3:n4-COT) (6.1) in which a non-planar COT ring is complexed between two CrAriPr4 moieties -- a configuration previously unknown for chromium complexes of COT. OneCr2+ ion is bonded primarily to three COT carbons (Cr--C= 2.22-2.30 A ) as well as an ipso carbon (Cr-C= ca. 2.47 A) from a flanking aryl ring of its terphenyl substituent. The otherCr2+ ion bonds to an ipso carbon (Cr-C= ca. 2.53 A) from its terphenyl substituent as well as four COT carbons (Cr--C= 2.24-2.32 A). The COT carbon-carbon distances display an alternating pattern, consistent with the non-planarity and non-aromatic character of the ring. The magnetic properties of 6.1 indicate that theCr2+ ions have a high-spin d4 configuration with S = 2. The temperature dependence of the magnetism indicates that their behavior is due to zero-field splitting of the S = 2 state. Attempts to prepare 6.1 by the direct reaction of quintuple-bonded (CrAriPr4)2 with COT were unsuccessful. (Abstract shortened by UMI.)

  3. (S)-5-(p-Nitrobenzyl)-PCTA, a Promising Bifunctional Ligand with Advantageous Metal Ion Complexation Kinetics

    PubMed Central

    Tircsó, Gyula; Benyó, Enikő Tircsóné; Suh, Eul Hyun; Jurek, Paul; Kiefer, Garry E.; Sherry, A. Dean; Kovács, Zoltán

    2009-01-01

    A bifunctional version of PCTA (3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9,-triacetic acid) that exhibits fast complexation kinetics with the trivalent lanthanide(III) ions was synthesized in reasonable yields starting from N, N′, N″-tristosyl-(S)-2-(p-nitrobenzyl)-diethylenetriamine. pH-potentiometric studies showed that the basicities of p-nitrobenzyl-PCTA and the parent ligand PCTA were similar. The stability of M(NO2-Bn-PCTA) (M = Mg2+, Ca2+, Cu2+, Zn2+) complexes was similar to that of the corresponding PCTA complexes while the stability of Ln3+ complexes of the bifunctional ligand is somewhat lower than that of PCTA chelates. The rate of complex formation of Ln(NO2-Bn-PCTA) complexes was found to be quite similar to that of PCTA, a ligand known to exhibit the fastest formation rates among all lanthanide macrocyclic ligand complexes studied to date. The acid catalyzed decomplexation kinetic studies of the selected Ln(NO2-Bn-PCTA) complexes showed that the kinetic inertness of the complexes was comparable to that of Ln(DOTA) chelates making the bifunctional ligand NO2-Bn-PCTA suitable for labeling biological vectors with radioisotopes for nuclear medicine applications. PMID:19220012

  4. Tetrathiafulvalene-based azine ligands for anion and metal cation coordination

    PubMed Central

    Ayadi, Awatef; El Alamy, Aziz; Alévêque, Olivier; Allain, Magali; Zouari, Nabil; Bouachrine, Mohammed

    2015-01-01

    Summary The synthesis and full characterization of two tetrathiafulvalene-appended azine ligands, namely 2-([2,2’-bi(1,3-dithiolylidene)]-4-yl)-6-((2,4-dinitrophenyl)hydrazono)methyl)pyridine (L1) and 5-([2,2’-bi(1,3-dithiolylidene)]-4-yl)-2-((2,4-dinitrophenyl)hydrazono)methyl)pyridine (L2) are described. The crystal structure of ligand L1 indicates that the ligand is completely planar with the presence of a strong intramolecular N3–H3···O1 hydrogen bonding. Titration experiments with inorganic anions showed that both ligands are suitable candidates for the sensing of fluoride anions. Ligand L2 was reacted with a Re(I) cation to yield the corresponding rhenium tricarbonyl complex 3. In the crystal structure of the newly prepared electroactive rhenium complex the TTF is neutral and the rhenium cation is hexacoordinated. The electrochemical behavior of the three compounds indicates that they are promising for the construction of crystalline radical cation salts. PMID:26425193

  5. Spectroscopic and thermal properties of short wavelength metal (II) complexes containing α-isoxazolylazo-β-diketones as co-ligands

    NASA Astrophysics Data System (ADS)

    Huang, Fuxin; Wu, Yiqun; Gu, Donghong; Gan, Fuxi

    2005-10-01

    Two new azo dyes of α-isoxazolylazo-β-diketones and their Ni(II) and Cu(II) complexes with blue-violet light wavelength were synthesized using a coupling component, different diazo components and metal (II) ions (Ni 2+ and Cu 2+). Based on the elemental analysis, MS spectra and FT-IR spectral analyses, azo dyes were unequivocally shown to exist as hydrazoketo and azoenol forms which were respectively obtained from the solution forms and from the solid forms. The action of sodium methoxide (NaOMe) on azo dyes in solutions converts hydrazoketo form into azoenol form, so azo dyes are coordinated with metal (II) ions as co-ligands in the azoenol forms. The solubility of all the compounds in common organic solvents such as 2,2,3,3-tetrafluoro-1-propanol (TFP) or chloroform (CHCl 3) and absorption properties of spin-coating thin films were measured. The difference of absorption maxima from the complexes to their ligands was discussed. In addition, the TG analysis of the complexes was also determined, and their thermal stability was evaluated. It is found that these new metal (II) complexes had potential application for high-density digital versatile disc-recordable (HD-DVD-R) system due to their good solubility in organic solvents, reasonable and controllable absorption spectra in blue-violet light region and high thermal stability.

  6. Chelating ligands for nanocrystals' surface functionalization.

    PubMed

    Querner, Claudia; Reiss, Peter; Bleuse, Joël; Pron, Adam

    2004-09-22

    A new family of ligands for the surface functionalization of CdSe nanocrystals is proposed, namely alkyl or aryl derivatives of carbodithioic acids (R-C(S)SH). The main advantages of these new ligands are as follows: they nearly quantitatively exchange the initial surface ligands (TOPO) in very mild conditions; they significantly improve the resistance of nanocrystals against photooxidation because of their ability of strong chelate-type binding to metal atoms; their relatively simple preparation via Grignard intermediates facilitates the development of new bifunctional ligands containing, in addition to the anchoring carbodithioate group, a second function, which enables the grafting of molecules or macromolecules of interest on the nanocrystal surface. To give an example of this approach, we report, for the first time, the grafting of an electroactive oligomer from the polyaniline family-aniline tetramer-on CdSe nanocrystals after their functionalization with 4-formyldithiobenzoic acid. The grafting proceeds via a condensation reaction between the aldehyde group of the ligand and the terminal primary amine group of the tetramer. The resulting organic/inorganic hybrid exhibits complete extinction of the fluorescence of its constituents, indicating efficient charge or energy transfer between the organic and the inorganic semiconductors. PMID:15366904

  7. A structure-based analysis of the vibrational spectra of nitrosyl ligands in transition-metal coordination complexes and clusters.

    PubMed

    De La Cruz, Carlos; Sheppard, Norman

    2011-01-01

    The vibrational spectra of nitrogen monoxide or nitric oxide (NO) bonded to one or to several transition-metal (M) atom(s) in coordination and cluster compounds are analyzed in relation to the various types of such structures identified by diffraction methods. These structures are classified in: (a) terminal (linear and bent) nitrosyls, [M(σ-NO)] or [M(NO)]; (b) twofold nitrosyl bridges, [M2(μ2-NO)]; (c) threefold nitrosyl bridges, [M3(μ3-NO)]; (d) σ/π-dihaptonitrosyls or "side-on" nitrosyls; and (e) isonitrosyls (oxygen-bonded nitrosyls). Typical ranges for the values of internuclear N-O and M-N bond-distances and M-N-O bond-angles for linear nitrosyls are: 1.14-1.20 Å/1.60-1.90 Å/180-160° and for bent nitrosyls are 1.16-1.22 Å/1.80-2.00 Å/140-110°. The [M2(μ2-NO)] bridges have been divided into those that contain one or several metal-metal bonds and those without a formal metal/metal bond (M⋯M). Typical ranges for the M-M, N-O, M-N bond distances and M-N-M bond angles for the normal twofold NO bridges are: 2.30-3.00 Å/1.18-1.22 Å/1.80-2.00 Å/90-70°, whereas for the analogous ranges of the long twofold NO bridges these are 3.10-3.40 Å/1.20-1.24 Å/1.90-2.10 Å/130-110°. In both situations the N-O vector is approximately at right angle to the M-M (or M⋯M) vector within the experimental error; i.e. the NO group is symmetrical bonded to the two metal atoms. In contrast the threefold NO bridges can be symmetrically or unsymmetrically bonded to an M3-plane of a cluster compound. Characteristic values for the N-O and M-N bond-distances of these NO bridges are: 1.24-1.28 Å/1.80-1.90 Å, respectively. As few dihaptonitrosyl and isonitrosyl complexes are known, the structural features of these are discussed on an individual basis. The very extensive vibrational spectroscopy literature considered gives emphasis to the data from linearly bonded NO ligands in stable closed-shell metal complexes; i.e. those which are consistent with the "effective atomic number (EAN)" or "18-electron" rule. In the paucity of enough vibrational spectroscopic data from complexes with only nitrosyl ligands, it turned out to be very advantageous to use wavenumbers from the spectra of uncharged and saturated nitrosyl/carbonyl metal complexes as references, because the presence of a carbonyl ligand was found to be neutral in its effect on the ν(NO)-values. The wide wavenumber range found for the ν(NO) values of linear MNO complexes are then presented in terms of the estimated effects of net ionic charges, or of electron-withdrawing or electron-donating ligands bonded to the same metal atom. Using this approach we have found that: (a) the effect for a unit positive charge is [plus 100 cm(-1)] whereas for a unit negative charge it is [minus 145 cm(-1)]. (b) For electron-withdrawing co-ligands the estimated effects are: terminal CN [plus 50 cm(-1)]; terminal halogens [plus 30 cm(-1)]; bridging or quasi-bridging halogens [plus 15 cm(-1)]. (c) For electro donating co-ligands they are: PF3 [plus 10 cm(-1)]; P(OPh)3 [-30 cm(-1)]; P(OR)3 (R=alkyl group) [-40 cm(-1)]; PPh3 [-55 cm(-1)]; PR3 (R=alkyl group) [-70 cm(-1)]; and η5-C5H5 [-60 cm(-1)]; η5-C5H4Me [-70 cm(-1)]; η5-C5Me5 [-80 cm(-1)]. These values were mostly derived from the spectra of nitrosyl complexes that have been corrected for the presence of only a single electronically-active co-ligand. After making allowance for ionic charges or strongly-perturbing ligands on the same metal atom, the adjusted 'neutral-co-ligand' ν(NO)*-values (in cm(-1)) are for linear nitrosyl complexes with transition metals of Period 4 of the Periodic Table, i.e. those with atomic orbitals (…4s3d4p): [ca. 1750, Cr(NO)]; [1775,Mn(NO)]; [1796,Fe(NO)]; [1817,Co(NO)]; [ca. 1840, Ni(NO)]. Period 5 (…5s4d5p): [1730 Mo(NO)]; [-, Tc(NO)]; [1745,Ru(NO)]; [1790,Rh(NO)]; [ca. 1845, Pd(NO)]. Period 6 (…6s4f5d6p), [1720,W(NO)]; [1730,Re(NO)]; [1738,Os(NO)]; [1760,Ir(NO)]; [-, Pt] respectively. Environmental differences to these values, e.g. data taken in polar solutions or in the crystalline state, can cause ν(NO)* variations (mostly reductions) of up to ca. 30 cm(-1). Three spectroscopic criteria are used to distinguish between linear and bent NO groups. These are: (i) the values of ν(14NO) themselves, and (ii) the isotopic band shift--(IBS)--parameter which is defined as [ν(14NO)-ν(15NO)], and, (iii) the isotopic band ratio--(IBR)--given by [ν(15NO/ν14NO)]. The former is illustrated with the ν(14NO)-data from trigonal bipyramidal (TBP) and tetragonal pyramidal (TP) structures of [M(NO(L)4] complexes (where M=Fe, Co, Ru, Rh, Os, Ir and L=ligand). These values indicate that linear (180-170°) and strongly bent (130-120°) NO groups in these compounds absorb over the 1862-1690 cm(-1) and 1720-1525 cm(-1)-regions, respectively. As was explicitly demonstrated for the linear nitrosyls, these extensive regions reflect the presence in different complexes of a very wide range of co-ligands or ionic charges associated with the metal atom of the nitrosyl group. A plot of the IBS parameter against M-N-O bond-angle for compounds with general formulae [M(NO)(L)y] (y=4, 5, 6) reveals that the IBS-values are clustered between 45 and 30 cm(-1) or between 37 and 25 cm(-1) for linear or bent NO groups, respectively. A plot of IBR shows a less well defined pattern. Overall it is suggested that bent nitrosyls absorb ca. 60-100 cm(-1) below, and have smaller co-ligand band-shifts, than their linear counterparts. Spectroscopic ν(NO) data of the bridging or other types of NO ligands are comparatively few and therefore it has not been possible to give other than general ranges for 'neutral co-ligand' values. Moreover the bridging species data often depend on corrections for the effects of electronically-active co-ligands such as cyclopentadienyl-like groups. The derived neutral co-ligand estimates, ν(NO)*, are: (a) twofold bridged nitrosyls with a metal-metal bond order of one, or greater than one, absorb at ca. 1610-1490 cm(-1); (b) twofold bridged nitrosyl ligands with a longer non-bonding M⋯M distance, ca. 1520-1490 cm(-1); (c) threefold bridged nitrosyls, ca. 1470-1410 cm(-1); (d) σ/π dihaptonitrosyl, [M(η2-NO)], where M=Cr, Mn and Ni; ca. 1490-1440 cm(-1). Isonitrosyls, from few examples, appear to absorb below ca. 1100 cm(-1). To be published DFT calculations of the infrared and Raman spectra of complexes with formulae [M(NO)4-n(CO)n] (M=Cr, Mn, Fe, Co, Ni, and n=0, 1, 2, 3, 4, respectively) are used as models for the assignments of the ν(MN) and δ(MNO) bands from more complex metal nitrosyls. PMID:21123107

  8. A structure-based analysis of the vibrational spectra of nitrosyl ligands in transition-metal coordination complexes and clusters

    NASA Astrophysics Data System (ADS)

    De La Cruz, Carlos; Sheppard, Norman

    2011-01-01

    The vibrational spectra of nitrogen monoxide or nitric oxide (NO) bonded to one or to several transition-metal (M) atom(s) in coordination and cluster compounds are analyzed in relation to the various types of such structures identified by diffraction methods. These structures are classified in: (a) terminal (linear and bent) nitrosyls, [M(σ-NO)] or [M(NO)]; (b) twofold nitrosyl bridges, [M 2(μ 2-NO)]; (c) threefold nitrosyl bridges, [M 3(μ 3-NO)]; (d) σ/π-dihaptonitrosyls or " side-on" nitrosyls; and (e) isonitrosyls (oxygen-bonded nitrosyls). Typical ranges for the values of internuclear N-O and M-N bond-distances and M-N-O bond-angles for linear nitrosyls are: 1.14-1.20 Å/1.60-1.90 Å/180-160° and for bent nitrosyls are 1.16-1.22 Å/1.80-2.00 Å/140-110°. The [M 2(μ 2-NO)] bridges have been divided into those that contain one or several metal-metal bonds and those without a formal metal/metal bond (M⋯M). Typical ranges for the M-M, N-O, M-N bond distances and M-N-M bond angles for the normal twofold NO bridges are: 2.30-3.00 Å/1.18-1.22 Å/1.80-2.00 Å/90-70°, whereas for the analogous ranges of the long twofold NO bridges these are 3.10-3.40 Å/1.20-1.24 Å/1.90-2.10 Å/130-110°. In both situations the N-O vector is approximately at right angle to the M-M (or M⋯M) vector within the experimental error; i.e. the NO group is symmetrical bonded to the two metal atoms. In contrast the threefold NO bridges can be symmetrically or unsymmetrically bonded to an M 3-plane of a cluster compound. Characteristic values for the N-O and M-N bond-distances of these NO bridges are: 1.24-1.28 Å/1.80-1.90 Å, respectively. As few dihaptonitrosyl and isonitrosyl complexes are known, the structural features of these are discussed on an individual basis. The very extensive vibrational spectroscopy literature considered gives emphasis to the data from linearly bonded NO ligands in stable closed-shell metal complexes; i.e. those which are consistent with the " effective atomic number (EAN)" or "18-electron" rule. In the paucity of enough vibrational spectroscopic data from complexes with only nitrosyl ligands, it turned out to be very advantageous to use wavenumbers from the spectra of uncharged and saturated nitrosyl/carbonyl metal complexes as references, because the presence of a carbonyl ligand was found to be neutral in its effect on the ν(NO)-values. The wide wavenumber range found for the ν(NO) values of linear MNO complexes are then presented in terms of the estimated effects of net ionic charges, or of electron-withdrawing or electron-donating ligands bonded to the same metal atom. Using this approach we have found that: (a) the effect for a unit positive charge is [plus 100 cm -1] whereas for a unit negative charge it is [minus 145 cm -1]. (b) For electron-withdrawing co-ligands the estimated effects are: terminal CN [plus 50 cm -1]; terminal halogens [plus 30 cm -1]; bridging or quasi-bridging halogens [plus 15 cm -1]. (c) For electro donating co-ligands they are: PF 3 [plus 10 cm -1]; P(OPh) 3 [-30 cm -1]; P(OR) 3 (R = alkyl group) [-40 cm -1]; PPh 3 [-55 cm -1]; PR 3 (R = alkyl group) [-70 cm -1]; and η 5-C 5H 5 [-60 cm -1]; η 5-C 5H 4Me [-70 cm -1]; η 5-C 5Me 5 [-80 cm -1]. These values were mostly derived from the spectra of nitrosyl complexes that have been corrected for the presence of only a single electronically-active co-ligand. After making allowance for ionic charges or strongly-perturbing ligands on the same metal atom, the adjusted 'neutral-co-ligand' ν(NO)*-values (in cm -1) are for linear nitrosyl complexes with transition metals of Period 4 of the Periodic Table, i.e. those with atomic orbitals (…4s3d4p): [ca. 1750, Cr(NO)]; [1775,Mn(NO)]; [1796,Fe(NO)]; [1817,Co(NO)]; [ca. 1840, Ni(NO)]. Period 5 (…5s4d5p): [1730 Mo(NO)]; [—, Tc(NO)]; [1745,Ru(NO)]; [1790,Rh(NO)]; [ca. 1845, Pd(NO)]. Period 6 (…6s4f5d6p), [1720,W(NO)]; [1730,Re(NO)]; [1738,Os(NO)]; [1760,Ir(NO)]; [—, Pt] respectively. Environmental differences to these values, e.g. data taken in polar solutions or in the crystalline state, can cause ν(NO)* variations (mostly reductions) of up to ca. 30 cm -1. Three spectroscopic criteria are used to distinguish between linear and bent NO groups. These are: (i) the values of ν( 14NO) themselves, and (ii) the isotopic band shift - (IBS) - parameter which is defined as [ν( 14NO)-ν( 15NO)], and, (iii) the isotopic band ratio - (IBR) - given by [ν( 15NO/ν 14NO)]. The former is illustrated with the ν( 14NO)-data from trigonal bipyramidal (TBP) and tetragonal pyramidal (TP) structures of [M(NO(L) 4] complexes (where M = Fe, Co, Ru, Rh, Os, Ir and L = ligand). These values indicate that linear (180-170°) and strongly bent (130-120°) NO groups in these compounds absorb over the 1862-1690 cm -1 and 1720-1525 cm -1-regions, respectively. As was explicitly demonstrated for the linear nitrosyls, these extensive regions reflect the presence in different complexes of a very wide range of co-ligands or ionic charges associated with the metal atom of the nitrosyl group. A plot of the IBS parameter against M-N-O bond-angle for compounds with general formulae [M(NO)(L) y] ( y = 4, 5, 6) reveals that the IBS-values are clustered between 45 and 30 cm -1 or between 37 and 25 cm -1 for linear or bent NO groups, respectively. A plot of IBR shows a less well defined pattern. Overall it is suggested that bent nitrosyls absorb ca. 60-100 cm -1 below, and have smaller co-ligand band-shifts, than their linear counterparts. Spectroscopic ν(NO) data of the bridging or other types of NO ligands are comparatively few and therefore it has not been possible to give other than general ranges for 'neutral co-ligand' values. Moreover the bridging species data often depend on corrections for the effects of electronically-active co-ligands such as cyclopentadienyl-like groups. The derived neutral co-ligand estimates, ν(NO)*, are: (a) twofold bridged nitrosyls with a metal-metal bond order of one, or greater than one, absorb at ca. 1610-1490 cm -1; (b) twofold bridged nitrosyl ligands with a longer non-bonding M⋯M distance, ca. 1520-1490 cm -1; (c) threefold bridged nitrosyls, ca. 1470-1410 cm -1; (d) σ/π dihaptonitrosyl, [M(η 2-NO)], where M = Cr, Mn and Ni; ca. 1490-1440 cm -1. Isonitrosyls, from few examples, appear to absorb below ca. 1100 cm -1. To be published DFT calculations of the infrared and Raman spectra of complexes with formulae [M(NO) 4- n(CO) n] (M = Cr, Mn, Fe, Co, Ni, and n = 0, 1, 2, 3, 4, respectively) are used as models for the assignments of the ν(MN) and δ(MNO) bands from more complex metal nitrosyls.

  9. Complications of bioabsorbable suture anchors in the shoulder.

    PubMed

    Dhawan, Aman; Ghodadra, Neil; Karas, Vasili; Salata, Michael J; Cole, Brian J

    2012-06-01

    The development of the suture anchor has played a pivotal role in the transition from open to arthroscopic techniques of the shoulder. Various suture anchors have been manufactured that help facilitate the ability to create a soft tissue to bone repair. Because of reported complications of loosening, migration, and chondral injury with metallic anchors, bioabsorbable anchors have become increasingly used among orthopaedic surgeons. In this review, the authors sought to evaluate complications associated with bioabsorbable anchors in or about the shoulder and understand these in the context of the total number of bioabsorbable anchors placed. In 2008, 10 bioabsorbable anchor-related complications were reported to the US Food and Drug Administration. The reported literature complications of bioabsorbable anchors implanted about the shoulder include glenoid osteolysis, synovitis, and chondrolysis. These potential complications should be kept in mind when forming a differential diagnosis in a patient in whom a bioabsorbable anchor has been previously used. These literature reports, which amount to but a fraction of the total bioabsorbable anchors implanted in the shoulder on a yearly basis, underscore the relative safety and successful clinical results with use of bioabsorbable suture anchors. Product development continues with newer composites such as PEEK (polyetheretherketone) and calcium ceramics (tricalcium phosphate) in an effort to hypothetically create a mechanically stable construct with and improve biocompatibility of the implant. Bioabsorbable anchors remain a safe, reproducible, and consistent implant to secure soft tissue to bone in and about the shoulder. Meticulous insertion technique must be followed in using bioabsorbable anchors and may obviate many of the reported complications found in the literature. The purpose of this review is to provide an overview of the existing literature as it relates to the rare complications seen with use of bioabsorbable suture anchors in the shoulder. PMID:21856927

  10. Synthesis, spectroscopic studies and inhibitory activity against bactria and fungi of acyclic and macrocyclic transition metal complexes containing a triamine coumarine Schiff base ligand

    NASA Astrophysics Data System (ADS)

    Abou-Hussein, A. A.; Linert, Wolfgang

    2015-04-01

    Two series of new mono and binuclear complexes with a Schiff base ligand derived from the condensation of 3-acetylcoumarine and diethylenetriamine, in the molar ratio 2:1 have been prepared. The ligand was characterized by elemental analysis, IR, UV-visible, 1H-NMR and mass spectra. The reaction of the Schiff base ligand with cobalt(II), nickel(II), copper(II), zinc(II) and oxovanadium(IV) lead to mono or binuclear species of cyclic or macrocyclic complexes, depending on the mole ratio of metal to ligand and as well as on the method of preparation. The Schiff base ligand behaves as a cyclic bidentate, tetradendate or pentaentadentae ligand. The formation of macrocyclic complexes depends significantly on the dimension of the internal cavity, the rigidity of the macrocycles, the nature of its donor atoms and on the complexing properties of the anion involved in the coordination. Electronic spectra and magnetic moments of the complexes indicate that the geometries of the metal centers are either square pyramidal or octahedral for acyclic or macro-cyclic complexes. The structures are consistent with the IR, UV-visible, ESR, 1H-NMR, mass spectra as well as conductivity and magnetic moment measurements. The Schiff base ligand and its metal complexes were tested against two pathogenic bacteria as Gram-positive and Gram-negative bacteria as well as one kind of fungi. Most of the complexes exhibit mild antibacterial and antifungal activities against these organisms.

  11. Mono, bi- and trinuclear metal complexes derived from new benzene-1,4-bis(3-pyridin-2-ylurea) ligand. Spectral, magnetic, thermal and 3D molecular modeling studies

    NASA Astrophysics Data System (ADS)

    El-ghamry, Mosad A.; Saleh, Akila A.; Khalil, Saied M. E.; Mohammed, Amira A.

    2013-06-01

    New bis (pyridylurea) ligand, H2L, was synthesized by the reaction of ethylpyridine-2-carbamate (EPC) and p-phenylenediamine. The ligand was characterized by elemental analysis, IR, 1H NMR, electronic and mass spectra. Reaction of the prepared ligand with Co2+, Ni2+, Cu2+, Fe3+, VO2+ and UO22+ ions afforded mono, bi- and trinuclear metal complexes. Also, new mixed ligand complexes of the ligand H2L and 8-hydroxyquinoline (8-HQ) with Co2+, Ni2+, Cu2+ and Fe3+ ions were synthesized. The ligand behaves as bi- and tetradentate toward the transition metal ions, coordination via the pyridine sbnd N, the carbonyl sbnd O and/or the amidic sbnd N atoms in a non, mono- and bis-deprotonated form. The complexes were characterized by elemental and thermal analyses, IR, electronic and mass spectra as well as conductance and magnetic susceptibility measurements. The results showed that the metal complexes exhibited different geometrical arrangements such as square planar, tetrahedral, octahedral and square pyramidal arrangements. The Coats-Redfern equation was used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition steps of some complexes. 3D molecular modeling of the ligand, H2L and a representative complex were studied.

  12. Synthesis, spectroscopic studies and inhibitory activity against bacteria and fungi of acyclic and macrocyclic transition metal complexes containing a triamine coumarine Schiff base ligand.

    PubMed

    Abou-Hussein, A A; Linert, Wolfgang

    2015-04-15

    Two series of new mono and binuclear complexes with a Schiff base ligand derived from the condensation of 3-acetylcoumarine and diethylenetriamine, in the molar ratio 2:1 have been prepared. The ligand was characterized by elemental analysis, IR, UV-visible, (1)H-NMR and mass spectra. The reaction of the Schiff base ligand with cobalt(II), nickel(II), copper(II), zinc(II) and oxovanadium(IV) lead to mono or binuclear species of cyclic or macrocyclic complexes, depending on the mole ratio of metal to ligand and as well as on the method of preparation. The Schiff base ligand behaves as a cyclic bidentate, tetradendate or pentaentadentae ligand. The formation of macrocyclic complexes depends significantly on the dimension of the internal cavity, the rigidity of the macrocycles, the nature of its donor atoms and on the complexing properties of the anion involved in the coordination. Electronic spectra and magnetic moments of the complexes indicate that the geometries of the metal centers are either square pyramidal or octahedral for acyclic or macro-cyclic complexes. The structures are consistent with the IR, UV-visible, ESR, (1)H-NMR, mass spectra as well as conductivity and magnetic moment measurements. The Schiff base ligand and its metal complexes were tested against two pathogenic bacteria as Gram-positive and Gram-negative bacteria as well as one kind of fungi. Most of the complexes exhibit mild antibacterial and antifungal activities against these organisms. PMID:25681806

  13. Excited state properties of a copper(I) benzene complex. Emission from a metal-to-ligand charge transfer state

    NASA Astrophysics Data System (ADS)

    Kunkely, Horst; Vogler, Arnd

    2003-01-01

    The solid compound Cu 2(CF 3SO 3) 2(C 6H 6) shows an intense emission at λ max=518 nm ( φ˜10 -2, τ=0.5 μs) which is suggested to originate from a Cu I to benzene metal-to-ligand charge transfer (MLCT) triplet. The spin-allowed MLCT transition gives rise to an excitation maximum at λ=318 nm which appears also as long-wavelength band at λ max=315 nm in the absorption spectrum of the complex in solution.

  14. Quest for highly porous metal-metalloporphyrin framework based upon a custom-designed octatopic porphyrin ligand

    SciTech Connect

    Wang, Xi-Sen; Chrzanowski, Matthew; Kim, Chungsik; Gao, Wen-Yang; Wojtas, Lukasz; Chen, Yu-Sheng; Zhang, X Peter; Ma, Shengqian

    2012-12-13

    A porous metal-metalloporphyrin framework, MMPF-2, has been constructed from a custom-designed octatopic porphyrin ligand, tetrakis(3,5-dicarboxyphenyl)porphine, that links a distorted cobalt trigonal prism secondary building unit. MMPF-2 possesses permanent microporosity with the highest surface area of 2037 mg2 g-1 among reported porphyrin-based MOFs, and demonstrates a high uptake capcity of 170 cm3 g-1 CO2 at 273 K and 1 bar.

  15. A comparative study of cytotoxicity and interaction with DNA/protein of five transition metal complexes with Schiff base ligands.

    PubMed

    Niu, Meiju; Hong, Min; Chang, Guoliang; Li, Xiao; Li, Zhen

    2015-07-01

    Five transition metal complexes NiL(1)2 (1), CuL(1)2 (2), ZnL(1)2 (3), [MnL(1)2(N3)]n·nCH2Cl2 (4), CuL(2)2 (5) {HL(1)=3-{[2-(2-hydroxy-ethoxy)-ethylimino]-methyl}-naphthalen-2-ol, HL(2)=2-{[2-(2-hydroxy-ethoxy)-ethylimino]-methyl}-phenol} have been synthesized and fully characterized. In all of the complexes, the ligands coordinated to the metal ion in a negative fashion via O and N donor atoms. The X-ray structures of nickel complex 1 and copper complexes 2 and 5 are four-coordinated monomers and show slightly distorted square-planar geometry in the vicinity of the central metal atom. Zinc complex 3 exhibits a four-coordinated tetrahedral structure. Differently, manganese complex 4 reveals a six-coordinated octahedral structure, one-dimensional chain is linked by azide in the end-to-end mode. In vitro cytotoxicity of these complexes to various tumor cell lines was assayed by the MTT method. The results showed that most of these metal-Schiff base complexes exhibited enhanced cytotoxicity than Schiff base ligands, which clearly implied a positive synergistic effect. Moreover, these complexes appeared to be selectively active against certain cell lines. The interactions of these metal complexes with CT-DNA were investigated by UV-vis, fluorescence and CD spectroscopy, the results indicated that these complexes are metallointercalators and can interact with CT-DNA. The study of interaction between complexes and BSA indicated that all of the complexes could quench the intrinsic fluorescence of BSA in a static quenching process. PMID:25974907

  16. Calix[6]azacryptand Ligand with a Sterically Protected Tren-Based Coordination Site for Metal Ions.

    PubMed

    Zahim, Sara; Wickramasinghe, Lasantha A; Evano, Gwilherm; Jabin, Ivan; Schrock, Richard R; Müller, Peter

    2016-04-01

    A new calix[6]azacryptand ligand has been prepared in six steps starting from 1,3,5-trismethoxycalix[6]arene. An X-ray study shows that this ligand has a sterically protected tren-based binding site at the bottom of a polyaromatic bowl and ether sites around its rim. It binds Zn(2+) to give a complex in which zinc is in a trigonal bipyramidal geometry with a water bound in one apical position and two additional hydrogen-bonded waters that fill the calixarene cavity. PMID:26999005

  17. Transition metal complexes bearing NHC ligands substituted with secondary polyfluoroalkyl groups.

    PubMed

    Kola?kov, V; im?nek, O; Ryb?kov, M; Cva?ka, J; B?ezinov, A; Kv?ala, J

    2015-12-01

    Using three different approaches, racemic 1-(perfluoroalkyl)ethylamines were synthesized from perfluoroalkyl iodides or perfluoroalkanoic acids, and further transformed to the corresponding N,N'-disubstituted ethane-1,2-diimines and ethane-1,2-diamines as mixtures of diastereoisomers. Their cyclization afforded imidazolium or dihydroimidazolium salts, which led to silver or palladium complexes bearing NHC ligands substituted with secondary polyfluoroalkyl groups. The palladium complexes bearing a throwaway 3-chloropyridine ligand proved to be moderately active in the model Suzuki-Miyaura coupling. PMID:26374142

  18. The synthesis, characterization, antimicrobial and antimutagenic activities of hydroxyphenylimino ligands and their metal complexes of usnic acid isolated from Usnea longissima.

    PubMed

    Koçer, Sibel; Uruş, Serhan; Çakır, Ahmet; Güllüce, Medine; Dığrak, Metin; Alan, Yusuf; Aslan, Ali; Tümer, Mehmet; Karadayı, Mehmet; Kazaz, Cavit; Dal, Hakan

    2014-04-28

    Novel multifunctional hydroxyphenylimino ligands (L1, L2 and L3) were synthesized by the condensation of 2-aminophenol, 3-aminophenol and 4-aminophenol with usnic acid, a lichen metabolite. The synthesized ligands and their Cu(II), Co(II), Ni(II) and Mn(II) complexes were characterized using FT-IR, UV-Vis, (1)H-NMR, (13)C-NMR, 1D- and 2D NMR (DEPT, COSY, HMQC and HMBC), LC-MS and TGA. In addition, the metal complexes of the novel ligands were prepared with high yields using Cu(II), Co(II), Ni(II) and Mn(II) salts and were characterized using the FT-MIR/FAR, UV-Vis, elemental analysis, ICP-OES and TG/DTA techniques. The ligands and their complexes were tested against ten important pathogen microorganisms using the disc diffusion method and the metal complexes of the ligands were more active against all of the microorganisms tested with a broad spectrum than the ligands exhibiting 11–32 mm inhibition zones. On the other hand, a broad spectrum of the strongest antimicrobial activity was determined for the Mn(II) and Cu(II) complexes of the hydroxyphenylimino ligand with usnic acid (L3). In addition, the antimutagenic activities of all of the ligands and their metal complexes were determined using the Ames-Salmonella and E. coli WP2 microbial assay systems and they showed varied and strong antimutagenic effects. In general, it has been found that the Co and Mn complexes of the ligands possess potent antimutagenic activity. In view of these results, it can be concluded that some metal complexes can be used as antimicrobial and anticancer agents. PMID:24589530

  19. Metal complexes of the nanosized ligand N-benzoyl-N‧-(p-amino phenyl) thiourea: Synthesis, characterization, antimicrobial activity and the metal uptake capacity of its ligating resin

    NASA Astrophysics Data System (ADS)

    Elhusseiny, Amel F.; Eldissouky, Ali; Al-Hamza, Ahmed M.; Hassan, Hammed H. A. M.

    2015-11-01

    The new nanosized N-benzoyl-N‧-(p-amino phenyl) thiourea ligand H2L was synthesized by nanoprecipitation method. The [Cu (H2L)2 Cl]·2H2O, [Zn (H2L)2(OAc)2], [Cd (H2L)2Cl2] and [Hg (H2L)2Cl2] complexes were synthesized and characterized by various physicochemical methods. Results revealed that the ligand act as hypodentate and bonded to the metal ion via the sulfur atom forming mononuclear non-electrolyte diamagnetic complex. Magnetic moment results indicated a reduction of Cu (II) to Cu (I) during the coordination process. Thermal studies demonstrated variable stabilities of the complexes and [Zn (H2L)2(OAc)2] exhibited the highest thermal stability while [Hg (H2L)2Cl2] was volatile. The prepared compounds were screened against different pathogenic microorganisms. The ligand performed high antibacterial activity against certain bacterial strain compared to its complexes, and the standard bacteriocide in use. The ligand was successfully immobilized on modified Amberlite XAD-16 forming the hypodentate ligating resin PS-SO2-H2L. The new resin was characterized and the extent of metal adsorption reached maximum at pH 6.0 for Cu (II), Cd (II) and Ag (I), with an adsorption amount of 4.3, 4.0 and 3.7 mmol g-1 respectively. The nanosized H2L represents a new category of promising adsorbent that would have a practical impact on biological and water treatment applications.

  20. Anchor Trial Launch

    Cancer.gov

    NCI has launched a multicenter phase III clinical trial called the ANCHOR Study -- Anal Cancer HSIL (High-grade Squamous Intraepithelial Lesion) Outcomes Research Study -- to determine if treatment of HSIL in HIV-infected individuals can prevent anal canc

  1. Enthused research on DNA-binding and DNA-cleavage aptitude of mixed ligand metal complexes

    NASA Astrophysics Data System (ADS)

    Mahalakshmi, Rajkumar; Raman, Natarajan

    2013-08-01

    Five new Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) mixed ligand complexes have been synthesized using a Schiff base precursor (obtained by the condensation of N-(4-aminophenyl)acetamide and 4-chlorobenzaldehyde) as main ligand and 1,10-phenanthroline as co-ligand. They have been characterized by microanalytical data, IR, UV-Vis, magnetic moment values, conductivity and electrochemical measurements. The spectral data reveal that all the complexes exhibit octahedral geometry. The high electrical conductance of the complexes supports their electrolytic nature. The monomeric nature of the complexes has been assessed from their magnetic susceptibility values. These complexes are better antimicrobial active agents than the free ligands. DNA (CT) binding properties of these complexes have been explored by UV-Vis., viscosity measurements, cyclic voltammetry, and differential pulse voltammetry measurements. The oxidative cleavage activity of the complexes has been studied using supercoiled pUC19 DNA by gel electrophoresis. The experimental results show that the complexes are good intercalators.

  2. A Tetrapositive Metal Ion in the Gas Phase: Thorium(IV) Coordinated by Neutral Tridentate Ligands

    SciTech Connect

    Gong, Yu; Hu, Han-Shi; Tian, Guoxin; Rao, Linfeng; Li, Jun; Gibson, John K.

    2013-07-01

    ESI of 1:1 mixtures of Th(ClO₄)₄ and ligand TMOGA in acetonitrile resulted in the observation of the TMOGA supported tetracation, Th(L)₃⁴⁺, in the gas phase. Three TMOGA ligands are necessary to stabilize the tetrapositive thorium ion; no Th(L)₂⁴⁺ or Th(L)₄⁴⁺ was observed. Theoretical calculations reveal that the Th(L)₃⁴⁺ complex possesses C₃ symmetry with the thorium center coordinated by nine oxygen atoms from three ligands, which forms a twisted TPP geometry. Actinide compounds with such a geometry feature a nine-coordinate chiral actinide center. The Th-L binding energy and bond orders of Th(L)n⁴⁺ decrease as the coordination number increases, consistent with the trend of concurrently increasing Th-O distances. The Th-O bonding is mainly electrostatic in nature, but the covalent interactions are not negligible. CID of the Th(L)₃⁴⁺ complex mainly resulted in charge reduction to form Th(L)₂(L-86)³⁺oss of neutral TMOGA was not observed. The protic ligand methanol stabilized only tri- and dications of ligated thorium. The intensity of the Th(L)₃⁴⁺ peak was reduced as the percentage of water increased in the Th(ClO₄)₄/TMOGA solution.

  3. Conformation preference of a flexible cyclohexanetetracarboxylate ligand in three new metal-organic frameworks: structures, magnetic and luminescent properties.

    PubMed

    Wang, Rongming; Zhang, Jian; Li, Lijuan

    2009-08-01

    Three novel complexes of formula [Co(5)(OH)(2)(cht)(2)(H(2)O)(10)](n) x 2nH(2)O (1) (H(4)cht = cyclohexane-1,2,4,5-tetracarboxylic acid), [Zn(2)(cht)(H(2)O)(3)](n) x nH(2)O (2), and [Cd(2)(cht)(H(2)O)(5)](n) x 2nH(2)O (3) were synthesized by a hydrothermal reaction of cyclohexane-1,2,4,5-tetracarboxylic acid in the presence of sodium hydroxide with Co(NO(3))(2) x 6H(2)O, Zn(NO(3))(2) x 6H(2)O, and Cd(NO(3))(2) x 4H(2)O, respectively. These complexes were obtained by controlling the molar ratios of starting materials and the pH values of reaction mixtures with an initial pH of 5.87 for 1, 5.50 for 2, and 5.57 for 3, respectively. The single-crystal X-ray investigations reveal that the cht ligands change their conformations exclusively to the a,e,e,a form in all three complexes. Complex 1 features a two-dimensional (2D) metal-organic framework (MOF) with an axis surrounded by two zigzag structures, a rectangular channel surrounded by two a-carboxylate-metal-a-carboxlate and two e-carboxylate-metal-e-carboxylate chains, and two smaller distorted square-pyramidal channels surrounded by hydroxyl oxygen, cyclohexane, and its two a-carboxylates. Each cht ligand connects five cobalt atoms and each cobalt atom is six-coordinated with carboxylate-oxygen, hydroxyl, and water molecules. Complex 2 possesses a three-dimensional (3D) MOF structure that consists of the cht ligands and two types of cobalt; one is four-coordinated with carboxylate-oxygens and the other is six-coordinated with carboxylate-oxygens and water molecules. Each cht ligand is bonded to seven zinc atoms. Complex 3 is also a 2D MOF structure constructed by seven-coordinated cadmium atoms and the cht ligands. The e-carboxylates of two parallel cht ligands are connected to a type of cadmium atoms to form 1D chains, and these chains are further connected through a-carboxylates of the ligands and another type of cadmium atoms to give the 2D structure. Extensive hydrogen bonding interactions involving carboxylate-oxygen atoms and crystallization water molecules afford 3D supramolecular networks in complexes 1 and 2. Magnetic susceptibility measurement of 1 confirmed a six-coordinated high-spin cobalt(II) ion and the presence of magnetic exchange coupling among the three hydroxyl-oxygen bridged cobalt ions. Fluorescent spectra of complexes 2 and 3 show strong fluorescent emissions in the blue region. PMID:19586018

  4. Removal of heavy metal species from industrial sludge with the aid of biodegradable iminodisuccinic acid as the chelating ligand.

    PubMed

    Wu, Qing; Duan, Gaoqi; Cui, Yanrui; Sun, Jianhui

    2015-01-01

    High level of heavy metals in industrial sludge was the obstacle of sludge disposal and resource recycling. In this study, iminodisuccinic acid (IDS), a biodegradable chelating ligand, was used to remove heavy metals from industrial sludge generated from battery industry. The extraction of cadmium, copper, nickel, and zinc from battery sludge with aqueous solution of IDS was studied under various conditions. It was found that removal efficiency greatly depends on pH, chelating agent's concentration, as well as species distribution of metals. The results showed that mildly acidic and neutral systems were not beneficial to remove cadmium. About 68 % of cadmium in the sample was extracted at the molar ratio of IDS to heavy metals 7:1 without pH adjustment (pH 11.5). Copper of 91.3 % and nickel of 90.7 % could be removed by IDS (molar ratio, IDS: metals = 1:1) with 1.2 % phosphoric acid effectively. Removal efficiency of zinc was very low throughout the experiment. Based on the experimental results, IDS could be a potentially useful chelant for heavy metal removal from battery industry sludge. PMID:25115899

  5. A new soft transglenoidal suture anchor for arthroscopic labrum fixation.

    PubMed

    Landsiedl, Franz; Wlk, Matthias V; Petje, Gerd; Aigner, Nicolas

    2004-10-01

    Inherent in most transglenoidal suture stabilization techniques of unstable shoulders is the unreliable fixation of posterior knots on the fascia. The transglenoidal suture anchor (TSA) technique overcomes this disadvantage. The TSA is a 1.5-cm loop of a No. 3 braided polyester thread with 5 knots. The loop is loaded with 1 or 2 sutures. Using a transglenoidal shuttle suture, it is pulled into a transglenoidal drill hole from the back in a retrograde fashion. The anchor is stopped at the posterior cortex of the glenoid by the knot. Using an arthroscopic suture passer technique (Bird Beak; Arthrex, Naples, FL) sutures are applied in the anterior-inferior part of the capsule, tied with a self-locking sliding knot, and secured with 2 or 3 additional throws. Two or 3 TSAs with 1 or 2 threads per anchor are used in most cases. The ultimate failure load of 10 samples of the anchor was tested with porcine scapulae. It was more than 156 N in every case. This technique enables the surgeon to use up to 4 anchors in the unstable shoulder with 1 or 2 sutures per anchor. The anchors are inexpensive. No problems are encountered in case of revision. There is no abrasion in the eyelet of the anchor as with metallic anchors and no synovitis as with some absorbable anchors. PMID:15483554

  6. Biodegradable shoulder anchors have unique modes of failure.

    PubMed

    Barber, F Alan

    2007-03-01

    Biodegradable suture anchors have facilitated and revolutionized arthroscopic tissue-to-bone repair, especially in the shoulder. However, the anchor is but a part of the repair construct, which also includes a suture, tied in a knot, that attaches the tissue (tendon or labrum) to bone. Bioabsorbable anchors may result in loose bodies. Two cases are reported as sentinel events highlighting this potential risk. In the first case, combining a nonabsorbable suture (forming the anchor eyelet) with an anchor body made from rapidly degrading copolymer resulted in the suture becoming a loose body as the anchor body reabsorbed. In the second case, a portion of the eyelet and upper screw thread, itself composed of a biodegradable copolymer, became a loose body as the anchor absorbed, perhaps because the eyelet became proud with regard to the host bone during cyclic loading. Biodegradable anchors offer many advantages over metal anchors but do not eliminate the risk of a glenohumeral loose body. Unexpected postoperative symptoms such as painful catching, popping, or "squeaking" may indicate a glenohumeral loose body and warrant an arthroscopic evaluation. In the future, improved shoulder suture anchor design may lower the risk of this complication. PMID:17349477

  7. Rapid Computer Aided Ligand Design and Screening of Precious Metal Extractants from TRUEX Raffinate with Experimental Validation

    SciTech Connect

    Clark, Aurora Sue; Wall, Nathalie; Benny, Paul

    2015-11-16

    Rhodium is the most extensively used metal in catalytic applications; it occurs in mixed ores with platinum group metals (PGMs) in the earth’s crust in low concentrations (0.4 - 10 ppb). It is resistant to aerial oxidation and insoluble in all acids, including aqua regia, making classical purification methods time-consuming and inefficient. To ensure adequate purity, several precipitation and dissolution steps are necessary during separation. Low abundance, high demand, and extensive processing make rhodium the most expensive of all PGMs. From alternative sources, rhodium is also produced in sufficient quantities (0.47 kg per ton initial heavy metal (tIHM)) during the fission of U-235 in nuclear reactors along with other PGMs (i.e., Ag, Pd, Ru). A typical power water reactor operating with UO2 fuel after cooling can generate PGMs in quantities greater than found in the earth’s crust (0.5-2 kg/tIHM). This currently untapped supply of PGMs has the potential to yield $5,000-30,000/tIHM. It is estimated that by the year 2030, the amount of rhodium generated in reactors could exceed natural reserves. Typical SNF processing removes the heavier lanthanides and actinides and can leave PGMs at ambient temperatures in aqueous acidic (Cl⁻ or NO3⁻; pH < 1) solutions at various activities. While the retrieval of these precious metals from SNF would minimize waste generation and improve resource utilization, it has been difficult to achieve thus far. Two general strategies have been utilized to extract Rh(III) from chloride media: ion pairing and coordination complexation. Ion pairing mechanisms have been studied primarily with the tertiary and quaternary amines. Additionally, mixed mechanism extractions have been observed in which ion pairing is the initial mechanism, and longer extraction equilibrium time generated coordination complexes. Very few coordination complexation extraction ligands have been studied. This project approached this problem through the design of a software program that uses state-of-the-art computational combinatorial chemistry, and is developed and validated with experimental data acquisition; the resulting tool allows for rapid design and screening of new ligands for the extraction of precious metals from SNF. This document describes the software that has been produced, ligands that have been designed, and fundamental new understandings of the extraction process of Rh(III) as a function of solution phase conditions (pH, nature of acid, etc.).

  8. Manipulating the Lateral Diffusion of Surface-Anchored EGF Demonstrates that Receptor Clustering Modulates its Phosphorylation Levels

    SciTech Connect

    Stabley, Daniel; Retterer, Scott T; Marshal, Stephen; Salaita, Khalid

    2013-01-01

    Upon activation, the epidermal growth factor (EGF) receptor becomes phosphorylated and triggers a vast signaling network that has profound effects on cell growth. The EGF receptor is observed to assemble into clusters after ligand binding and tyrosine kinase autophosphorylation, but the role of these assemblies in the receptor signaling pathway remains unclear. To address this question, we measured the phosphorylation of EGFR when the EGF ligand was anchored onto laterally mobile and immobile surfaces. We found that cells generated clusters of ligand-receptor complex on mobile EGF surfaces, and generated a lower ratio of phosphorylated EGFR to EGF than when compared to immobilized EGF that is unable to cluster. This result was verified by tuning the lateral assembly of ligand-receptor complexes on the surface of living cells using patterned supported lipid bilayers. Nanoscale metal lines fabricated into the supported membrane constrained lipid diffusion and EGF receptor assembly into micron and sub-micron scale corrals. Single cell analysis indicated that clustering impacts EGF receptor activation, and larger clusters (> 1 m2) of ligand-receptor complex generated lower EGF receptor phosphorylation per ligand than smaller assemblies (< 1 m2) in HCC1143 cells that were engaged to ligand-functionalized surfaces. We investigated EGFR clustering by treating cells with compounds that disrupt the cytoskeleton (Latrunculin-B), clathrin-mediated endocytosis (Pitstop2), and inhibit EGFR activation (Gefitinib). These results help elucidate the nature of large-scale EGFR clustering, thus underscoring the general significance of receptor spatial organization in tuning function.

  9. Structural diversity and magnetic properties of six metal-organic coordination polymers based on semi-rigid V-shape tetracarboxylic acid ligand

    NASA Astrophysics Data System (ADS)

    Yang, Shanshan; Bai, Yue-Ling; Xing, Feifei; Zhao, Yongmei; Li, Ming-Xing; Shao, Min; Zhu, Shourong

    2016-04-01

    Six Mn metal-organic frameworks have been synthesized under solvothermal conditions with V-shaped terphenyl tetracarboxylate ligands (H4ttac). Their structures were characterized by elemental analysis, infrared spectra, PXRD, thermogravimetric analysis, and single-crystal X-ray diffraction analysis. Crystal structures reveal that the coordination number of H4ttac ligand varies from 6 to 10, and each ligand links 4-8 Mn(II) ions. Coordination modes vary from η6μ4 to η10μ8. The existence of DMF solvent can increase coordination number of the ligand. The first coordination saturated phthalate is presented. The variable-temperature magnetic studies indicate that complexes exhibit dominant antiferromagnetic behaviors. Structural parameters and coordination modes were summarized. The porosity of these complexes is less than 15%, indicating that the V-shape ligand is not a good choice to construct porous coordination polymers.

  10. DNA binding, anti-inflammatory and analgesic evaluation of metal complexes of N/S/O donor ligands; synthesis, spectral characterization.

    PubMed

    Kumar Naik, K H; Ashok, B; Naik, Nagaraja; Mulla, Jameel Ahmed S; Prakasha, Avinash

    2015-04-15

    Transition metal complexes containing tri-dentate NSN donor ligands i.e., 5-((1(aminomethyl)cyclohexyl)methyl)-1,3,4-thiadiazol-2-amine (AMTA) (2) and 5-(2-aminophenyl)-1,3,4-thiadiazol-2-amine (ATA) (4i-ii) have been synthesized. The newly synthesized ligands and their respective complexes were characterized by elemental analysis, molar conductance measurement and various spectral studies [infrared (IR), electronic, and NMR (for ligands only)]. Metal complexes are like [M(AMTA)2], [M(ATA)2] type, where M=Mn(II), Co(II) and Cu(II). The proposed geometries of the complexes are octahedral in nature. The synthesized ligands and their complexes were exhibits effective anti-inflammatory, analgesic and DNA binding activities. All the tested compounds exhibited significant analgesic activity, whereas the compound 4i, 4(ia) and 4(iib) is equipotent with Diclofenac sodium. PMID:25666328

  11. DNA binding, anti-inflammatory and analgesic evaluation of metal complexes of N/S/O donor ligands; Synthesis, spectral characterization

    NASA Astrophysics Data System (ADS)

    Kumar Naik, K. H.; Ashok, B.; Naik, Nagaraja; Mulla, Jameel Ahmed S.; Prakasha, Avinash

    2015-04-01

    Transition metal complexes containing tri-dentate NSN donor ligands i.e., 5-((1(aminomethyl)cyclohexyl)methyl)-1,3,4-thiadiazol-2-amine (AMTA) (2) and 5-(2-aminophenyl)-1,3,4-thiadiazol-2-amine (ATA) (4i-ii) have been synthesized. The newly synthesized ligands and their respective complexes were characterized by elemental analysis, molar conductance measurement and various spectral studies [infrared (IR), electronic, and NMR (for ligands only)]. Metal complexes are like [M(AMTA)2], [M(ATA)2] type, where M = Mn(II), Co(II) and Cu(II). The proposed geometries of the complexes are octahedral in nature. The synthesized ligands and their complexes were exhibits effective anti-inflammatory, analgesic and DNA binding activities. All the tested compounds exhibited significant analgesic activity, whereas the compound 4i, 4(ia) and 4(iib) is equipotent with Diclofenac sodium.

  12. Proposed Ligand-Centered Electrocatalytic Hydrogen Evolution and Hydrogen Oxidation at a Noninnocent Mononuclear Metal-Thiolate.

    PubMed

    Haddad, Andrew Z; Kumar, Davinder; Ouch Sampson, Kagna; Matzner, Anna M; Mashuta, Mark S; Grapperhaus, Craig A

    2015-07-29

    The noninnocent coordinatively saturated mononuclear metal-thiolate complex ReL3 (L = diphenylphosphinobenzenethiolate) serves as an electrocatalyst for hydrogen evolution or hydrogen oxidation dependent on the presence of acid or base and the applied potential. ReL3 reduces acids to H2 in dichloromethane with an overpotential of 380 mV and a turnover frequency of 32 ± 3 s(-1). The rate law displays a second-order dependence on acid concentration and a first-order dependence on catalyst concentration with an overall third-order rate constant (k) of 184 ± 2 M(-2) s(-1). Reactions with deuterated acid display a kinetic isotope effect of 9 ± 1. In the presence of base, ReL3 oxidizes H2 with a turnover frequency of 4 ± 1 s(-1). The X-ray crystal structure of the monoprotonated species [Re(LH)L2](+), an intermediate in both catalytic H2 evolution and oxidation, has been determined. A ligand-centered mechanism, which does not require metal hydride intermediates, is suggested based on similarities to the redox-regulated, ligand-centered binding of ethylene to ReL3. PMID:26161802

  13. Ligand-centred fluorescence and electronic relaxation cascade at vibrational time scales in transition-metal complexes.

    PubMed

    Messina, Fabrizio; Pomarico, Enrico; Silatani, Mahsa; Baranoff, Etienne; Chergui, Majed

    2015-11-19

    Using femtosecond-resolved photoluminescence up-conversion, we report the observation of the fluorescence of the high-lying ligand-centered (LC) electronic state upon 266 nm excitation of an iridium complex, Ir(ppy)3, with a lifetime of 70 ± 10 fs. It is accompanied by a simultaneous emission of all lower-lying electronic states, except the lowest triplet metal-to-ligand charge-transfer ((3)MLCT) state that shows a rise on the same time scale. Thus, we observe the departure, the intermediate steps, and the arrival of the relaxation cascade spanning ∼1.6 eV from the (1)LC state to the lowest (3)MLCT state, which then yields the long-lived luminescence of the molecule. This represents the first measurement of the total relaxation time over an entire cascade of electronic states in a polyatomic molecule. We find that the relaxation cascade proceeds in ≤10 fs, which is faster than some of the highest-frequency modes of the system. We invoke the participation of the latter modes in conical intersections and their overdamping to low-frequency intramolecular modes. On the basis of literature, we also conclude that this behavior is not specific to transition-metal complexes but also applies to organic molecules. PMID:26509329

  14. Molecular tectonics of mixed-ligand metal-organic frameworks: Positional isomeric effect, and structural diversification

    NASA Astrophysics Data System (ADS)

    Cai, Hua; Xu, Chong; Zhou, Yu-Ping; Tong, Xiao-Qiang; Guo, Ying

    2016-03-01

    To explore the influence of three structurally different polycarboxylate ligands H2L1 to H4L3 in the system Cd(II)/PPAN, three coordination polymers, formulated as {Cd2(PPAA)2(L1)2}n (1), {[Cd2(PPAA)2(HL2) (H2O)].2H2O}n (2), {Cd2(PPAN)2(L3) (H2O)2}n (3) have been obtained under similar conditions (PPAA- = 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl)acetate, PPAN = 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl)acetonitrile, H2L1 = 1,3-benzenedicarboxylic acid, H3L2 = 1,3,5-benzenetricarboxylic acid, H4L3 = 1,2,4,5-benzenetetracarboxylic acid). In 1-2, PPAN are hydrolyzed into a novel PPAA- ligand. The structure determination reveals that complex 1 contains 1D double chains of {[Cd(PPAA)]+}n cation structural units, which are further extended by these μ3-(L1)2- ligands forming a novel 2D three-layered framework with (4.82)2(43.62.8)2(4383)2(48.66.8) topology. Complex 2 is one-dimensional (1D) ribbon-like chains having two kinds of dimerics [Cd(PPAA)]2 and [Cd(COO)]2 subunits and dimeric Cd(II) units bridged by μ3-(HL2)2- ligands. Complex 3 shows an undulating 2D (4, 4)-network by μ4-(L3)4-. In addition, photoluminescent properties of three coordination polymers were also investigated in this paper.

  15. Spectroscopic and biological studies of new mononuclear metal complexes of a bidentate NN and NO hydrazone-oxime ligand derived from egonol

    NASA Astrophysics Data System (ADS)

    Babahan, Ilknur; Emirdağ-Öztürk, Safiye; Poyrazoğlu-Çoban, Esin

    2015-04-01

    A novel ligand, vicinal dioxime ligand (egonol-hydrazone glyoxime) (LH2) was synthesized and characterized using 1H NMR, 13C NMR, MS, AAS, infrared spectroscopy, and magnetic susceptibility measurements. Mononuclear nickel (II), copper (II) and cobalt (II) complexes with a metal:ligand ratio of 1:2 for LH2 were also synthesized. Zn(II) forms complex [Zn(LH)Cl2] with a metal to ligand ratio of 1:1. IR spectrum shows that the ligand act in a bidentate manner and coordinates N4 donor groups of the ligands to NiII, CuII, CoII and ZnII ions. The detection of H-bonding (Osbnd H⋯O) in the [M(LH)2] metal complexes by IR spectra supported the square-planar MN4 coordination of Ni(II), Cu(II) and Co(II) complexes. The antimicrobial activities of compounds LH2 and their Ni(II), Cu(II), Co(II) and Zn(II) complexes were evaluated using the disc diffusion method against 16 bacteria and 5 yeasts. The minimal inhibitory concentrations (MICs) against all the bacteria and yeasts were also determined. Among the attempted test compounds, it is showed that all the compounds (L, LH2, [Ni(LH)2], [Cu(LH)2], [Co(LH)2(H2O)2], [Zn(LH)Cl2]) were effective against used test microorganisms.

  16. Synthesis, Characterization, Antimicrobial, DNA Cleavage, and In Vitro Cytotoxic Studies of Some Metal Complexes of Schiff Base Ligand Derived from Thiazole and Quinoline Moiety

    PubMed Central

    Yernale, Nagesh Gunvanthrao; Bennikallu Hire Mathada, Mruthyunjayaswamy

    2014-01-01

    A novel Schiff base ligand N-(4-phenylthiazol-2yl)-2-((2-thiaxo-1,2-dihydroquinolin-3-yl)methylene)hydrazinecarboxamide (L) obtained by the condensation of N-(4-phenylthiazol-2-yl)hydrazinecarboxamide with 2-thioxo-1,2-dihydroquinoline-3-carbaldehyde and its newly synthesized Cu(II), Co(II), Ni(II), and Zn(II) complexes have been characterized by elemental analysis and various spectral studies like FT-IR, 1H NMR, ESI mass, UV-Visible, ESR, TGA/DTA, and powder X-ray diffraction studies. The Schiff base ligand (L) behaves as tridentate ONS donor and forms the complexes of type [ML(Cl)2] with square pyramidal geometry. The Schiff base ligand (L) and its metal complexes have been screened in vitro for their antibacterial and antifungal activities by minimum inhibitory concentration (MIC) method. The DNA cleavage activity of ligand and its metal complexes were studied using plasmid DNA pBR322 as a target molecule by gel electrophoresis method. The brine shrimp bioassay was also carried out to study the in vitro cytotoxicity properties for the ligand and its metal complexes against Artemia salina. The results showed that the biological activities of the ligand were found to be increased on complexation. PMID:24729778

  17. Spectroscopic and biological studies of new mononuclear metal complexes of a bidentate NN and NO hydrazone-oxime ligand derived from egonol.

    PubMed

    Babahan, Ilknur; Emirdağ-Öztürk, Safiye; Poyrazoğlu-Çoban, Esin

    2015-04-15

    A novel ligand, vicinal dioxime ligand (egonol-hydrazone glyoxime) (LH2) was synthesized and characterized using (1)H NMR, (13)C NMR, MS, AAS, infrared spectroscopy, and magnetic susceptibility measurements. Mononuclear nickel (II), copper (II) and cobalt (II) complexes with a metal:ligand ratio of 1:2 for LH2 were also synthesized. Zn(II) forms complex [Zn(LH)Cl2] with a metal to ligand ratio of 1:1. IR spectrum shows that the ligand act in a bidentate manner and coordinates N4 donor groups of the ligands to Ni(II), Cu(II), Co(II) and Zn(II) ions. The detection of H-bonding (OH⋯O) in the [M(LH)2] metal complexes by IR spectra supported the square-planar MN4 coordination of Ni(II), Cu(II) and Co(II) complexes. The antimicrobial activities of compounds LH2 and their Ni(II), Cu(II), Co(II) and Zn(II) complexes were evaluated using the disc diffusion method against 16 bacteria and 5 yeasts. The minimal inhibitory concentrations (MICs) against all the bacteria and yeasts were also determined. Among the attempted test compounds, it is showed that all the compounds (L, LH2, [Ni(LH)2], [Cu(LH)2], [Co(LH)2(H2O)2], [Zn(LH)Cl2]) were effective against used test microorganisms. PMID:25686861

  18. A theoretical investigation into the luminescent properties of d8-transition-metal complexes with tetradentate Schiff base ligands.

    PubMed

    Tong, Glenna So Ming; Chow, Pui Keong; To, Wai-Pong; Kwok, Wai-Ming; Che, Chi-Ming

    2014-05-19

    A theoretical investigation on the luminescence efficiency of a series of d(8) transition-metal Schiff base complexes was undertaken. The aim was to understand the different photophysics of [M-salen](n) complexes (salen = N,N'-bis(salicylidene)ethylenediamine; M = Pt, Pd (n = 0); Au (n = +1)) in acetonitrile solutions at room temperature: [Pt-salen] is phosphorescent and [Au-salen](+) is fluorescent, but [Pd-salen] is nonemissive. Based on the calculation results, it was proposed that incorporation of electron-withdrawing groups at the 4-position of the Schiff base ligand should widen the (3)MLCT-(3)MC gap (MLCT = metal-to-ligand charge transfer and MC = metal centered, that is, the dd excited state); thus permitting phosphorescence of the corresponding Pd(II) Schiff base complex. Although it is experimentally proven that [Pd-salph-4E] (salph = N,N'-bis(salicylidene)-1,2-phenylenediamine; 4E means an electron-withdrawing substituent at the 4-position of the salicylidene) displays triplet emission, its quantum yield is low at room temperature. The corresponding Pt(II) Schiff base complex, [Pt-salph-4E], is also much less emissive than the unsubstituted analogue, [Pt-salph]. Thus, a detailed theoretical analysis of how the substituent and central metal affected the photophysics of [M-salph-X] (X is a substituent on the salph ligand, M = Pt or Pd) was performed. Temperature effects were also investigated. The simple energy gap law underestimated the nonradiative decay rates and was insufficient to account for the temperature dependence of the nonradiative decay rates of the complexes studied herein. On the other hand, the present analysis demonstrates that inclusions of low-frequency modes and the associated frequency shifts are decisive in providing better quantitative estimates of the nonradiative decay rates and the experimentally observed temperature effects. Moreover, spin-orbit coupling, which is often considered only in the context of radiative decay rate, has a significant role in determining the nonradiative rate as well. PMID:24715418

  19. Synthesis, spectroscopic characterization, electrochemistry and biological evaluation of some binuclear transition metal complexes of bicompartmental ONO donor ligands containing benzo[b]thiophene moiety

    NASA Astrophysics Data System (ADS)

    Mahendra Raj, K.; Vivekanand, B.; Nagesh, G. Y.; Mruthyunjayaswamy, B. H. M.

    2014-02-01

    A series of new binucleating Cu(II), Co(II), Ni(II) and Zn(II) complexes of bicompartmental ligands with ONO donor were synthesized. The ligands were obtained by the condensation of 3-chloro-6-substituted benzo[b]thiophene-2-carbohydrazides and 4,6-diacetylresorcinol. The synthesized ligands and their complexes were characterized by elemental analysis and various spectroscopic techniques. Elemental analysis, IR, 1H NMR, ESI-mass, UV-Visible, TG-DTA, magnetic measurements, molar conductance and powder-XRD data has been used to elucidate their structures. The bonding sites are the oxygen atom of amide carbonyl, azomethine nitrogen and phenolic oxygen for ligands 1 and 2. The binuclear nature of the complexes was confirmed by ESR spectral data. TG-DTA studies for some complexes showed the presence of coordinated water molecules and the final product is the metal oxide. All the complexes were investigated for their electrochemical activity, only the Cu(II) complexes showed the redox property. Cu(II) complexes were square planar, whereas Co(II), Ni(II) and Zn(II) complexes were octahedral. Powder-XRD pattern have been studied in order to test the degree of crystallinity of the complexes and unit cell calculations were made. In order to evaluate the effect of antimicrobial activity of metal ions upon chelation, both the ligands and their metal complexes 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 ligands. The DNA cleaving capacities of all the complexes were analyzed by agarose gel electrophoresis method against supercoiled plasmid DNA. Among the compounds tested for antioxidant capacity, ligand 1 displayed excellent activity than its metal complexes.

  20. Syntheses, crystal structures, anticancer activities of three reduce Schiff base ligand based transition metal complexes

    NASA Astrophysics Data System (ADS)

    Chang, Hui-Qin; Jia, Lei; Xu, Jun; Zhu, Tao-Feng; Xu, Zhou-Qing; Chen, Ru-Hua; Ma, Tie-Liang; Wang, Yuan; Wu, Wei-Na

    2016-02-01

    Three nickel(II) complexes, [Ni2(L1)2(tren)2(H2O)](ClO4)3 (1), [NiL2(tren)2](ClO4)·2.5H2O (2), [NiL2(tren)2]I·1.5H2O·CH3OH (3) based on amino acid reduced Schiff ligands are synthesized and characterized by physico-chemical and spectroscopic methods. The results show that in all complexes, the amino acid ligand is deprotonated and acts as an anionic ligand. In the dinuclear complex 1, each Ni(II) atom has a distorted octahedron geometry while with different coordination environment. However, the complexes 2 and 3 are mononuclear, almost with the same coordination environment. Furthermore, in vitro experiments are carried out, including MTT assay, Annexin V/PI flow cytometry and western blotting, to assess whether the complexes have antitumor effect. And the results show that all the three complexes have moderate anticancer activity towards human hepatic cancer (HepG2), human cervical cancer (HeLa) and human prostate (PC3) cell lines, in a concentration dependent way. The complex 1 exhibit higher cytotoxicity than the other two complexes and can induce human hepatic cancer cell (HepG2) to cell apoptosis by activating caspase 3.

  1. Probing the interface between semiconducting nanocrystals and molecular metal chalcogenide surface ligands: insights from first principles

    NASA Astrophysics Data System (ADS)

    Scalise, Emilio; Wippermann, Stefan; Galli, Giulia; Talapin, Dmitri

    Colloidal nanocrystals (NCs) are emerging as cost-effective materials offering exciting prospects for solar energy conversion, light emission and electronic applications. Recent experimental advances demonstrate the synthesis of fully inorganic nanocrystal solids from chemical solution processing. The properties of the NC-solids are heavily determined by the NCs surface and their interactions with the host matrix. However, information on the atomistic structure of such composites is hard to obtain, due to the complexity of the synthesis conditions and the unavailability of robust experimental techniques to probe nanointerfaces at the microscopic level. Here we present a systematic theoretical study of the interaction between InAs and InP NCs with Sn2S64- ligands. Employing a grand canonical ab initio thermodynamic approach we investigate the relative stability of a multitude of configurations possibly realized at the NC-ligand interface. Our study highlights the importance of different structural details and their strong impact on the resulting composite's properties. We show that to obtain a detailed understanding of experimental data it is necessary to take into account complex interfacial structures beyond simplified NC-ligand model interfaces. S. W. acknowledges BMBF NanoMatFutur Grant No. 13N12972. G.G. acknowledges DOE-BES for funding part of this work.

  2. Preorganized and immobilized ligands for metal ion separations. Final report, June, 1994--May, 1997

    SciTech Connect

    Paine, R.T.

    1997-12-01

    Historically, much of the interest shown in f-element ion coordination chemistry has been driven by practical needs to devise separation schemes for lanthanide (Ln) and actinide (An) ions. However, few of the separations are completely satisfactory, and the basic chemical framework needed to achieve improvements is still poorly developed. As a result, studies of the fundamental aspects of f-element coordination chemistry are still pertinent not only to the evolution of improved separations, but also waste remediation, biological and medical applications of Ln ions, biochemistry of An ion decorporation, and new solid state materials preparations. The research objectives during the present grant period were to (1) synthesize new bifunctional and trifunctional chelating ligands, particularly in the class of new phosphonopyridine N-oxides; (2) characterize the structural features of the Ln and An coordination complexes formed by these ligands; (3) determine the extraction efficacy of these ligands; and (4) explore synthetic approaches for formation of dendritic polymers containing phosphoryl terminating groups. Some highlights of recently accomplished work and still-in-progress research are outlined.

  3. Grafting a new metal ligand in the cocatalytic site of B. cereus metallo-beta-lactamase: structural flexibility without loss of activity.

    PubMed

    Rasia, Rodolfo M; Ceolín, Marcelo; Vila, Alejandro J

    2003-07-01

    Metallo-beta-lactamases are zinc enzymes able to hydrolyze the four-membered ring of beta-lactam antibiotics, representing one of the latest generations of beta-lactamases. These enzymes belong to the zinc metallo-hydrolase family of the beta-lactamase fold. Enzymes belonging to this family have a bimetallic active site whose structure varies among different members by point substitutions of the metal ligands. In this work, we have grafted new metal ligands into the metal binding site of BcII from Bacillus cereus that mimic the ligands present in other members of this superfamily. We have characterized spectroscopically and modeled the structure of the redesigned sites, which differ substantially from the wild-type enzyme. Despite the changes introduced in the active site, the mutant enzymes retain almost full activity. These results shed some light on the possible evolutionary origin of these metalloenzymes. PMID:12824499

  4. Syntheses, crystal structures, and optical properties of five metal complexes constructed from a V-shaped thiophene-containing ligand and different dicarboxylate ligands.

    PubMed

    Shi, Zhi-Qiang; Guo, Zi-Jian; Zheng, He-Gen

    2014-09-21

    Five new metal complexes, {[Ni(DIDP)(m-bdc)(H2O)]·5H2O}n (1), {[Zn(DIDP)(hfipbb)]·2DMA}n (2), {[Zn(DIDP)(4,4'-sdb)]·H2O}n (3), {[Co(DIDP)(p-bdc)]}n (4), and {[Co2(DIDP)(hfipbb)2]·H2O}n (5), have been synthesized by reactions of the corresponding metal ions with a V-shaped ligand 2,8-di(1H-imidazol-1-yl)dibenzothiophene (DIDP) and different aromatic dicarboxylic acids, namely isophthalic acid (m-H2bdc), terephthalic acid (p-H2bdc), 4,4'-(hexafluoroisopropylidene)bis(benzoic acid) (H2hfipbb), and 4,4'-sulfonyldicarboxylic acid (4,4'-H2sdb), respectively. The structures of the complexes were determined by X-ray single-crystal diffraction. Complex 1 is a 1D chain structure containing a one-dimensional channel along the a direction and is further extended via O-H···S hydrogen bonds and C-H···π stacking interactions into a 3D framework. Complex 2 exhibits a quasi 2D + 2D → 2D with parallel polycatenation of 2D (4, 4) nets. Complex 3 displays an unusual 2D + 2D → 3D parallel polycatenated framework based on a 2D 6(3)-hcb network. Complex 4 shows a 2D 4-connected {4(4)·6(2)}-sql network containing a one-dimensional channel along the b direction. The adjacent 2D networks are further extended via C-H···O hydrogen bonds into a 3D supramolecular framework. Complex 5 features a 2-fold interpenetrating 3D framework with a 6-connected {4(12)·6(3)} pcu topology. Furthermore, the thermal stability for 1-5 and luminescence properties of 2 and 3 have been studied. Moreover, the solid-state UV-visible spectroscopy experiments show that complexes 1-5 are all optical semiconductors with band gaps of 3.06, 3.18, 3.23, 2.98, and 3.17 eV, respectively. PMID:25050987

  5. Selective fluorescence sensors for detection of nitroaniline and metal Ions based on ligand-based luminescent metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Yu, Zongchao; Wang, Fengqin; Lin, Xiangyi; Wang, Chengmiao; Fu, Yiyuan; Wang, Xiaojun; Zhao, Yongnan; Li, Guodong

    2015-12-01

    Metal-organic frameworks (MOFs) are porous crystalline materials with high potential for applications in fluorescence sensors. In this work, two solvent-induced Zn(II)-based metal-organic frameworks, Zn3L3(DMF)2 (1) and Zn3L3(DMA)2(H2O)3 (2) (L=4,4‧-stilbenedicarboxylic acid), were investigated as selective sensing materials for detection of nitroaromatic compounds and metal ions. The sensing experiments show that 1 and 2 both exhibit selective fluorescence quenching toward nitroaniline with a low detection limit. In addition, 1 exhibits high selectivity for detection of Fe3+ and Al3+ by significant fluorescence quenching or enhancement effect. While for 2, it only exhibits significant fluorescence quenching effect for Fe3+. The results indicate that 1 and 2 are both promising fluorescence sensors for detecting and recognizing nitroaniline and metal ions with high sensitivity and selectivity.

  6. Exploiting metal-ligand bifunctional reactions in the design of iron asymmetric hydrogenation catalysts.

    PubMed

    Morris, Robert H

    2015-05-19

    This is an Account of our development of iron-based catalysts for the asymmetric transfer hydrogenation (ATH) and asymmetric pressure hydrogenation (AH) of ketones and imines. These chemical processes provide enantiopure alcohols and amines for use in the pharmaceutical, agrochemical, fragrance, and other fine chemical industries. Fundamental principles of bifunctional reactivity obtained by studies of ruthenium catalysts by Noyori's group and our own with tetradentate ligands with tertiary phosphine and secondary amine donor groups were applied to improve the performance of these first iron(II) catalysts. In particular the correct positioning of a bifunctional H-Fe-NH unit in an iron hydride amine complex leads to exceptional catalyst activity because of the low energy barrier of dihydrogen transfer to the polar bond of the substrate. In addition the ligand structure with this NH group along with an asymmetric array of aryl groups orients the incoming substrate by hydrogen-bonding, and steric interactions provide the hydrogenated product in high enantioselectivity for several classes of substrates. Enantiomerically pure diamines or diphenylphosphino-amine compounds are used as the source of the asymmetry in the tetradentate ligands formed by the condensation of the amines with dialkyl- or diaryl-phosphinoaldehydes, a synthesis that is templated by Fe(II). The commercially available ortho-diphenylphosphinobenzaldehyde was used in the initial studies, but then diaryl-phosphinoacetaldehydes were found to produce much more effective ligands for iron(II). Once the mechanism of catalysis became clearer, the iron-templated synthesis of (S,S)-PAr2CH2CH2NHCHPhCHPhNH2 ligand precursors was developed to specifically introduce a secondary amine in the precatalyst structures. The reaction of a precatalyst with strong base yields a key iron-amido complex that reacts with isopropanol (in ATH) or dihydrogen (in AH) to generate an iron hydride with the Fe-H bond parallel to the secondary amine N-H. In the AH reactions, the correct acidity of the intermediate iron-dihydrogen complex and correct basicity of the amide are important factors for the heterolytic splitting of the dihydrogen to generate the H-Fe-N-H unit; the acidity of dihydrogen complexes including those found in hydrogenases can be estimated by a simple additive ligand acidity constant method. The placement of the hydridic-protonic Fe-H···HN interaction in the asymmetric catalyst structure influences the enantioinduction. The sense of enantioinduction is predictable from the structure of the H-Fe-N-H-containing catalyst interacting with the ketone in the same way as related H-Ru-N-H-containing catalysts. The modular construction of the catalysts permits large variations in order to produce alcohol or amine products with enantiomeric excess in the 90-100% range in several cases. PMID:25897779

  7. Synthesis and spectroscopic studies of some transition metal complexes of a novel Schiff base ligands derived from 5-phenylazo-salicyladehyde and o-amino benzoic acid

    NASA Astrophysics Data System (ADS)

    Refat, Moamen S.; El-Deen, Ibrahim M.; Ibrahim, Hassan K.; El-Ghool, Samir

    2006-12-01

    Cu(II), Mn(II), Ni(II), and Zn(II) metal complexes with novel heterocyclic Schiff base derived from 5-phenyl azo-salicyladehyde and o-amino benzoic acid have been synthesized and characterized on the basis of elemental analyses, electronic, IR, and 1H NMR spectra, and also by aid of scanning electron microscopy (SEM), X-ray powder diffraction, molar ratio measurements, molar conductivity measurements, and thermogravimetric analyses. It has been found that the Schiff base behaves as neutral tridentate (ONO) ligand forming chelates with 1:1 (metal:ligand) stoichiometry.

  8. On the Question of Site-Selective Ligand Exchange in Carboxylate-Substituted Metal Oxo Clusters

    PubMed Central

    Kreutzer, Johannes; Czakler, Matthias; Puchberger, Michael; Pittenauer, Ernst; Schubert, Ulrich

    2015-01-01

    Reaction of [Ti4Zr4O6(OBu)4(OMc)16] (OMc = methacrylate) with acetylacetone (acacH) resulted in dissection of the cluster and formation of [Ti(OBu)2(acac)2] and the smaller cluster [Ti2Zr4O4(OMc)16]. In contrast, the same reaction with [Zr6O4(OH)4(OOCR)12]2·6RCOOH (R = Et, CH2CH=CH2) led to site-selective substitution of two carboxylate ligands and formation of isostructural [Zr6O4(OH)4(OOCR)12–x(acac)x]2·6RCOOH (x ≤ 1). PMID:26300687

  9. Disintegration of an absorbable rotator cuff anchor six weeks after implantation.

    PubMed

    Kelly, James D

    2005-04-01

    Rotator cuff failure by suture-bone or suture anchor pull-out, suture breakage, knot slippage, and tendon pull-out are well described. I report a case of early disintegration of a bioabsorbable suture anchor. A 77-year-old woman underwent arthroscopic rotator cuff repair. On suspecting failure, the repair was repeated 40 days later. Arthroscopy revealed disintegration of the suture loop from the anchor. Open rotator cuff repair was then performed with transosseous suture and metallic anchors. PMID:15800531

  10. Ferrocenylphenylphosphine and diferrocenylphosphine: new two-electron ligands in complexes of group VIB and VII transition metals

    SciTech Connect

    Losilkina, V.I.; Baranetskaya, N.K.; Tolkunova, V.S.; Krylova, A.I.; Vil'chevskaya, V.D.; Setkina, V.N.

    1987-10-10

    Previously unknown carbonyl complexes were synthesized: C/sub 6/H/sub 6/Cr(CO)/sub 2/PFcPhH, C/sub 6/H/sub 6/Cr(CO)/sub 2/PFc/sub 2/H, C/sub 5/H/sub 5/Mn(CO)/sub 2/PFcPhH, C/sub 5/H/sub 5/Mn(CO)/sub 2/PFc/sub 2/H, and M(CO)/sub 5/PFc/sub 2/H (M = Cr, Mo, W). The ligands PFcPhH and PFc/sub 2/H have weaker electron-donor properties than the ligand PFc/sub 3/ in analogous systems. Under the conditions of isotopic exchange of hydrogen in CF/sub 3/COOH there occurs the protonation of C/sub 6/H/sub 6/Cr(CO)/sub 2/PFcH on the chromium atom. For the complex C/sub 6/H/sub 6/Cr(CO)/sub 2/PFc/sub 2/H it was found that, in the reaction of the isotopic exchange of hydrogen, hydrogens of both the ..pi..-benzene ring and the ..pi..-cyclopentadienyl rings of the phosphine ligand take part, and, moreover, at equal rates. By the method of the isotopic exchange of hydrogen and by spectral methods (IR and PMR) it was shown that the nature of the central metal atom in the complexes M(CO)/sub 5/PFc/sub 2/H, in which M = Cr, Mo, W, has no substantial influence on the spectral characteristics and on the reactivities of these complexes.

  11. Interfacial metal flux in ligand mixtures. 3. Unexpected flux enhancement due to kinetic interplay at the consuming surface, computed for aquatic systems.

    PubMed

    Zhang, Zeshi; Buffle, Jacques

    2009-08-01

    Understanding the processes controlling metal biouptake in a mixture of ligands is a requirement for making predictions on dynamic risk assessment in ecotoxicology. In ligand mixtures, the metal uptake flux, due to the dissociation of non labile complexes, can be significantly enhanced by the presence of ligands forming labile complexes, even when the proportions of the latter are very small in the bulk solution. The flux enhancement results from a peculiar kinetic interplay, at the interface, between the labile and non labile species, which influences the lifetime of free metal ion and the reaction layer thickness. An extension of the concept of reaction layer, to multiligand systems, is used here, to explain the physicochemical basis of this flux enhancement and to compute the flux of trace metals in a simple way. This phenomenon is exemplified with four environmentally relevant systems including: (i) simple ligands (Pb-NTA-diglycolate; Cu-OH(-)-CO3(2-)), (ii) fulvic substances (Cu-fulvics-citrate), and (iii) aggregate complexants (Pb-aggregate-CO3(2-)). These examples are typical cases in laboratory experiments, in natural freshwaters and in soil-waters. They show that the flux enhancement effect may occur with all major inorganic and organic environmental complexants. It may be ubiquitous in natural waters or in biological systems and might play an important role in biouptake of toxic or vital metals. PMID:19731674

  12. Composite materials formed with anchored nanostructures

    DOEpatents

    Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei

    2015-03-10

    A method of forming nano-structure composite materials that have a binder material and a nanostructure fiber material is described. A precursor material may be formed using a mixture of at least one metal powder and anchored nanostructure materials. The metal powder mixture may be (a) Ni powder and (b) NiAl powder. The anchored nanostructure materials may comprise (i) NiAl powder as a support material and (ii) carbon nanotubes attached to nanoparticles adjacent to a surface of the support material. The process of forming nano-structure composite materials typically involves sintering the mixture under vacuum in a die. When Ni and NiAl are used in the metal powder mixture Ni.sub.3Al may form as the binder material after sintering. The mixture is sintered until it consolidates to form the nano-structure composite material.

  13. Schiff base ligands and their transition metal complexes in the mixtures of ionic liquid + organic solvent: a thermodynamic study.

    PubMed

    Shekaari, Hemayat; Kazempour, Amir; Khoshalhan, Maryam

    2015-01-21

    Schiff bases and their metal complexes in the mixtures of ionic liquid (IL) + organic solvent have shown great potential in attractive oxidation catalytic processes. The efficiency of such a process is strongly dependent on the various molecular interactions occurring between components. Thermodynamic properties of these systems can provide valuable information about structural interactions. Therefore, in this work, the interactions of the IL 1-hexyl-3-methylimidazolium chloride ([HMIm]Cl) with Schiff bases in organic solvents were studied through the measurements of density, viscosity, and electrical conductivity. The effect of solvent on the interactions was examined by the solutions of IL + BPIC Schiff base + solvent (C2H6O-C3H8O-C4H10O). Moreover, the influence of Schiff base ligand and Schiff base complex structures was probed by the solutions of IL + DMA + ligand (salcn/salpr/salen) and IL + DMA + complex (VO(3-OMe-salen)/VO(salophen)/VO(salen)), respectively. Using the experimental data, some important thermodynamic properties, such as standard partial molar volume (V(0)(φ,IL)), experimental slope (Sv), viscosity B-coefficient, solvation number (B/V(0)(φ,IL) and limiting molar conductivity (Λ0) were calculated and discussed in terms of solute-solvent (IL-DMF/alcohol) and solute-cosolute (IL-Schiff base) interactions. PMID:25482659

  14. One-step purification of rabbit histidine rich glycoprotein by dye-ligand affinity chromatography with metal ion requirement.

    PubMed

    Mori, S; Nishibori, M; Yamaoka, K; Okamoto, M

    2000-11-15

    A simple method for purification of the histidine rich glycoprotein (rHRG) from rabbit sera was developed. The rHRG was purified by one-step affinity chromatography using the triphenylmethane dye "acid fuchsin" as a specific ligand, which gave an overall yield above 80%. Interestingly, the binding of rHRG to the ligand required the divalent transition-metal ions such as Zn2+, Ni2+, and Co2+ at pH 9.5. In the presence of 0.5 mM ZnCl2, the binding was enhanced 15 times compared with that in the absence of ZnCl2. Bound rHRG was efficiently eluted from the affinity absorbent with 100 mM imidazole or histidine. Purified rHRG was homogeneous with an Mr of 94 kDa when analyzed by SDS-PAGE, whereas isoelectric focusing revealed microheterogeniety with pI values ranging from 6.3 to 6.8. Blotting analysis with lectins specific for carbohydrate moieties and treatment with glycosidases demonstrated that rHRG is a highly N-glycosylated protein with diverse carbohydrate structures. PMID:11185553

  15. Metal flux and dynamic speciation at (bio)interfaces. Part I: Critical evaluation and compilation of physicochemical parameters for complexes with simple ligands and fulvic/humic substances.

    PubMed

    Buffle, Jacques; Zhang, Zeshi; Startchev, Konstantin

    2007-11-15

    In the computation of metal flux in aquatic systems, at consuming surfaces like organism membranes, diffusion processes of metal ions, ligands, and complex species, as well as the kinetic and thermodynamic aspects of their chemical interactions, must be considered. The properties of many natural ligands, however, are complicated (formation of successive complexes for simple ligands, polyelectrolytic properties and chemical heterogeneity for macromolecular ligands, large size distribution and fractal structure for suspended aggregates). These properties should be properly modeled to get the correct values of the chemical rate constants and diffusion coefficients required for flux computations. The selection of the most appropriate models and parameter values is far from straightforward. This series of papers discusses the various models and compiles the parameters needed for the three most important types of complexants found in aquatic systems: the small, simple ligands, the fulvic and humic compounds, and the colloidal "particles" or aggregates. In particular, new approaches are presented to compute the rate constants of metal complex formation, with both fulvics/humics and particles/aggregates. The method to include the site distribution of fulvics/humics and the size distribution of particles/aggregates in metal flux computation at consuming interfaces is also discussed in detail. These models and parameters are discussed critically and presented in the same framework, forthe computation of metal flux in presence of any of the above complexants or mixtures. Such parameters, largely spread in the literature, are gathered here and selected specifically for environmental applications. The focus in Part I of the series is on simple ligands and fulvic/humic compounds. Part II deals with particulate and aggregate complexants. PMID:18075065

  16. Anchoring the Deficit of the Anchor Deficit: Dyslexia or Attention?

    ERIC Educational Resources Information Center

    Willburger, Edith; Landerl, Karin

    2010-01-01

    In the anchoring deficit hypothesis of dyslexia ("Trends Cogn. Sci.", 2007; 11: 458-465), it is proposed that perceptual problems arise from the lack of forming a perceptual anchor for repeatedly presented stimuli. A study designed to explicitly test the specificity of the anchoring deficit for dyslexia is presented. Four groups, representing all…

  17. Synthesis and characterization of ML and ML2 metal complexes with amino acid substituted bis(2-picolyl)amine ligands.

    PubMed

    Škalamera, Đani; Sanders, Ernest; Vianello, Robert; Maršavelski, Aleksandra; Pevec, Andrej; Turel, Iztok; Kirin, Srećko I

    2016-02-21

    Metal complexes with ML or ML2 stoichiometry have been isolated in the reaction of Zn(NO3)2, ZnBr2 or M(NO3)2/NaBF4, M = Zn(ii), Co(ii) or Ni(ii), with either amino acid or amine substituted tridentate nitrogen ligands based on bis(2-picolyl)amine (bpa) or bis(2-quinaldyl)amine (bqa). The stoichiometry (M : L = 1 : 1 or 1 : 2) and stereochemistry (mer, trans-fac or cis-fac) of the products have been studied by NMR and IR spectroscopy, X-ray single crystal analysis and quantum-chemical calculations with an implicit SMD solvation model. PMID:26616422

  18. An Isoreticular Series of Metal-Organic Frameworks with Dendritic Hexacarboxylate Ligands and Exceptionally High Gas-Uptake Capacity

    SciTech Connect

    Yuan, Daqiang; Zhao, Dan; Sun, Daofeng; Zhou, Hong-Cai

    2010-10-01

    Metal-organic frameworks (MOFs) are newly emerging porous materials. Owing to their large surface area and tunable pore size and geometry, they have been studied for applications in gas storage and separation, especially in hydrogen and methane storage and carbon dioxide capture. It has been well established that the high-pressure gravimetric hydrogen-adsorption capacity of an MOF is directly proportional to its surface area. However, MOFs of high surface areas tend to decompose upon activation. In our previous work, we described an approach toward stable MOFs with high surface areas by incorporating mesocavities with microwindows. To extend this work, we now present an isoreticular series of (3,24)-connected MOFs made from dendritic hexacarboxylate ligands, one of which has a Langmuir surface area as high as 6033 m2 g-1. In addition, the gas-adsorption properties of this new isoreticular MOF series have been studied.

  19. Photogenerated avenues in macromolecules containing Re(I), Ru(II), Os(II), and Ir(III) metal complexes of pyridine-based ligands.

    PubMed

    Happ, Bobby; Winter, Andreas; Hager, Martin D; Schubert, Ulrich S

    2012-03-21

    Pyridine-based ligands, such as 2,2'-bipyridine and 1,10-phenanthroline, have gained much interest in the fields of supramolecular chemistry as well as materials science. The appealing optoelectronic properties of their complexes with heavy d(6) transition metal ions, such as Ru(ii), Os(II), Re(I) and Ir(III), primarily based on the metal-to-ligand charge-transfer (MLCT) nature featuring access to charge-separated states, have provided the starting point for many studies in the field of dye-sensitized solar cells (DSSCs), organic light emitting diodes (OLEDs), artificial photosynthesis and photogenerated electron as well as energy transfer processes. This critical review provides a comprehensive survey over central advances in the field of soluble metal-containing macromolecules in the last few decades. The synthesis and properties of functionalized 2,2'-bipyridyine- and 1,10-phenanthroline-based d(6) metal complexes, in particular, their introduction into different prevailing polymeric structures are highlighted. In the most part of the review metal complexes which have been attached as pendant groups on the polymer side chain are covered. Selected applications of the herein discussed metal-containing macromolecules are addressed, particularly, with respect to photogenerated electron/energy transfer processes. In order to enable a deeper understanding of the properties of the ligands and metal complexes, the fundamentals of selected photophysical processes will be discussed (223 references). PMID:22080248

  20. Characteristics of Anchor Tests.

    ERIC Educational Resources Information Center

    Chang, S. Tai; Bashaw, W. L.

    The purpose of this study was twofold: to investigate to what extent characteristics of anchor tests may affect precision of item calibration, and to estimate to what extent precision of item calibration may be affected by removal of persons whose response patterns deviate from those normally expected from the Rasch one-parameter logistic model.…

  1. Manipulating the Lateral Diffusion of Surface-Anchored EGF Demonstrates that Receptor Clustering Modulates Phosphorylation Levels

    PubMed Central

    Stabley, D.; Retterer, S.; Marshall, S.; Salaita, K.

    2013-01-01

    Upon activation, the epidermal growth factor (EGF) receptor becomes phosphorylated and triggers a vast signaling network that has profound effects on cell growth. The EGF receptor is observed to assemble into clusters after ligand binding and tyrosine kinase autophosphorylation, but the role of these assemblies in the receptor signaling pathway remains unclear. To address this question, we measured the phosphorylation of EGFR when the EGF ligand was anchored onto laterally mobile and immobile surfaces. We found that cells generated clusters of ligand-receptor complex on mobile EGF surfaces, and displayed a lower ratio of phosphorylated EGFR to EGF when compared to immobilized EGF that is unable to cluster. This result was verified by tuning the lateral assembly of ligand-receptor complexes on the surface of living cells using patterned supported lipid bilayers. Nanoscale metal lines fabricated into the supported membrane constrained lipid diffusion and EGF receptor assembly into micron and sub-micron scale corrals. Single cell analysis indicated that clustering impacts EGF receptor activation, and larger clusters (> 1 µm2) of ligand-receptor complex generated lower EGF receptor phosphorylation per ligand than smaller assemblies (< 1 µm2) in HCC1143 cells that were engaged to ligand-functionalized surfaces. We investigated the mechanism of EGFR clustering by treating cells with compounds that disrupt the cytoskeleton (Latrunculin-B), clathrin-mediated endocytosis (Pitstop2), and inhibit EGFR activation (Gefitinib). These results help elucidate the nature of large-scale EGFR clustering, thus underscoring the general significance of receptor spatial organization in tuning function. PMID:23416883

  2. High-dimensional assembly depending on polyoxoanion templates, metal ion coordination geometries, and a flexible bis(imidazole) ligand.

    PubMed

    Dong, Bao-xia; Peng, Jun; Gómez-García, Carlos J; Benmansour, Samia; Jia, Heng-qing; Hu, Ning-hai

    2007-07-23

    By introducing the flexible 1,1'-(1,4-butanediyl)bis(imidazole) (bbi) ligand into the polyoxovanadate system, five novel polyoxoanion-templated architectures based on [As(8)V(14)O(42)](4-) and [V(16)O(38)Cl](6-) building blocks were obtained: [M(bbi)(2)](2)[As(8)V(14)O(42)(H(2)O)] [M = Co (1), Ni (2), and Zn (3)], [Cu(bbi)](4)[As(8)V(14)O(42)(H(2)O)] (4), and [Cu(bbi)](6)[V(16)O(38)Cl] (5). Compounds 1-3 are isostructural, and they exhibit a binodal (4,6)-connected 2D structure with Schläfli symbol (3(4) x 4(2))(3(4) x 4(4) x 5(4) x 6(3))(2), in which the polyoxoanion induces a closed four-membered circuit of M(4)(bbi)(4). Compound 4 exhibits an interesting 3D framework constructed from tetradentate [As(8)V(14)O(42)](4-) cluster anions and cationic ladderlike double chains. There exists a bigger M(8)(bbi)(6)O(2) circuit in 4. The 3D extended structure of 5 is composed of heptadentate [V(16)O(38)Cl](6-) anions and flexural cationic chains; the latter consists of six Cu(bbi) segments arranged alternately. It presents the largest 24-membered circuit of M(24)(bbi)(24) so far observed made of bbi molecules and transition-metal cations. Investigation of their structural relations shows the important template role of the polyoxoanions and the synergetic interactions among the polyoxoanions, transition-metal ions, and flexible ligand in the assembly process. The magnetic properties of compounds 1-3 were also studied. PMID:17592834

  3. Synthesis, spectral and thermal studies of some transition metal mixed ligand complexes: Modeling of equilibrium composition and biological activity

    NASA Astrophysics Data System (ADS)

    Neelakantan, M. A.; Sundaram, M.; Nair, M. Sivasankaran

    2011-09-01

    Several mixed ligand Ni(II), Cu(II) and Zn(II) complexes of 2-amino-3-hydroxypyridine (AHP) and imidazoles viz., imidazole (him), benzimidazole (bim), histamine (hist) and L-histidine (his) have been synthesized and characterized by elemental and spectral (vibrational, electronic, 1H NMR and EPR) data as well as by magnetic moment values. On the basis of elemental analysis and molar conductance values, all the complexes can be formulated as [MAB]Cl except histidine complexes as MAB. Thermogravimetric studies reveal the presence of coordinated water molecules in most of the complexes. From the magnetic measurements and electronic spectral data, octahedral structure was proposed for Ni(II) and Cu(II)-AHP-his, tetrahedral for Cu(II)-AHP-him/bim/hist, but square planar for the Cu(II)-AHP complex. The g∥/ A∥ calculated supports tetrahedral environment around the Cu(II) in Cu(II)-AHP-him/bim/hist and distorted octahedral for Cu(II)-AHP-his complexes. The morphology of the reported metal complexes was investigated by scanning electron micrographs (SEM). The potentiometric study has been performed in aqueous solution at 37 °C and I = 0.15 mol dm -3 NaClO 4. MABH, MAB and MAB 2 species has been identified in the present systems. Proton dissociation constants of AHP and stability constants of metal complexes were determined using MINIQUAD-75. The most probable structure of the mixed ligand species is discussed based upon their stability constants. The in vitro biological activity of the complexes was tested against the Gram positive and Gram negative bacteria, fungus and yeast. The oxidative DNA cleavage studies of the complexes were performed using gel electrophoresis method. Cu(II) complexes have been found to promote DNA cleavage in presence of biological reductant such as ascorbate and oxidant like hydrogen peroxide.

  4. Di-maltol-polyamine ligands to form heterotrinuclear metal complexes: solid state, aqueous solution and magnetic characterization.

    PubMed

    Benelli, Cristiano; Borgogelli, Elisa; Formica, Mauro; Fusi, Vieri; Giorgi, Luca; Macedi, Eleonora; Micheloni, Mauro; Paoli, Paola; Rossi, Patrizia

    2013-04-28

    The binding properties of the two ligands (L) N,N'-bis[(3-hydroxy-4-pyron-2-yl)methyl]-N,N'-dimethylethylendiamine (Malten) and 4,10-bis[(3-hydroxy-4-pyron-2-yl)methyl]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane (Maltonis) towards M(II) transition metal ions (M(II) = Cu(II) for Malten and Co(II) for Maltonis, respectively), were investigated in aqueous solution. Each compound contains two 3-hydroxy-2-methyl-4-pyrone units (Maltol) symmetrically spaced by a different polyamine fragment. The formation of only mononuclear complexes was detected and the main species present in a wide range of pH is the neutral [M(II)(H-2L)] complex. This is able to stabilize one hard M(III) metal ion such as Gd(III) and Y(III), giving rise to the formation of new hetero-trinuclear complexes of M(II)-M(III)-M(II) sequence. The trinuclear species having the formula {M(III)[M(II)(H-2L)]2}(3+) (M(II) = Cu(II) and M(III) = Y(III) or Gd(III) for Malten and M(II) = Co(II) and M(III) = Gd(III) for Maltonis) are also formed in a wide range of pH, including pH = 7 and can be isolated in high yield as a perchlorate salt. The crystal structures of all the studied hetero-trinuclear species highlight that such systems are formed thanks to the synergy between the different stereochemical requirement of the transition metal (Cu(II) or Co(II)) and the different donor atoms set of the ligands which preorganize the maltol units for the binding of the hard M(III) metal, otherwise difficult to bind in water, through L/M(II)/M(III) self-assembling. The magnetic properties of the hetero-trinuclear spin systems were investigated; in the M(II)-Gd(III)-M(II) species, Gd(III) interacts with the two 3d ions of this class of compounds by similar coupling mechanism. PMID:23462930

  5. Metal-ligand Covalency of Iron Complexes from High-Resolution Resonant Inelastic X-ray Scattering

    PubMed Central

    Lundberg, Marcus; Kroll, Thomas; DeBeer, Serena; Bergmann, Uwe; Wilson, Samuel A.; Glatzel, Pieter; Nordlund, Dennis; Hedman, Britt; Hodgson, Keith O.; Solomon, Edward I.

    2013-01-01

    Data from Kα resonant inelastic X-ray scattering (RIXS) have been used to extract electronic structure information, i.e., the covalency of metal-ligand bonds, for four iron complexes using an experimentally based theoretical model. Kα RIXS involves resonant 1s → 3d excitation and detection of the 2p → 1s (Kα) emission. This two-photon process reaches similar final states as single-photon L-edge (2p → 3d) X-ray absorption spectroscopy (XAS), but involves only hard X-rays and can therefore be used to get high-resolution L-edge-like spectra for metal proteins, solution catalysts and their intermediates. To analyze the information content of Kα RIXS spectra, data have been collected for four characteristic σ-donor and π-backdonation complexes; ferrous tacn [FeII(tacn)2]Br2, ferrocyanide [FeII(CN)6]K4, ferric tacn [FeIII(tacn)2]Br3 and ferricyanide [FeIII(CN)6]K3. From these spectra metal-ligand covalencies can be extracted using a charge-transfer multiplet model, without previous information from the L-edge XAS experiment. A direct comparison of L-edge XAS and Kα RIXS spectra show that the latter reaches additional final states, e.g., when exciting into the eg (σ*) orbitals, and the splitting between final states of different symmetry provides an extra dimension that makes Kα RIXS a more sensitive probe of σ-bonding. Another key difference between L-edge XAS and Kα RIXS is the π-backbonding features in ferro- and ferricyanide that are significantly more intense in L-edge XAS compared to Kα RIXS. This shows that two methods are complimentary in assigning electronic structure. The Kα RIXS approach can thus be used as a stand-alone method, in combination with L-edge XAS for strongly covalent systems that are difficult to probe by UV/Vis spectroscopy, or as an extension to conventional absorption spectroscopy for a wide range of transition metal enzymes and catalysts. PMID:24131028

  6. A mechanistic insight into metal-cluster π-envelopment: a dual binding mode involving bent and planar ligand-conformers.

    PubMed

    Masai, Kohei; Shirato, Katsunori; Yamamoto, Koji; Kurashige, Yuki; Murahashi, Tetsuro

    2016-05-11

    Metal clusters are effectively stabilized by bridging π-coordination of planar π-conjugated unsaturated hydrocarbons. However, the mechanism of π-envelopment of a metal cluster has been elusive. By employing 1,2-bis(4-aryl-1,3-butadienyl)benzene as the π-conjugated ligand, we found that the π-envelopment of a Pd4 cluster proceeded in a stepwise manner, where the sp(2)-carbon ligands initially envelop the Pd4 cluster through a bent binding mode, and then isomerized to a thermodynamically more stable planar mode under mild heating or visible light irradiation. The involvement of a bent binding mode indicates the kinetically preferred coordination at the axial coordination site trans to a metal-metal bond. PMID:27093889

  7. Zinc ligands in the metal hyperaccumulator Thlaspi caerulescens as determined using X-ray absorption spectroscopy

    SciTech Connect

    Salt, D.E.; Prince, R.C.; Baker, A.J.M.; Raskin, I.; Pickering, I.J.

    1999-03-01

    Using the noninvasive technique of X-ray absorption spectroscopy (XAS), the authors have been able to determine the ligand environment of Zn in different tissues of the Zn-hyperaccumulator Thlaspi caerulescens. The majority of intracellular Zn in roots of T. caerulescens was found to be coordinated with histidine. In the xylem sap Zn was found to be transported mainly as the free hydrated Zn{sup 2+} cation with a smaller proportion coordinated with organic acids. In the shoots, Zn coordination occurred mainly via organic acids, with a smaller proportion present as the hydrated cation and coordinated with histidine and the cell wall. Their data suggest that histidine plays an important role in Zn homeostasis in the roots, whereas organic acids are involved in xylem transport and Zn storage in shoots.

  8. Cyclam glycoconjugates as lectin ligands and protective agents of metal-induced amyloid aggregation.

    PubMed

    Lanza, Valeria; D'Agata, Roberta; Iacono, Giuseppe; Bellia, Francesco; Spoto, Giuseppe; Vecchio, Graziella

    2015-12-01

    Transition metal ion complexes of a number of chelators have been widely investigated due to their biological properties. The sugar conjugation of metal complexes has resulted in improved properties of the systems, such as solubility and lectin recognition. In this paper, we report the synthesis, the characterization of new glucose and galactose conjugates of 1,4,8,11-tetraazacyclotetradecane (cyclam) and their Cu(II) complexes. The glycoconjugates were proved to be protective agents of metal-induced amyloid aggregation. The binding constants of the galactose conjugate KA1=(3.07±0.16)×10(7) and KA2=(2.13±0.04)×10(7)M(-1) with the lectin Ricinus communis agglutinin (RCA120) as a model of galactose-specific human lectin were obtained with surface plasmon resonance. PMID:26112151

  9. Synthesis of N₄ donor macrocyclic Schiff base ligands and their Ru (II), Pd (II), Pt (II) metal complexes for biological studies and catalytic oxidation of didanosine in pharmaceuticals.

    PubMed

    Ravi Krishna, E; Muralidhar Reddy, P; Sarangapani, M; Hanmanthu, G; Geeta, B; Shoba Rani, K; Ravinder, V

    2012-11-01

    A series of tetraaza (N(4) donor) macrocyclic ligands (L(1)-L(4)) were derived from the condensation of o-phthalaldehyde (OPA) with some substituted aromatic amines/azide, and subsequently used to synthesize the metal complexes of Ru(II), Pd(II) and Pt(II). The structures of macrocyclic ligands and their metal complexes were characterized by elemental analyses, IR, (1)H &(13)C NMR, mass and electronic spectroscopy, thermal, magnetic and conductance measurements. Both the ligands and their complexes were screened for their antibacterial activities against Gram positive and Gram negative bacteria by MIC method. Besides, these macrocyclic complexes were investigated as catalysts in the oxidation of pharmaceutical drug didanosine. The oxidized products were further treated with sulphanilic acid to develop the colored products to determine by spectrophotometrically. The current oxidation method is an environmentally friendly, simple to set-up, requires short reaction time, produces high yields and does not require co-oxidant. PMID:22750687

  10. Identification of nonprotein ligands to the metal ions bound to glutamine synthetase

    SciTech Connect

    Eads, C.D.; LoBrutto, R.; Kumar, A.; Villafranca, J.J.

    1988-01-12

    Electron paramagnetic resonance (EPR) was used to study the environment of Mn/sup 2 +/ bound to the tight (n/sub 1/) metal ion binding site of glutamine synthetase in the presence of analogues of the tetrahedral adduct, L-methionine (S)-sulfoximine (Met(O)(NM)-S) and L-methionine (R)-sulfoximine (Met(O)(NH)-R). The Mn/sup 2 +/ EPR spectrum in the presence of Met(O)(NH)-S is identical with the previously published spectrum obtained from a mixture of isomers and is characteristic of a highly octahedral metal ion environment with a small zero field splitting. The presence of Met(O)(NH)-R produces and EPR spectrum that appears characteristic of a more distorted metal ion environment, with a larger zero field splitting. These data demonstrate that the two isomers interact differently with the enzyme-bound Mn/sup 2 +/. Broadening of the Mn/sup 2 +/ EPR spectrum in the presence of Met(O)NH) is observed in /sup 17/O-enriched water due to superhyperfine coupling of water to the metal ion. Superhyperfine coupling due to the /sup 14/N nucleus of the imine nitrogen of the sulfoximine moiety of Met(O)(NH)-S but not of Met-(O)(NH)-R has been detected by electron spin-echo envelope modulation spectroscopy. Two intense peaks are evident in the presence of Met(O)(NH)-S with frequencies at 1.7 and 3.3 MHz. These peaks are absent when (/sup 15/N)imine-labeled Met(O)(NH) is used, indicating the presence of the sulfoximine nitrogen of Met(O)(NH)-S in the inner coordination sphere of the metal ion. Taken together, these results suggest a model of the active site in which the metal ion is directly involved in the catalytic mechanism, serving to stabilize the tetrahedral adduct formed from ammonia and ..gamma..-glutamyl phosphate.

  11. Blind-Anchor-Nut-Installation Fixture (BANIF)

    NASA Technical Reports Server (NTRS)

    Willey, Norman F., Jr.; Linker, James F.

    1994-01-01

    Blind-anchor-nut-installation fixture, BANIF, developed for replacing or installing anchor nuts in blind holes or other inaccessible places. Attachment of anchor nut to BANIF enables placement of anchor nut on blind side of component.

  12. Synthesis and Reactivity of Group 4 Metal Benzyl Complexes Supported by Carbazolide-Based PNP Pincer Ligands.

    PubMed

    Plundrich, Gudrun T; Wadepohl, Hubert; Gade, Lutz H

    2016-01-01

    This study focuses on the viability of the carbazole-based Cbzdiphos PNP pincer ligand as a stabilizing element for group 4 metal complexes, and both the diphenylphosphino- and di-isopropylphosphino-substituted Cbzdiphos protioligands 1(Ph)H and 1(iPr)H were used. Treatment of the lithiated protioligands with the corresponding chlorido precursor compounds of the metals (titanium, zirconium, and hafnium) afforded the trichlorido complexes [(Cbzdiphos(iPr))MCl3] 2(iPr)M and [(Cbzdiphos(Ph))MCl3] 2(Ph)M (M = Ti, Zr, Hf), which were converted to the corresponding iodido complexes [(Cbzdiphos(iPr))MI3] 3(iPr)M and [(Cbzdiphos(Ph))MI3] 3(Ph)M (M = Ti, Zr, Hf) by reaction with an excess of trimethylsilyl iodide. Reaction of 2(iPr)Ti and 3(Ph)Ti with 1 equiv of dibenzyl magnesium tetrahydrofuran adduct led to the formation of the alkylidene complexes 4(iPr)Ti and 5(Ph)Ti, respectively, while the zirconium and hafnium complexes 2(iPr)Zr and 3(Ph)Zr/Hf formed the cyclometalated monoalkyl compounds [(Cbzdiphos(iPr)-CH)ZrBnCl] 6(iPr)Zr as well as [(Cbzdiphos(Ph)-CH)MBnX] 6(Ph)Hf (X = Cl) and 7(Ph)Zr/Hf (X = I) under analogous reaction conditions. On the other hand, stirring 2(Ph)Zr with 0.25 equiv of tetrabenzyl zirconium afforded [(Cbzdiphos(Ph))ZrBnCl2] (8(Ph)Zr), which contained the PNP ligand intact, while its alkylation with benzyl potassium led to the formation of the cyclometalated monobenzyl complex [(Cbzdiphos(Ph)-CH)ZrBnCl] (6(Ph)Zr). The remaining coordination site occupied by the halogenido ligand in the cyclometalated monobenzyl complexes [(Cbzdiphos-CH)MBnX] 6(iPr)Zr, 6(Ph)Zr/Hf, and 7(Ph)Zr/Hf was readily benzylated by treatment with benzyl potassium to afford the cyclometalated dibenzyl complexes [(Cbzdiphos-CH)MBn2] 9(iPr)Zr and 9(Ph)Zr/Hf. Further reaction of 9(Ph)Zr with an excess of benzyl potassium led to the formation of the anionic tribenzyl zirconium ate complex [(Cbzdiphos-CH)MBn3]K (10(Ph)Zr). Upon heating a solution of 8(Ph)Zr in the presence of 1 mol equiv of trimethyl phosphine, one of the ligand methylene groups was deprotonated, yielding the cyclometalated complex [(Cbzdiphos(Ph)-CH)ZrCl2(PMe3)] 11(Ph)Zr. Finally, reaction of 7(Ph)Zr with methylene triphenylphosphorane produced the ortho-metalated product [(Cbzdiphos(Ph)-CH)Zr(o-C6H4PPh2CH2)I] (12(Ph)Zr), which is characterized by a slightly puckered five-membered Zr-C(48)-P(3)-C(49)-C(50) metallacycle. PMID:26684178

  13. Structural, spectral and biological studies of binuclear tetradentate metal complexes of N 3O Schiff base ligand synthesized from 4,6-diacetylresorcinol and diethylenetriamine

    NASA Astrophysics Data System (ADS)

    Emara, Adel A. A.

    2010-09-01

    The binuclear Schiff base, H 2L, ligand was synthesized by reaction of 4,6-diacetylresorcinol with diethylenetriamine in the molar ratio 1:2. The coordination behavior of the H 2L towards Cu(II), Ni(II), Co(II), Zn(II), Fe(III), Cr(III), VO(IV) and UO 2(VI) ions has been investigated. The elemental analyses, magnetic moments, thermal studies and IR, electronic, 1H NMR, ESR and mass spectra were used to characterize the isolated ligand and its metal complexes. The ligand acts as dibasic with two N 3O-tetradentate sites and can coordinate with two metal ions to form binuclear complexes. The bonding sites are the nitrogen atoms of the azomethine and amine groups and the oxygen atoms of the phenolic groups. The metal complexes exhibit either square planar, tetrahedral, square pyramid or octahedral structures. The Schiff base ligand and its metal complexes were tested against four pathogenic bacteria ( Staphylococcus aureus and Streptococcus pyogenes) as Gram-positive bacteria, and ( Pseudomonas fluorescens and Pseudomonas phaseolicola) as Gram-negative bacteria and two pathogenic fungi ( Fusarium oxysporum and Aspergillus fumigatus) to assess their antimicrobial properties. Most of the complexes exhibit mild antibacterial and antifungal activities against these organisms.

  14. Structural, spectral and biological studies of binuclear tetradentate metal complexes of N3O Schiff base ligand synthesized from 4,6-diacetylresorcinol and diethylenetriamine.

    PubMed

    Emara, Adel A A

    2010-09-15

    The binuclear Schiff base, H2L, ligand was synthesized by reaction of 4,6-diacetylresorcinol with diethylenetriamine in the molar ratio 1:2. The coordination behavior of the H2L towards Cu(II), Ni(II), Co(II), Zn(II), Fe(III), Cr(III), VO(IV) and UO2(VI) ions has been investigated. The elemental analyses, magnetic moments, thermal studies and IR, electronic, 1H NMR, ESR and mass spectra were used to characterize the isolated ligand and its metal complexes. The ligand acts as dibasic with two N3O-tetradentate sites and can coordinate with two metal ions to form binuclear complexes. The bonding sites are the nitrogen atoms of the azomethine and amine groups and the oxygen atoms of the phenolic groups. The metal complexes exhibit either square planar, tetrahedral, square pyramid or octahedral structures. The Schiff base ligand and its metal complexes were tested against four pathogenic bacteria (Staphylococcus aureus and Streptococcus pyogenes) as Gram-positive bacteria, and (Pseudomonas fluorescens and Pseudomonas phaseolicola) as Gram-negative bacteria and two pathogenic fungi (Fusarium oxysporum and Aspergillus fumigatus) to assess their antimicrobial properties. Most of the complexes exhibit mild antibacterial and antifungal activities against these organisms. PMID:20627808

  15. YTTRIUM-89 NMR: A POSSIBLE SPIN RELAXATION PROBE FOR STUDYING METAL ION INTERACTIONS WITH ORGANIC LIGANDS

    EPA Science Inventory

    The spin-lattice relaxation mechanisms for aqueous and dimethyl sulfoxide solutions of Y(NO3)3 have been found to be mainly spin-rotation and dipolar relaxation with solvent protons, unlike most heavy spin=1/2 metal ions which are relaxed mainly by spin-rotation and chemical shif...

  16. Heterobimetallic metal-complex assemblies constructed from the flexible arm-like ligand 1,1'-bis[(3-pyridylamino)carbonyl]ferrocene: structural versatility in the solid state.

    PubMed

    Wei, Kai-Ju; Ni, Jia; Liu, Yangzhong

    2010-02-15

    The bidentate ferrocenyl sandwich molecule 1,1'-bis[(3-pyridylamino)carbonyl]ferrocene (3-BPFA) has been employed as an organometallic ligand in reactions with a series of transition metal salts to construct heterobimetallic architectures. X-ray crystallographic characterization reveals that the crystal packing of free ligand 3-BPFA induces spontaneous resolution of helical chains via intermolecular hydrogen bonds. By combining the flexibility from the arm-like molecule (3-BPFA) with the variation of the coordination property from different metal ions and/or the different counteranions, five different types of architectures are prepared: one octahedral coordination cage (copper(II) complex 1); two discrete pseudocapsules for combination of chlorine anions (nickel(II) complex 2 and cobalt(II) complex 3); two dimers with metal-metal interactions (silver(I) complexes 4 and 5); one macrocyclic complex (mercury(II) complex 6); and five two-dimensional mixed-metal-organic frameworks (M'-MOFs) (zinc(II), cadmium(II), and mercury(II) complexes 7-11). The structures of all complexes are characterized in detail by IR, elementary analysis, and single-crystal X-ray diffraction analysis. The factors inducing the structure variation among the complexes are discussed by taking account of the coordination geometry of different metal ions, the span angle between the two "arms", and the coordination mode of the 3-BPFA ligand. PMID:20095640

  17. Enhancing gas adsorption and separation capacity through ligand functionalization of microporous metal-organic framework structures.

    PubMed

    Zhao, Yonggang; Wu, Haohan; Emge, Thomas J; Gong, Qihan; Nijem, Nour; Chabal, Yves J; Kong, Lingzhu; Langreth, David C; Liu, Hui; Zeng, Heping; Li, Jing

    2011-04-26

    Hydroxyl- and amino- functionalized [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O leads to two new structures, [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O (BDC=terephthalic acid, TED=triethylenediamine, BDC-OH=2-hydroxylterephthalic acid, BDC-NH(2)=2-aminoterephthalic acid). Single-crystal X-ray diffraction and powder X-ray diffraction studies confirmed that the structures of both functionalized compounds are very similar to that of their parent structure. Compound [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O can be considered a 3D porous structure with three interlacing 1D channels, whereas both [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O contain only 1D open channels as a result of functionalization of the BDC ligand by the OH and NH(2) groups. A notable decrease in surface area and pore size is thus observed in both compounds. Consequently, [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O takes up the highest amount of H(2) at low temperatures. Interestingly, however, both [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O show significant enhancement in CO(2) uptake at room temperature, suggesting that the strong interactions between CO(2) and the functionalized ligands, indicating that surface chemistry, rather than porosity, plays a more important role in CO(2) adsorption. A comparison of single-component CO(2), CH(4), CO, N(2), and O(2) adsorption isotherms demonstrates that the adsorption selectivity of CO(2) over other small gases is considerably enhanced through functionalization of the frameworks. Infrared absorption spectroscopic measurements and theoretical calculations are also carried out to assess the effect of functional groups on CO(2) and H(2) adsorption potentials. PMID:21433121

  18. Three coordination polymers based on different carboxylates, metals and a tri(4-imidazolylphenyl)amine ligand

    NASA Astrophysics Data System (ADS)

    Wu, Hua; Shi, Chenjie; Zhao, Yanqing; Jiang, Yutong; Tao, Yuehong

    2015-04-01

    In this paper, three new coordination complexes based on a flexible tri(4-imidazolylphenyl)amine (Tipa) ligand, namely [Co(Tipa)(L1)2]·H2O (1), [Zn2(Tipa)(L1)4(H2O)]·2H2O (2) and [Mn(Tipa)(L2)]·2H2O (3), where HL1 = benzoic acid H2L2 = 5-OH-1,3-benzenedicarboxylic acid and Tipa = tri(4-imidazolylphenyl)amine, have been synthesized under the hydrothermal condition and characterized by single-crystal X-ray diffraction, elemental analysis and IR spectra. Compound 1 exhibits a 1D ladder chain with the benzoic anions hanging on the two sides of the chain. For compound 2, it shows a fascinating 1D zigzag chain. Compound 3 displays (3,5)-connected (42·6)(42·67·8) topology, where the identical 2D networks entangle in highly rare parallel fashions to give a fascinating 2D → 3D framework with polycatenation and polyrotaxane characters. Moreover, the photoluminescent properties for the compounds 2 and 3 were also investigated.

  19. Enhanced association for C70 over C60 with a metal complex with corannulene derivate ligands.

    PubMed

    Álvarez, Celedonio M; García-Escudero, Luis A; García-Rodríguez, Raúl; Martín-Álvarez, Jose M; Miguel, Daniel; Rayón, Víctor M

    2014-11-14

    The geometry imposed by the coordination sphere around the metal, together with the choice of the "arms" can be advantageously used to build corannulene-based molecular tweezers, which show great affinities for C60 and C70, as revealed by NMR titration experiments, mass spectroscopy, DFT calculations and the single crystal X-ray structural analysis of the compound C60 ⊂1. PMID:25181755

  20. A high voltage organic-inorganic hybrid photovoltaic cell sensitized with metal-ligand interfacial complexes.

    PubMed

    Ishii, Ayumi; Miyasaka, Tsutomu

    2012-10-11

    A thin solid-state photovoltaic cell of organic-inorganic hetero junctions was fabricated by forming a dye-metal charge-transfer complex as the sensitizer monolayer at the interface of crystalline state organic and inorganic semiconductors. The organic-inorganic hybrid thin-film photocell generates a high photovoltage of 1.2 V, yielding an energy conversion efficiency of up to 1.5%. PMID:22932690

  1. Cluster synthesis via ligand-arrested solid growth: triethylphosphine-capped fragments of binary metal chalcogenides.

    PubMed

    Crawford, Nathan R M; Hee, Allan G; Long, Jeffrey R

    2002-12-18

    A new and potentially highly generalizable technique for synthesizing molecular fragments of binary solids is demonstrated through application to selected transition metal chalcogenides. Employing a metal atom reactor, the solids are evaporated with a tungsten heating boat, and the resulting vapor is co-condensed with triethylphosphine. Major cluster products identified from a survey of first-row transition metal sulfides include the known species Cr6S8(PEt3)6, Co6S8(PEt3)6, and Cu12S6(PEt3)8, as well as the unprecedented species Fe4S4(PBun3)4, Ni4S4(PEt3)8, and Cu6S4(PEt3)4. Reactions utilizing Cu2Se resulted in the much larger clusters Cu26Se13(PEt3)14 and Cu70Se35(PEt3)21. The core of the former has a Th-symmetry structure featuring a body-centered icosahedron of Se2- anions, while the latter adopts a triangular structure based on three hexagonal closest packed layers of Se2- anions. In both cases, the Cu+ cations occupy distorted tetrahedral or trigonal planar sites similar to those encountered in Cu2Se; however, emergence of the face-centered cubic anion lattice of the bulk solid is not yet apparent at these cluster sizes. PMID:12475314

  2. Mixed ligand complexation of some transition metal ions in solution and solid state: spectral characterization, antimicrobial, antioxidant, DNA cleavage activities and molecular modeling.

    PubMed

    Shobana, Sutha; Dharmaraja, Jeyaprakash; Selvaraj, Shanmugaperumal

    2013-04-15

    Equilibrium studies of Ni(II), Cu(II) and Zn(II) mixed ligand complexes involving a primary ligand 5-fluorouracil (5-FU; A) and imidazoles viz., imidazole (him), benzimidazole (bim), histamine (hist) and L-histidine (his) as co-ligands(B) were carried out pH-metrically in aqueous medium at 310±0.1K with I=0.15 M (NaClO4). In solution state, the stoichiometry of MABH, MAB and MAB2 species have been detected. The primary ligand(A) binds the central M(II) ions in a monodentate manner whereas him, bim, hist and his co-ligands(B) bind in mono, mono, bi and tridentate modes respectively. The calculated ΔlogK, logX and logX' values indicate higher stability of the mixed ligand complexes in comparison to binary species. Stability of the mixed ligand complex equilibria follows the Irving-Williams order of stability. In vitro biological evaluations of the free ligand(A) and their metal complexes by well diffusion technique show moderate activities against common bacterial and fungal strains. Oxidative cleavage interaction of ligand(A) and their copper complexes with CT DNA is also studied by gel electrophoresis method in the presence of oxidant. In vitro antioxidant evaluations of the primary ligand(A), CuA and CuAB complexes by DPPH free radical scavenging model were carried out. In solid, the MAB type of M(II)5-FU(A)his(B) complexes were isolated and characterized by various physico-chemical and spectral techniques. Both the magnetic susceptibility and electronic spectral analysis suggest distorted octahedral geometry. Thermal studies on the synthesized mixed ligand complexes show loss of coordinated water molecule in the first step followed by decomposition of the organic residues subsequently. XRD and SEM analysis suggest that the microcrystalline nature and homogeneous morphology of MAB complexes. Further, the 3D molecular modeling and analysis for the mixed ligand MAB complexes have also been carried out. PMID:23416916

  3. Mixed ligand complexation of some transition metal ions in solution and solid state: Spectral characterization, antimicrobial, antioxidant, DNA cleavage activities and molecular modeling

    NASA Astrophysics Data System (ADS)

    Shobana, Sutha; Dharmaraja, Jeyaprakash; Selvaraj, Shanmugaperumal

    2013-04-01

    Equilibrium studies of Ni(II), Cu(II) and Zn(II) mixed ligand complexes involving a primary ligand 5-fluorouracil (5-FU; A) and imidazoles viz., imidazole (him), benzimidazole (bim), histamine (hist) and L-histidine (his) as co-ligands(B) were carried out pH-metrically in aqueous medium at 310 ± 0.1 K with I = 0.15 M (NaClO4). In solution state, the stoichiometry of MABH, MAB and MAB2 species have been detected. The primary ligand(A) binds the central M(II) ions in a monodentate manner whereas him, bim, hist and his co-ligands(B) bind in mono, mono, bi and tridentate modes respectively. The calculated Δ log K, log X and log X' values indicate higher stability of the mixed ligand complexes in comparison to binary species. Stability of the mixed ligand complex equilibria follows the Irving-Williams order of stability. In vitro biological evaluations of the free ligand(A) and their metal complexes by well diffusion technique show moderate activities against common bacterial and fungal strains. Oxidative cleavage interaction of ligand(A) and their copper complexes with CT DNA is also studied by gel electrophoresis method in the presence of oxidant. In vitro antioxidant evaluations of the primary ligand(A), CuA and CuAB complexes by DPPH free radical scavenging model were carried out. In solid, the MAB type of M(II)sbnd 5-FU(A)sbnd his(B) complexes were isolated and characterized by various physico-chemical and spectral techniques. Both the magnetic susceptibility and electronic spectral analysis suggest distorted octahedral geometry. Thermal studies on the synthesized mixed ligand complexes show loss of coordinated water molecule in the first step followed by decomposition of the organic residues subsequently. XRD and SEM analysis suggest that the microcrystalline nature and homogeneous morphology of MAB complexes. Further, the 3D molecular modeling and analysis for the mixed ligand MAB complexes have also been carried out.

  4. Polymer pendant ligand chemistry. 3. A biomimetic approach to selective metal ion removal and recovery from aqueous solution with polymer-supported sulfonated catechol and linear catechol amide ligands

    SciTech Connect

    Huang, Song-Ping; Li, Wei; Franz, K.J.; Albright, R.L.; Fish, R.H.

    1995-05-24

    The design of organic ligands to selectively remove and recover metal ions from aqueous solution is a new and important area of environmental inorganic chemistry. One approach to designing organic ligands for these purposes is to use biological systems as examples for selective metal ion complexation. Thus, the authors report results on the synthesis of several biomimetically important polymer-supported, sulfonated catechol (PS-CATS), sulfonated bis(catechol) linear amide (PS-2-6-LICAMS), and sulfonated 3.3-linear tris(catechol) amide (PS-3,3-LICAMS) ligands that are chemically bonded to modified 6% cross-linked macroporous polystyrene-divinylbenzene beads (PS-DVB) for selective removal and recovery of environmentally and economically important metal ions from aqueous solution, as a function of pH. The Fe{sup 3+} ion selectivity was dramatically shown for PS-CATS, PS-2-6-LICAMS and PS-3,3-LICAMS polymer beads in competition with a similar concentration of Cu{sup 2+}, Zn{sup 2+}, Mn{sup 2+}, Ni{sup 2+}, Mg{sup 2+}, Al{sup 3+}, and Cr{sup 3+} ions at pH 1-3, while metal ion selectivity could be changed at higher pH values in the absence of Fe{sup 3+} (for example, Hg{sup 2+} at pH 3). Rates of removal and recovery of the Fe{sup 3+} ion with the PS-CATS, PS-2-6LICAMS and PS-3,3-LICAMS polymer beads were also studied as well as relative equilibrium selectivity coefficient (K{sub m}) values for all metal competition studies.

  5. Functional Analysis of the Citrate Activator CitO from Enterococcus faecalis Implicates a Divalent Metal in Ligand Binding.

    PubMed

    Blancato, Víctor S; Pagliai, Fernando A; Magni, Christian; Gonzalez, Claudio F; Lorca, Graciela L

    2016-01-01

    The regulator of citrate metabolism, CitO, from Enterococcus faecalis belongs to the FCD family within the GntR superfamily. In the presence of citrate, CitO binds to cis-acting sequences located upstream of the cit promoters inducing the expression of genes involved in citrate utilization. The quantification of the molecular binding affinities, performed by isothermal titration calorimetry (ITC), indicated that CitO has a high affinity for citrate (K D = 1.2 ± 0.2 μM), while it did not recognize other metabolic intermediates. Based on a structural model of CitO where a putative small molecule and a metal binding site were identified, it was hypothesized that the metal ion is required for citrate binding. In agreement with this model, citrate binding to CitO sharply decreased when the protein was incubated with EDTA. This effect was reverted by the addition of Ni(2+), and Zn(2+) to a lesser extent. Structure-based site-directed mutagenesis was conducted and it was found that changes to alanine in residues Arg97 and His191 resulted in decreased binding affinities for citrate, as determined by EMSA and ITC. Further assays using lacZ fusions confirmed that these residues in CitO are involved in sensing citrate in vivo. These results indicate that the molecular modifications induced by a ligand and a metal binding in the C-terminal domain of CitO are required for optimal DNA binding activity, and consequently, transcriptional activation. PMID:26903980

  6. Functional Analysis of the Citrate Activator CitO from Enterococcus faecalis Implicates a Divalent Metal in Ligand Binding

    PubMed Central

    Blancato, Víctor S.; Pagliai, Fernando A.; Magni, Christian; Gonzalez, Claudio F.; Lorca, Graciela L.

    2016-01-01

    The regulator of citrate metabolism, CitO, from Enterococcus faecalis belongs to the FCD family within the GntR superfamily. In the presence of citrate, CitO binds to cis-acting sequences located upstream of the cit promoters inducing the expression of genes involved in citrate utilization. The quantification of the molecular binding affinities, performed by isothermal titration calorimetry (ITC), indicated that CitO has a high affinity for citrate (KD = 1.2 ± 0.2 μM), while it did not recognize other metabolic intermediates. Based on a structural model of CitO where a putative small molecule and a metal binding site were identified, it was hypothesized that the metal ion is required for citrate binding. In agreement with this model, citrate binding to CitO sharply decreased when the protein was incubated with EDTA. This effect was reverted by the addition of Ni2+, and Zn2+ to a lesser extent. Structure-based site-directed mutagenesis was conducted and it was found that changes to alanine in residues Arg97 and His191 resulted in decreased binding affinities for citrate, as determined by EMSA and ITC. Further assays using lacZ fusions confirmed that these residues in CitO are involved in sensing citrate in vivo. These results indicate that the molecular modifications induced by a ligand and a metal binding in the C-terminal domain of CitO are required for optimal DNA binding activity, and consequently, transcriptional activation. PMID:26903980

  7. Dye-ligand and immobilized metal ion interaction chromatography for the purification of enzymes of prenyl pyrophosphate metabolism.

    PubMed

    Lanznaster, N; Croteau, R

    1991-02-01

    Dye-ligand and immobilized metal ion interaction chromatography were shown to be efficient techniques for the rapid batchwise fractionation, from crude plant extracts, of a series of enzymes of prenyl pyrophosphate metabolism. Isopentenyl pyrophosphate isomerase, two prenyltransferases, and a number of terpene cyclases (synthases) were readily adsorbed to Matrex Gel Red A (a dimeric triazine dye coupled to cross-linked agarose beads), and desorbed in good yield with relatively high concentrations of KCl and increasing pH. Although all of these enzymes exhibit the common feature of employing a pyrophosphorylated substrate, selective elution could not be achieved with substrate or substrate analogues bearing a pyrophosphate function. Nor could the strong binding of these enzymes to triazine dyes be attributed solely to metal ion interactions or to hydrophobic effects. In a similar way, the isomerase, the prenyltransferases, and all of the terpene cyclases bound to a column of iminodiacetate-immobilized Ni(II) and were desorbed in relatively high fold purity with 15 mM imidazole. Although all of these enzymes bear accessible histidine residues, the interactions with the chelated metal ion were not sufficiently different to permit selective enzyme desorbtion by imidazole gradient elution. However, the use of columns charged with Zn(II) or Co(II) did allow some separation of the different cyclase and transferase types. While empirical in nature, these techniques offer simple, effective, and high-capacity methods for the preliminary concentration and purification of a group of enzymes that utilize prenyl pyrophosphate intermediates of isoprenoid biosynthesis. PMID:1821775

  8. Multiply bonded metal(II) acetate (rhodium, ruthenium, and molybdenum) complexes with the trans-1,2-bis(N-methylimidazol-2-yl)ethylene ligand.

    PubMed

    Fritsch, Nico; Wick, Christian R; Waidmann, Thomas; Dral, Pavlo O; Tucher, Johannes; Heinemann, Frank W; Shubina, Tatyana E; Clark, Timothy; Burzlaff, Nicolai

    2014-12-01

    The synthesis and structural characterization of new coordination polymers with the N,N-donor ligand trans-1,2-bis(N-methylimidazol-2-yl)ethylene (trans-bie) are reported. It was found that the acetate-bridged paddlewheel metal(II) complexes [M2(O2CCH3)4(trans-bie)]n with M = Rh, Ru, Mo, and Cr are linked by the trans-bie ligand to give a one-dimensional alternating chain. The metal-metal multiple bonds were analyzed with density functional theory and CASSCF/CASPT2 calculations (bond orders: Rh, 0.8; Ru, 1.7; Mo, 3.3). PMID:25393757

  9. Anchoring groups for dye-sensitized solar cells.

    PubMed

    Zhang, Lei; Cole, Jacqueline M

    2015-02-18

    The dyes in dye-sensitized solar cells (DSSCs) require one or more chemical substituents that can act as an anchor, enabling their adsorption onto a metal oxide substrate. This adsorption provides a means for electron injection, which is the process that initiates the electrical circuit in a DSSC. Understanding the structure of various DSSC anchors and the search for new anchors are critical factors for the development of improved DSSCs. Traditionally, carboxylic acid and cyanoacrylic acid groups are employed as dye anchors in DSSCs. In recent years, novel anchor groups have emerged, which make a larger pool of materials available for DSSC dyes, and their associated physical and chemical characteristics offer interesting effects at the interface between dye and metal oxide. This review focuses especially on the structural aspects of these novel dye anchors for TiO2-based DSSCs, including pyridine, phosphonic acid, tetracyanate, perylene dicarboxylic acid anhydride, 2-hydroxylbenzonitrile, 8-hydroxylquinoline, pyridine-N-oxide, hydroxylpyridium, catechol, hydroxamate, sulfonic acid, acetylacetanate, boronic acid, nitro, tetrazole, rhodanine, and salicylic acid substituents. We anticipate that further exploration and understanding of these new types of anchoring groups for TiO2 substrates will not only contribute to the development of advanced DSSCs, but also of quantum dot-sensitized solar cells, water splitting systems, and other self-assembled monolayer-based technologies. PMID:25594514

  10. Sliding tethered ligands add topological interactions to the toolbox of ligand-receptor design.

    PubMed

    Bauer, Martin; Kékicheff, Patrick; Iss, Jean; Fajolles, Christophe; Charitat, Thierry; Daillant, Jean; Marques, Carlos M

    2015-01-01

    Adhesion in the biological realm is mediated by specific lock-and-key interactions between ligand-receptor pairs. These complementary moieties are ubiquitously anchored to substrates by tethers that control the interaction range and the mobility of the ligands and receptors, thus tuning the kinetics and strength of the binding events. Here we add sliding anchoring to the toolbox of ligand-receptor design by developing a family of tethered ligands for which the spacer can slide at the anchoring point. Our results show that this additional sliding degree of freedom changes the nature of the adhesive contact by extending the spatial range over which binding may sustain a significant force. By introducing sliding tethered ligands with self-regulating length, this work paves the way for the development of versatile and reusable bio-adhesive substrates with potential applications for drug delivery and tissue engineering. PMID:26350224

  11. Sliding tethered ligands add topological interactions to the toolbox of ligand-receptor design

    NASA Astrophysics Data System (ADS)

    Bauer, Martin; Kékicheff, Patrick; Iss, Jean; Fajolles, Christophe; Charitat, Thierry; Daillant, Jean; Marques, Carlos M.

    2015-09-01

    Adhesion in the biological realm is mediated by specific lock-and-key interactions between ligand-receptor pairs. These complementary moieties are ubiquitously anchored to substrates by tethers that control the interaction range and the mobility of the ligands and receptors, thus tuning the kinetics and strength of the binding events. Here we add sliding anchoring to the toolbox of ligand-receptor design by developing a family of tethered ligands for which the spacer can slide at the anchoring point. Our results show that this additional sliding degree of freedom changes the nature of the adhesive contact by extending the spatial range over which binding may sustain a significant force. By introducing sliding tethered ligands with self-regulating length, this work paves the way for the development of versatile and reusable bio-adhesive substrates with potential applications for drug delivery and tissue engineering.

  12. A series of transition and non-transition metal complexes from a N 4O 2 hexadentate Schiff base ligand: Synthesis, spectroscopic characterization and efficient antimicrobial activities

    NASA Astrophysics Data System (ADS)

    Sarkar, Saikat; Dey, Kamalendu

    2010-11-01

    Some transition and non-transition metal complexes of the hexadentate N 4O 2 donor Schiff base ligand 1,8- N-bis(3-carboxy)disalicylidene-3,6-diazaoctane-1,8-diamine, abbreviated to H 4fsatrien, have been synthesized. All the 14 metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic (UV-Vis, IR, NMR, ESR) data. The analytical data helped to elucidate the structures of the metal complexes. The Schiff base, H 4fsatrien, is found to act as a dibasic hexadentate ligand using N 2N 2O 2 donor set of atoms (leaving the COOH group uncoordinated) leading to an octahedral geometry for the complexes around all the metal ions except VO 2+ and UO 22+. However, surprisingly the same ligand functions as a neutral hexadentate and neutral tetradentate one towards UO 22+ and VO 2+, respectively. In case of divalent metal complexes they have the general formula [M(H 2fsatrien)] (where M stands for Cu, Co, Hg and Zn); for trivalent metal complexes it is [M(H 2fsatrien)]X· nH 2O (where M stands for Cr, Mn, Fe, Co and X stands for CH 3COO, Cl, NO 3, ClO 4) and for the complexes of VO 2+ and UO 22+, [M(H 4fsatrien)]Y (where M = VO and Y = SO 4; M = UO 2 and Y = 2 NO 3). The Schiff base ligand and most of the complexes have been screened in vitro to judge their antibacterial ( Escherichia coli and Staphylococcus aureus) and antifungal ( Aspergillus niger and Pencillium chrysogenum) activities.

  13. A Coordination Chemistry Approach for Lithium-Ion Batteries: The Coexistence of Metal and Ligand Redox Activities in a One-Dimensional Metal-Organic Material.

    PubMed

    Li, Gaihua; Yang, Hao; Li, Fengcai; Cheng, Fangyi; Shi, Wei; Chen, Jun; Cheng, Peng

    2016-05-16

    We demonstrate herein the use of a one-dimensional metal-organic material as a new type of electrode material for lithium-ion batteries (LIBs) in place of the classic porous three-dimensional materials, which are subject to the size of the channel for lithium-ion diffusion and blocking of the windows of the framework by organic solvents during the charging and discharging processes. Introducing a one-dimensional coordination compound can keep organic active substances insoluble in the electrolyte during the charging and discharging processes, providing a facile and general new system for further studies. The results show that both the aromatic ligand and the metal center can participate in lithium storage simultaneously, illustrating a new energy storage mechanism that has been well-characterized by X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy, and cyclic voltammetry. In addition, the fact that the one-dimensional chains are linked by weak hydrogen bonds rather than strong π-π stacking interactions or covalent bonds is beneficial for the release of capacity entirely without the negative effect of burying the active sites. PMID:27120483

  14. Polymer-supported sulfonated catechol and linear catechol amide ligands and their use in selective metal ion removal recovery from aqueous solutions

    DOEpatents

    Fish, Richard H.

    1998-01-01

    The present invention concerns the synthesis of several biomimetically important polymer-supported, sulfonated catechol (PS-CATS), sulfonated bis-catechol linear amide (PS-2-6-LICAMS) and sulfonated 3,3-linear tris-catechol amide (PS-3,3-LICAMS) ligands, which chemically bond to modified 6% crosslinked macroporous polystyrene-divinylbenzene beads (PS-DVB). These polymers are useful for the for selective removal and recovery of environmentally and economically important metal ions from aqueous solution, as a function of pH. The Fe.sup.3+ ion selectivity shown for PS-CATS, PS-2-6-LICAMS, and PS-3,3-LICAMS polymer beads in competition with a similar concentration of Cu.sup.2+, Zn.sup.2+, Mn.sup.2+, Ni.sup.2+, Mg.sup.2+, Al.sup.3+, and Cr.sup.3+ ions at pH 1-3. Further, the metal ion selectivity is changed at higher pH values in the absence of Fe.sup.3+ (for example, Hg.sup.2+ at pH 3). The rates of selective removal and recovery of the trivalent metal ions, e.g. Fe.sup.3+ Al.sup.3+ ion etc. with the PS-CATS, PS-2-6-LICAMS, and PS-3,3-LICAMS polymer beads used determined are useful as well as equilibrium selectivity coefficient (K.sub.m) values for all metal competition studies. The chelate effect for the predisposed octahedral PS-3,3-LICAMS polymer pendant ligand is the reason that this ligand has a more pronounced selectivity for Fe.sup.3+ ion in comparison to the PS-CATS polymer beads. The predisposed square planar PS-2,6-LICAMS series of polymer pendant ligands are more selective to divalent metal ions Cu.sup.2+, Zn.sup.2+, Mn.sup.2+, Ni.sup.2+, and Mg.sup.2+, than either PS-CATS or PS-3,3-LICAMS. However, Fe.sup.3+ ion still dominates in competition with other divalent and trivalent metal ions. In the absence of Fe.sup.3+, the polymer ligand is selective for Al.sup.3+, Cu.sup.2+ or Hg.sup.2+. The changing of the cavity size from two CH.sub.2 groups to six CH.sub.2 groups in the PS-2-6-LICAMS polymer pendant ligand series does not effect the order of metal ion selectivity.

  15. Polymer-supported sulfonated catechol and linear catechol amide ligands and their use in selective metal ion removal recovery from aqueous solutions

    DOEpatents

    Fish, R.H.

    1998-11-10

    The present invention concerns the synthesis of several biomimetically important polymer-supported, sulfonated catechol (PS-CATS), sulfonated bis-catechol linear amide (PS-2-6-LICAMS) and sulfonated 3,3-linear tris-catechol amide (PS-3,3-LICAMS) ligands, which chemically bond to modified 6% crosslinked macroporous polystyrene-divinylbenzene beads (PS-DVB). These polymers are useful for the for selective removal and recovery of environmentally and economically important metal ions from aqueous solution, as a function of pH. The Fe{sup 3+} ion selectivity shown for PS-CATS, PS-2-6-LICAMS, and PS-3,3-LICAMS polymer beads in competition with a similar concentration of Cu{sup 2+}, Zn{sup 2+}, Mn{sup 2+}, Ni{sup 2+}, Mg{sup 2+}, Al{sup 3+}, and Cr{sup 3+} ions at pH 1--3. Further, the metal ion selectivity is changed at higher pH values in the absence of Fe{sup 3+} (for example, Hg{sup 2+} at pH 3). The rates of selective removal and recovery of the trivalent metal ions, e.g. Fe{sup 3+}, Al{sup 3+} ion etc. with the PS-CATS, PS-2-6-LICAMS, and PS-3,3-LICAMS polymer beads used determined are useful as well as equilibrium selectivity coefficient (K{sub m}) values for all metal competition studies. The chelate effect for the predisposed octahedral PS-3,3-LICAMS polymer pendant ligand is the reason that this ligand has a more pronounced selectivity for Fe{sup 3+} ion in comparison to the PS-CATS polymer beads. The predisposed square planar PS-2,6-LICAMS series of polymer pendant ligands are more selective to divalent metal ions Cu{sup 2+}, Zn{sup 2+}, Mn{sup 2+}, Ni{sup 2+}, and Mg{sup 2+}, than either PS-CATS or PS-3,3-LICAMS. However, Fe{sup 3+} ion still dominates in competition with other divalent and trivalent metal ions. In the absence of Fe{sup 3+}, the polymer ligand is selective for Al{sup 3+}, Cu{sup 2+} or Hg{sup 2+}. The changing of the cavity size from two CH{sub 2} groups to six CH{sub 2} groups in the PS-2-6-LICAMS polymer pendant ligand series does not effect the order of metal ion selectivity. 9 figs.

  16. Versatile tuning of supramolecular hydrogels through metal complexation of oxidation-resistant catechol-inspired ligands

    PubMed Central

    Menyo, Matthew S.

    2013-01-01

    The mussel byssal cuticle employs DOPA-Fe3+ complexation to provide strong, yet reversible crosslinking. Synthetic constructs employing this design motif based on catechol units are plagued by oxidation-driven degradation of the catechol units and the requirement for highly alkaline pH conditions leading to decreased performance and loss of supramolecular properties. Herein, a platform based on a 4-arm poly(ethylene glycol) hydrogel system is used to explore the utility of DOPA analogues such as the parent catechol and derivatives, 4-nitrocatechol (nCat) and 3-hydroxy-4-pyridinonone (HOPO), as structural crosslinking agents upon complexation with metal ions. HOPO moieties are found to hold particular promise, as robust gelation with Fe3+ occurs at physiological pH and is found to be largely resistant to oxidative degradation. Gelation is also shown to be triggered by other biorelevant metal ions such as Al3+, Ga3+ and Cu2+ which allows for tuning of the release and dissolution profiles with potential application as injectable delivery systems. PMID:24285981

  17. The effect of the nature of peripheral platinated and bridging mercapto ligands on the optical and electrochemical properties of binuclear Pt(II) complexes with a metal-metal chemical bond

    NASA Astrophysics Data System (ADS)

    Katlenok, E. A.; Balashev, K. P.

    2014-09-01

    The effect of heterocyclic metalated and bridging ligands on the optical and electrochemical properties of [Pt(C^N)(?-N^S)]2 complexes ((C^N)- and (N^S)- are the deprotonated forms of 1-phenylpyrazole, 2-tolylpyridine, benzo[h]quinoline, 2-phenylbenzothiazole and 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptopyridine) is studied by 1H NMR, electronic absorption, and emission spectroscopy, as well as by voltammetry. The long-wavelength spin-allowed (415-540 nm) absorption bands of the complexes are attributed to the metal-metal-to-ligand charge transfer (MMLCT) optical transitions. It is shown that the interaction of the d Z2 and ?{(C^N/*)} orbitals of two {Pt(C^N)} fragments of binuclear complexes leads to a cathodic shift (0.5-1.0 V) of their metal-centered oxidation potential and to an anodic shift (0.1-0.2 V) of their ligand-centered reduction potential with respect to [Pt(C^N)En]+ complexes. The luminescence of binuclear complexes in solutions at room temperature is assigned to the spin-forbidden MMLCT transition. It is shown that, in frozen (77 K) solutions, in addition to the MMLCT optical transitions, spin-forbidden radiative processes occur from the intraligand (?(C^N)-?{(C^N)/*}) and metal-to-ligand charge transfer (dPt-?{(C^N)/*}) excited states.

  18. 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).

  19. Synthesis, characterization and biological relevance of some metal (II) complexes with oxygen, nitrogen and oxygen (ONO) donor Schiff base ligand derived from thiazole and 2-hydroxy-1-naphthaldehyde

    NASA Astrophysics Data System (ADS)

    Nagesh, G. Y.; Mruthyunjayaswamy, B. H. M.

    2015-04-01

    The novel Schiff base ligand 2-((2-hydroxynaphthalen-1-yl)methylene)-N-(4-phenylthiazol-2-yl)hydrazinecarboxamide (L) obtained by the condensation of N-(4-phenylthiazol-2-yl)hydrazinecarboxamide with 2-hydroxy-1-naphthaldehyde and its newly synthesized Cu(II), Co(II), Ni(II), Zn(II) and Cd(II) complexes have been characterized by microanalysis, molar conductance, IR, 1H NMR, ESI-mass, UV-Visible, TGA/DTA, ESR and powder X-ray diffraction data to explicate their structures. The IR results confirmed the tridentate binding of the ligand involving oxygen atom of amide carbonyl, azomethine nitrogen and naphthol oxygen. 1H NMR spectral data of the ligand (L) and its Zn(II) complex agreed well with the proposed structures. Thermogravimetric studies for Cu(II) and Ni(II) complexes indicated the presence of coordinated water molecules and the final product is the metal oxide. In order to appraise the effect of antimicrobial activity of metal ions upon chelation, the newly synthesized ligand and its metal complexes were screened for their antimicrobial activity by minimum inhibitory concentration (MIC) method. The DNA cleavage activities were studied using plasmid DNA pBR322 (Bangal re Genei, Bengaluru, Cat. No 105850) as a target molecule by agarose gel electrophoresis method. The brine shrimp bioassay was also carried out to study the in vitro cytotoxicity properties against Artemia salina. Furthermore, the antioxidant activity were determined in vitro by reduction of 1,1-diphenyl-2-picryl hydrazyl (DPPH). The ligand exhibited better in vitro-antioxidant activity than its metal complexes.

  20. Growth modes of thin films of ligand-free metal clusters

    SciTech Connect

    Dollinger, A.; Strobel, C. H.; Bleuel, H.; Marsteller, A.; Gantefoer, G.; Fairbrother, D. H.; Tang, Xin; Bowen, K. H.; Kim, Young Dok

    2015-05-21

    Size-selected Mo{sub n}{sup −}, W{sub n}{sup −}, and Fe{sub n}{sup −} cluster anions are deposited on a weakly interacting substrate (highly oriented pyrolytic graphite) and studied ex-situ using atomic force microscopy. Depending on size, three growth modes can be distinguished. Very small clusters consisting of less than 10–30 atoms behave similar to atoms and coalesce into 3-dimensional bulk-like islands. Medium sized clusters consisting of hundreds of atoms do not coalesce and follow a Stanski-Krastanov growth pattern. At low coverage, an almost perfect monolayer is formed. This is a new finding different from all previous studies on deposited metal clusters. For clusters with several thousands of atoms, the growth pattern again changes. At low coverage, the substrate is dotted with individual clusters, while at high coverage, the surface becomes extremely rough.

  1. N-aryl pyrrolo-tetrathiafulvalene based ligands: synthesis and metal coordination.

    PubMed

    Balandier, Jean-Yves; Chas, Marcos; Dron, Paul I; Goeb, Sébastien; Canevet, David; Belyasmine, Ahmed; Allain, Magali; Sallé, Marc

    2010-03-01

    A straightforward general synthetic access to N-aryl-1,3-dithiolo[4,5-c]pyrrole-2-thione derivatives 6 from acetylenedicarbaldehyde monoacetal is depicted. In addition to their potentiality as precursors to dithioalkyl-pyrrole derivatives, thiones 6 are key building blocks to N-aryl monopyrrolo-tetrathiafulvalene (MPTTF) derivatives 10. X-ray structures of four of these thiones intermediates, reminiscent of the corresponding MPTTF derivatives, are provided. When the aryl group is a binding pyridyl unit, the MPTTF derivative 10a can coordinate M(II) salts (M = Pt, Pd). The first examples of metal-directed orthogonal MPTTF-based dimers 11-14, obtained through coordination of 10a to cis-blocked square planar Pt or Pd complexes are described. Studies on the parameters influencing the dimer construction are presented, as well as first recognition properties of the resulting electron-rich clip for C(60). PMID:20143799

  2. The influence of selected metals on the electronic system of biologically important ligands

    NASA Astrophysics Data System (ADS)

    Lewandowski, W.; Fuks, L.; Kalinowska, M.; Koczoń, P.

    2003-12-01

    The influence of (i) halogens, (ii) different alkaline cations, Li(I), Na(I), K(I), Rb(I) and Cs(I), and (iii) lanthanide cations, Pr(III), Nd(III), Dy(III) and Er(III) on the electronic structure of the aromatic ring as well as of the carboxylic anion of the substituted benzoic acids was investigated. Systematic change (decrease or increase) in the wavenumbers of selected bands along the F→Cl→Br→I series was observed. This change correlates in linear fashion with a decrease in the ionic potential of the halogens. A shift of the selected bands along with the alkaline and the lanthanide metal series was also observed and correlated with the ionic potential of the metal. It was noticed that the increase in the ionic potential of halogen atoms causes a remarkable increase in the difference (Δ ν) between the wavenumbers of νasym(COO -) and νsym(COO -). Among the halogens the ionic potential is the lowest for iodine and this substituent brings about maximal proximity of the asymmetric and symmetric bands of the carboxylic anion. The change of cation in the molecule causes a characteristic change in the difference (Δ ν) between the wavenumbers of νasym(COO -) and νsym(COO -) as well. Along with the lanthanide series under study (Pr→Nd→Dy→Er) this difference decreases, while between alkaline cations lithium broadens these bands to the highest degree. The influence of the alkaline and the lanthanide cations on the vibrational structure of the whole molecule was analysed and compared.

  3. Reactivity of functionalized indoles with rare-earth metal amides. Synthesis, characterization and catalytic activity of rare-earth metal complexes incorporating indolyl ligands.

    PubMed

    Feng, Zhijun; Wei, Yun; Zhou, Shuangliu; Zhang, Guangchao; Zhu, Xiancui; Guo, Liping; Wang, Shaowu; Mu, Xiaolong

    2015-12-21

    The reactivity of several functionalized indoles 2-(RNHCH2)C8H5NH (R = C6H5 (1), (t)Bu (2), 2,6-(i)Pr2C6H3 (3)) with rare-earth metal amides is described. Reactions of 1 or 2 with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 (RE = Eu, Yb) respectively produced the europium complexes [2-(C6H5N[double bond, length as m-dash]CH)C8H5N]2Eu[N(SiMe3)2] (4) and [2-((t)BuN[double bond, length as m-dash]CH)C8H5N]Eu[N(SiMe3)2]2 (5), and the ytterbium complex [2-((t)BuN[double bond, length as m-dash]CH)C8H5N]2Yb[N(SiMe3)2] (6), containing bidentate anionic indolyl ligands via dehydrogenation of the amine to the imine. In contrast, reactions of the more sterically bulky indole 3 with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 afforded complexes [2-(2,6-(i)Pr2C6H3NCH2)C8H5N]RE[N(SiMe3)2](THF)2 (RE = Yb (7), Y (8), Er (9), Dy (10)) with the deprotonated indolyl ligand. While reactions of 3 with yttrium and ytterbium amides in refluxing toluene respectively gave the complexes [2-(2,6-(i)Pr2C6H3N[double bond, length as m-dash]CH)C8H5N]3Y (11) and [2-(2,6-(i)Pr2C6H3N[double bond, length as m-dash]CH)C8H5N]2Yb(II)(THF)2 (12), along with transformation of the amino group to the imino group, and also with a reduction of Yb(3+) to Yb(2+) in the formation of 12. Reactions of 3 with samarium and neodymium amides provided novel dinuclear complexes {[μ-η(5):η(1):η(1)-2-(2,6-(i)Pr2C6H3NCH2)C8H5N]RE[N(SiMe3)2]}2 (RE = Sm (13), Nd (14)) having indolyl ligands in μ-η(5):η(1):η(1) hapticities. The pathway for the transformation of the amino group to the imino group is proposed on the basis of the experimental results. The new complexes displayed excellent activity in the intramolecular hydroamination of aminoalkenes. PMID:26548974

  4. Solution pH effects on arsenic removal by drinking water treatment residuals in presence of metals and ligands

    NASA Astrophysics Data System (ADS)

    Nagar, R.; Sarkar, D.; Datta, R.; Makris, K.

    2006-05-01

    Arsenic (As) is a Group A carcinogen whose presence in soils in higher than background concentrations has become a serious concern with increasing suburban encroachment on former agricultural lands. One of the most promising methods to decrease the mobility of As in soil and water environments is by promoting its adsorption onto amorphous Fe/Al hydroxides. Drinking water treatment residuals (WTRs) are cost-effective sources of such Fe/Al hydroxides, and generated during the drinking water treatment process as a byproduct. Preliminary work in our laboratory showed that the WTRs are characterized by large specific surface and a net positive charge, ideal for retention of oxyanions such as those of As. However, the overall magnitude of As retention by the WTRs is a function of solution factors such as pH, presence of competing ions and complexing metals. A comprehensive understanding of the aforementioned parameters is, therefore, needed to quantify As mobility and bioaccessibility. The primary objective of the studying progress is to determine the effect of solution pH (range: 3-10) on the amount of As sorbed by the WTRs in the presence of competing ligands such as phosphate, sulfate and silicate as well as complexing metals (e.g., calcium and lead). Experiments are being conducted at 3 solid/solution ratios- 1:5, 1:10 and 1:20 and four initial As loads (375, 750, 1500 and 3000 mgAs L-1). Sodium arsenate is used as the As source. Arsenate adsorption is expected to decrease with increasing pH because generally when solution pH is less than pH of the zero point of charge, the positively charged surface on the soil prefers to complex with the negatively charged arsenate oxyanions. Furthermore, phosphate, sulfate and silicate are expected to compete with arsenate for sorption sites because like arsenate, these ions are typically sorbed via formation of inner-sphere complexes with suface functional groups. On the other hand, the presence of metals like lead and calcium are expected to decrease As mobility due to their tendency to complex with As oxyanions, thereby promoting precipitation when the ion activity product (IAP) is equal to or higher then the solubility equilibrium constant (Ksp) of the respective mineral precipitate. Keywords: Adsorption, arsenic, water treatment residuals, oxyanions, complexing metals, competing ions.

  5. In search for new bonding modes of the methylenedithiolato ligand: novel tri- and tetra-metallic clusters.

    PubMed

    Anju, R S; Saha, Koushik; Mondal, Bijan; Roisnel, Thierry; Halet, Jean-François; Ghosh, Sundargopal

    2015-07-01

    Building upon our earlier results on the chemistry of diruthenium analogue of pentaborane (9) with heterocumulenes, we continued to investigate the reactivity of arachno-[(Cp*Ru)2(B3H8)(CS2H)], 1, (Cp* = η(5)-C5Me5) towards group 7 and 8 transition metal carbonyl compounds under photolytic and thermolytic conditions. The metal carbonyl compounds show diverse reactivity pattern with arachno-1. For example, the photolysis of arachno-1 with [Re2(CO)10] yielded [(Cp*Ru)2B3H5(CH2S2){Re(CO)4}2], 2, [(Cp*RuCO)2(μ-H)2(CH2S2){Re(CO)4}{Re(CO)3}], 3 and [(Cp*Ru)2(μ-CO)(μ-H)(CH2S2){Re(CO)3}], 4. The geometry of 2 with a nearly planar eight-membered ring containing heavier transition metals rhenium, ruthenium is unprecedented. Compounds 3 and 4 can be considered as M4-quadrilateral and M3-triangle with a methylenedithiolato ligand attached to the metal centres, respectively. [Mn2(CO)10], on the other hand, reacts with arachno-1 to yield heterometallic binuclear [(Cp*RuCO){Mn(CO)4}(μ-H)(SCH3)], 5 and homocubane [(Cp*Ru)2{Mn(CO)3}-(CS2H2)B3H4], 6. In an attempt to generate group 8 analogues of 2-5, we performed the reaction of arachno-1 with [Fe2(CO)9] and [Ru3(CO)12]. Although, the objective of isolating analogous compounds was not achieved, the reaction with [Fe2(CO)9] led to novel tetrahedral cluster [(Cp*RuCO){(Fe(CO)3}2S(μ-H)], 7. [Ru3(CO)12], in contrast, yielded known compounds [{Cp*Ru(CO)}2B2H6], 9 and [Cp*Ru(CO)2]2, 10. All the cluster compounds have been characterized by mass spectrometry, IR, and (1)H, (11)B, and (13)C NMR spectroscopy, and the geometric structures were unequivocally established by crystallographic analysis of 2-5 and 7. PMID:25723783

  6. CMPO-functionalized C3-symmetric tripodal ligands in liquid/liquid extractions: efficient, selective recognition of Pu(IV) with low affinity for 3+ metal ions.

    PubMed

    Matloka, Kornelia; Sah, Ajay K; Peters, Matthew W; Srinivasan, Priya; Gelis, Artem V; Regalbuto, Monica; Scott, Michael J

    2007-12-10

    Structural modifications of carbamoylmethylphosphine oxide (CPMO)-functionalized triphenoxymethane platforms are described, and the influence of these changes on the ability of the ligand to extract actinides from simulated acidic nuclear waste streams has been evaluated. The ligand system has been shown to have excellent binding efficiency and a selectivity for An(IV) in comparison to the a simple monomeric CMPO ligand under analogous conditions. Both the extraction efficiency and selectivity are strongly dependent on the flexibility and electronic properties of the ligating units in the triphenoxymethane construct. The Tb(III) and Bi(III) nitrate complexes of tris-CMPO derivatives have been isolated, and their structures were elucidated by NMR, ESI FT-ICR MS, and X-ray analysis, providing information on the interactions between metal ions and the tris-CMPO molecules. PMID:17999487

  7. Spectroscopic, cyclic voltammetric and biological studies of transition metal complexes with mixed nitrogen-sulphur (NS) donor macrocyclic ligand derived from thiosemicarbazide

    NASA Astrophysics Data System (ADS)

    Chandra, Sulekh; Gupta, Lokesh Kumar; Sangeetika

    2005-11-01

    The complexation of new mixed thia-aza-oxa macrocycle viz., 2,12-dithio-5,9,14,18-tetraoxo-7,16-dithia-1,3,4,10,11,13-hexaazacyclooctadecane containing thiosemicarba-zone unit with a series of transition metals Co(II), Ni(II) and Cu(II) has been investigated, by different spectroscopic techniques. The structural features of the ligand have been studied by EI-mass, 1H NMR and IR spectral techniques. Elemental analyses, magnetic moment susceptibility, molar conductance, IR, electronic, and EPR spectral studies characterized the complexes. Electronic absorption and IR spectra of the complexes indicate octahedral geometry for chloro, nitrato, thiocyanato or acetato complexes. The dimeric and neutral nature of the sulphato complexes are confirmed from magnetic susceptibility and low conductance values. Electronic spectra suggests square-planar geometry for all sulphato complexes. The redox behaviour was studied by cyclic voltammetry, show metal-centered reduction processes for all complexes. The complexes of copper show both oxidation and reduction process. The redox potentials depend on the conformation of central atom in the macrocyclic complexes. Newly synthesized macrocyclic ligand and its transition metal complexes show markedly growth inhibitory activity against pathogenic bacterias and plant pathogenic fungi under study. Most of the complexes have higher activity than that of the metal free ligand.

  8. Assessing electronic structure approaches for gas-ligand interactions in metal-organic frameworks: the CO2-benzene complex.

    PubMed

    Witte, Jonathon; Neaton, Jeffrey B; Head-Gordon, Martin

    2014-03-14

    Adsorption of gas molecules in metal-organic frameworks is governed by many factors, the most dominant of which are the interaction of the gas with open metal sites, and the interaction of the gas with the ligands. Herein, we examine the latter class of interaction in the context of CO2 binding to benzene. We begin by clarifying the geometry of the CO2-benzene complex. We then generate a benchmark binding curve using a coupled-cluster approach with single, double, and perturbative triple excitations [CCSD(T)] at the complete basis set (CBS) limit. Against this ΔCCSD(T)/CBS standard, we evaluate a plethora of electronic structure approximations: Hartree-Fock, second-order Møller-Plesset perturbation theory (MP2) with the resolution-of-the-identity approximation, attenuated MP2, and a number of density functionals with and without different empirical and nonempirical van der Waals corrections. We find that finite-basis MP2 significantly overbinds the complex. On the other hand, even the simplest empirical correction to standard density functionals is sufficient to bring the binding energies to well within 1 kJ/mol of the benchmark, corresponding to an error of less than 10%; PBE-D in particular performs well. Methods that explicitly include nonlocal correlation kernels, such as VV10, vdW-DF2, and ωB97X-V, perform with similar accuracy for this system, as do ωB97X and M06-L. PMID:24628196

  9. Synthesis, structures, and properties of two three-dimensional metal-organic frameworks, based on concurrent ligand extension.

    PubMed

    Shi, Dabin; Ren, Yanwei; Jiang, Huanfeng; Cai, Bowei; Lu, Jiaxian

    2012-06-18

    A tritopic carboxylate ligand, tris(4'-carboxybiphenyl)amine (L-H(3)), has been synthesized and applied in the construction of microporous metal-organic frameworks (MOFs). Two novel metal-organic frameworks (MOFs), {[Zn(2)(L)(OH)]·2DMF·H(2)O}(∞) (1) and {[Cu(L-H)(DMA)]·DMA·2H(2)O}(∞) (2), have been constructed out of L-H(3), Zn(2+), and Cu(2+), respectively. 1 has a 2-fold interpenetrating three-dimensional framework formed by L connectors and the [Zn(2)(CO(2))(3)] secondary building units (SBUs). As for 1, it is worth pointing out that one μ(2)-OH group links two Zn atoms between two neighboring SBUs to produce interesting Zn-O-Zn zigzag chains in the structure. 2 has a two-dimensional grid sheet formed by L-H connectors and the typical paddle-wheel [Cu(2)(CO(2))(4)] SBUs. Two-dimensional (2D) sheets nest with each other, which finally forms a three-dimensional (3D) nested framework. Two MOFs are characterized by infrared (IR) spectroscopy, thermogravimetry, single-crystal and elemental analyses, and powder X-ray diffraction methods. Framework 1' exhibits high permanent porosity (Langmuir surface area = 848 m(2)/g), high thermal stability (up to 450 °C), highly active properties for Friedel-Crafts alkylation reaction, as well as the potential application for the CO(2) gas storage and luminescent material. The catalytic results reveal that 2' is indeed an efficient heterogeneous catalyst for olefin epoxidation reactions. PMID:22670898

  10. Bellow seal and anchor

    DOEpatents

    Mansure, Arthur J.

    2001-01-01

    An annular seal is made of a collapsible bellows. The bellows can function as an anchor or a seal and is easily set into position using relative component movement. The bellows folds can be slanted and their outer sealing edges can have different profiles to meet expected conditions. The bellows is expanded for insertion to reduce its outer dimension and sets by compaction as a result of relative movement. The bellows can be straight or tapered and is settable with a minimal axial force.

  11. Hydroxylated derivatives of dimethoxy-1,4-benzoquinone as redox switchable earth-alkaline metal ligands and radical scavengers

    NASA Astrophysics Data System (ADS)

    Gulaboski, Rubin; Bogeski, Ivan; Mirčeski, Valentin; Saul, Stephanie; Pasieka, Bastian; Haeri, Haleh H.; Stefova, Marina; Stanoeva, Jasmina Petreska; Mitrev, Saša; Hoth, Markus; Kappl, Reinhard

    2013-05-01

    Benzoquinones (BQ) have important functions in many biological processes. In alkaline environments, BQs can be hydroxylated at quinoid ring proton positions. Very little is known about the chemical reaction leading to these structural transformations as well as about the properties of the obtained hydroxyl benzoquinones. We analyzed the behavior of the naturally occurring 2,6-dimethoxy-1,4-benzoquinone under alkaline conditions and show that upon substitution of methoxy-groups, poly-hydroxyl-derivatives (OHBQ) are formed. The emerging compounds with one or several hydroxyl-substituents on single or fused quinone-rings exist in oxidized or reduced states and are very stable under physiological conditions. In comparison with the parent BQs, OHBQs are stronger radical scavengers and redox switchable earth-alkaline metal ligands. Considering that hydroxylated quinones appear as biosynthetic intermediates or as products of enzymatic reactions, and that BQs present in food or administered as drugs can be hydroxylated by enzymatic pathways, highlights their potential importance in biological systems.

  12. Cyclic (Amino)(aryl)carbenes (CAArCs) as Strong ?-Donating and ?-Accepting Ligands for Transition Metals.

    PubMed

    Rao, Bin; Tang, Huarong; Zeng, Xiaoming; Liu, Liu; Melaimi, Mohand; Bertrand, Guy

    2015-12-01

    Cyclic (amino)(aryl)carbenes (CAArCs) result from the replacement of the alkyl substituent of cyclic (alkyl)(amino) carbenes (CAACs) by an aryl group. This structural modification leads to enhanced electrophilicity of the carbene center with retention of the high nucleophilicity of CAACs, and therefore CAArCs feature a small singlet-triplet gap. The isoindolium precursors are readily prepared in good yields, and deprotonation at low temperature, in the presence of [RhCl(cod)]2 and [(Me2 S)AuCl] lead to air-stable rhodium and gold CAArC-supported complexes, respectively. The rhodium complexes promote the [3+2] cycloaddition of diphenylcyclopropenone with ethyl phenylpropiolate, and induce the addition of 2-vinylpyridine to alkenes by CH activation. The gold complexes allow for the catalytic three-component preparation of 1,2-dihydroquinolines from aniline and phenyl acetylene. These preliminary results illustrate the potential of CAArC ligands in transition-metal catalysis. PMID:26457345

  13. Three new 3D coordination polymers constructed by biphenyl-2,2‧,4,4‧-tetracarboxylic acid: Effect of metal ions and the second ligands

    NASA Astrophysics Data System (ADS)

    Cheng, Lin; Gou, Shaohua; Wang, Jianquan

    2011-04-01

    Three new coordination polymers with different architectures, {[Zn 2(bta)(2,2'-bipy) 2]·H 2O} n ( 1), {[Cd 2(bta)(2,2'-bipy) 2(H 2O)]·H 2O} n ( 2) and [Cd 3(bta)(Hbiim) 2(H 2biim)] n ( 3), where H 4bta = biphenyl-2,2',4,4'-tetracarboxylic acid, 2,2'-bipy = 2,2'-bipyridine and H 2biim = 1 H,1' H-2,2'-biimidazole, have been obtained by the reactions of metal nitrates, H 4bta, the second ligands and H 2O under similar hydrothermal conditions. All the polymers are three-dimensional (3D) constructions with different networks, in which 1, 2 and 3 exhibit a (4 2·8 4)- pts, (4 2·6 3·8)- sra and (4 16·6 5) topology, respectively. The bta ligands in 1- 3 adopt η 6,μ 6-hexadentate, η 8,μ 5-tetradentate and η 10,μ 7-decadaldentate coordination modes, respectively, and the corresponding angles of two benzene rings in the ligand of each compound are 45.96°, 54.93° and 52.50°, respectively. This study indicates that the natures of metal ions and the second ligands are crucial factors for self-assemble of coordination polymers.

  14. 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.

  15. Metal flux in ligand mixtures. 2. Flux enhancement due to kinetic interplay: comparison of the reaction layer approximation with a rigorous approach.

    PubMed

    Zhang, Zeshi; Buffle, Jacques; Town, Raewyn M; Puy, Jaume; van Leeuwen, Herman P

    2009-06-18

    The revisited reaction layer approximation (RLA) of metal flux at consuming interfaces in ligand mixtures, discussed in the previous paper (part 1 of this series) is systematically validated by comparison with the results of rigorous numerical simulations. The current paper focuses on conditions under which the total metal flux is enhanced in the ligand (and complex) mixture compared to the case where the individual fluxes of metal complexes are independent of each other. Such an effect is exhibited only in ligand mixtures and results from the kinetic interplay between the various complexes with different labilities. It is exemplified by the Cu/NTA/N-(2-carboxyphenyl)glycine system (see part 1 paper), in which we show that the flux due to the less labile complex (CuNTA) is increased in the presence of a ligand (2-carboxyphenyl)glycine) that forms labile Cu complexes, even when the latter is in negligible proportion in the bulk solution. This paper first explains how the so-called composite and equivalent reaction layer thicknesses computed by RLA can be determined graphically from the concentration profiles of free metal and its complexes, as obtained by rigorous calculations. This approach allows comparison between the latter and RLA predictions. Comparison between these reaction layer thicknesses is then done using the chemical system mentioned above. The mechanism of flux enhancement with this system is studied in detail by following the change of the concentration profiles and reaction layer thicknesses with the increase of concentration of the ligand forming labile complexes. The mechanism of flux enhancement is well explained by the RLA and is validated by the concentration profiles obtained by rigorous numerical simulations. Based on this validation, the RLA is used to predict the conditions of the individual complex labilities and degree of complexation required to get flux enhancement in a two-ligand system. Due to compensation effects between kinetic and thermodynamic factors, a maximum flux enhancement is observed in a specific range of ratios of the lability indices of the two complexes. Flux enhancement might play a significant role in metal uptake in environmental or biological systems and should be considered in data interpretation. PMID:19459605

  16. Group 4 metal compounds incorporating the amide ligand, [N(SiMe2{C6H4-2-OMe})2](-).

    PubMed

    Evans, Lloyd T J; Farnaby, Joy H; Coles, Martyn P; Cloke, F Geoffrey N; Hitchcock, Peter B

    2015-05-21

    The anisole-substituted silyl-amide anion, [N(SiMe2{C6H4-2-OMe})2](-) (L), has been used as a pincer-type ligand in coordination chemistry. X-ray diffraction data for the lithium salt shows a trimetallic structure consisting of two equivalents of Li(L) that sequester a molecule of LiCl. The potassium salt K(L) is dimeric in the solid-state with bridging amide ligands. Each structure shows chelation of both O-donor groups to the electropositive metal. In contrast, the titanium compound Ti(L)Cl3 is four-coordinate with a monodentate amide. The zirconium compound Zr(L)2Cl2 is monometallic with a six-coordinate metal and two N,O-bidentate amides. PMID:25876026

  17. Hydrothermal synthesis of Group 13 metal trifluoride complexes with neutral N-donor ligands.

    PubMed

    Bhalla, Rajiv; Levason, William; Luthra, Sajinder K; McRobbie, Graeme; Monzittu, Francesco M; Palmer, Jazmyn; Reid, Gillian; Sanderson, George; Zhang, Wenjian

    2015-05-28

    The reactions of the hydrated Group 13 fluorides, MF3·3H2O (M = Al, Ga or In) with 2,2':6',2''-terpyridyl, 2,2'-bipyridyl or 1,10-phenanthroline under hydrothermal conditions (180 °C/15 h) produced high yields of the complexes [MF3(terpy)]·3H2O, [MF3(bipy)(OH2)]·2H2O and [MF3(phen)(OH2)]. X-Ray crystal structures of [M'F3(terpy)]·3H2O (M' = Al or Ga), [M'F3(bipy)(OH2)]·2H2O and [GaF3(phen)(OH2)] show that all of them contain distorted octahedral geometries at the metal with mer-trifluoride coordination. Extensive H-bonding (FH-OH) links the molecules. The complexes have been further characterised by microanalysis, IR, (1)H, (19)F{(1)H} and (27)Al NMR spectroscopy. In contrast, reactions of the trifluorides with the acyclic triamine, N,N,N',N',N''-pentamethyldiethylenetriamine, under similar hydrothermal conditions results in cleavage of the triamine and ring-closure to form the 1,1,4-trimethylpiperazinium cation, [⊂Me2N(CH2)2NMe(CH2)2](+), with fluorometallate anions, and confirmed by X-ray analysis of [⊂Me2N(CH2)2NMe(CH2)2]2[Al2F8(OH2)2]·2H2O. The strongly H-bonded [GaF3(terpy)]·3H2O was also obtained by Cl/F exchange from [GaCl3(terpy)] and [NBu4]F or [K(2,2,2-crypt)]F. Crystallisation of a mixture of [NH4][PF6] and [GaF3(terpy)]·3H2O from aqueous solution produced the edge-bridged cationic complex, [{Ga(terpy)F}2(μ-F)2][PF6]2. The synthesis of the more sterically bulky [GaCl3((t)Bu3-terpy)] ((t)Bu3-terpy = 4,4'4''-tris-(t)Bu-2,2':6',2''-terpyridyl) and the crystal structure of [GaCl2((t)Bu3-terpy)][GaCl4], which contains a trigonal bipyramidal cation, are also reported. PMID:25921724

  18. Extreme metal carbonyl back bonding in cyclopentadienylthorium carbonyls generates bridging C2O2 ligands by carbonyl coupling.

    PubMed

    Li, Huidong; Feng, Hao; Sun, Weiguo; King, R Bruce; Schaefer, Henry F

    2013-06-17

    Laboratory studies of the interaction of carbon monoxide with organoactinides result in the formation of isolable complexes such as Cp3UCO derivatives (Cp = cyclopentadienyl) as well as coupling reactions to give derivatives of the oligomeric anions C(n)O(n)(2-) (n = 2, 3, 4). To gain some insight into actinide carbonyl chemistry, binuclear cyclopentadienylthorium carbonyls Cp2Th2(CO)n (n = 2 to 5) as model compounds have been investigated using density functional theory. The most favorable such structures in terms of energy and thermochemistry are the tricarbonyl Cp2Th2(η(2)-μ-CO)3 having three four-electron donor bridging carbonyl groups and the tetracarbonyl Cp2Th2(η(4)-μ-C2O2)(η(2)-μ-CO)2 having not only two four-electron donor bridging carbonyl groups but also a bridging ethynediolate ligand formed by coupling two CO groups through C-C bond formation. The bridging infrared ν(CO) frequencies ranging from 1140 to 1560 cm(-1) in these Cp2Th2(CO)n (n = 3, 4) derivatives indicate extremely strong Th→CO back bonding in these structures, corresponding to formally dianionic CO(2-) and C2O2(2-) ligands and the favorable +4 thorium oxidation state. A characteristic of the Cp2Th2(η(2)-μ-CO)3 and Cp2Th2(η(4)-μ-C2O2)(η(2)-μ-CO)2 structures is their ability to add terminal CO groups, preferably to the thorium atom bonded to the fewest oxygen atoms. These terminal CO groups exhibit ν(CO) frequencies in a similar range as terminal CO groups in d-block metal carbonyls. However, these terminal CO groups are relatively weakly bonded to the thorium atoms as indicated by predicted CO dissociation energies of 14 kcal/mol for Cp2Th2(CO)5. Two low energy structures for the dicarbonyl Cp2Th2(CO)2 are found with two separate four-electron donor bridging CO groups and relatively short Th-Th distances of 3.3 to 3.4 Å suggesting formal single bonds and +3 thorium formal oxidation states. However, a QTAIM analysis of this formal Th-Th bond does not reveal a bond critical point thus suggesting a multicenter bonding model involving the bridging CO groups. PMID:23721544

  19. Polymer-supported sulfonated catechol and linear catechol amide ligands and their use in selective metal ion removal and recovery from aqueous solutions

    DOEpatents

    Fish, R.H.

    1997-04-22

    The present invention concerns the synthesis of several biomimetically important polymer-supported, sulfonated catechol (PS-CATS), sulfonated bis-catechol linear amide (PS-2-6-LICAMS) and sulfonated 3,3-linear tris-catechol amide (PS-3,3-LICAMS) ligands, which chemically bond to modified 6% crosslinked macroporous polystyrene-divinylbenzene beads (PS-DVB). These polymers are useful for the for selective removal and recovery of environmentally and economically important metal ions from aqueous solution, as a function of pH. The Fe{sup 3+} ion selectivity shown for PS-CATS, PS-2-6-LICAMS, and PS-3,3-LICAMS polymer beads in competition with a similar concentration of Cu{sup 2+}, Zn{sup 2+}, Mn{sup 2+}, Ni{sup 2+}, Mg{sup 2+}, Al{sup 3+}, and Cr{sup 3+} ions at pH 1--3. Further, the metal ion selectivity is changed at higher pH values in the absence of Fe{sup 3+} (for example, Hg{sup 2+} at pH 3). The rates of selective removal and recovery of the trivalent metal ions, e.g. Fe{sup 3+}, Al{sup 3+} ion etc. with the PS-CATS, PS-2-6-LICAMS, and PS-3,3-LICAMS polymer beads use determined are useful as well as equilibrium selectivity coefficient (K{sub m}) values for all metal competition studies. The chelate effect for the predisposed octahedral PS-3,3-LICAMS polymer pendant ligand is the reason that this ligand has a more pronounced selectivity for Fe{sup 3+} ion in comparison to the PS-CATS polymer beads. The predisposed square planar PS-2-6-Mn{sup 2+}, Ni{sup 2+}, and Mg{sup 2+}, than either PS-CATS or PS-3,3-LICAMS. However, Fe{sup 3+} ion still dominates in competition with other divalent and trivalent metal ions. In the absence of Fe{sup 3+}, the polymer ligand is selective for Al{sup 3+}, Cu{sup 2+} or Hg{sup 2+}. The changing of the cavity size from two CH{sub 2} groups to six CH{sub 2} groups in the PS-2-6-LICAMS polymer pendant ligand series does not effect the order of metal ion selectivity. 9 figs.

  20. Polymer-supported sulfonated catechol and linear catechol amide ligands and their use in selective metal ion removal and recovery from aqueous solutions

    DOEpatents

    Fish, Richard H.

    1997-01-01

    The present invention concerns the synthesis of several biomimetically important polymer-supported, sulfonated catechol (PS-CATS), sulfonated bis-catechol linear amide (PS-2-6-LICAMS) and sulfonated 3,3-linear tris-catechol amide (PS-3,3-LICAMS) ligands, which chemically bond to modified 6% crosslinked macroporous polystyrene-divinylbenzene beads (PS-DVB). These polymers are useful for the for selective removal and recovery of environmentally and economically important metal ions from aqueous solution, as a function of pH. The Fe.sup.3+ ion selectivity shown for PS-CATS, PS-2-6-LICAMS, and PS-3,3-LICAMS polymer beads in competition with a similar concentration of Cu.sup.2+, Zn.sup.2+, Mn.sup.2+, Ni.sup.2+,Mg.sup.2+, Al.sup.3+, and Cr.sup.3+ ions at pH 1-3. Further, the metal ion selectivity is changed at higher pH values in the absence of Fe.sup.3+ (for example, Hg.sup.2+ at pH 3). The rates of selective removal and recovery of the trivalent metal ions, e.g. Fe.sup.3+ Al.sup.3+ ion etc. with the PS-CATS, PS-2-6-LICAMS, and PS-3,3-LICAMS polymer beads use determined are useful as well as equilibrium selectivity coefficient (K.sub.m) values for all metal competition studies. The chelate effect for the predisposed octahedral PS-3,3-LICAMS polymer pendant ligand is the reason that this ligand has a more pronounced selectivity for Fe.sup.3+ ion in comparison to the PS-CATS polymer beads. The predisposed square planar PS-2-6-Mn.sup.2+, Ni.sup.2+, and Mg.sup.2+, than either PS-CATS or PS-3,3-LICAMS. However, Fe.sup.3+ ion still dominates in competition with other divalent and trivalent metal ions. In the absence of Fe.sup.3+, the polymer ligand is selective for Al.sup.3+, Cu.sup.2+ or Hg.sup.2+. The changing of the cavity size from two CH.sub.2 groups to six CH.sub.2 groups in the PS-2-6-LICAMS polymer pendant ligand series does not effect the order of metal ion selectivity.

  1. Studies with an immobilized metal affinity chromatography cassette system involving binuclear triazacyclononane-derived ligands: automation of batch adsorption measurements with tagged recombinant proteins.

    PubMed

    Petzold, Martin; Coghlan, Campbell J; Hearn, Milton T W

    2014-07-18

    This study describes the determination of the adsorption isotherms and binding kinetics of tagged recombinant proteins using a recently developed IMAC cassette system and employing automated robotic liquid handling procedures for IMAC resin screening. These results confirm that these new IMAC resins, generated from a variety of different metal-charged binuclear 1,4,7-triaza-cyclononane (tacn) ligands, interact with recombinant proteins containing a novel N-terminal metal binding tag, NT1A, with static binding capacities similar to those obtained with conventional hexa-His tagged proteins, but with significantly increased association constants. In addition, higher kinetic binding rates were observed with these new IMAC systems, an attribute that can be positively exploited to increase process productivity. The results from this investigation demonstrate that enhancements in binding capacities and affinities were achieved with these new IMAC resins and chosen NT1A tagged protein. Further, differences in the binding performances of the bis(tacn) xylenyl-bridged ligands were consistent with the distance between the metal binding centres of the two tacn moieties, the flexibility of the ligand and the potential contribution from the aromatic ring of the xylenyl group to undergo π/π stacking interactions with the tagged proteins. PMID:24891160

  2. Covalent attachment of diphosphine ligands to glassy carbon electrodes via Cu-catalyzed alkyne-azide cycloaddition. Metallation with Ni(II).

    PubMed

    Das, Atanu K; Engelhard, Mark H; Lense, Sheri; Roberts, John A S; Bullock, R Morris

    2015-07-21

    Covalent tethering of P(Ph)2N(C6H4C≡CH)2 ligands (P(Ph)2N(C6H4C≡CH)2 = 1,5-di-(4-ethynylphenyl)-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane) to planar, azide-terminated glassy carbon electrode surfaces has been accomplished using a Cu(I)-catalyzed alkyne-azide cycloaddition (CuAAC) coupling reaction, using a BH3←P protection-deprotection strategy. Deprotected, surface-confined ligands were metallated using [Ni(II)(MeCN)6](BF4)2. X-ray photoelectron spectroscopic measurements demonstrate that metallation introduced 1.3 equivalents Ni(II) per diphosphine onto the electrode surface. Exposure of the surface to a second diphosphine ligand, P(Ph)2N(Ph)2, resulted in the removal of Ni from the surface. Protection, coupling, deprotection, and metallation conditions were optimized using solution-phase model systems, with benzyl azide as a model for the azide-terminated carbon surface; these reactions generate a [Ni(II)(diphosphine)2](2+) complex. PMID:25811536

  3. Halogen-bridged metal-organic frameworks constructed from bipyridinium-based ligand: structures, photochromism and non-destructive readout luminescence switching.

    PubMed

    Yang, Xiao-Dong; Chen, Cheng; Zhang, Ya-Jun; Cai, Li-Xuan; Tan, Bin; Zhang, Jie

    2016-03-21

    Two isomorphous halogen-bridged metal-organic frameworks have been solvothermally synthesized based on the bipyridinium ligand and structurally characterized. The two compounds show an eye-detectable color development upon light irradiation, but different coloration degrees. The relationship between the structure and photosensitivity has been studied in detail. The photochromic properties of the bipyridinium unit have been used to modulate the luminescence under light illumination. Compound 1 is the first example showing photo-modulated luminescence switching featuring a non-destructive readout capability based on transition metals. PMID:26740121

  4. Extraction of Micronutrient Metals from Peat-based Media Using Various Chelate-ligand and Iron-source Extractants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Objectives of the study were to determine effects of chelate-ligand (experiment 1) and iron-source (experiment 2) unbuffrered extractant solutions on substrate pH and Cu, Fe, Mn, and Zn extraction from peat-based media. Chelate-ligand extractants consisted of 5 mM solutions of ethylenediaminedisucc...

  5. Synthesis and some first-row transition-metal complexes of the 1,2,4-triazole-based Bis(terdentate) ligands TsPMAT and PMAT.

    PubMed

    Klingele, Marco H; Moubaraki, Boujemaa; Murray, Keith S; Brooker, Sally

    2005-11-18

    The employment of a strategy based on nucleophilic substitution, rather than Schiff base condensation, for the preparation of 1,2,4-triazole-based ligands has been investigated and has led to the synthesis of two new ligands, 4-amino-3,5-bis{[N-(2-pyridylmethyl)-N-(4-toluenesulfonyl)amino]methyl}-4H-1,2,4-triazole (TsPMAT, 14) and 4-amino-3,5-bis{[(2-pyridylmethyl)amino]methyl}-4H-1,2,4-triazole (PMAT, 15). These are the first examples of bis(terdentate) ligands incorporating the 1,2,4-triazole unit. TsPMAT (14) forms a dinuclear 2:2 complex with Co(BF4)2.6 H2O even when reacted in a metal-to-ligand molar ratio of 2:1. Similarly, the reaction of PMAT (15) with Mn(ClO4)2.6H2O or M(BF4)2.6 H2O (M=Fe, Co, Ni, Zn) in a ligand-to-metal molar ratio of 1:1 has afforded a series of complexes with the general formula [M(II) (2)(PMAT)2]X4. The metal centres in these complexes of TsPMAT (14) and PMAT (15) are encapsulated by two ligand molecules and doubly bridged by the N2 units of the 1,2,4-triazole moieties, which gives rise to N6 coordination spheres that are strongly distorted from octahedral, as evidenced by the X-ray crystal structure analyses of [Co(II) (2)(TsPMAT)(2)](BF(4))(4)6 MeCN (246 MeCN) and [Fe(II) 2(PMAT)2](BF4)4DMF (27DMF). Studies of the magnetic properties of [Co(II) 2(TsPMAT)2](BF4)4.4 H2O (244 H2O), [Mn(II) 2(PMAT)2](ClO4)4 (26), and [Co(II) 2(PMAT)2](BF4)4 (28) have revealed weak antiferromagnetic coupling (J=-3.3, -0.16, and -2.4 cm(-1), respectively) between the two metal centres in these complexes. PMID:16163767

  6. Monitoring the solid-state electrochemistry of Cu(2,7-AQDC) (AQDC = anthraquinone dicarboxylate) in a lithium battery: coexistence of metal and ligand redox activities in a metal-organic framework.

    PubMed

    Zhang, Zhongyue; Yoshikawa, Hirofumi; Awaga, Kunio

    2014-11-19

    By adopting a facile synthetic strategy, we obtained a microporous redox-active metal-organic framework (MOF), namely, Cu(2,7-AQDC) (2,7-H2AQDC = 2,7-anthraquinonedicarboxylic acid) (1), and utilized it as a cathode active material in lithium batteries. With a voltage window of 4.0-1.7 V, both metal clusters and anthraquinone groups in the ligands exhibited reversible redox activity. The valence change of copper cations was clearly evidenced by in situ XANES analysis. By controlling the voltage window of operation, extremely high recyclability of batteries was achieved, suggesting the framework was robust. This MOF is the first example of a porous material showing independent redox activity on both metal cluster nodes and ligand sites. PMID:25365211

  7. CHEMICAL SYNTHESIS OF GLYCOSYLPHOSPHATIDYLINOSITOL ANCHORS

    PubMed Central

    Swarts, Benjamin M.; Guo, Zhongwu

    2013-01-01

    Many eukaryotic cell-surface proteins and glycoproteins are anchored to the plasma membrane by glycosylphosphatidylinositols (GPIs), a family of glycolipids that are post-translationally attached to proteins at their C-termini. GPIs and GPI-anchored proteins play important roles in many biological and pathological events, such as cell recognition and adhesion, signal transduction, host defense, and acting as receptors for viruses and toxins. Chemical synthesis of structurally defined GPI anchors and GPI derivatives is a necessary step toward understanding the properties and functions of these molecules in biological systems and exploring their potential therapeutic applications. In the first part of this comprehensive article on the chemical synthesis of GPIs, classic syntheses of naturally occurring GPI anchors from protozoan parasites, yeast, and mammals are covered. The second part of the article focuses on recent diversity-oriented strategies for the synthesis of GPI anchors containing unsaturated lipids, “click chemistry” tags, and highly branched and modified structures. PMID:22794184

  8. Role of the chemically non-innocent ligand in the catalytic formation of hydrogen and carbon dioxide from methanol and water with the metal as the spectator.

    PubMed

    Li, Haixia; Hall, Michael B

    2015-09-30

    The catalytic mechanism for the production of H2 and CO2 from CH3OH and H2O by [K(dme)2][Ru(H) (trop2dad)] (K(dme)2.1_exp) was investigated by density functional theory (DFT) calculations. Since the reaction occurs under mild conditions and at reasonable rates, it could be considered an ideal way to use methanol to store hydrogen. The predicted mechanism begins with the dehydrogenation of methanol to formaldehyde through a new ligand-ligand bifunctional mechanism, where two hydrogen atoms of CH3OH eliminate to the ligand's N and C atoms, a mechanism that is more favorable than the previously known mechanisms, β-H elimination, or the metal-ligand bifunctional. The key initiator of this first step is formed by migration of the hydride in 1 from the ruthenium to the meta-carbon atom, which generates 1″ with a frustrated Lewis pair in the ring between N and C. Hydroxide, formed when 1″ cleaves H2O, reacts rapidly with CH2O to give H2C(OH)O(-), which subsequently donates a hydride to 6 to generate HCOOH and 5. HCOOH then protonates 5 to give formate and a neutral complex, 4, with a fully hydrogenated ligand. The hydride of formate transfers to 6, releasing CO2. The fully hydrogenated complex, 4, is first deprotonated by OH(-) to form 5, which then releases hydrogen to regenerate the catalyst, 1″. In this mechanism, which explains the experimental observations, the whole reaction occurs on the chemically non-innocent ligand with the ruthenium atom appearing as a spectator. PMID:26320885

  9. Mixed ligand two dimensional Cd(ii)/Ni(ii) metal organic frameworks containing dicarboxylate and tripodal N-donor ligands: Cd(ii) MOF is an efficient luminescent sensor for detection of picric acid in aqueous media.

    PubMed

    Rachuri, Yadagiri; Parmar, Bhavesh; Bisht, Kamal Kumar; Suresh, Eringathodi

    2016-05-01

    Two dimensional metal organic frameworks (MOFs) [Cd(5-BrIP)(TIB)]n () and [Ni2(5-BrIP)2(TIB)2]n (), involving the aromatic polycarboxylate ligand 5-bromo isophthalic acid (H2BrIP), flexible tripodal ligand 1,3,5-tris(imidazol-1-ylmethyl)benzene (TIB) and Cd(ii)/Ni(ii) metal nodes have been synthesized by different methods. These compounds were characterized by various analytical methods, and variable temperature X-ray diffraction data showed thermal stability of both MOFs up to 350 °C. Phase purity as well as water stability of the MOFs were established by powder X-ray diffraction, and the structural diversity of the compounds were investigated by single-crystal X-ray diffraction. Both the MOFs are mixed ligand 2D nets, and the topology of the network can be described as a binodal 3,5-c connected net with 3,5L2 topology having the point symbol {4(2)·6(7)·8}{4(2)·6}. Sensing of picric acid [2,4,6-trinitrophenol, TNP] by luminescence quenching among a large range of nitroanalytes in aqueous phase by the Cd(ii) luminescent MOF (LMOF) were been investigated. Structural studies on 1 : 1 co-crystals () of TIB and TNP were carried out. The selective and sensitive fluorescence quenching response of towards electron-deficient TNP over other nitro analytes in aqueous phase was demonstrated by fluorescence quenching titration. Concomitant occurrence of electron transfer/energy transfer processes and electrostatic interaction favours the selective sensing of TNP. A Cd(ii) LMOF ()-coated paper strip that we developed demonstrated fast and selective response to TNP, by the complete quenching of the blue fluorescence upon excitation of the paper strip at 365 nm radiation in its presence. PMID:27067118

  10. Synthesis and spectroscopic characterization of some transition metal complexes of a new hexadentate N 2S 2O 2 Schiff base ligand

    NASA Astrophysics Data System (ADS)

    Sarkar, Saikat; Dey, Kamalendu

    2005-11-01

    A novel interesting hexadentate dibasic N 2S 2O 2 donor Schiff base ligand, H4dcsalpte, was synthesized by the condensation of 3-formylsalicylic acid and 1,2-di( o-aminophenylthio)ethane and characterized. The reactions of the ligand with different metal(II/III)salts under varied reaction conditions afforded a series of metal complexes. The ligand, H4dcsalpte, behaves either as a dibasic or neutral hexadentate one, depending on the reaction conditions. Structural investigations on the ligand and their complexes have been made based on elemental analyses, molar conductance values, magnetic moment values, cryomagnetic and spectral (UV-vis, IR, 1H NMR, and Mössbauer) data. Based on magnetic susceptibility, Mössbauer and electronic spectral data the iron(III) complex [Fe III( H2dcsalpte)]ClO 4 ( 8), isolated in the present investigation, it is inferred that the spin states 5/2 and 1/2 are in equilibrium. Similarly a tri-iron(III) complex [Fe III3( H2dcsalpte)( H3dcsalpte)Cl 3]Cl 3 ( 7), isolated in this study, has been inferred to contain two iron(III) sites in tetrahedral environment and one in the octahedral environment. The aerial oxidation of an equimolar mixture of H4dcsalpte and Co(CH 3COO) 2·4H 2O in ethanol under reflux gave two products, [Co( H2dcsalpte)]CH 3COO ( 10) and [( Hbtcsaldm)Co( Hbvcsaldm)] ( 11), a cobalt(III) complex bound to two dissimilar tridentate NSO donor ligands formed as a result of the oxidative cleavage of the C sbnd S bond. In the complex 11, Hbtcsaldm stands for the dianion of the tridentate Schiff base ligand N-(2'-benzenethiol)-3-carboxysalicylaldimine and Hbvcsaldm stands for the mono anion of the tridentate Schiff base ligand N-(benzene-2'-S-vinyl)-3-carboxysalicylaldimine, both being formed as a result of the oxidative cleavage of H4dcsalpte.

  11. Bio-sensitive activities of coordination compounds containing 1,10-phenanthroline as co-ligand: Synthesis, structural elucidation and DNA binding properties of metal(II) complexes

    NASA Astrophysics Data System (ADS)

    Raman, Natarajan; Mahalakshmi, Rajkumar; Mitu, Liviu

    2014-10-01

    Present work reports the DNA binding and cleavage characteristics of a series of mixed-ligand complexes having the composition [M(L)(phen)2]Cl2 (where M = Cu(II), Ni(II), Co(II) and Zn(II) and phen as co-ligand) in detail. Their structural features and other properties have been deduced from their elemental analyses, magnetic susceptibility and molar conductivity as well as from IR, UV-Vis, 1H NMR and EPR spectral studies. The UV-Vis, magnetic susceptibility and EPR spectral data of metal complexes suggest an octahedral geometry. The binding properties of these complexes with calf thymus DNA (CT-DNA) have been explored using electronic absorption spectroscopy, viscosity measurement, cyclic voltammetry and differential pulse voltammetry. The DNA-binding constants for Cu(II), Ni(II), Co(II), and Zn(II) complexes are 6.14 × 105 M-1, 1.8 × 105 M-1, 6.7 × 104 M-1 and 2.5 × 104 M-1 respectively. Detailed analysis reveals that these complexes interact with DNA through intercalation binding. Nuclease activity has also been investigated by gel electrophoresis. Moreover, the synthesized Schiff base and its mixed-ligand complexes have been screened for antibacterial and antifungal activities. The data reveal that the complexes exhibit higher activity than the parent ligand.

  12. Granular Simulation of NEO Anchoring

    NASA Technical Reports Server (NTRS)

    Mazhar, Hammad

    2011-01-01

    NASA is interested in designing a spacecraft capable of visiting a Near Earth Object (NEO), performing experiments, and then returning safely. Certain periods of this mission will require the spacecraft to remain stationary relative to the NEO. Such situations require an anchoring mechanism that is compact, easy to deploy and upon mission completion, easily removed. The design philosophy used in the project relies on the simulation capability of a multibody dynamics physics engine. On Earth it is difficult to create low gravity conditions and testing in low gravity environments, whether artificial or in space is costly and therefore not feasible. Through simulation, gravity can be controlled with great accuracy, making it ideally suited to analyze the problem at hand. Using Chrono::Engine [1], a simulation package capable of utilizing massively parallel GPU hardware, several validation experiments will be performed. Once there is sufficient confidence, modeling of the NEO regolith interaction will begin after which the anchor tests will be performed and analyzed. The outcome of this task is a study with an analysis of several different anchor designs, along with a recommendation on which anchor is better suited to the task of anchoring. With the anchors tested against a range of parameters relating to soil, environment and anchor penetration angles/velocities on a NEO.

  13. Quinoxaline based bio-active mixed ligand transition metal complexes: Synthesis, characterization, electrochemical, antimicrobial, DNA binding, cleavage, antioxidant and molecular docking studies.

    PubMed

    Dhanaraj, C Justin; Johnson, Jijo

    2015-10-01

    Co(II), Ni(II), Cu(II) and Zn(II) mixed ligand complexes have been synthesized from N(2), N(3)-bis(4-nitrophenyl)quinoxaline-2,3-diamine and 1,10-phenanthroline. The compounds were characterized by elemental analyses, molar conductance, magnetic susceptibility, IR, UV-Vis., (1)H NMR, mass and ESR spectra. Octahedral geometry has been assigned for Co(II), Ni(II) and Zn(II) complexes and distorted octahedral geometry for Cu(II) complex. Electrochemical behavior of the synthesized complexes was studied using cyclic voltammetry. Grain size and surface morphologies of the complexes were determined by powder XRD and SEM analyses. The mixed ligand metal complexes were screened for antimicrobial activity against bacterial species Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus; fungal species Aspergillus niger, and Candida albicans by disc diffusion method. The DNA binding and DNA cleavage activities of the compounds were determined using electronic absorption titration and agarose gel electrophoresis respectively. The superoxide radical scavenging and free radical scavenging activities of the Cu(II) complex was also evaluated. Molecular docking studies of the synthesized mixed ligand metal complexes were carried out against B-DNA dodecamer and the protein Plasmodium falciparum dihydrofolate reductase (pf DHFR). PMID:26232747

  14. Syntheses, characterization and redox properties of oxo-centred triruthenium cluster dimers and trimers linked by ortho-metallated polypyridyl ligands.

    PubMed

    Dai, Feng-Rong; Chen, Jing-Lin; Ye, Heng-Yun; Zhang, Li-Yi; Chen, Zhong-Ning

    2008-03-21

    A series of mono-, di- and trimeric oxo-centred triruthenium cluster compounds with ortho-metallated polypyridyl ligands were prepared by reaction of oxo-centred triruthenium precursor compound [Ru3O(OAc)6(py)2(CH3OH)]+ (1) with bis(2,2'-bipyridin-5-yl)butadiyne (bpyC[triple bond, length as m-dash]C-C[triple bond, length as m-dash]Cbpy), bis(2,2'-bipridin-5-yl)ethyne (bpyC[triple bond, length as m-dash]Cbpy), 2,2'-bipyrazine (bpz), pyrazino[2,3-f]quinoxaline (pyq), or 4,7-phenanthroline (4,7-phen). As revealed by redox wave splitting, electronic interactions are operating between two Ru3O redox centres in most of the triruthenium cluster dimers and trimers. The cluster-cluster interactions are highly sensitive to the variations in bonding modes of the polypyridyl ligands. Ortho-metallation of the bridging ligand induces an enhanced electronic interaction between two triruthenium centres. PMID:18322630

  15. Radical Monocationic Guanidino-Functionalized Aromatic Compounds (GFAs) as Bridging Ligands in Dinuclear Metal Acetate Complexes: Synthesis, Electronic Structure, and Magnetic Coupling.

    PubMed

    Eberle, Benjamin; Damjanović, Marko; Enders, Markus; Leingang, Simone; Pfisterer, Jessica; Krämer, Christoph; Hübner, Olaf; Kaifer, Elisabeth; Himmel, Hans-Jörg

    2016-02-15

    In this work, the oxidation of several new dinuclear metal (M) acetate complexes of the redox-active guanidino-functionalized aromatic compound (GFA) 1,2,4,5-tetrakis(tetramethylguanidino)benzene (1) was studied. The complexes [1{M(OAc)2}2] (M = Ni or Pd) were oxidized to the radical monocationic complexes [1{M(OAc)2}2](+ •). From CV (cyclic voltammetry) measurements, the Gibbs free enthalpy for disproportionation of [1{M(OAc)2}2](+ •) into [1{M(OAc)2}2] and [1{M(OAc)2}2](2+) could be estimated to be roughly +20 kJ mol(-1) in CH2Cl2 solution. A characteristic feature of the [1{M(OAc)2}2](+ •) complexes is the presence of intense metal-ligand charge-transfer bands in the electronic absorption spectra. The complex [1{Ni(OAc)2}2](+ •) combines three paramagnetic centers with four metal-centered unpaired electrons and a ligand centered π-radical and exhibits a sextet electronic ground state. Spin distribution of the Ni complexes was evaluated by paramagnetic (1)H and (13)C NMR and was correlated with calculations. The strong ferromagnetic metal-ligand magnetic coupling was studied in the solid state by magnetometric (SQUID) measurements and by quantum chemical (DFT) calculations. The temperature dependence of the paramagnetic NMR shift was used for the evaluation of the magnetic coupling between the Ni centers and the π-radical in solution. PMID:26814470

  16. Assemblies of a new flexible multicarboxylate ligand and d10 metal centers toward the construction of homochiral helical coordination polymers: structures, luminescence, and NLO-active properties.

    PubMed

    Zang, Shuangquan; Su, Yang; Li, Yizhi; Ni, Zhaoping; Meng, Qingjin

    2006-01-01

    Hydro(solvo)thermal reactions between a new flexible multicarboxylate ligand of 2,2',3,3'-oxydiphthalic acid (2,2',3,3'-H(4)ODPA) and M(NO(3))(2).xH(2)O (M = Zn, x = 6; M = Cd, x = 4) in the presence of 4,4'-bipyridine (bpy) afford two novel homochiral helical coordination polymers [[Zn(2)(2,2',3,3'-ODPA)(bpy)(H(2)O)(3)].(H(2)O)(2) for 1 and [Cd(2)(2,2',3,3'-ODPA)(bpy)(H(2)O)(3)].(H(2)O)(2) for 2]. Though having almost the same chemical formula, they have different space groups (P2(1)2(1)2(1) for 1 and P2(1) for 2) and different bridging modes of the 2,2',3,3'-ODPA ligand. Two kinds of homochiral helices (right-handed) are found in both 1 and 2, each of which discriminates only one kind of crystallographical nonequivalent metal atom. 1 has a 2D metal-organic framework and can be seen as the unity of two parallel homochiral Zn1 and Zn2 helices, in which the nodes are etheric oxygen atoms. In contrast, 2 has a 3D metal-organic framework and consists of two partially overlapped homochiral Cd1 and Cd2 helices in the two dimensions. Moreover, metal-ODPA helices give a 2D chiral herringbone structural motif in both 1 and 2 in the two dimensions, which are further strengthened by the second ligand of bpy. Bulk materials for 1 and 2 all have good second-harmonic generation activity, approximately 1 and 0.8 times that of urea. PMID:16390053

  17. Unusual metal ion selectivities of the highly preorganized tetradentrate ligand 1,10-phenanthroline-2,9-dicarboxamide: a thermodynamic and fluorescence study.

    PubMed

    Merrill, Danielle; Harrington, James M; Lee, Hee-Seung; Hancock, Robert D

    2011-09-01

    Some metal ion complexing properties of the ligand PDAM (1,10-phenanthroline-2,9-dicarboxamide) in aqueous solution are reported. Using UV-visible spectroscopy to follow the intense π-π* transitions of PDAM as a function of metal ion concentration, log K(1) values in 0.1 M NaClO(4) and at 25 °C are, for Cu(II), 3.56(5); Ni(II), 3.06(5); Zn(II), 3.77(5); Co(II), 3.8(1); Mg(II), 0.1(1); Ca(II), 1.94(4); and Ba(II), 0.7(1). For more strongly bound metal ions, competition reactions between PDAM and EDTA (ethylenedinitrilo-tetraacetic acid) or tetren (1,4,7,10,13-pentaazatridecane), monitored following the UV spectrum of PDAM, gave the following log K(1) values in 0.1 M NaClO(4) and at 25 °C: Cd(II), 7.1(1); Pb(II), 5.82(5); In(III), 9.4(1); and Bi(III), 9.4(1). The very low log K(1)(PDAM) values for small metal ions such as Cu(II) or Zn(II) are unprecedented for a phen-based ligand (phen = 1,10-phenanthroline), which is rationalized in terms of the low basicity of the N donors of the ligand (pK(a) = 0.6) and the fact that PDAM has a best-fit size corresponding to large metal ions of ionic radius ~1.0 Å. Large metal ions with ionic radius ≥1.0 Å show large increases in log K(1) relative to their phen complexes, which in turn produces unparalleled selectivities, such as a 3.5 log units greater log K(1)(PDAM) for Cd(II) than for Cu(II). PDAM shows strong fluorescence in aqueous solution, suggesting that its carboxamide groups do not produce a fluorescence-quenching photon-induced electron transfer (PET) effect. Only Ca(II) produces a weak CHEF (chelation enhanced fluorescence) effect with PDAM, while all other metal ions tested produce a decrease in fluorescence, a CHEQ (chelation enhanced quenching effect). The production of the CHEQ effect is rationalized in terms of the idea that coordination of metal ions to PDAM stabilizes a canonical form of the carboxamide groups that promotes a PET effect. PMID:21790135

  18. Complexation of nitrogen and sulphur donor Schiff's base ligand to Cr(III) and Ni(II) metal ions: Synthesis, spectroscopic and antipathogenic studies

    NASA Astrophysics Data System (ADS)

    Sharma, Amit Kumar; Chandra, Sulekh

    2011-01-01

    2,6-Diacetyl pyridine based ligand was synthesized by the reaction of 2,6-diacetyl pyridine with thiocarbohydrazide in presence of acetic acid. The coordination compounds with Cr(III) and Ni(II) metal ions having [Cr(L)X]X 2 and [Ni(L)X]X compositions (where L = ligand and X = NO 3-, Cl - and CH 3COO -) were synthesized and characterized by physicochemical and spectral studies. The studies like elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, UV-Vis, NMR, mass and EPR reveal that the complexes are octahedral. The compounds were examined against the pathogenic fungal and bacterial strains like Alternaria brassicae, Aspergillus niger, Fusarium oxysporum, Xanthomonas compestris and Pseudomonas aeruginosa. A. niger causes the diseases Apergillosis and Otomycosis in humans.

  19. Trifluoropropynyl as a surrogate for the cyano ligand and intense, room-temperature, metal-centered emission from its Rh(III) complex.

    PubMed

    Sun, Chivin; Thakker, Parth U; Khulordava, Levan; Tobben, Daniel J; Greenstein, Seth M; Grisenti, David L; Kantor, Andrew G; Wagenknecht, Paul S

    2012-10-15

    The trifluoropropynyl ligand -C≡CCF(3) was studied as a possible surrogate for the cyano ligand. Complexes of the type trans-[M(cyclam)(C≡CCF(3))(2)]OTf (where M = Cr(3+), Co(3+), and Rh(3+); OTf = trifluoromethanesulfonate) were prepared and then characterized by electronic spectroscopy and by cyclic voltammetry for the Co(3+) complex. The UV-vis spectra for all three bear a remarkable similarity to that of the trans-M(cyclam)(CN)(2)(+) cations. The trifluoropropynyl complex of Co(3+) shows electrochemical behavior nearly identical with that of its dicyano analogue. Metal-centered phosphorescence from the Rh(III) complex in room-temperature aqueous solution has a quantum yield of 0.12 and a lifetime of 73 μs, nearly 10 times higher than those of its dicyano analogue. PMID:23013542

  20. Retrievable anchor assembly

    SciTech Connect

    Greenlee, D.R.; Lustig, L.M.

    1988-06-14

    A retrievable anchor assembly is described for use in well bores and the like, the assembly including: a hollow mandrel having an upper end, a lower end, and having a thread on the exterior thereof between the ends; an annular upper expander member having a threaded interior mating with the thread on the mandrel and having a tapered lower end portion, the mating threads providing for movement of the upper expander member relatively along the mandrel; an annular lower expander member releasably secured to the mandrel between the exterior thread and the lower end of the mandrel in spaced relation to the upper expander and having a tapered upper end portion; an annular slip cage encircling a portion of the mandrel and the upper and lower expander members, the cage having a plurality of circumferentially spaced openings extending therethrough; slip means located in space ones of the openings and resiliently retained on the mandrel by a plurality of resilient annular members extending through the slip means and encircling the mandrel, each slip means including, a convex top surface, a concave lower surface with concave end portions of the lower surface forming surfaces tapering toward the top surface for engaging the tapered end portions of the expander members, end surfaces formed by segments of circles, spaced lug portions projecting outwardly from a pair of side surfaces for engaging the slip cage, an a plurality of holes extending along accurate paths therethrough intersecting the side surfaces.

  1. Synthesis and characterization of metal complexes containing tetrazolate, poly(tetrazolyl)borate, and poly(azolyl)aluminate ligands as high energy density materials

    NASA Astrophysics Data System (ADS)

    Snyder, Christopher James

    A series of heavy alkaline earth metal tetrazolate complexes has been synthesized that contain metal ions saturated by aqua ligands. Tetrazolates with small ring-core carbon substituents favor formation of two dimensional polymers with micro3-coordination of the tetrazolate to the metal centers. Tetrazolates with bulkier groups block coordination to the 1- and 4-nitrogen atoms, resulting in monomer formation. The first example of a trihydro(tetrazolyl)borate was prepared, and its bonding is heavily influenced by the basic BH3 moiety. 18-Crown-6 adducts of dihydrobis(tetrazolyl)borate complexes have been prepared that contain B-N bonding to the 2-nitrogen atoms, due to bulky ring-core atom substituents. A series of alkali metal hydrotris(tetrazolyl)borate complexes has been prepared by closely monitoring the reactions by electrospray ionization-mass spectrometry. The lithium hydrotris(tetrazolyl)borate complex contains kappa3-N,N,N bonding that is analgous to the bonding mode of hydrotris(pyrazolyl)borate ligands. The 18-crown-6 adducts of the sodium and potassium hydrotris(tetrazolyl)borate salts adopt eta 2-N,N and kappa2-N,H coordination modes, respectively, due to steric hindrances between the 18-crown-6 and hydrotris(tetrazolyl)borate ligands. The bonding modes of the hydrotris(tetrazolyl)borate complexes are stabilized by many hydrogen-bonding and dihydrogen-bonding contacts between the hydrotris(tetrazolyl)borate ligand and the ancillary ligand on the metal center. A series of poly(pyrazolyl)aluminate complexes containing aluminum-hydrogen bonds has been prepared, and these complexes exhibit similar coordination modes to their poly(pyrazolyl)borate analogues. Pyrazolyl exchange processes occur at room temperature in solution due to the weak Al-N and Al-H bonds. Salt metathesis of the new complexes with metal(II) halides yielded ligand, hydride, or pyrazolate transfer, depending on the metal and reaction conditions. The reactivity of 5-substituted tetrazoles with lithium aluminum hydride was investigated in an attempt to prepare tetrakis(tetrazolyl)aluminate salts at low temperatures to avoid thermal decomposition of the parent tetrazoles. The reactions yielded complex reaction mixtures that were only soluble in polar solvents. A lithium tetrazolate was isolated from one of the reaction mixtures, which may be due to an equilibrium between the lithium tetrakis(tetrazolyl)aluminate complex and lithium and aluminum tetrazolate complexes in solution. All tetrazolate and poly(tetrazolyl)borate complexes presented herein are thermally stable above 200 °C, are insensitive to shock, friction, and electrical discharge, and can be handled safely. The tetrazolate complexes described herein deflagrate or explode upon exposure to a flame, and therefore may serve as secondary energetic materials or colorants in pyrotechnics. The poly(tetrazolyl)borate complexes are insensitive to the flame test, with the exception of the lithium hydrotris(tetrazolyl)borate, which explodes upon exposure to a flame.

  2. Formation of metal-nicotianamine complexes as affected by pH, ligand exchange with citrate and metal exchange. A study by electrospray ionization time-of-flight mass spectrometry.

    PubMed

    Rellán-Alvarez, Rubén; Abadía, Javier; Alvarez-Fernández, Ana

    2008-05-01

    Nicotianamine (NA) is considered as a key element in plant metal homeostasis. This non-proteinogenic amino acid has an optimal structure for chelation of metal ions, with six functional groups that allow octahedral coordination. The ability to chelate metals by NA is largely dependent on the pK of the resulting complex and the pH of the solution, with most metals being chelated at neutral or basic pH values. In silico calculations using pKa and pK values have predicted the occurrence of metal-NA complexes in plant fluids, but the use of soft ionization techniques (e.g. electrospray), together with high-resolution mass spectrometers (e.g. time-of-flight mass detector), can offer direct and metal-specific information on the speciation of NA in solution. We have used direct infusion electrospray ionization mass spectrometry (time-of-flight) ESI-MS(TOF) to study the complexation of Mn, Fe(II), Fe(III), Ni, Cu by NA. The pH dependence of the metal-NA complexes in ESI-MS was compared to that predicted in silico. Possible exchange reactions that may occur between Fe-NA and other metal micronutrients as Zn and Cu, as well as between Fe-NA and citrate, another possible Fe ligand candidate in plants, were studied at pH 5.5 and 7.5, values typical of the plant xylem and phloem saps. Metal-NA complexes were generally observed in the ESI-MS experiments at a pH value approximately 1-2 units lower than that predicted in silico, and this difference could be only partially explained by the estimated error, approximately 0.3 pH units, associated with measuring pH in organic solvent-containing solutions. Iron-NA complexes are less likely to participate in ligand- and metal-exchange reactions at pH 7.5 than at pH 5.5. Results support that NA may be the ligand chelating Fe at pH values usually found in phloem sap, whereas in the xylem sap NA is not likely to be involved in Fe transport, conversely to what occurs with other metals such as Cu and Ni. Some considerations that need to be addressed when studying metal complexes in plant compartments by ESI-MS are also discussed. PMID:18421700

  3. Synthesis, crystal structures and luminescent properties of zinc(II) metal-organic frameworks constructed from terpyridyl derivative ligand

    NASA Astrophysics Data System (ADS)

    Yang, Xiao-Le; Shangguan, Yi-Qing; Hu, Huai-Ming; Xu, Bing; Wang, Bao-Cheng; Xie, Juan; Yuan, Fei; Yang, Meng-Lin; Dong, Fa-Xin; Xue, Gang-Lin

    2014-08-01

    Five zinc(II) metal-organic frameworks, [Zn3(344-pytpy)2Cl6]n·n(H2O) (1), [Zn(344-pytpy)(ox)]n (2), [Zn2(344-pytpy)(bdc)2]n·1.5n(H2O) (3), [Zn2(344-pytpy)2 (sfdb)2]n·1.5n(H2O) (4) and [Zn3(344-pytpy)2(btc)2]n·2n(H2O) (5), (344-pytpy=4‧-(3-pyridyl)-4,2‧:6‧,4″-terpyridine, H2ox=oxalic acid, H2bdc=1,4-benzenedi-carboxylic acid, H2sfdb=4,4‧-sulfonyldibenzoic acid and H3btc=1,3,5-benzene-tricarboxylic acid) have been prepared by hydrothermal reactions. Compound 1 is a 1D chain structure, in which 344-pytpy ligand links three ZnII centers through three of terminal N-donors. Compound 2 is a 4-connected 3D framework with the dia topological net and the Schläfli symbol of 66. Compound 3 displays a unusual 3-fold interpenetrating 3D coordination network which exhibits a new intriguing (3,3,4)-connected topological net with the Schläfli symbol of (4.82)(4.85)(83). Compound 4 features a two-fold interpenetrating 4-connected 2D framework with the sql topological net and the Schläfli symbol of (44.62). Compound 5 is a new self-interpenetrating (3,3,4,4)-connected topological net with the Schläfli symbol of (6.82)2(62.82.10.12)(62.83.10)2(62.8)2. The luminescence properties of 1-5 have been investigated by emission spectra and they possess great thermal stabilities which can be stable up to around 400 °C.

  4. Synthesis, spectroscopic characterization and antimicrobial activity of binuclear metal complexes of a new asymmetrical Schiff base ligand: DNA binding affinity of copper(II) complexes.

    PubMed

    Shebl, Magdy

    2014-01-01

    The 1:1 condensation of o-acetoacetylphenol and 1,2-diaminopropane under condition of high dilution gives the mono-condensed Schiff base, (E)-3-(1-aminopropan-2-ylimino)-1-(2-hydroxyphenyl)butan-1-one. The mono-condensed Schiff base has been used for further condensation with isatin to obtain the new asymmetrical dicompartmental Schiff base ligand, (E)-3-(2-((E)-4-(2-hydroxyphenyl)-4-oxobutan-2-ylideneamino) propylimino)indolin-2-one (H3L) with a N2O3 donor set. Reactions of the ligand with metal salts give a series of new binuclear complexes. The ligand and its metal complexes were characterized by elemental analyses, IR, (1)H and (13)C NMR, electronic, ESR and mass spectra, conductivity and magnetic susceptibility measurements as well as thermal analyses. The analytical and spectroscopic tools showed that the complexes can be formulated as: [(HL)(VO)2(SO4)(H2O)]·4H2O, [(HL)Fe2Cl4(H2O)3]·EtOH, [(HL)Fe2(ox)Cl2(H2O)3]·2H2O, [(L)M2(OAc)(H2O)m]·nH2O; M=Co, Ni or Cu, m=4, 0 and n=2, 3, [(HL)Cu2Cl]Cl·6H2O and [(L)(UO2)2(OAc)(H2O)3]·6H2O. The metal complexes exhibited octahedral geometrical arrangements except copper complexes that exhibited tetrahedral geometries and uranyl complex in which the metal ion is octa-coordinated. The Schiff base and its metal complexes were evaluated for antimicrobial activity against Gram positive bacteria (Staphylococcus aureus), Gram negative bacteria (Escherichia coli) and fungi (Candida albicans and Aspergillus flavus). The ligand and some of its complexes were found to be biologically active. The DNA-binding properties of the copper complexes (6 and 7) have been investigated by electronic absorption, fluorescence and viscosity measurements. The results obtained indicate that these complexes bind to DNA via an intercalation binding mode with an intrinsic binding constant, Kb of 1.34×10(4) and 2.5×10(4) M(-1), respectively. PMID:23988527

  5. Synthesis, spectroscopic characterization and antimicrobial activity of binuclear metal complexes of a new asymmetrical Schiff base ligand: DNA binding affinity of copper(II) complexes

    NASA Astrophysics Data System (ADS)

    Shebl, Magdy

    2014-01-01

    The 1:1 condensation of o-acetoacetylphenol and 1,2-diaminopropane under condition of high dilution gives the mono-condensed Schiff base, (E)-3-(1-aminopropan-2-ylimino)-1-(2-hydroxyphenyl)butan-1-one. The mono-condensed Schiff base has been used for further condensation with isatin to obtain the new asymmetrical dicompartmental Schiff base ligand, (E)-3-(2-((E)-4-(2-hydroxyphenyl)-4-oxobutan-2-ylideneamino) propylimino)indolin-2-one (H3L) with a N2O3 donor set. Reactions of the ligand with metal salts give a series of new binuclear complexes. The ligand and its metal complexes were characterized by elemental analyses, IR, 1H and 13C NMR, electronic, ESR and mass spectra, conductivity and magnetic susceptibility measurements as well as thermal analyses. The analytical and spectroscopic tools showed that the complexes can be formulated as: [(HL)(VO)2(SO4)(H2O)]·4H2O, [(HL)Fe2Cl4(H2O)3]·EtOH, [(HL)Fe2(ox)Cl2(H2O)3]·2H2O, [(L)M2(OAc)(H2O)m]·nH2O; M = Co, Ni or Cu, m = 4, 0 and n = 2, 3, [(HL)Cu2Cl]Cl·6H2O and [(L)(UO2)2(OAc)(H2O)3]·6H2O. The metal complexes exhibited octahedral geometrical arrangements except copper complexes that exhibited tetrahedral geometries and uranyl complex in which the metal ion is octa-coordinated. The Schiff base and its metal complexes were evaluated for antimicrobial activity against Gram positive bacteria (Staphylococcus aureus), Gram negative bacteria (Escherichia coli) and fungi (Candida albicans and Aspergillus flavus). The ligand and some of its complexes were found to be biologically active. The DNA-binding properties of the copper complexes (6 and 7) have been investigated by electronic absorption, fluorescence and viscosity measurements. The results obtained indicate that these complexes bind to DNA via an intercalation binding mode with an intrinsic binding constant, Kb of 1.34 × 104 and 2.5 × 104 M-1, respectively.

  6. Synthesis, spectroscopic characterization and antimicrobial activity of mono-, bi- and tri-nuclear metal complexes of a new Schiff base ligand

    NASA Astrophysics Data System (ADS)

    Shebl, Magdy; Khalil, Saied M. E.; Ahmed, Saleh A.; Medien, Hesham A. A.

    2010-09-01

    Condensation of o-acetoacetylphenol and 1,2-diaminopropane in 1:1 molar ratio under condition of high dilution yielded the mono-condensed dibasic Schiff base ligand with a N 2O 2 donors. The mono-condensed ligand has been used for further condensation with 2-hydroxy-5-nitrobenzaldehyde to obtain the new asymmetrical dicompartmental Schiff base ligand, H 3L, with N 2O 3 donors. The structure of the ligand was elucidated by analytical and spectroscopic tools (IR, 1H and 13C NMR spectra) which indicated that the coordinating sites are oxygen atoms of the phenolic OH groups, nitrogen atoms of the azomethine groups and the oxygen atom of the ketonic group. Reactions of the ligand with metal salts yielded mono- and homo-bi-nuclear complexes formulated as [M(HL)], where M dbnd Co(II), Ni(II) and Cu(II), [Fe(H 2L)Cl 2(H 2O)]ṡ2½H 2O, [Fe 2(HL)(ox)Cl 3(H 2O) 2]ṡ5H 2O, [UO 2(H 2L)(OAc)(H 2O) 2], [VO(H 3L)(SO 4)(H 2O)]ṡH 2O, [M 2(L)Cl(H 2O) 2]ṡ½H 2O, where M dbnd Co(II) and Ni(II) and [Cu(H 2L)Cl]. The mononuclear Ni(II) complex, [Ni(HL)], was used to synthesize homo- and hetero-bi- and tri-nuclear complexes with the molecular formulae [Ni 2(L)Cl(H 2O) 2], [Ni 2(L) 2FeCl(H 2O)]ṡH 2O and [Ni 2(HL) 2CoCl 2]. The structures of the complexes were characterized by various techniques such as elemental and thermal analyses, IR, 1H and 13C NMR, mass and electronic spectra as well as conductivity and magnetic moment measurements. Square-planar and octahedral geometries are suggested for the Cu(II), Co(II) and Ni(II) complexes, octahedral geometry for the Fe(III) and VO 2+ complexes while uranium(VI) ion is octa-coordinated in its complex. The Schiff base and its metal complexes were evaluated for antimicrobial activity against Gram positive bacteria ( Staphylococcus aureus), Gram negative bacteria ( Escherichia coli) and fungi ( Candida albicans and Aspergillus flavus). The ligand and some of its complexes were found to be biologically active.

  7. The Glycophosphatidylinositol Anchor of the MCMV Evasin, m157, Facilitates Optimal Cell Surface Expression and Ly49 Receptor Recognition

    PubMed Central

    Carlin, Lindsey E.; Guseva, Natalya V.; Shey, Michael R.; Ballas, Zuhair K.; Heusel, Jonathan W.

    2013-01-01

    The murine cytomegalovirus-encoded protein m157 is a cognate ligand for both inhibitory and activating receptors expressed by natural killer cells. Additionally, m157 is expressed on the surface of infected cells by a glycophosphatidylinositol (GPI) anchor. Although endogenous GPI-anchored proteins are known to be ligands for the NK cell receptor, NKG2D, the contribution of the GPI anchor for viral m157 ligand function is unknown. To determine whether the GPI anchor for m157 is dispensable for m157 function, we generated m157 variants expressed as transmembrane fusion proteins and tested cells expressing transmembrane m157 for the capacity to activate cognate Ly49 receptors. We found that the GPI anchor is required for high-level cell surface expression of m157, and that the transmembrane m157 ligand retains the capacity to activate reporter cells and NK cells expressing Ly49H, as well as Ly49I129 reporter cells, but with reduced potency. Importantly, target cells expressing the transmembrane form of m157 were killed less efficiently and failed to mediate Ly49H receptor downregulation on fresh NK cells compared to targets expressing GPI-anchored m157. Taken together, these results show that the GPI anchor for m157 facilitates robust cell surface expression, and that NK cells are sensitive to the altered cell surface expression of this potent viral evasin. PMID:23840655

  8. Metal flux and dynamic speciation at (bio)interfaces. Part IV: MHEDYN, a general code for metal flux computation; application to particulate complexants and their mixtures with the other natural ligands.

    PubMed

    Alemani, Davide; Buffle, Jacques; Zhang, Zeshi; Galceran, Josep; Chopard, Bastien

    2008-03-15

    Metal flux at consuming interfaces (e.g., sensors or microorganisms) is simulated in environmental multiligand systems using a new numerical code, MHEDYN (Multispecies HEterogeneous DYNamics), based on the lattice Boltzmann method. The attention is focused on the computation of the maximum flux (i.e.,the flux controlled by diffusion-reaction in solution) of Cu(II). Part III described flux computation in the presence of simple ligands and fulvic/humic substances. This paper (Part IV) discusses the case of metal complexes formed with aggregates including a broad range of sizes and diffusion coefficients and their mixture with simple and fulvic ligands under typical natural water conditions. This paper describes the dynamic contribution of the various size classes of aggregate Cu(II) complexes for the first time. In two typical waters containing mixtures of ligands, the contribution of aggregates is found to be small, whereas that of fulvics may play a major role, even under pH conditions where the lability of their Cu(II) complexes is low. These results point out the great usefulness of MHEDYN for dynamic speciation in very complex mixtures. In all cases, MHEDYN enables us to compute the concentration profile of each complex and itstime evolution, as well as the steady-state flux and the corresponding contribution of each complex to the flux. Thus, MHEDYN should be very useful for comparing theoretical predictions with experimental measurements of metal bioavailability or of dynamic sensor response in a complete aquatic medium. PMID:18409632

  9. Synthesis, spectroscopic studies, thermal analyses, biological activity of tridentate coordinated transition metal complexes of bi(pyridyl-2-ylmethyl)amine]ligand

    NASA Astrophysics Data System (ADS)

    Abd El-Halim, Hanan F.; Mohamed, Gehad G.

    2016-01-01

    A new tridentate acyclic pincer ligand, [bi(pyridin-2-methyl)amine] (bpma, HL), was synthesized and reacted to form complexes with copper(II), nickel(II), iron(II), cobalt(II) and zinc(II) ions. Both the ligand and its complexes were characterized using elemental analysis, molar conductance, infrared, 1H-NMR-spectroscopy, mass and thermal analyses. According to the spectroscopic data, all of the complexes share the same coordination environment around the metal atoms, consisting two nitrogen-pyridine entities, one nitrogen-methylamine entity, one/two water molecules and/or one/two chloride or bromide ions. Complexes also showed molar conductivity according to the presence of two halide anions outer the coordination sphere except Co(II) and Zn(II) complexes are non electrolytes. Analysis indicates that the metal ions have trigonal bipyramidal structure. Cu(II), Ni(II), Fe(II), Co(II), and Zn(II) metal complexes were screened for their antibacterial activity against Bacillus subtilis, Staphylococcus aureus (G+) and Escherichia coli, and Pseudomonas aeruginosa (G-) bacteria. They showed remarkable antimicrobial activity.

  10. Building complexity in O2-binding copper complexes. Site-selective metalation and intermolecular O2-binding at dicopper and heterometallic complexes derived from an unsymmetric ligand.

    PubMed

    Serrano-Plana, Joan; Costas, Miquel; Company, Anna

    2014-12-15

    A novel unsymmetric dinucleating ligand (L(N3N4)) combining a tridentate and a tetradentate binding sites linked through a m-xylyl spacer was synthesized as ligand scaffold for preparing homo- and dimetallic complexes, where the two metal ions are bound in two different coordination environments. Site-selective binding of different metal ions is demonstrated. L(N3N4) is able to discriminate between Cu(I) and a complementary metal (M' = Cu(I), Zn(II), Fe(II), Cu(II), or Ga(III)) so that pure heterodimetallic complexes with a general formula [Cu(I)M'(L(N3N4))](n+) are synthesized. Reaction of the dicopper(I) complex [Cu(I)2(L(N3N4))](2+) with O2 leads to the formation of two different copper-dioxygen (Cu2O2) intermolecular species (O and (T)P) between two copper atoms located in the same site from different complex molecules. Taking advantage of this feature, reaction of the heterodimetallic complexes [CuM'(L(N3N4))](n+) with O2 at low temperature is used as a tool to determine the final position of the Cu(I) center in the system because only one of the two Cu2O2 species is formed. PMID:25424176

  11. Synthesis and characterisation of a novel mixed donor P,O,P' nixantphos ligand and its metal complex

    NASA Astrophysics Data System (ADS)

    Marimuthu, Thashree; Bala, Muhammad D.; Friedrich, Holger B.

    2016-02-01

    The complex [(NixC8OH)Ir(cod)Cl] 4 has been synthesized and structurally characterized by NMR, IR and single crystal X-ray diffraction. The synthesis and characterisation of the novel ligand NixC8OH is also presented. The coordination around Ir is trigonal bipyramidal with both P groups of the NixC8OH ligand bound in a bis-equatorial mode. The bis-chelating cod (C8H12) ligand occupies the remaining equatorial position and an axial position. This mode of bonding has resulted in a large bite angle (P1-Ir-P2) of 102.92(12)° for the title complex 4. The IR and NMR data further support the elucidated structure. Thermal analyses of 4 indicate that it is thermally stable up to a decomposition temperature of >400 °C.

  12. Highly Efficient Heterogeneous Hydroformylation over Rh-Metalated Porous Organic Polymers: Synergistic Effect of High Ligand Concentration and Flexible Framework.

    PubMed

    Sun, Qi; Dai, Zhifeng; Liu, Xiaolong; Sheng, Na; Deng, Feng; Meng, Xiangju; Xiao, Feng-Shou

    2015-04-22

    A series of diphosphine ligand constructed porous polymers with stable and flexible frameworks have been successfully synthesized under the solvothermal conditions from polymerizing the corresponding vinyl-functionalized diphosphine monomers. These insoluble porous polymers can be swollen by a wide range of organic solvents, showing similar behavior to those of soluble analogues. Rather than just as immobilizing homogeneous catalysts, these porous polymers supported with Rh species demonstrate even better catalytic performance in the hydroformylations than the analogue homogeneous catalysts. The sample extraordinary performance could be attributed to the combination of high ligand concentration and flexible framework of the porous polymers. Meanwhile, they can be easily separated and recycled from the reaction systems without losing any activity and selectivity. This excellent catalytic performance and easy recycling heterogeneous catalyst property make them be very attractive. These diphosphine ligand constructed porous polymers may provide new platforms for the hydroformylation of olefins in the future. PMID:25848868

  13. Antifungal activity of α-methyl trans cinnamaldehyde, its ligand and metal complexes: promising growth and ergosterol inhibitors.

    PubMed

    Shreaz, Sheikh; Sheikh, Rayees A; Bhatia, Rimple; Neelofar, Khan; Imran, Sheikh; Hashmi, Athar A; Manzoor, Nikhat; Basir, Seemi F; Khan, Luqman A

    2011-10-01

    Antifungal effectivity and utility of cinnamaldehyde is limited because of its high MIC and skin sensitivity. In this study, α-methyl trans cinnamaldehyde, a less irritating derivative, have been self coupled and complexed with Co(II) and Ni(II) to generate N, N'-Bis (α-methyl trans cinnamadehyde) ethylenediimine [C(22)H(24)N(2)], [Co(C(44)H(48)N(4))Cl(2)] and [Ni(C(44)H(48)N(4))Cl(2)]. Ligand and complexes were characterized on the basis of FTIR, ESI-MS, IR and (1)HNMR techniques. Synthesized ligand [L] and complexes were investigated for their MICs, inhibition of ergosterol biosynthesis and H(+) extrusion against three strains of Candida: C. albicans 44829, C. tropicalis 750 and C. krusei 6258. Average of three species MIC of methyl cinnamaldehyde is 317 μg/ml (2168 μM). Compared to methyl cinnamaldehyde ligand [L], Co(II) and Ni(II) complex are found to be 4.48, 17.78 and 21.46 times more effective in liquid medium and 2.73, 8.93 and 10.38 times more effective in solid medium. At their respective MIC(90) average inhibition of ergosterol biosynthesis caused by methyl cinnamaldehyde, ligand [L], Co(II) and Ni(II) complex, respectively was 80, 78, 90 and 93%. H(+) extrusion was also significantly inhibited but did not co-relate well with MIC(90). Results indicate ergosterol biosynthesis as site of action of α-methyl cinnamaldehyde, synthesized ligand and complexes. α-methyl cinnamaldehyde and ligand did not show any toxicity against H9c2 rat cardiac myoblast cell, whereas Co(II) and Ni(II) complexes on an average produced 19% cellular toxicity. PMID:21476019

  14. A Highly Porous and Robust (3,3,4)-Connected Metal?Organic Framework Assembled with a 90 Bridging-Angle Embedded Octacarboxylate Ligand

    SciTech Connect

    Lu, Weigang; Yuan, Daqiang; Makal, Trevor A.; Li, Jian-Rong; Zhou, Hong-Cai

    2012-03-15

    A dicopper(II)-paddle-wheel-based metal-organic framework (PCN-80, see picture) with a rare (3,3,4)-connected topology has been synthesized by using a unique octatopic ligand featuring 90{sup o} bridging-angle dicarboxylate moieties. PCN-80 has Brunauer-Emmett-Teller (BET) and Langmuir surface areas of 3850 and 4150 m{sup 2}g{sup -1}, respectively. It exhibits high gas-uptake capacity for H{sub 2} and large adsorption selectivity of CO{sub 2} over N{sub 2}.

  15. Group 1 and group 2 metal complexes supported by a bidentate bulky iminopyrrolyl ligand: synthesis, structural diversity, and ε-caprolactone polymerization study.

    PubMed

    Kottalanka, Ravi K; Harinath, A; Rej, Supriya; Panda, Tarun K

    2015-12-14

    We report here a series of alkali and alkaline earth metal complexes, each with a bulky iminopyrrolyl ligand [2-(Ph3CN=CH)C4H3NH] (1-H) moiety in their coordination sphere, synthesized using either alkane elimination or silylamine elimination methods or the salt metathesis route. The lithium salt of molecular composition [Li(2-(Ph3CN=CH)C4H3N)(THF)2] (2) was prepared using the alkane elimination method, and the silylamine elimination method was used to synthesize the dimeric sodium and tetra-nuclear potassium salts of composition [(2-(Ph3CN=CH)C4H3N)Na(THF)]2 (3) and [(2-(Ph3CN=CH)C4H3N)K(THF)0.5]4 (4) respectively. The magnesium complex of composition [(THF)2Mg(CH2Ph){2-(Ph3CN=CH)C4H3N}] (5) was synthesized through the alkane elimination method, in which [Mg(CH2Ph)2(OEt2)2] was treated with the bulky iminopyrrole ligand 1-H in 1 : 1 molar ratio, whereas the bis(iminopyrrolyl)magnesium complex [(THF)2Mg{2-(Ph3CN=CH)C4H3N}2] (6) was isolated using the salt metathesis route. The heavier alkaline earth metal complexes of the general formula {(THF)nM(2-(Ph3CN=CH)C4H3N)2} [M = Ca (7), Sr (8), and n = 2; M = Ba (9), n = 3] were prepared in pure form using two synthetic methods: in the first method, the bulky iminopyrrole ligand 1-H was directly treated with the alkaline earth metal precursor [M{N(SiMe3)2}2(THF)n] (where M = Ca, Sr and Ba) in 2 : 1 molar ratio in THF solvent at ambient temperature. The complexes 7-9 were also obtained using the salt metathesis reaction, which involves the treatment of the potassium salt (4) with the corresponding metal diiodides MI2 (M = Ca, Sr and Ba) in 2 : 1 molar ratio in THF solvent. The molecular structures of all the metal complexes (1-H, 2-9) in the solid state were established through single-crystal X-ray diffraction analysis. The complexes 5-9 were tested as catalysts for the ring-opening polymerization of ε-caprolactone. High activity was observed in the heavier alkaline earth metal complexes 7-9, with a very narrow polydispersity index in comparison to that of magnesium complexes 5 and 6. PMID:26511076

  16. Structures and multiple properties of two polar metal-organic frameworks based on achiral N,O-coordinated ligands: toward multifunctional materials.

    PubMed

    Liu, Guang-Ning; Zhang, Ming-Jian; Liu, Wan-Qing; Sun, Hui; Li, Xin-Yu; Li, Ke; Ren, Cai-Ze; Zhang, Zhen-Wei; Li, Cuncheng

    2015-11-21

    Two novel metal-organic frameworks (MOFs) [Cd3(padc)(Hpadc)(H2padc)(H2O)]nnH2O (1, H3padc = pyrazole-3,5-dicarboxylic acid) and [Co4(pidc)2(Hpidc)4(H2O)3]n12nH2O (2, H2pidc = pyridine-2,5-dicarboxylic acid), that both crystallize in polar space groups, were solvothermally synthesized by using achiral N,O-coordinated ligands. Compound 1 consists of trinuclear Cd(II)-based units that are further bridged by the backbone of H3padc ligands to form a three-dimensional (3-D) (4,6)-connected fsc topology network, while compound 2 features two types of double-helical tubes with different chiralities connecting with each other alternatively to construct a typical 2-D (3,6)-connected kgd topology network. Importantly, 1 exhibits combined properties of photoluminescence (PL) and second harmonic generation (SHG), and represents the first noncentrosymmetric H3padc-based MOF that was obtained without any ancillary ligands. While 2 shows strong antiferromagnetic interactions between paramagnetic Co(II) centers, and the aqueous solution of 2 exhibits effective homogeneous photocatalysis properties under visible irradiation. Further, the mechanisms of the physical properties of 1 and 2 are discussed in detail. PMID:26465876

  17. Preparation of Core-Shell Coordination Molecular Assemblies via the Enrichment of Structure-Directing "Codes" of Bridging Ligands and Metathesis of Metal Units

    SciTech Connect

    Park, J; Chen, YP; Perry, Z; Li, JR; Zhou, HC

    2014-12-03

    A series of molybdenum- and copper-based MOPs were synthesized through coordination-driven process of a bridging ligand (3,3'-PDBAD, L-1) and dimetal paddlewheel clusters. Three conformers of the ligand exist with an ideal bridging angle between the two carboxylate groups of 0 degrees (H-2 zeta-L(1)), 120 degrees (H-2 beta-L-1), and of 90 degrees (H-2 beta-L-1), respectively. At ambient or lower temperature, (HL1)-L-2 and Mo-2(OAc)(4) or Cu-2(OAc)(4) were crystallized into a molecular square with ?-L-1 and Mo-2/Cu-2 units. With proper temperature elevation, not only the molecular square with ?-L-1 but also a lantern-shaped cage with a-L-1 formed simultaneously. Similar to how Watson-Crick pairs stabilize the helical structure of duplex DNA, the core-shell molecular assembly possesses favorable H-bonding interaction sites. This is dictated by the ligand conformation in the shell, coding for the formation and providing stabilization of the central lantern shaped core, which was not observed without this complementary interaction. On the basis of the crystallographic implications, a heterobimetallic cage was obtained through a postsynthetic metal ion metathesis, showing different reactivity of coordination bonds in the core and shell. As an innovative synthetic strategy, the site-selective metathesis broadens the structural diversity and properties of coordination assemblies.

  18. Preparation of core-shell coordination molecular assemblies via the enrichment of structure-directing "codes" of bridging ligands and metathesis of metal units.

    PubMed

    Park, Jinhee; Chen, Ying-Pin; Perry, Zachary; Li, Jian-Rong; Zhou, Hong-Cai

    2014-12-01

    A series of molybdenum- and copper-based MOPs were synthesized through coordination-driven process of a bridging ligand (3,3'-PDBAD, L(1)) and dimetal paddlewheel clusters. Three conformers of the ligand exist with an ideal bridging angle between the two carboxylate groups of 0° (H2α-L(1)), 120° (H2β-L(1)), and of 90° (H2γ-L(1)), respectively. At ambient or lower temperature, H2L(1) and Mo2(OAc)4 or Cu2(OAc)4 were crystallized into a molecular square with γ-L(1) and Mo2/Cu2 units. With proper temperature elevation, not only the molecular square with γ-L(1) but also a lantern-shaped cage with α-L(1) formed simultaneously. Similar to how Watson-Crick pairs stabilize the helical structure of duplex DNA, the core-shell molecular assembly possesses favorable H-bonding interaction sites. This is dictated by the ligand conformation in the shell, coding for the formation and providing stabilization of the central lantern shaped core, which was not observed without this complementary interaction. On the basis of the crystallographic implications, a heterobimetallic cage was obtained through a postsynthetic metal ion metathesis, showing different reactivity of coordination bonds in the core and shell. As an innovative synthetic strategy, the site-selective metathesis broadens the structural diversity and properties of coordination assemblies. PMID:25384026

  19. Enhanced selectivity for actinides over lanthanides with CMPO ligands secured to a C(3)-symmetric triphenoxymethane platform.

    PubMed

    Peters, Matthew W; Werner, Eric J; Scott, Michael J

    2002-04-01

    A ligand system containing three preorganized carbamoylmethylphosphine oxide (CMPO) moieties anchored onto a rigid C(3)-symmetric triphenoxymethane platform has been developed for facile metal complexation and subsequent extraction from aqueous acidic nuclear waste streams. Intended to mimic the 3:1 CMPO-actinide stoichiometry of the extracted species in the TRUEX nuclear waste treatment process, the CMPO arms on this ligand are oriented such that all three CMPO moieties can cooperatively bind a metal ion. Extractions of simulated nuclear waste streams (10(-4) M metal in 1 M nitric acid) with solutions of this ligand in methylene chloride (10(-3) M) reveal a high affinity for the actinide thorium and a very low, but constant, affinity for the lanthanides across the series. Thorium and five lanthanide (lanthanum, cerium, neodymium, europium, and ytterbium) nitrate complexes of this ligand have been synthesized and fully characterized by X-ray crystallography, (1)H and (31)P NMR spectra, and FT-ICR-MS to elucidate the mechanism of this unique actinide selectivity. All six oxygen donors from the three CMPO arms of the ligand and one or two nitrate counterions coordinate these metals to afford 2+ cationic complexes in every case. Because of the large size of the ligand, both the thorium and lanthanide complexes present similarly charged and sized surfaces to the extraction solvents, but the thorium complex is extracted quantitatively over the lanthanide complexes. A possible rationale for this extraction behavior difference is presented and further illustrated by the extraction properties of this ligand system for the alkali metals (lithium, sodium, potassium, rubidium, and cesium) as picrate salts and by the solid- and solution-state structures of its lithium picrate complex. PMID:11925161

  20. 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

  1. Chiral crystallization and optical properties of three metal complexes based on two non-centrosymmetric tripodal ligands.

    PubMed

    Zhang, Ming-Dao; Shi, Zhi-Qiang; Chen, Min-Dong; Zheng, He-Gen

    2015-03-28

    Chiral coordination polymers have attracted much attention due to their special properties and significant applications. In this work, we synthesized two non-centrosymmetric ligands, N,N-bis(4-(1H-imidazol-1-yl)phenyl)-4-(pyridin-4-yl)aniline (DIMPPA) and N-(4-(1H-imidazol-1-yl)phenyl)-4-(pyridin-4-yl)-N-(4-(pyridin-4-yl)phenyl)aniline (MIDPPA), via structural modification of two reported centrosymmetric ligands; after that achiral ? chiral induction occurred in the construction of three coordination polymers namely {[Cd(DIMPPA)(5-OH-bdc)](H2O)}n (1), {[Co(DIMPPA)(5-OH-bdc)](H2O)}n (2) and {[Cd2(MIDPPA)2(D-ca)2(H2O)2](H2O)5}n (3), when replacing the reported centrosymmetric ligands with non-centrosymmetric ligands (5-OH-H2bdc = 5-hydroxyisophthalic acid, D-H2ca = D-camphoric acid). Isostructural complexes 1 and 2 exhibit chiral 2D ? 3D frameworks with the coexistence of polyrotaxane and parallel polycatenation features. Complex 3 shows two-fold interpenetrating 3D chiral architecture with cds-type topology. The luminescence emissions of both complexes 1 and 3 are mostly assignable to the internal ???* electron transition in DIMPPA and MIDPPA, respectively. Complex 3 can satisfy the fundamental requirement of second-order nonlinear optical materials. PMID:25715030

  2. Porous metal-organic framework based on a macrocyclic tetracarboxylate ligand exhibiting selective CO2 uptake

    SciTech Connect

    Gao, Wen-Yang; Niu, Youhong; Chen, Yao; Wojtas, Lukasz; Cai, Jianfeng; Chen, Yu-Sheng; Ma, Shengqian

    2012-11-14

    A two-fold interpenetrating microporous metal–organic framework, MMCF-1, has been constructed via the self-assembly of a custom-designed macrocyclic tetracarboxylate ligand and Cd(II), and it exhibits interesting selective uptake of CO2 over N2.

  3. 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…

  4. Topotactic elimination of water across a C-C ligand bond in a dense 3-D metal-organic framework.

    PubMed

    Yeung, Hamish H-M; Kosa, Monica; Griffin, John M; Grey, Clare P; Major, Dan T; Cheetham, Anthony K

    2014-11-11

    Upon heating, lithium L-malate undergoes topotactic dehydration to form a phase containing the unsaturated fumarate ligand, in which the original 3-D framework remains intact. Insight into this unusual transformation has been obtained by single crystal X-ray diffraction, MAS-NMR, in situ powder X-ray diffraction and DFT calculations. PMID:25232700

  5. Consideration of the bioavailability of metal/metalloid species in freshwaters: experiences regarding the implementation of biotic ligand model-based approaches in risk assessment frameworks.

    PubMed

    Rüdel, Heinz; Díaz Muñiz, Cristina; Garelick, Hemda; Kandile, Nadia G; Miller, Bradley W; Pantoja Munoz, Leonardo; Peijnenburg, Willie J G M; Purchase, Diane; Shevah, Yehuda; van Sprang, Patrick; Vijver, Martina; Vink, Jos P M

    2015-05-01

    After the scientific development of biotic ligand models (BLMs) in recent decades, these models are now considered suitable for implementation in regulatory risk assessment of metals in freshwater bodies. The BLM approach has been described in many peer-reviewed publications, and the original complex BLMs have been applied in prospective risk assessment reports for metals and metal compounds. BLMs are now also recommended as suitable concepts for the site-specific evaluation of monitoring data in the context of the European Water Framework Directive. However, the use is hampered by the data requirements for the original BLMs (about 10 water parameters). Recently, several user-friendly BLM-based bioavailability software tools for assessing the aquatic toxicity of relevant metals (mainly copper, nickel, and zinc) became available. These tools only need a basic set of commonly determined water parameters as input (i.e., pH, hardness, dissolved organic matter, and dissolved metal concentration). Such tools seem appropriate to foster the implementation of routine site-specific water quality assessments. This work aims to review the existing bioavailability-based regulatory approaches and the application of available BLM-based bioavailability tools for this purpose. Advantages and possible drawbacks of these tools (e.g., feasibility, boundaries of validity) are discussed, and recommendations for further implementation are given. PMID:25750051

  6. Electrochemically induced FTIR difference spectroscopy in the mid- to far infrared (200 microm) domain: a new setup for the analysis of metal-ligand interactions in redox proteins.

    PubMed

    Berthomieu, Catherine; Marboutin, Laure; Dupeyrat, François; Bouyer, Pierre

    2006-07-01

    We report the setup of an electrochemical cell with chemical-vapor deposition diamond windows and the use of a Bruker 66 SX FTIR spectrometer equipped with DTGS and Si-bolometer detectors and KBr and mylar beam splitters, to record on the same sample, FTIR difference spectra corresponding to the structural changes associated with the change in redox state of active sites in proteins in the whole 1800-50 cm(-1) region. With cytochrome c we show that reliable reduced-minus-oxidized FTIR difference spectra are obtained, which correspond to single molecular vibrations. Redox-sensitive IR modes of the cytochrome c are detected until 140 cm(-1) with a good signal to noise. This new setup is promising to analyze the infrared spectral region where metal-ligand vibrations are expected to contribute and to extend the analysis of vibrational properties to metal sites or redox states not accessible to (resonance) Raman spectroscopy. PMID:16453337

  7. Activity of N-coordinated multi-metal-atom active site structures for Pt-free oxygen reduction reaction catalysis: Role of *OH ligands

    SciTech Connect

    Holby, Edward F.; Taylor, Christopher D.

    2015-03-19

    We report calculated oxygen reduction reaction energy pathways on multi-metal-atom structures that have previously been shown to be thermodynamically favorable. We predict that such sites have the ability to spontaneously cleave the O₂ bond and then will proceed to over-bind reaction intermediates. In particular, the *OH bound state has lower energy than the final 2 H₂O state at positive potentials. Contrary to traditional surface catalysts, this *OH binding does not poison the multi-metal-atom site but acts as a modifying ligand that will spontaneously form in aqueous environments leading to new active sites that have higher catalytic activities. These *OH bound structures have the highest calculated activity to date.

  8. Activity of N-coordinated multi-metal-atom active site structures for Pt-free oxygen reduction reaction catalysis: Role of *OH ligands

    DOE PAGESBeta

    Holby, Edward F.; Taylor, Christopher D.

    2015-03-19

    We report calculated oxygen reduction reaction energy pathways on multi-metal-atom structures that have previously been shown to be thermodynamically favorable. We predict that such sites have the ability to spontaneously cleave the O₂ bond and then will proceed to over-bind reaction intermediates. In particular, the *OH bound state has lower energy than the final 2 H₂O state at positive potentials. Contrary to traditional surface catalysts, this *OH binding does not poison the multi-metal-atom site but acts as a modifying ligand that will spontaneously form in aqueous environments leading to new active sites that have higher catalytic activities. These *OH boundmore » structures have the highest calculated activity to date.« less

  9. Activity of N-coordinated multi-metal-atom active site structures for Pt-free oxygen reduction reaction catalysis: role of *OH ligands.

    PubMed

    Holby, Edward F; Taylor, Christopher D

    2015-01-01

    We report calculated oxygen reduction reaction energy pathways on multi-metal-atom structures that have previously been shown to be thermodynamically favorable. We predict that such sites have the ability to spontaneously cleave the O2 bond and then will proceed to over-bind reaction intermediates. In particular, the *OH bound state has lower energy than the final 2 H2O state at positive potentials. Contrary to traditional surface catalysts, this *OH binding does not poison the multi-metal-atom site but acts as a modifying ligand that will spontaneously form in aqueous environments leading to new active sites that have higher catalytic activities. These *OH bound structures have the highest calculated activity to date. PMID:25788358

  10. Activity of N-coordinated multi-metal-atom active site structures for Pt-free oxygen reduction reaction catalysis: Role of *OH ligands

    PubMed Central

    Holby, Edward F.; Taylor, Christopher D.

    2015-01-01

    We report calculated oxygen reduction reaction energy pathways on multi-metal-atom structures that have previously been shown to be thermodynamically favorable. We predict that such sites have the ability to spontaneously cleave the O2 bond and then will proceed to over-bind reaction intermediates. In particular, the *OH bound state has lower energy than the final 2 H2O state at positive potentials. Contrary to traditional surface catalysts, this *OH binding does not poison the multi-metal-atom site but acts as a modifying ligand that will spontaneously form in aqueous environments leading to new active sites that have higher catalytic activities. These *OH bound structures have the highest calculated activity to date. PMID:25788358

  11. Activity of N-coordinated multi-metal-atom active site structures for Pt-free oxygen reduction reaction catalysis: Role of *OH ligands

    NASA Astrophysics Data System (ADS)

    Holby, Edward F.; Taylor, Christopher D.

    2015-03-01

    We report calculated oxygen reduction reaction energy pathways on multi-metal-atom structures that have previously been shown to be thermodynamically favorable. We predict that such sites have the ability to spontaneously cleave the O2 bond and then will proceed to over-bind reaction intermediates. In particular, the *OH bound state has lower energy than the final 2 H2O state at positive potentials. Contrary to traditional surface catalysts, this *OH binding does not poison the multi-metal-atom site but acts as a modifying ligand that will spontaneously form in aqueous environments leading to new active sites that have higher catalytic activities. These *OH bound structures have the highest calculated activity to date.

  12. Transition metal complexes bearing a 2,2-bis(3,5-dimethylpyrazol-1-yl)propionate ligand: one methyl more matters.

    PubMed

    Türkoglu, Gazi; Heinemann, Frank W; Burzlaff, Nicolai

    2011-05-01

    The new N,N,O ligand 2,2-bis(3,5-dimethylpyrazol-1-yl)propionic acid (2,2-Hbdmpzp) (2) and its transition metal complexes [Mn(2,2-bdmpzp)(CO)(3)] (3), [Re(2,2-bdmpzp)(CO)(3)] (4), [Cu(2,2-bdmpzp)(2)] (5), and [Ru(2,2-bdmpzp)Cl(L)(PPh(3))] [L = PPh(3) (6), N(2) (7), CO (8a/b), SO(2) (9a/b)] have been synthesized, characterized and compared to analogous complexes bearing a bis(3,5-dimethylpyrazol-1-yl)acetic acid. It was found that the additional methyl group has a remarkable influence on the stability and reactivity of transition metal complexes. PMID:21409218

  13. Polyoxometalate-based organic-inorganic hybrid compounds containing transition metal mixed-organic-ligand complexes of N-containing and pyridinecarboxylate ligands.

    PubMed

    Zhao, De-Chuan; Hu, Yang-Yang; Ding, Hong; Guo, Hai-Yang; Cui, Xiao-Bing; Zhang, Xiao; Huo, Qi-Sheng; Xu, Ji-Qing

    2015-05-21

    Five new organic–inorganic hybrid compounds based on the Keggin-type polyoxoanion [SiW12O40]4−, namely [Cu3(2,2′-bpy)3(inic)(μ2-OH)(H2O)][SiW12O40]·2H2O (1), [Cu6(phen)6(μ3-Cl)2(μ2-Cl)2Cl2(inic)2][SiW12O40]·6H2O (2), [Cu2(hnic)(2,2′-bpy)2Cl]2[H2SiW12O40] (3), [Cu2(nic)(phen)2Cl2]2[SiW12O40] (4) and [Cu2(pic)(2,2′-bpy)2Cl]2[SiW12O40] (5) (inic = isonicotinic acid, hnic = 2-hydroxy-nicotinic acid, nic = nicotinic acid, pic = picolinic acid, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline) have been synthesized and characterized by IR, UV-Vis, XPS, XRD, cyclic voltammetric measurements, photoluminescence analysis and single crystal X-ray diffraction analysis. Crystal analysis reveals that compound 1 exhibits a 2-D double layered framework structure constructed from [SiW12O40]4− and copper-aqua-2,2′-bipy-hydroxyl-isonicotinate complexes. Compound 2 is a 0-D discrete structure formed by [SiW12O40]4− and copper-chloro-isonicotinate-phenanthroline complexes. Compound 3 shows a 1-D single chain structure based on the linkage of copper-2,2-bpy-chloro-2-hydroxy-nicotinate complexes and [SiW12O40]4−. Compounds 4 and 5 both contain polyoxometalate supported transition metal complexes, one is a polyoxometalate supported copper-chloro-nicotinate-phenanthroline complex in 4, and the other is a polyoxometalate supported copper-2,2-bpy-chloro-nicotinate complex in 5. It should be noted that nicotinic, isonicotinic and picolinic acids are structural isomers and 2-hydroxy-nicotinic acid is an in situ hydroxylated product of nicotinic acid. In addition, photocatalytic degradation of Rhodamine B (RhB) by compounds 1–5 has been investigated in aqueous solutions. PMID:25882351

  14. The influence of metals on the electronic system of biologically important ligands. Spectroscopic study of benzoates, salicylates, nicotinates and isoorotates. Review.

    PubMed

    Lewandowski, W; Kalinowska, M; Lewandowska, H

    2005-07-01

    This paper reviews the results of the intense experimental and theoretical studies on the influence of selected metals on the electronic system of biologically important molecules such as benzoic, 2-hydroxybenzoic and 3-pyridine carboxylic acids as well as 5-carboxyuracil. The research involved following techniques: infrared (FT-IR), Raman (FT-Raman), FT-IR Ar matrix, electronic absorption spectroscopy (UV/visible), nuclear magnetic resonance ((1)H, (13)C, (15)N, (17)O NMR), X-ray and quantum mechanical calculations. The influence of metals on the electronic system was examined through comparison of the changes in so called "logical series". The exemplary series are: Li-->Na-->K-->Rb-->Cs, Na(I)-->Ca(II)-->La(III)-->Th(IV); Na(I)-->Mg(II)-->Al(III) or long series of La(III) and fourteen lanthanides La(III)-->Ce(III)-->Lu(III). The correlation between the perturbation of the electronic system of ligands and the position of metals in the periodic table was found. The influence of the carboxylic anion structure and the effect of hydration on the perturbation of the electronic system of molecule were also discussed. The partial explanation in what way metals disturb and stabilize electronic system of studied ligands was done. It is necessary to carry out the physico-chemical studies of benzoates, salicylates, 3-pyridine carboxylates and isoorotates in order to understand the nature of the interactions of these compounds with their biological targets (e.g., receptors in the cell or important cell components). The results of this study make possible to predict some properties of a molecule, such as its reactivity, durability of complex compounds, and kinship to enzymes. PMID:15927261

  15. A 3D chiral metal-organic framework based on left-handed helices containing 3-amino-1 H-1,2,4-triazole ligand

    NASA Astrophysics Data System (ADS)

    Liu, Bing; Yang, Tian-Yi; Feng, Hui-Jun; Zhang, Zong-Hui; Xu, Ling

    2015-10-01

    A chiral metal-organic framework, [Cu(atr)(OH)]·0.5H2O·0.5en (1) (Hatr=3-amino-1 H-1,2,4-triazole, en=ethylenediamine), was constructed via diffusion reaction of the achiral Hatr ligand and CuSO4 as starting materials. Compound 1 crystallizes in the chiral space group P3221 and features a porous metal-organic framework with 44.1% solvent-accessible volume fabricated by left-handed helices with a pitch height of lp=10.442 Å. Six helices gather around in a cycle forming a large honeycomb channel with a 6.58 Å inner diameter. Cu(II) center and atr‒ ligand regarded as 3-connected nodes, compound 1 can be simplified to a 3-c uninodal {4.122} (qtz-h) topological network. A gradual decreasing in the magnetic moment depending on temperature decreasing indicates an antiferromagnetic interaction in 1. The powder XRD confirms the bulk sample is a single crystal pure phase, and the thermogravimetric analysis shows the thermal stability of 1 is up to ca. 240 °C.

  16. Investigation of the electronic structures of organolanthanide sandwich complex anions by photoelectron spectroscopy: 4f orbital contribution in the metal-ligand interaction.

    PubMed

    Hosoya, Natsuki; Yada, Keizo; Masuda, Tomohide; Nakajo, Erika; Yabushita, Satoshi; Nakajima, Atsushi

    2014-05-01

    The electronic structures of lanthanide (Ln) ions sandwiched between 1,3,5,7-cyclooctatetraene (COT), Ln(COT)2(-), have been investigated by anion photoelectron spectroscopy. Complexes of 12 Ln atoms were investigated (excluding promethium (Pm), europium (Eu), and ytterbium (Yb)). The 213 nm photoelectron (PE) spectra of Ln(COT)2(-) exhibit two peaks assignable to the highest occupied molecular orbital (HOMO; e2u) and the next HOMO (HOMO-1; e2g) approximately at 2.6 and 3.6 eV, respectively, and their energy gap increases as the central metal atom progresses from lanthanum (La) to lutetium (Lu). Since lanthanide contraction shortens the distance between the Ln atom and the COT ligands, the widening energy gap represents the destabilization of the e2u orbital as well as the stabilization of the e2g orbital. Evidence for 4f orbital contribution in the metal-ligand interaction has been revealed by the Ln atom dependence in which the same e2u orbital symmetry enables an interaction between the 4f orbital of Ln atoms and the π orbital of COT. PMID:24742246

  17. Synthesis, characterization, and antipathogenic studies of some transition metal complexes with N,O-chelating Schiff's base ligand incorporating azo and sulfonamide Moieties

    NASA Astrophysics Data System (ADS)

    Alaghaz, Abdel-Nasser M. A.; Bayoumi, Hoda A.; Ammar, Yousry A.; Aldhlmani, Sharah A.

    2013-03-01

    Chromium(III), Manganese(II), Cobalt(II), nickel(II), copper(II) and cadmium(II) complexes of 4-[4-hydroxy-3-(phenyliminomethyl)-phenylazo]benzenesulfonamide, were prepared and characterized on the basis of elemental analyses, spectral, magnetic, molar conductance and thermal analysis. Square planar, tetrahedral and octahedral geometries have been assigned to the prepared complexes. Dimeric complexes are obtained with 2:2 molar ratio except chromium(III) complex is monomeric which is obtained with 1:1 molar ratios. The IR spectra of the prepared complexes were suggested that the Schiff base ligand(HL) behaves as a bi-dentate ligand through the azomethine nitrogen atom and phenolic oxygen atom. The crystal field splitting, Racah repulsion and nepheloauxetic parameters and determined from the electronic spectra of the complexes. Thermal studies suggest a mechanism for degradation of HL and its metal complexes as function of temperature supporting the chelation modes. Also, the activation thermodynamic parameters, such as ΔE*, ΔH*, ΔS* and ΔG* for the different thermal decomposition steps of HL and its metal complexes were calculated. The pathogenic activities of the synthesized compounds were tested in vitro against the sensitive organisms Staphylococcus aureus (RCMB010027), Staphylococcus epidermidis (RCMB010024) as Gram positive bacteria, Klebsiella pneumonia (RCMB 010093), Shigella flexneri (RCMB 0100542), as Gram negative bacteria and Aspergillus fumigates (RCMB 02564), Aspergillus clavatus (RCMB 02593) and Candida albicans (RCMB05035) as fungus strain, and the results are discussed.

  18. Development of a bioabsorbable suture anchor.

    PubMed

    Pirhonen, E; Kaikkonen, A; Helevirta, P; Pohjonen, T; Tamminmäki, M; Törmälä, P

    1999-01-01

    In this article, the design and properties of a new bioabsorbable suture anchor (SmartAnchor(trade mark)) are described and its properties are compared with those of some commercial anchors. Two comparative experiments were carried out in order to measure (1) the breaking force of suture/anchor attachment for SmartAnchor, MitekGII, and for Ogden anchors; and (2) the fixation force of the following anchors and tacks: SmartAnchor, MitekGII, BankartTack, and Suretac. The average suture/anchor attachment breaking force of SmartAnchor (204, 9 N) was 32% higher in comparison to MitekGII (155, 6 N) and 84% higher in comparison to the Ogden anchor (111, 4). The mean fixation force of the SmartAnchor (195, 5 N) was 40% higher than that of MitekGII (139, 2 N), but the T-test showed no statistical differences between MitekGII and SmartAnchor (p = 0.05). Both tested tacks behaved very similarly in this test. The average fixation force (pull-out force) for both tacks was about 210 N. Therefore, it is evident that the bioabsorbable SmartAnchor has a high enough initial mechanical performance for clinical investigation. PMID:10556854

  19. Group 11 Metal Compounds with Tripodal Bis(imidazole) Thioether Ligands. Applications as Catalysts in the Oxidation of Alkenes and as Antimicrobial Agents

    PubMed Central

    Liu, Fangwei; Anis, Reema; Hwang, Eunmi; Ovalle, Rafael; Varela-Ramírez, Armando; Aguilera, Renato J.; Contel, María

    2011-01-01

    New group 11 metal complexes have been prepared using the previously described tripodal bis(imidazole) thioether ligand (N-methyl-4,5-diphenyl-2-imidazolyl)2C(OMe)C(CH3)2S(tert-Bu) ({BITOMe,StBu}, 2). The pincer ligand offers a N2S donor atom set that can be used to coordinate the group 11 metals in different oxidation states [AuI, AuIII, AgI, CuI and CuII]. Thus the new compounds [Au{BITOMe,StBu}Cl][AuCl4]2 (3), [Au{BITOMe,StBu}Cl] (4), [Ag{BITOMe,StBu}X] (X = OSO2CF3 − 5, PF6 − 6) and [Cu{BITOMe,StBu}Cl2] (7) have been synthesized from reaction of 2 with the appropriate metal precursors, and characterized in solution. While attempting characterization in the solid state of 3, single crystals of the neutral dinuclear mixed AuIII-AuI species [Au2{BITOMe,S}Cl3] (8) were obtained and its crystal structure was determined by X-ray diffraction studies. The structure shows a AuIII center coordinated to the pincer ligand through one N and the S atom. The soft AuI center coordinates to the ligand through the same S atom that has lost the tert-butyl group, thus becoming a thiolate ligand. The short distance between the AuI–AuIII atoms (3.383 Å) may indicate a weak metal-metal interaction. Complexes 2–7 and the previously described CuI compound [Cu{BITOMe,StBu}]PF6 (9) have been evaluated in the oxidation of biphenyl ethylene with tert-butyl hydrogen peroxide (TBHP) as the oxidant. Results have shown that the AuI and AgI complexes 4 and 6 (at 10 mol % loading) are the more active catalysts in this oxidative cleavage. The antimicrobial activity of compounds 2–5, 7 and 9 against Gram-positive and Gram-negative bacteria and yeast has also been evaluated. The new gold and silver compounds display moderate to high antibacterial activity, while the copper derivatives are mostly inactive. The gold and silver complexes were also potent against fungi. Their cytotoxic properties have been analyzed in vitro utilizing HeLa human cervical carcinoma cells. The compounds displayed a very low cytotoxicity on this cell line (5 to 10 times lower than cisplatin) and on normal primary cells derived from C57B6 mouse muscle explants, which may make them promising candidates as potential antimicrobial agents and safer catalysts due to low toxicity in human and other mammalian tissues. PMID:25134773

  20. Microgravity Drill and Anchor System

    NASA Technical Reports Server (NTRS)

    Parness, Aaron; Frost, Matthew A.; King, Jonathan P.

    2013-01-01

    This work is a method to drill into a rock surface regardless of the gravitational field or orientation. The required weight-on-bit (WOB) is supplied by a self-contained anchoring mechanism. The system includes a rotary percussive coring drill, forming a complete sampling instrument usable by robot or human. This method of in situ sample acquisition using micro - spine anchoring technology enables several NASA mission concepts not currently possible with existing technology, including sampling from consolidated rock on asteroids, providing a bolt network for astronauts visiting a near-Earth asteroid, and sampling from the ceilings or vertical walls of lava tubes and cliff faces on Mars. One of the most fundamental parameters of drilling is the WOB; essentially, the load applied to the bit that allows it to cut, creating a reaction force normal to the surface. In every drilling application, there is a minimum WOB that must be maintained for the system to function properly. In microgravity (asteroids and comets), even a small WOB could not be supported conventionally by the weight of the robot or astronaut. An anchoring mechanism would be needed to resist the reactions, or the robot or astronaut would push themselves off the surface and into space. The ability of the system to anchor itself to a surface creates potential applications that reach beyond use in low gravity. The use of these anchoring mechanisms as end effectors on climbing robots has the potential of vastly expanding the scope of what is considered accessible terrain. Further, because the drill is supported by its own anchor rather than by a robotic arm, the workspace is not constrained by the reach of such an arm. Yet, if the drill is on a robotic arm, it has the benefit of not reflecting the forces of drilling back to the arm s joints. Combining the drill with the anchoring feet will create a highly mobile, highly stable, and highly reliable system. The drilling system s anchor uses hundreds of microspine toes that independently find holes and ledges on a rock to create an anchor. Once the system is anchored, a linear translation mechanism moves the drill axially into the surface while maintaining the proper WOB. The linear translation mechanism is composed of a ball screw and stepper motor that can translate a carriage with high precision and applied load. The carriage slides along rails using self-aligning linear bearings that correct any axial misalignment caused by bending and torsion. The carriage then compresses a series of springs that simultaneously transmit the load to the drill along the bit axis and act as a suspension that compensates for the vibration caused by percussive drilling. The drill is a compacted, modified version of an off-the-shelf rotary percussive drill, which uses a custom carbide-tipped coring bit. By using rotary percussive drilling, the drill time is greatly reduced. The percussive action fractures the rock debris, which is removed during rotation. The final result is a 0.75-in. (.1.9- cm) diameter hole and a preserved 0.5- in. (.1.3-cm) diameter rock core. This work extends microspine technology, making it applicable to astronaut missions to asteroids and a host of robotic sampling concepts. At the time of this reporting, it is the first instrument to be demonstrated using microspine anchors, and is the first self-contained drill/anchor system to be demonstrated that is capable of drilling in inverted configurations and would be capable of drilling in microgravity.

  1. Ligand-enabled multiple absolute stereocontrol in metal-catalysed cycloaddition for construction of contiguous all-carbon quaternary stereocentres

    NASA Astrophysics Data System (ADS)

    Ohmatsu, Kohsuke; Imagawa, Naomichi; Ooi, Takashi

    2014-01-01

    The development of a general catalytic method for the direct and stereoselective construction of contiguous all-carbon quaternary stereocentres remains a formidable challenge in chemical synthesis. Here, we report a highly enantio- and diastereoselective [3+2] annulation reaction of 5-vinyloxazolidinones and activated trisubstituted alkenes catalysed by a palladium complex bearing a newly devised phosphine ligand with a chiral ammonium salt component, which enables the single-step construction of three contiguous stereocentres, including vicinal all-carbon quaternary stereocentres, in a five-membered heterocyclic framework. This stereoselective cycloaddition protocol relies on the remarkable ability of the chiral ligand to rigorously control the absolute stereochemistry of each chiral centre associated with the multiple bond-forming events, and provides a reliable catalytic process for the asymmetric synthesis of densely functionalized pyrrolidines.

  2. Efficient Light-Driven Oxidation of Alcohols Using an Organic Chromophore-Catalyst Assembly Anchored to TiO2.

    PubMed

    Pho, Toan V; Sheridan, Matthew V; Morseth, Zachary A; Sherman, Benjamin D; Meyer, Thomas J; Papanikolas, John M; Schanze, Kirk S; Reynolds, John R

    2016-04-13

    The ligand 5-PO3H2-2,2':5',2″-terthiophene-5-trpy, T3 (trpy = 2,2':6',2″-terpyridine), was prepared and studied in aqueous solutions along with its metal complex assembly [Ru(T3)(bpy)(OH2)](2+) (T3-Ru-OH2, bpy = 2,2'-bipyridine). T3 contains a phosphonic acid group for anchoring to a TiO2 photoanode under aqueous conditions, a terthiophene fragment for light absorption and electron injection into TiO2, and a terminal trpy ligand for the construction of assemblies comprising a molecular oxidation catalyst. At a TiO2 photoanode, T3 displays efficient injection at pH 4.35 as evidenced by the high photocurrents (∼350 uA/cm(2)) arising from hydroquinone oxidation. Addition of [Ru(bpy)(OTf)][OTf]2 (bpy = 2,2'-bipyridine, OTf(-) = triflate) to T3 at the free trpy ligand forms the molecular assembly, T3-Ru-OH2, with the oxidative catalyst fragment: [Ru(trpy)(bpy)(OH2)](2+). The new assembly, T3-Ru-OH2, was used to perform efficient light-driven oxidation of phenol (230 μA/cm(2)) and benzyl alcohol (25 μA/cm(2)) in a dye-sensitized photoelectrosynthesis cell. PMID:27032068

  3. Liposome Surface Functionalization Based on Different Anchoring Lipids via Staudinger Ligation

    PubMed Central

    Vabbilisetty, Pratima; Sun, Xue-Long

    2014-01-01

    Liposome surface functionalization facilitates enormous potential applications of liposomes, such as enhanced stability, bioactive liposome conjugates, and targeted drug, gene and image agent delivery. Anchoring lipids are needed for grafting ligands of interest and play important roles in ligands grafting density, liposome stability, and liposome chemical and physical characteristics as well. In this report, glyco-functionalized liposome systems based on two kinds of anchoring lipid, phosphatidylethonalamine (PE) and cholesterol (Chol) were prepared by post chemically selective functionalization via Staudinger ligation. The size and stability of the liposomes were confirmed by dynamic light scattering (DLS). Particularly, the impact of anchor lipids on the stability of glyco-functionalized liposomes was investigated by comparing two different anchor lipids, namely Chol-PEG2000-TP and DSPE-PEG2000-TP. In addition, the encapsulation and releasing capacity of the glycosylated liposome based on the two anchoring lipids were investigated by entrapping 5, 6-carboxyfluorescein (CF) dye and monitoring the fluorescence leakage, respectively. Furthermore, the density and accessibility of grafted carbohydrate residues on the liposome surface were evaluated for the two anchoring lipids-derived liposomes with lectin binding, respectively. PMID:24413731

  4. Disodium diselenide in colloidal nanocrystals: acting as an anion exchange precursor, a metal selenide precursor, and a chalcogenide ligand.

    PubMed

    Choi, Donghyeuk; Lee, Seungyeol; Lee, Junho; Cho, Kyung-Sang; Kim, Sang-Wook

    2015-01-18

    A new application area using a very simple alkali metal chalcogenide, disodium diselenide (Na2Se2), has been developed. The prepared alkali metal chalcogenide (disodium diselenide, Na2Se2) acts as an anionic exchange precursor (PbS to PbS-PbSe), a Se precursor for metal selenide nanoparticles (Ag to Ag2Se), and a MCC (FeO-MCC) depending on the type of colloidal nanoparticles. PMID:25431810

  5. A delicate electronic balance between metal and ligand in [Cu-P-Cu-P] diamondoids: oxidation state dependent plasticity and the formation of a singlet diradicaloid.

    PubMed

    Rhee, Young Min; Head-Gordon, Martin

    2008-03-26

    Transition metal atoms often participate in redox reactions as catalytic sites, where ligand groups play an important role in orchestrating catalytic activity, especially in metalloenzymes. A major issue is to understand connections between oxidation state and geometry at the metal center, because geometric reorganization is directly related to reaction rate. In this article, we analyze an intriguing oxidation-induced geometrical change in [Cu-P-Cu-P] ring structures ( approximately 0.6 A change in metal-metal distance) using quantum chemical approaches. We find that the Cu-P interactions in the ring of the neutral species consist of four localized P --> Cu dative bonds. Successive oxidations extract electrons predominantly from P atoms on the ring rather than Cu sites. It emerges that as a result, the Cu-P interactions change and also exhibit partial Cu(3d) --> P donation, which causes the large distortion in geometry. We also find that the dication possesses a large degree of diradical character, forming a rare example of an observed species that is a singlet diradicaloid. This hypothesis is supported by our computational results as well as previously reported experimental features. PMID:18314976

  6. Bone Anchored Hearing Aid

    PubMed Central

    2002-01-01

    Executive Summary Objective The objective of this health technology policy assessment was to determine the effectiveness and cost-effectiveness of bone-anchored hearing aid (BAHA) in improving the hearing of people with conduction or mixed hearing loss. The Technology The (BAHA) is a bone conduction hearing device that includes a titanium fixture permanently implanted into the mastoid bone of the skull and an external percutaneous sound processor. The sound processor is attached to the fixture by means of a skin penetrating abutment. Because the device bypasses the middle ear and directly stimulates the cochlea, it has been recommended for individuals with conduction hearing loss or discharging middle ear infection. The titanium implant is expected to last a lifetime while the external sound processor is expected to last 5 years. The total initial device cost is approximately $5,300 and the external sound processor costs approximately $3,500. Review of BAHA by the Medical Advisory Secretariat The Medical Advisory Secretariat’s review is a descriptive synthesis of findings from 36 research articles published between January 1990 and May 2002. Summary of Findings No randomized controlled studies were found. The evidence was derived from level 4 case series with relative small sample sizes (ranging from 30-188). The majority of the studies have follow-up periods of eight years or longer. All except one study were based on monaural BAHA implant on the side with the best bone conduction threshold. Safety Level 4 evidence showed that BAHA has been be implanted safely in adults and children with success rates of 90% or higher in most studies. No mortality or life threatening morbidity has been reported. Revision rates for tissue reduction or resiting were generally under 10% for adults but have been reported to be as high as 25% in pediatric studies. Adverse skin reaction around the skin penetration site was the most common complication reported. Most of these conditions were successfully treated with antibiotics, and only 1% to 2% required surgical revision. Less than 1% required removal of the fixture. Other complications included failure to osseointegrate and loss of fixture and/or abutment due to trauma or infection. Effectiveness Studies showed that BAHAs were implanted in people who have conduction or mixed hearing loss, congenital atresia or suppurative otitis media who were not candidates for surgical repair, and who cannot use conventional bone conduction hearing aids. The need for BAHA is not age- related. Objective audiometric measures and subjective patient satisfaction surveys showed that BAHA significantly improved the unaided and aided free field and sound field thresholds as well as speech discrimination in quiet and in noise for former users of conventional bone conduction hearing aids. The outcomes were ambiguous for former users of air conduction hearing aids. BAHA has been shown to reduce the frequency of ear infection and reduce the discharge particularly among patients with suppurative otitis media. Patients have reported that BAHA improved their quality of life. Reported benefits were improved speech intelligibility, better sound comfort, less pressure on the head, less skin irritation, greater cosmetic acceptance and increase in confidence. Main reported shortcomings were wind noise, feedback and difficulty in using the telephone. Experts and the BAHA manufacturer recommended that recipients of a BAHA implant be at least 5 years old. Challenges associated with the implantation of BAHA in pediatric patients include thin bone, soft bone, higher rates of fixture loss due to trauma, psychological problems, and higher revision rates due to rapid bone growth. The overall outcomes are comparable to adult BAHA. The benefits of pediatric BAHA (e.g. on speech development) appear to outweigh the disadvantages. Screening according to strict eligibility criteria, preoperative counselling, close monitoring by a physician with BAHA expertise and on-going follow-up were identified as critical factors for long-term implant survival. Examples of eligibility criteria were provided. Cost-effectiveness No literature on cost-effectiveness of BAHA was found. PMID:23074440

  7. Charge and Spin States in Schiff Base Metal Complexes with a Disiloxane Unit Exhibiting a Strong Noninnocent Ligand Character: Synthesis, Structure, Spectroelectrochemistry, and Theoretical Calculations.

    PubMed

    Cazacu, Maria; Shova, Sergiu; Soroceanu, Alina; Machata, Peter; Bucinsky, Lukas; Breza, Martin; Rapta, Peter; Telser, Joshua; Krzystek, J; Arion, Vladimir B

    2015-06-15

    Mononuclear nickel(II), copper(II), and manganese(III) complexes with a noninnocent tetradentate Schiff base ligand containing a disiloxane unit were prepared in situ by reaction of 3,5-di-tert-butyl-2-hydroxybenzaldehyde with 1,3-bis(3-aminopropyl)tetramethyldisiloxane followed by addition of the appropriate metal(II) salt. The ligand H2L resulting from these reactions is a 2:1 condensation product of 3,5-di-tert-butyl-2-hydroxybenzaldehyde with 1,3-bis(3-aminopropyl)tetramethyldisiloxane. The resulting metal complexes, NiL·0.5CH2Cl2, CuL·1.5H2O, and MnL(OAc)·0.15H2O, were characterized by elemental analysis, spectroscopic methods (IR, UV-vis, X-band EPR, HFEPR, (1)H NMR), ESI mass spectrometry, and single crystal X-ray diffraction. Taking into account the well-known strong stabilizing effects of tert-butyl groups in positions 3 and 5 of the aromatic ring on phenoxyl radicals, we studied the one-electron and two-electron oxidation of the compounds using both experimental (chiefly spectroelectrochemistry) and computational (DFT) techniques. The calculated spin-density distribution and localized orbitals analysis revealed the oxidation locus and the effect of the electrochemical electron transfer on the molecular structure of the complexes, while time-dependent DFT calculations helped to explain the absorption spectra of the electrochemically generated species. Hyperfine coupling constants, g-tensors, and zero-field splitting parameters have been calculated at the DFT level of theory. Finally, the CASSCF approach has been employed to theoretically explore the zero-field splitting of the S = 2 MnL(OAc) complex for comparison purposes with the DFT and experimental HFEPR results. It is found that the D parameter sign strongly depends on the metal coordination geometry. PMID:26030801

  8. ATHLETE : Double Auger Anchoring Mechanism

    NASA Technical Reports Server (NTRS)

    Shin, Joseph

    2011-01-01

    The All-Terrain Hex-Legged Extra-Terrestrial Explorer (ATHLETE) is a six-limbed robot designed to support surface explorations on Near Earth Objects, the Moon and Mars. ATHLETE can carry large payloads on its top deck and can carry a fully equipped pressurized habitat in low gravity. The robot has wheels on each of its six articulated limbs, allowing it to actively conform to terrain while driving and to walk when driving is impractical. With the use of a tool adapter, ATHLETE limbs can be equipped with end effectors to support various mission objectives. For work on Near Earth Objects and other microgravity environments, an anchoring mechanism is needed to keep the ATHLETE from floating off the surface. My goal for this spring session at JPL was to design and build a counter rotating, double auger, anchoring mechanism. The mechanism mates to the tool adapter and is driven off the wheel motor. The double auger anchoring mechanism will be tested in a regolith simulant that will determine the uplift capacity of the anchoring mechanism.

  9. Quantifying the density of surface capping ligands on semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Zhan, Naiqian; Palui, Goutam; Merkl, Jan-Philip; Mattoussi, Hedi

    2015-03-01

    We have designed a new set of coordinating ligands made of a lipoic acid (LA) anchor and poly(ethylene glycol) (PEG) hydrophilic moiety appended with a terminal aldehyde for the surface functionalization of QDs. This ligand design was combined with a recently developed photoligation strategy to prepare hydrophilic CdSe-ZnS QDs with good control over the fraction of intact aldehyde (-CHO) groups per nanocrystal. We further applied the efficient hydrazone ligation to react aldehyde-QDs with 2-hydrazinopyridine (2-HP). This covalent modification produces QD-conjugates with a well-defined absorption feature at 350 nm ascribed to the hydrazone chromophore. We exploited this unique optical signature to accurately measure the number of aldehyde groups per QD when the fraction of LA-PEG-CHO per nanocrystal was varied. This allowed us to extract an estimate for the number of LA-PEG ligands per QD. These results suggest that hydrazone ligation has the potential to provide a simple and general analytical method to estimate the number of surface ligands for a variety of nanocrystals such as metal, metal oxide and semiconductor nanocrystals.

  10. Metal-organic coordination architectures of tetrazole heterocycle ligands bearing acetate groups: Synthesis, characterization and magnetic properties

    NASA Astrophysics Data System (ADS)

    Hu, Bo-Wen; Zheng, Xiang-Yu; Ding, Cheng

    2015-12-01

    Two new coordination complexes with tetrazole heterocycle ligands bearing acetate groups, [Co(L)2]n (1) and [Co3(L)4(N3)2·2MeOH]n (2) (L=tetrazole-1-acetate) have been synthesized and structurally characterized. Single crystal structure analysis shows that the cobalt-complex 1 has the 3D 3,6-connected (42.6)2(44.62.88.10)-ant topology. By introducing azide in this system, complex 2 forms the 2D network containing the [Co3] units. And the magnetic properties of 1 and 2 have been studied.

  11. Ir Spectroscopy of Au-...(CO2)n Clusters: Strong Cluster Size Dependence of Metal-Ligand Interaction

    NASA Astrophysics Data System (ADS)

    Knurr, Benjamin J.; Weber, J. Mathias

    2012-06-01

    Gold is a widely used catalyst in many reactions. For example, negatively charged gold clusters have been shown to catalyze the oxidation of CO to CO2 [1], although the precise role of negative charge has not been understood. A previous study from our laboratory has shown that the binary complex [AuCO2]- has the CO2 ligand covalently bound to the gold, leading to significant charge transfer onto the CO2 unit and concomitant decrease of the OCO bond angle and weakening of the CO bonds [2]. The structure of this aurylformate anion is reminiscent of structural motifs assumed to play a role in a recent approach towards production of solar fuels using reductive activation of CO2 [3]. We report infrared spectra of Au-...(CO2)n clusters highlighting solvation mediated changes in the infrared signatures of the ligands. These results are discussed in the framework of quantum chemistry calculations. 1. U. Heiz and W.D. Schneider, J. Phys. D - Appl. Phys., 33 (2000) R85- R102. 2. A.D. Boese, H. Schneider, A.N. Gloess, and J.M. Weber, J. Chem. Phys., 122 (2005) 154301. 3. E.E. Barton, D.M. Rampulla, and A.B. Bocarsly, J. Am. Chem. Soc., 130 (2008) 6342.

  12. Metal-organic coordination architectures of azole heterocycle ligands bearing acetic acid groups: Synthesis, structure and magnetic properties

    SciTech Connect

    Hu Bowen; Zhao Jiongpeng; Yang Qian; Hu Tongliang; Du Wenping; Bu Xianhe

    2009-10-15

    Four new coordination complexes with azole heterocycle ligands bearing acetic acid groups, [Co(L{sup 1}){sub 2}]{sub n} (1), [CuL{sup 1}N{sub 3}]{sub n} (2), [Cu(L{sup 2}){sub 2}.0.5C{sub 2}H{sub 5}OH.H{sub 2}O]{sub n} (3) and [Co(L{sup 2}){sub 2}]{sub n} (4) (here, HL{sup 1}=1H-imidazole-1-yl-acetic acid, HL{sup 2}=1H-benzimidazole-1-yl-acetic acid) have been synthesized and structurally characterized. Single-crystal structure analysis shows that 3 and 4 are 2D complexes with 4{sup 4}-sql topologies, while another 2D complex 1 has a (4{sup 3}){sub 2}(4{sup 6})-kgd topology. And 2 is a 3D complex composed dinuclear mu{sub 1,1}-bridging azido Cu{sup II} entities with distorted rutile topology. The magnetic properties of 1 and 2 have been studied. - Graphical Abstract: The synthesis, crystal structure, and magnetic properties of the new coordination complexes with azole heterocycle ligands bearing acetic acid groups are reported.

  13. Two 2D metal-organic frameworks based on N-heterocyclic and polycarboxylates ligands: Syntheses, structures, and photoluminescent properties

    NASA Astrophysics Data System (ADS)

    Yan, Li; Li, Chuanbi; Zhu, Dongsheng

    2013-02-01

    Two novel complexes constructed from aromatic acid and N-heterocyclic ligands have been synthesized by hydrothermal reaction: {[Mn(dipt)(BDC)3ṡH2O]n (1) [dipt = 2-(2,4-dichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, BDC = terephthalic acid] and [Pb(dnpt)(BDC)2]n (2) [dnpt = 2-(4-nitrophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline]. Complexes 1 and 2 were characterized by elemental analysis, IR, single crystal X-ray diffraction and thermogravimetric analysis (TGA). The results suggest that complexes 1-2 exhibit 1D chain structure. The intermolecular C-H⋯O and N-H⋯O interactions extend the complexes into 2D networks, and the existing H-bonds further stabilized the title complexes, which can be proved by TGA experiment. Furthermore, the solid-state fluorescence spectrum of complexes 1 and 2 were also investigated, as well as the ligands dipt and dnpt.

  14. Modern spectroscopic techniques in the characterization of Schiff base macrocyclic ligand and its complexes with transition metals

    NASA Astrophysics Data System (ADS)

    Chandra, Sulekh; Gupta, Lokesh Kumar

    2005-11-01

    Mn(II), Co(II), Ni(II), and Cu(II) complexes with a new azamacrocyclic tetradentate [N 4] ligand i.e. 2,3,9,10-tetraphenyl;l,4,8,11-tetraazacyclotetradeca;1,3,8,10-tetraene (L) have been synthesized and characterized by elemental analysis, molar conductance measurements, magnetic susceptibility measurements, mass, 1HNMR, IR, electronic and EPR spectral studies. On the basis of their non-electrolytic nature, the probable formula of the complexes is proposed to be [M(L)X 2], where M = Mn(II), Co(II), Ni(II), and Cu(II), X = Cl - and NO 3-, in dimethylformamide (DMF). All the complexes are of high-spin type and found to have six coordinated, octahedral geometry for Mn(II), Co(II), and Ni(II) complexes, and tetragonal for Cu(II) complexes. Macrocyclic ligand and its complexes have also been screened against pathogenic bacteria and fungi in vitro as growth inhibiting agent.

  15. 76 FR 30301 - Commercial Acquisition; Anchor Tenancy

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-25

    ... SPACE ADMINISTRATION 48 CFR Part 1812 RIN 2700-AD64 Commercial Acquisition; Anchor Tenancy AGENCY... authority under Section 401 of the Commercial Space Competitiveness Act (CSCA) of 1992. NASA may enter into multi-year anchor tenancy contracts for commercial space goods or services. Anchor Tenancy means...

  16. pH-induced metal-ligand cross-links inspired by mussel yield self-healing polymer networks with near-covalent elastic moduli

    PubMed Central

    Holten-Andersen, Niels; Harrington, Matthew J.; Birkedal, Henrik; Lee, Bruce P.; Messersmith, Phillip B.; Lee, Ka Yee C.; Waite, J. Herbert

    2011-01-01

    Growing evidence supports a critical role of metal-ligand coordination in many attributes of biological materials including adhesion, self-assembly, toughness, and hardness without mineralization [Rubin DJ, Miserez A, Waite JH (2010) Advances in Insect Physiology: Insect Integument and Color, eds Jérôme C, Stephen JS (Academic Press, London), pp 75–133]. Coordination between Fe and catechol ligands has recently been correlated to the hardness and high extensibility of the cuticle of mussel byssal threads and proposed to endow self-healing properties [Harrington MJ, Masic A, Holten-Andersen N, Waite JH, Fratzl P (2010) Science 328:216–220]. Inspired by the pH jump experienced by proteins during maturation of a mussel byssus secretion, we have developed a simple method to control catechol-Fe3+ interpolymer cross-linking via pH. The resonance Raman signature of catechol-Fe3+ cross-linked polymer gels at high pH was similar to that from native mussel thread cuticle and the gels displayed elastic moduli (G′) that approach covalently cross-linked gels as well as self-healing properties. PMID:21278337

  17. Fluorescent Cross-Linked Supramolecular Polymer Constructed by Orthogonal Self-Assembly of Metal-Ligand Coordination and Host-Guest Interaction.

    PubMed

    Qian, Xiaomin; Gong, Weitao; Li, Xiaopeng; Fang, Le; Kuang, Xiaojun; Ning, Guiling

    2016-05-10

    A new host molecule consists of four terpyridine groups as the binding sites with zinc(II) ion and a copillar[5]arene incorporated in the center as a spacer to interact with guest molecule was designed and synthesized. Due to the 120 ° angle of the rigid aromatic segment, a cross-linked dimeric hexagonal supramolecular polymer was therefore generated as the result of the orthogonal self-assembly of metal-ligand coordination and host-guest interaction. UV/Vis spectroscopy, (1) H NMR spectroscopy, viscosity and dynamic light-scattering techniques were employed to characterize and understand the cross-linking process with the introduction of zinc(II) ion and guest molecule. More importantly, well-defined morphology of the self-assembled supramolecular structure can be tuned by altering the adding sequence of the two components, that is, the zinc(II) ion and the guest molecule. In addition, introduction of a competitive ligand suggested the dynamic nature of the supramolecular structure. PMID:27062539

  18. pH-induced metal-ligand cross-links inspired by mussel yield self-healing polymer networks with near-covalent elastic moduli.

    PubMed

    Holten-Andersen, Niels; Harrington, Matthew J; Birkedal, Henrik; Lee, Bruce P; Messersmith, Phillip B; Lee, Ka Yee C; Waite, J Herbert

    2011-02-15

    Growing evidence supports a critical role of metal-ligand coordination in many attributes of biological materials including adhesion, self-assembly, toughness, and hardness without mineralization [Rubin DJ, Miserez A, Waite JH (2010) Advances in Insect Physiology: Insect Integument and Color, eds Jérôme C, Stephen JS (Academic Press, London), pp 75-133]. Coordination between Fe and catechol ligands has recently been correlated to the hardness and high extensibility of the cuticle of mussel byssal threads and proposed to endow self-healing properties [Harrington MJ, Masic A, Holten-Andersen N, Waite JH, Fratzl P (2010) Science 328:216-220]. Inspired by the pH jump experienced by proteins during maturation of a mussel byssus secretion, we have developed a simple method to control catechol-Fe(3+) interpolymer cross-linking via pH. The resonance Raman signature of catechol-Fe(3+) cross-linked polymer gels at high pH was similar to that from native mussel thread cuticle and the gels displayed elastic moduli (G') that approach covalently cross-linked gels as well as self-healing properties. PMID:21278337

  19. Some metal complexes of three new potentially heptadentate (N4O3) tripodal Schiff base ligands; synthesis, characterizatin and X-ray crystal structure of a novel eight coordinate Gd(III) complex

    NASA Astrophysics Data System (ADS)

    Golbedaghi, Reza; Moradi, Somaeyh; Salehzadeh, Sadegh; Blackman, Allan G.

    2016-03-01

    The symmetrical and asymmetrical potentially heptadentate (N4O3) tripodal Schiff base ligands (H3L1-H3L3) were synthesized from the condensation reaction of three tripodal tetraamine ligands tpt (trpn), tris (3-aminopropyl) amine; ppe (abap), (2-aminoethyl)bis(3-aminopropyl)amine, and tren, tris(2-aminoethyl)amine, with 5-methoxysalicylaldehyde. Then, the reaction of Ln(III) (Ln = Gd, La and Sm), Al(III), and Fe(III) metal ions with the above ligands was investigated. The resulting compounds were characterized by IR, mass spectrometry and elemental analysis in all cases and NMR spectroscopy in the case of the Schiff base ligands. The X-ray crystal structure of the Gd complex of H3L3 ligand showed that in addition to all donor atoms of the ligand one molecule of H2O is also coordinated to the metal ion and a neutral eight-coordinate complex is formed.

  20. Bifunctional DTPA-type ligand

    SciTech Connect

    Gansow, O.A.; Brechbiel, M.W.

    1990-03-26

    The subject matter of the invention relates to bifunctional cyclohexyl DTPA ligands and methods of using these compounds. Specifically, such ligands are useful for radiolabeling proteins with radioactive metals, and can consequently be utilized with respect to radioimmunoimaging and/or radioimmunotherapy.

  1. Synthesis and characterization of a three dimensional zinc(II) metal-organic framework constructed from flexible 1,2,3,4-tetra-(4-pyridyl)-butane ligand

    NASA Astrophysics Data System (ADS)

    Lin, Jianguo; Wu, Peiheng; Kang, Lin; Lu, Changsheng; Meng, Qingjin

    2011-08-01

    Employing the flexible tetrapodal ligand 1,2,3,4-tetra-(4-pyridyl)-butane (TPB) along with fumaric acid (H 2FMA) as the bridges, a metal-organic framework of [Zn(TPB)(FMA)·(2H 2O)] ( 1) was obtained and characterized by elemental analysis, spectral method (IR), single crystal X-ray diffraction, thermal gravimetric analysis (TGA) and fluorescent property. This polymer exhibits a three dimensional (3D) dense network with an interesting (4,4)-connected PtS topology. It also displays good thermal stability and strong photoluminescence in the blue region band. Thus it may serve as a candidate of thermally stable blue-light-emitting photoluminescent material.

  2. Influence of polyoxometalate ligands on the nature of high-valent transition metal nitrido species. A theoretical analysis of experimentally known and unprecedented compounds.

    PubMed

    Romo, Susanna; Antonova, Nadya S; Carbó, Jorge J; Poblet, Josep M

    2008-10-14

    The electronic structure of group 6-8 transition metal (TM) nitrido derivatives [PW(11)O(39){TM(VI)N}](4-) is studied computationally and the potential reactivity of the polyoxoanions is discussed. The observed electrophilic reactivity for the Ru(VI) nitrido derivative is rationalized from frontier molecular orbital analysis. When we move to the left or down in the periodic table (TM = Os, Tc, Re, Mo and W) the electrophilic character of the polyoxometalate decreases or the cluster should be better regarded as a nucleophile. The DFT analysis of the redox properties suggests that the still unknown high-valent Mn(VI)N and Fe(VI)N units could be stabilized by the porphyrin-like ligand [PW(11)O(39)](7-) and their electronic structure indicates that these anions should have a high potential reactivity towards nucleophiles. PMID:18813370

  3. Cross-Linking the Fibers of Supramolecular Gels Formed from a Tripodal Terpyridine Derived Ligand with d-Block Metal Ions.

    PubMed

    Kotova, Oxana; Daly, Ronan; dos Santos, Cidália M G; Kruger, Paul E; Boland, John J; Gunnlaugsson, Thorfinnur

    2015-08-17

    The tripodal terpyridine ligand, L, forms 1D helical supramolecular polymers/gels in H2O-CH3OH solution mediated through hydrogen bonding and π-π interactions. These gels further cross-link into 3D supramolecular metallogels with a range of metal ions (M) such as Fe(II), Ni(II), Cu(II), Zn(II), and Ru(III); the cross-linking resulting in the formation of colored or colorless gels. The fibrous morphology of these gels was confirmed using scanning electron microscopy (SEM); while the self-assembly processes between L and M were investigated by absorbance and emission spectroscopy from which their binding constants were determined by using a nonlinear regression analysis. PMID:26222397

  4. Metal flux and dynamic speciation at (bio)interfaces. Part VI: The roles of simple, fulvic and aggregate complexes on computed metal flux in freshwater ligand mixtures; comparison of Pb, Zn and Ni at planar and microspherical interfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Zeshi; Buffle, Jacques

    2009-03-01

    The computations of metal flux in aquatic systems, at consuming interfaces like microorganism surfaces are of major importance in ecotoxicology and dynamic risk assessment. In this paper, the flux of Zn(II) and Ni(II), at a planar consuming interface in a typical natural freshwater, are studied. The system includes (a) simple ligands (OH -, CO32-); (b) fulvics; (c) aggregates, as complexants, i.e., those which play the major roles in controlling the metal distribution and/or metal flux in aquatic media. The above two metals are chosen because they participate, respectively, to intermediate and very slow chemical reactions with complexing sites, and are thus complementary to Pb(II) and Cu(II) (two metals with very fast reactions) studied in Parts III-V of this series. The effects of the various physico-chemical factors, in particular, the diffusion layer thickness, the stability constants and complexing site distribution of fulvics and the size distribution of aggregates, are studied in details. The contribution to the flux, of each complex type, is computed. This paper also compares the dynamic behaviour of Pb(II), Zn(II) and Ni(II) as well as the labilities and flux contributions of their various complexes at planar and microspherical interfaces. This enables to make predictions on biouptake by microorganisms.

  5. Electrochemical, linear optical, and nonlinear optical properties and interpretation by density functional theory calculations of (4-N,N-dimethylaminostyryl)-pyridinium pendant group associated with polypyridinic ligands and respective multifunctional metal complexes (Ru(II) or Zn(II)).

    PubMed

    Dumur, Frédéric; Mayer, Cédric R; Hoang-Thi, Khuyen; Ledoux-Rak, Isabelle; Miomandre, Fabien; Clavier, Gilles; Dumas, Eddy; Méallet-Renault, Rachel; Frigoli, Michel; Zyss, Joseph; Sécheresse, Francis

    2009-09-01

    The synthesis, linear optical and nonlinear optical properties, as well as the electrochemical behavior of a series of pro-ligands containing the 4-(4-N,N-dimethylaminostyryl)-1-methyl pyridinium (DASP(+)) group as a push-pull moiety covalently linked to terpyridine or bipyridine as chelating ligands are reported in this full paper. The corresponding multifunctional Ru(II) and Zn(II) complexes were prepared and investigated. The structural, electronic, and optical properties of the pro-ligands and the ruthenium complexes were investigated using density functional theory (DFT) and time-dependent (TD) DFT calculations. A fairly good agreement was observed between the experimental and the calculated electronic spectra of the pro-ligands and their corresponding ruthenium complexes. A quenching of luminescence was evidenced in all ruthenium complexes compared with the free pro-ligands but even the terpyridine-functionalized metal complexes exhibited detectable luminescence at room temperature. Second order nonlinear optical (NLO) measurements were performed by Harmonic Light Scattering and the contribution of the DASP(+) moieties (and their relative ordering) and the metal-polypyridyl core need to be considered to explain the nonlinear optical properties of the metal complexes. PMID:19642646

  6. Coordination mode of pentadentate ligand derivative of 5-amino-1,3,4-thiadiazole-2-thiol with nickel(II) and copper(II) metal ions: Synthesis, spectroscopic characterization, molecular modeling and fungicidal study

    NASA Astrophysics Data System (ADS)

    Chandra, Sulekh; Gautam, Seema; Kumar, Amit; Madan, Molly

    2015-02-01

    Complexes of nickel(II), and copper(II) were synthesized with pantadentate ligand i.e. 3,3‧-thiodipropionicacid-bis(5-amino-1,3,4-thiadiazole-2-thiol) (L). The ligand was synthesized by the condensation of thiodipropionic acid and 5-amino-1,3,4-thiadiazole-2-thiol in 1:2 ratio, respectively. Synthesized ligand was characterized by elemental analysis, mass, 1H NMR, IR, and molecular modeling. All the complexes were characterized by elemental analysis, molar conductance, magnetic moment, IR, electronic spectra, ESR, and molecular modeling. The newly synthesized complexes possessed general composition [M(L)X2] where M = Ni(II), Cu(II), L = pantadentate ligand and X = Cl-, CH3COO-. The IR spectral data indicated that the ligand behaved as a pantadentate ligand and coordinated to the metal ion through N2S3 donor atoms. The molar conductance value of Ni(II), and Cu(II) complexes in DMSO corresponded to their electrolytic behavior. On the basis of spectral study, octahedral and tetragonal geometry was assigned for Ni(II) and Cu(II) complexes, respectively. In vitro fungicidal study of ligand and its complexes was investigated against fungi Candida albicans, Candida parapsilosis, Candidia krusei, and Candida tropicalis by means of well diffusion method.

  7. Tuning the Formations of Metal-Organic Frameworks by Modification of Ratio of Reactant, Acidity of Reaction System, and Use of a Secondary Ligand

    SciTech Connect

    Gao, Q; Xie, YB; Li, JR; Yuan, DQ; Yakovenko, AA; Sun, JH; Zhou, HC

    2012-01-01

    Four porous coordination networks (PCNs), {[Zn3O(H2O)(3)(adc)(3)]center dot 2(C2H6NH2)center dot 2(DMF)center dot 3(H2O)}(n) (PCN-131), Zn-2(DMA)(2)(adc)(2)]center dot 2(DMA)}(n) (PCN-132), {[Zn3O(DMF)(adc)(3)(4,4'-bpy)]center dot 2(C2H6NH2)center dot S}(n) (PCN-131'), and {[Zn(adc)(4,4'-bpy)(0.5)]center dot S}(n) (PCN-132'), have been synthesized by the assembly of anthrancene-9,10-dicarboxylic acid (H(2)adc) with Zn(II) under different reaction conditions, including modifications of reactant ratio, acidity variations, and the use of a secondary ligand. Single-crystal X-ray diffraction studies reveal that PCN-131, obtained from the dimethylformamide (DMF) solution under acid condition, has a three-dimentional (3D) framework structure with one-dimensional (1D) honeycomb channels. PCN-132 isolated from dimethylacetamide (DMA) solution without adding acid in synthesis is a two-dimensional (2D) layer compound. By employing 4,4'-bipyridyl (4,4'-bpy) as a secondary ligand, PCN-131' and PCN-132' were synchronously synthesized as a mixture outcome with more PCN-131' than PCN-132'. In PCN-131', 4,4'-bpy acting as a secondary ligand is arranged inside the honeycomb channel of the 3D PCN-131, resulting in an effective improvement of thermal stability of the network, while in PCN-132', 4,4'-bpy ligands link 2D layers of PCN-132 to form a pillared-layer 3D framework Gas adsorption has been performed for selected materials. The results show that the framework of PCN-131 is thermally unstable after removing the solvent molecules coordinated to their metal sites. While PCN-131' is stable for gas uptake, with an evaluated Langmuir surface area of 199.04 m(2) g(-1), it shows a selective adsorption of CO2 over CH4.

  8. Gas adsorption and gas mixture separations using mixed-ligand MOF material

    DOEpatents

    Hupp, Joseph T.; Mulfort, Karen L.; Snurr, Randall Q.; Bae, Youn-Sang

    2011-01-04

    A method of separating a mixture of carbon dioxiode and hydrocarbon gas using a mixed-ligand, metal-organic framework (MOF) material having metal ions coordinated to carboxylate ligands and pyridyl ligands.

  9. Tetrasilacyclobutadiene ((t)Bu(2)MeSi)(4)Si(4): a new ligand for transition-metal complexes.

    PubMed

    Takanashi, Kazunori; Lee, Vladimir Ya; Matsuno, Tadahiro; Ichinohe, Masaaki; Sekiguchi, Akira

    2005-04-27

    The anionic complex of [tetrakis(di-tert-butylmethylsilyl) tetrasilacyclobutadiene]dicarbonylcobalt, [(R4Si4)Co(CO)2]-.K+ (R = SiMetBu2) 2-.K+, was synthesized by the reaction of tetrasilacyclobutadiene dianion dipotassium salt [R4Si4]2-.2K+ 1 with an excess of CpCo(CO)2 in THF. X-ray analysis of 2-.[K+(diglyme)2(THF)] showed an almost planar Si4 ring of rectangular shape with an in-plane arrangement of the silyl substituents. 2- was also prepared as a free anion with the [K+[2.2.2]cryptand] counterion by complexation with [2.2.2]cryptand and as a dimer {2-.[K+(THF)3]}2 without complexing reagents in THF. Such a tetrasilacyclobutadiene fragment represents a new type of ligand for Co complexes, being the first example of a cyclobutadiene containing only heavier group 14 elements. PMID:15839657

  10. Liquid Injection Field Desorption Ionization Mass Spectrometry of Cyclic Metal Carbonyl Complexes with Tetra-Antimony Ligands

    NASA Astrophysics Data System (ADS)

    Breunig, Hans J.; Linden, H. Bernhard; Moldovan, Ovidiu

    2013-01-01

    Reactions of (norbornadiene)Cr(CO)4 or cis-(piperidine)2Mo(CO)4 with R2Sb-SbR2, and cyclo-(R'Sb)n (R' = Et, n-Pr; n = 4, 5) give the complexes cyclo-[M(CO)4(R2Sb-SbR'- SbR'-SbR2)] ( 1: M = Cr, R = Me, R'= Et; 2: M = Mo, R = Et, R' = Et; 3: M = Mo, R = Et, R' = n-Pr). Not accessible to established characterization methods, the oily, extremely reactive unpurified mixture of 3 with scrambled ligands was characterized by mass spectrometry using liquid injection field desorption ionization (LIFDI). [Figure not available: see fulltext.

  11. Deepwater operations demand safe, stable anchoring

    SciTech Connect

    Olsen, O.A.; Kvalstad, T.; Lereim, J.; Lohne, P.W.; Namork, J.

    1982-05-01

    The tension-leg system is characterized by the ability to suppress first-order wave-induced motions in addition to the position-keeping ability. A different philosophy is followed for the catenary system, allowing the platform to be free floating. The anchoring system affects the motion behavior of the structure only to a minor degree. A discussion is presented of excitation sources, quasistatic method, anchor design and performance, fluke anchors, pile anchors, gravity anchors, mooring lines, corrosion protection systems, and, maintenance. 10 refs.

  12. Synthesis and characterization of d{sup 10} metal complexes with mixed 1,3-di(1H-imidazol-4-yl)benzene and multicarboxylate ligands

    SciTech Connect

    Chen, Zhi-Hao; Zhao, Yue; Chen, Shui-Sheng; Wang, Peng; Sun, Wei-Yin

    2013-06-15

    Seven new coordination polymers [Zn(H{sub 2}L)(mbdc)] (1), [Zn(H{sub 3}L)(btc)] (2), [Zn(H{sub 2}L)(Hbtc)] (3), [Zn(H{sub 2}L)(Hbtc)]·H{sub 2}O (4), [Zn{sub 2}(H{sub 2}L)(btc)(μ{sub 2}-OH)] (5), [Cd(H{sub 2}L)(mbdc)] (6) and [Cd{sub 3}(H{sub 2}L){sub 2}(btc){sub 2}(H{sub 2}O)]·5H{sub 2}O (7) were synthesized by reactions of the corresponding metal salt with rigid ligand 1,3-di(1H-imidazol-4-yl)benzene (H{sub 2}L) and different carboxylic acids of 1,3-benzenedicarboxylic acid (H{sub 2}mbdc) and benzene-1,3,5-tricarboxylic acid (H{sub 3}btc), respectively. The results of X-ray crystallographic analysis indicate that complex 1 is 1D chain while 2 is a (3,3)-connected 2D network with Point (Schläfli) symbol of (4,8{sup 2}). Complexes 3 and 6 are 2D networks, 4 is a 3-fold interpenetrating 3D framework with Point (Schläfli) symbol of (6{sup 5},8) and 5 is a (3,8)-connected 2D network with Point (Schläfli) symbol of (3,4{sup 2}){sub 2}(3{sup 4},4{sup 6},5{sup 6},6{sup 8},7{sup 3},8), while 7 is a (3,10)-connected 3D net with Schläfli symbol of (3,4,5){sub 2}(3{sup 4},4{sup 8},5{sup 18},6{sup 12},7{sup 2},8). The thermal stability and photoluminescence of the complexes were investigated. Furthermore, DFT calculations were performed for 2–4 to discuss the temperature controlled self-assembly of the complexes. - Graphical abstract: Seven new coordination polymers with multicarboxylate and rigid ditopic 4-imidazole containing ligands have been obtained and found to show different structures and topologies. - Highlights: • Metal complexes with diverse structures of 1D chain, 2D network and 3D framework. • Mixed ligands of 1,3-di(1H-imidazol-4-yl)benzene and multicarboxylate. • Photoluminescence property.

  13. Cyclopentaneteracarboxylic Metal-Organic Frameworks: Tuning the Distance between Layers and Pore Structures with N-Ligands.

    PubMed

    Yang, Qingxiang; Ren, ShuangShuang; Hao, Ying; Zhao, Qianqian; Chen, Zhijun; Zheng, Hegen

    2016-05-16

    Five new isomorphic coordination polymers of the Co(II) ion, namely, {[Co2L(bpy)0.5(H2O)2]·2H2O}n (1), {[Co2L(pbyb)0.5(H2O)2]·3H2O}n (2), {[Co2L(dpe)0.5(H2O)2]·2H2O}n (3), {[Co2L(dpa)0.5(H2O)2]·2.5H2O}n (4), and {[Co2L(dip)0.5(H2O)2]·3.5H2O}n (5) (H4L = cis,cis,cis,cis-1,2,3,4-cyclopentaneteracarboxylic acid, bpy = 4,4'-bipyridine, pbyb = 1,4-di(pyridine-4-yl)benzene, dpe = 1,2-di(pyridine-4-yl)ethane, dpa = (E)-1,2-di(pyridin-4-yl)diazene, and dip = 1,4-di(1H-imidazol-1-yl)benzene), have been synthesized under hydrothermal conditions. The L(4-) ligand maintains its original conformation of SSRR in all of these compounds, but {Co5L}n clusters show mirror coordination symmetry in 1, 2, and 4 while the clusters in 3 and 5 do not. The addition of different N-ligands can tune the distance between {Co2L}n layers and change the pore structures of the frameworks. Magnetic susceptibility measurements indicate that 1-5 exhibit antiferromagnetic behavior. PMID:27111488

  14. Synthesis of N4 donor macrocyclic Schiff base ligands and their Ru (II), Pd (II), Pt (II) metal complexes for biological studies and catalytic oxidation of didanosine in pharmaceuticals

    NASA Astrophysics Data System (ADS)

    Ravi krishna, E.; Muralidhar Reddy, P.; Sarangapani, M.; Hanmanthu, G.; Geeta, B.; Shoba Rani, K.; Ravinder, V.

    2012-11-01

    A series of tetraaza (N4 donor) macrocyclic ligands (L1-L4) were derived from the condensation of o-phthalaldehyde (OPA) with some substituted aromatic amines/azide, and subsequently used to synthesize the metal complexes of Ru(II), Pd(II) and Pt(II). The structures of macrocyclic ligands and their metal complexes were characterized by elemental analyses, IR, 1H &13C NMR, mass and electronic spectroscopy, thermal, magnetic and conductance measurements. Both the ligands and their complexes were screened for their antibacterial activities against Gram positive and Gram negative bacteria by MIC method. Besides, these macrocyclic complexes were investigated as catalysts in the oxidation of pharmaceutical drug didanosine. The oxidized products were further treated with sulphanilic acid to develop the colored products to determine by spectrophotometrically. The current oxidation method is an environmentally friendly, simple to set-up, requires short reaction time, produces high yields and does not require co-oxidant.

  15. The ROSETTA Lander anchoring system

    NASA Astrophysics Data System (ADS)

    Thiel, Markus; Stöcker, Jakob; Rohe, Christian; Kömle, Norbert I.; Kargl, Günter; Hillenmaier, Olaf; Lell, Peter

    2003-09-01

    A major goal of the ESA cornerstone mission ROSETTA is to land a package of scientific instruments known as the ROSETTA Lander on the nucleus of a comet. Due to the low gravity a highly reliable fixation of the ROSETTA Lander to the target comet 67P/Churyumov-Gerasimenko (3rd) is essential. For that purpose a redundant Anchoring System, consisting of two pyrotechnically actuated Anchoring Harpoons and a redundant Control Electronics has been developed, built and qualified at the Max-Planck-Institut für extraterrestrische Physik (MPE), Garching. The pyrotechnical gas generator has been developed jointly by Pyroglobe GmbH and MPE, the procurement of the control electronics has been sub-contracted to Magson GmbH, Berlin. A study to obtain a suitable lubrication method for the commutator of a brushed DC motor has been conducted at the European Space Tribology Laboratory (ESTL; S. D. Lewis et al., 2003).

  16. Anchoring in Numeric Judgments of Visual Stimuli.

    PubMed

    Langeborg, Linda; Eriksson, Mårten

    2016-01-01

    This article investigates effects of anchoring in age estimation and estimation of quantities, two tasks which to different extents are based on visual stimuli. The results are compared to anchoring in answers to classic general knowledge questions that rely on semantic knowledge. Cognitive load was manipulated to explore possible differences between domains. Effects of source credibility, manipulated by differing instructions regarding the selection of anchor values (no information regarding anchor selection, information that the anchors are randomly generated or information that the anchors are answers from an expert) on anchoring were also investigated. Effects of anchoring were large for all types of judgments but were not affected by cognitive load or by source credibility in either one of the researched domains. A main effect of cognitive load on quantity estimations and main effects of source credibility in the two visually based domains indicate that the manipulations were efficient. Implications for theoretical explanations of anchoring are discussed. In particular, because anchoring did not interact with cognitive load, the results imply that the process behind anchoring in visual tasks is predominantly automatic and unconscious. PMID:26941684

  17. Anchoring in Numeric Judgments of Visual Stimuli

    PubMed Central

    Langeborg, Linda; Eriksson, Mårten

    2016-01-01

    This article investigates effects of anchoring in age estimation and estimation of quantities, two tasks which to different extents are based on visual stimuli. The results are compared to anchoring in answers to classic general knowledge questions that rely on semantic knowledge. Cognitive load was manipulated to explore possible differences between domains. Effects of source credibility, manipulated by differing instructions regarding the selection of anchor values (no information regarding anchor selection, information that the anchors are randomly generated or information that the anchors are answers from an expert) on anchoring were also investigated. Effects of anchoring were large for all types of judgments but were not affected by cognitive load or by source credibility in either one of the researched domains. A main effect of cognitive load on quantity estimations and main effects of source credibility in the two visually based domains indicate that the manipulations were efficient. Implications for theoretical explanations of anchoring are discussed. In particular, because anchoring did not interact with cognitive load, the results imply that the process behind anchoring in visual tasks is predominantly automatic and unconscious. PMID:26941684

  18. Application of biotic ligand and toxicokinetic-toxicodynamic modeling to predict the accumulation and toxicity of metal mixtures to zebrafish larvae.

    PubMed

    Gao, Yongfei; Feng, Jianfeng; Han, Feng; Zhu, Lin

    2016-06-01

    Predicting the accumulation and toxicity of mixtures of metals to aquatic organisms is a key challenge in ecotoxicological studies. In this study, the accumulation and toxicity of mixed essential (Cu) and nonessential (Cd and Pb) metals in zebrafish larvae exposed to a binary mixture of these elements at environmentally relevant concentrations were predicted using a refined toxicokinetic (TK)-toxicodynamic (TD) model aided with biotic ligand model (BLM) and toxic equivalent factor (TEF) approach. Competitive inhibition and non-competitive interaction/inhibition were observed in bio-uptake. Both Pb and Cd behaved as competitive inhibitors of Cu uptake at high Cu concentrations (>0.1 μM). By contrast, Cu uptake was independent of Cd or Pb when the Cu concentrations were below 10(-7) M. Furthermore, low concentrations of Cu had an adiaphorous effect on Cd or Pb uptake. Cd uptake was inhibited by Pb, and the Pb uptake rates consistently decreased in the presence of Cd. The accumulation processes of Cd-Pb, Cu-Cd, and Cu-Pb were accurately predicted by the BLM-aided TK models. The traditional TD model could successfully predict the toxicity of Cd-Pb mixtures, but not those of Cu-Cd or Cu-Pb mixtures. The revised TD model, which considered the possible different killing rates (Kk) above or below the threshold, offered better prediction for the toxicity of Cu-Cd or Cu-Pb mixtures. The overall findings may be of key significance in understanding and predicting metal uptake, accumulation, and toxicity in binary or multiple metal exposure scenarios. PMID:26874871

  19. Ab initio and density functional theoretical design and screening of model crown ether based ligand (host) for extraction of lithium metal ion (guest): effect of donor and electronic induction.

    PubMed

    Boda, Anil; Ali, Sk Musharaf; Rao, Hanmanth; Ghosh, Sandip K

    2012-08-01

    The structures, energetic and thermodynamic parameters of model crown ethers with different donor, cavity and electron donating/ withdrawing functional group have been determined with ab initio MP2 and density functional theory in gas and solvent phase. The calculated values of binding energy/ enthalpy for lithium ion complexation are marginally higher for hard donor based aza and oxa crown compared to soft donor based thia and phospha crown. The calculated values of binding enthalpy for lithium metal ion with 12C4 at MP2 level of theory is in good agreement with the available experimental result. The binding energy is altered due to the inductive effect imparted by the electron donating/ withdrawing group in crown ether, which is well correlated with the values of electron transfer. The role of entropy for extraction of hydrated lithium metal ion by different donor and functional group based ligand has been demonstrated. The HOMO-LUMO gap is decreased and dipole moment of the ligand is increased from gas phase to organic phase because of the dielectric constant of the solvent. The gas phase binding energy is reduced in solvent phase as the solvent molecules weaken the metal-ligand binding. The theoretical values of extraction energy for LiCl salt from aqueous solution in different organic solvent is validated by the experimental trend. The study presented here should contribute to the design of model host ligand and screening of solvent for metal ion recognition and thus can contribute in planning the experiments. PMID:22318713

  20. "Click" tetradentate ligands.

    PubMed

    Hao, Erhong; Wang, Zhaoyun; Jiao, Lijuan; Wang, Shaowu

    2010-03-14

    A series of triazole-based N4 tetradentate ligands 1a-d are efficiently synthesized using Cu(I)-catalyzed azide-alkyne "click" strategy and are readily coordinated to many metal ions (e.g. Mn(II), Ni(II), Zn(II) and Fe(II)). The X-ray structures of the resultant metal-complexes (4a-d, 5a, 6a and 7a) reveal an octahedral mononuclear structure with two co-ligands bonded in cis sites and the two triazoles as nitrogen donors to the metal center. The Mn(II)-complexes (4a-d) show efficient catalytic activities in the epoxidation of various aliphatic terminal olefins with peracetic acid, and feature with low catalyst loading, fast conversion and high yields. PMID:20179861

  1. Phosphonate-anchored monolayers for antibody binding to magnetic nanoparticles.

    PubMed

    Benbenishty-Shamir, Helly; Gilert, Roni; Gotman, Irena; Gutmanas, Elazar Y; Sukenik, Chaim N

    2011-10-01

    Targeted delivery of magnetic iron oxide nanoparticles (IONPs) to a specific tissue can be achieved by conjugation with particular biological ligands on an appropriately functionalized IONP surface. To take best advantage of the unique magnetic properties of IONPs and to maximize their blood half-life, thin, strongly bonded, functionalized coatings are required. The work reported herein demonstrates the successful application of phosphonate-anchored self-assembled monolayers (SAMs) as ultrathin coatings for such particles. It also describes a new chemical approach to the anchoring of antibodies on the surface of SAM-coated IONPs (using nucleophilic aromatic substitution). This anchoring strategy results in stable, nonhydrolyzable, covalent attachment and allows the reactivity of the particles toward antibody binding to be activated in situ, such that prior to the activation the modified surface is stable for long-term storage. While the SAMs do not have the well-packed crystallinity of other such monolayers, their structure was studied using smooth model substrates based on an iron oxide layer on a double-side polished silicon wafer. In this way, atomic force microscopy, ellipsometry, and contact angle goniometry (tools that could not be applied to the nanoparticles' surfaces) could contribute to the determination of their monomolecular thickness and uniformity. Finally, the successful conjugation of IgG antibodies to the SAM-coated IONPs such that the antibodies retain their biological activity is verified by their complexation to a secondary fluorescent antibody. PMID:21863873

  2. Transition metal coordination polymers based on tetrabromoterephthalic and bis(imidazole) ligands: Syntheses, structures, topological analysis and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaowei; Xing, Peiqi; Geng, Xiujuan; Sun, Daofeng; Xiao, Zhenyu; Wang, Lei

    2015-09-01

    Eight new coordination polymers (CPs), namely, [Zn(1,2-mbix)(tbtpa)]n (1), [Co(1,2-mbix)(tbtpa)]n (2), [CdCl(1,2-mbix)(tbtpa)0.5]n (3), {[Cd(1,2-bix)(tbtpa)]·H2O}n (4), {[Cd0.5(1,2-bix)(tbtpa)0.5]·H2O}n (5), {[Co0.5(1,2-bix)(tbtpa)0.5]·2H2O}n (6), {[Co(1,2-bix)(tbtpa)]·H2O}n (7) and {[Co(1,2-bix)(tbtpa)]·Diox·2H2O}n (8), were synthesized under solvothermal conditions based on mix-ligand strategy (H2tbtpa=tetrabromoterephthalic acid and 1,2-mbix=1,2-bis((2-methyl-1H-imidazol-1-yl)methyl)benzene, 1,2-bix=1,2-bis(imidazol-1-ylmethyl)benzene). All of the CPs have been structurally characterized by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analyses (TGA). X-ray diffraction analyses show that 1 and 2 are isotypics which have 2D highly undulated networks with (4,4)-sql topology with the existence of C-H ⋯Br interactions; for 3, it has a 2D planar network with (4,4)-sql topology with the occurrence of C-H ⋯Cl interactions other than C-H ⋯Br interactions; 4 shows a 3D 2-fold interpenetrated nets with rare 65·8-mok topology which has a self-catention property. As the same case as 1 and 2, 5 and 6 are also isostructural with planar layers with 44-sql topology which further assembled into 3D supramolecular structure through the interdigitated stacking fashion and the C-Br ⋯Cph interactions. As for 7, it has a 2D slightly undulated networks with (4,4)-sql topology which has one dimension channel. While 8 has a 2-fold interpenetrated networks with (3,4)-connect jeb topology with point symbol {63}{65·8}. And their structures can be tuned by conformations of bis(imidazol) ligands and solvent mixture. Besides, the TGA properties for all compounds and the luminescent properties for 1, 3, 4, 5 are discussed in detail.

  3. Energy Dependence of the Ruthenium(II)-Bipyridine Metal-to-Ligand-Charge-Transfer Excited State Radiative Lifetimes: Effects of ??*(bipyridine) Mixing.

    PubMed

    Thomas, Ryan A; Tsai, Chia Nung; Mazumder, Shivnath; Lu, I Chen; Lord, Richard L; Schlegel, H Bernhard; Chen, Yuan Jang; Endicott, John F

    2015-06-18

    The variations in band shape with excited state energy found for the triplet metal to ligand charge transfer ((3)MLCT) emission spectra of ruthenium-bipyridine (Ru-bpy) chromophores at 77 K have been postulated to arise from excited state/excited state configurational mixing. This issue is more critically examined through the determination of the excited state energy dependence of the radiative rate constants (kRAD) for these emissions. Experimental values for kRAD were determined relative to known literature references for Ru-bpy complexes. When the lowest energy excited states are metal centered, kRAD can be anomalously small and such complexes have been identified using density functional theory (DFT) modeling. When such complexes are removed from the energy correlation, there is a strong (3)MLCT energy-dependent contribution to kRAD in addition to the expected classical energy cubed factor for complexes with excited state energies greater than 10?000 cm(-1). This correlates with the DFT calculations which show significant excited state electronic delocalization between a ?(bpy-orbital) and a half-filled d?*-(Ru(III)-orbital) for Ru-bpy complexes with (3)MLCT excited state energies greater than about 16?000 cm(-1). Overall, this work implicates the "stealing" of emission bandshapes as well as intensity from the higher energy, strongly allowed bpy-centered singlet ??* excited state. PMID:25761649

  4. Five novel transition metal coordination polymers with 2D/3D framework structure based on flexible H{sub 2}tzda and ancillary ligand bpe

    SciTech Connect

    Wang Yuting; Xu Yan; Fan Yaoting; Hou Hongwei

    2009-10-15

    Five new transition metal coordination polymers based on H{sub 2}tzda and co-ligand bpe, {l_brace}[M(tzda)(bpe)].H{sub 2}O{r_brace}{sub n} [M=Zn(1), Cd(2), Mn(3), Co(4)] and [Ni{sub 2}(tzda){sub 2}(bpe){sub 2}(H{sub 2}O)]{sub n} (5) [H{sub 2}tzda=(1,3,4-thiadiazole-2,5-diyldithio)diacetic acid, bpe=1,2-bis(4-pyridyl)ethane], have been hydrothermally synthesized and structurally characterized. Compounds 1-4 feature a 2D-layered architecture generated from [M(tzda)]{sub n} moiety with double-chain structure cross-linking bpe spacers. However, the conformations bpe adopts in 3 and 4 are different from those in 1 and 2 due to the rotation of C-C single bond in bpe. Polymer 5 exhibits an interesting 3D porous framework with 2-fold interpenetration, in which intriguing 1D double helix chains are observed. The photoluminescence properties of 1 and 2 in the solid-state at room temperature are investigated. In addition, variable-temperature magnetic data show weak antiferromagnetic behavior in 3-5. - Graphical abstract: Five new transition metal coordination polymers based on flexible H{sub 2}tzda and bpe have been hydrothermally synthesized and characterized by X-ray diffraction, luminescent emission spectra and low-temperature magnetic measurements, respectively.

  5. Diverse entangled metal-organic framework materials incorporating kinked organodiimine and flexible aliphatic dicarboxylate ligands: synthesis, structure, physical properties, and reversible structural reorganization.

    PubMed

    Montney, Matthew R; Krishnan, Subhashree Mallika; Supkowski, Ronald M; LaDuca, Robert L

    2007-09-01

    Hydrothermal synthesis has afforded a family of divalent metal adipate (adp) coordination polymers incorporating the kinked dipodal organodiimine 4,4'-dipyridylamine (dpa). As revealed by single-crystal X-ray diffraction, the structures of these materials are critically dependent on the metal coordination geometry, the carboxylate binding modes, and the conformations of the flexible adipate moieties. In all cases, hydrogen-bonding interactions imparted by the dpa tethers also play a structure-directing role. All materials were further characterized via infrared spectroscopy and elemental and thermogravimetric analysis. [Co(adp)(dpa)] (1) displays doubly interpenetrated three-dimensional (3-D) networks with a decorated alpha-Po-type (pcu) topology. In contrast, [Ni(adp)(dpa)(H2O)] (2) possesses a triply interpenetrated binodal cooperite-type (pts) framework, the highest level of interpenetration yet reported for this structure type. [Zn(adp)(dpa)].H2O (3) presents mutually inclined polycatenated 2-D graphitic layers consisting of neutral dimeric [Zn2(mu2-adp)2] kernels conjoined by dipodal dpa ligands. Compound 1 exhibited weak antiferromagnetic coupling between its carboxylate-bridged Co atoms, following Curie-Weiss behavior with Theta=-3.3 K. Compound 3 manifested blue light emission under ultraviolet excitation, as well as a reversible structural reorganization upon dehydration/rehydration. PMID:17691722

  6. Insights into metal-ligand and metal-metal interaction in coinage metal triangles. Insights of d10-d10, d10-d8 and d8-d8 contacts from [Au3In(CH3Ndbnd COCH3)3] (n = 2, 4, 6) via relativistic DFT calculations

    NASA Astrophysics Data System (ADS)

    Guajardo Maturana, R.; Muñoz-Castro, A.

    2016-05-01

    The successive addition of one, two and three equivalents of iodide to [Au3(CH3Ndbnd COCH3)3], gives rise to the [Au3In(CH3Ndbnd COCH3)3] (n = 2, 4, 6) oxidized systems. Such structures have been studied by using scalar relativistic DFT calculations and TD-DFT. Our results demonstrate a stronger ligand-to-metal charge donation, which increases in covalency. The long metal-metal contacts observed through the series result from the similarly population of bonding, non-bonding and slightly anti-bonding combinations of the 6s-Au atomic shells in the [Au3]n+ core, leading to distances in the range of the sum of their van der Waals radii for all the systems.

  7. Metal and ligand binding to the HIV-RNase H active site are remotely monitored by Ile556.

    PubMed

    Zheng, Xunhai; Mueller, Geoffrey A; DeRose, Eugene F; London, Robert E

    2012-11-01

    HIV-1 reverse transcriptase (RT) contains a C-terminal ribonuclease H (RH) domain on its p66 subunit that can be expressed as a stable, although inactive protein. Recent studies of several RH enzymes demonstrate that substrate binding plays a major role in the creation of the active site. In the absence of substrate, the C-terminal helix E of the RT RNase H domain is dynamic, characterized by severe exchange broadening of its backbone amide resonances, so that the solution characterization of this region of the protein has been limited. Nuclear magnetic resonance studies of 13C-labeled RH as a function of experimental conditions reveal that the ?1 methyl resonance of Ile556, located in a short, random coil segment following helix E, experiences a large 13C shift corresponding to a conformational change of Ile556 that results from packing of helix E against the central ?-sheet. This shift provides a useful basis for monitoring the effects of various ligands on active site formation. Additionally, we report that the RNase H complexes formed with one or both divalent ions can be individually observed and characterized using diamagnetic Zn2+ as a substitute for Mg2+. Ordering of helix E results specifically from the interaction with the lower affinity binding to the A divalent ion site. PMID:22941642

  8. Synthesis, crystal structures, luminescence properties of two metal coordination polymers derived from 5-substituted isophthalate and flexible bis (triazole) ligands

    NASA Astrophysics Data System (ADS)

    Ming, Chun-lun; Wang, Li-na; Hecke, Kristof Van; Cui, Guang-hua

    2014-08-01

    Two new metal complexes, [Ni(btx)(nip)(H2O)]n (1), {[Cd(btx)(mip)(H2O)]·H2O}n (2) (btx = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene, H2nip = 5-nitroisophthalic acid, H2mip = 5-methyisophthalic acid) were synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction methods, IR spectroscopy, TGA and elemental analysis. Complex 1 features a 3D metal-organic framework with three-fold interpenetrating CdSO4-type topology. Complex 2 exhibits a 2D network with square grid units, which is further extended into a rare 3,5T1 three-dimensional supramolecular network via three modes of classical Osbnd H⋯O hydrogen bonds. In addition, luminescence properties of 1 and 2 have also been investigated in the solid state.

  9. Synthesis, Ion Recognition Ability, and Metal-Assisted Aggregation Behavior of Dinuclear Metallohosts Having a Bis(Saloph) Macrocyclic Ligand.

    PubMed

    Akine, Shigehisa; Utsuno, Fumihiko; Piao, Shunjin; Orita, Hideo; Tsuzuki, Seiji; Nabeshima, Tatsuya

    2016-01-19

    Macrocyclic molecule 1 that has two saloph coordination sites was designed and synthesized. The macrocycle 1 was easily converted into the corresponding metallohosts 2 and 3 by the reaction with nickel(II) and palladium(II), respectively. As expected from the molecular structure of these metallohosts having an 18-crown-6-like cavity, the nickel(II) metallohost 2 showed excellent binding affinity toward Na(+), Ca(2+), and Sr(2+) to give 1:1 host-guest complexes. Preorganization effect due to the extremely rigid metal-containing macrocycle was suggested to be a major factor for the strong binding. Larger cations such as K(+), Rb(+), Cs(+), and Ba(2+) gave higher aggregated host-guest complexes such as 22M, 23M2, and 24M3. Density functional theory calculations revealed that smaller metal ions do not occupy the center of each macrocycle in the sandwich structures 22M, while larger Cs(+) simultaneously interacts with all the 12 oxygen donor atoms. On the basis of the interaction energy calculations, the preference for 2·Na over 22Na can be explained by destabilization of 22Na due to the elongated Na-O bonds and repulsive three-body interactions. When the ionic radius of the guest ion increases (K(+), Rb(+), Cs(+)), this destabilization becomes less significant and the formation of sandwich complexes 22M is favored. Such aggregation would significantly affect the physical and chemical properties of the metal complexes due to the interplane interactions between the metal centers. PMID:26734931

  10. Ligand-independent tyrosine kinase signalling in RTH 149 trout hepatoma cells: comparison among heavy metals and pro-oxidants.

    PubMed

    Burlando, Bruno; Magnelli, Valeria; Panfoli, Isabella; Berti, Elena; Viarengo, Aldo

    2003-01-01

    Tyrosine phosphorylation depends on the activity of receptor and non-receptor tyrosine kinases and promote cell growth, differentiation and apoptosis. Different stressors are known to stimulate tyrosine kinase activities and this could explain a wide spectrum of effects that these agents produce on different organisms. We studied the effects of heavy metals and pro-oxidants on tyrosine kinase signalling in trout hepatoma cells (RTH 149) by Western immunoblotting. Use of antiphosphotyrosine showed that Hg(2+) and Cu(2+)in the microM range, and H(2)O(2) in the mM range, induced tyrosine phosphorylation. The effect of Cu(2+)was prevented by pre-incubation with genistein, while those of Hg(2+)and H(2)O(2) were only decreased, probably due to tyrosine kinase stimulation coupled to phosphatase inhibition. Phosphospecific antibodies against the three types of MAPKs showed that ERK is activated by heavy metals only, while p38 and SAPK/JNK are activated by H(2)O(2), Hg(2+), and Cu(2+) plus low H(2)O(2). Cell pre-incubation with p38 inhibitors indicated that ERK activation by H(2)O(2) is prevented by concomitant activation of p38. Phosphospecific STAT antibodies revealed activation by H(2)O(2) only. In conclusion, fish cell exposure to heavy metals and pro-oxidants produce specific tyrosine kinase responses, involving cross talk and redox modulatory effects. PMID:12876385

  11. Metallic influence on the atomic structure and optical activity of ligand-protected nanoparticles: a comparison between Ag and Au

    NASA Astrophysics Data System (ADS)

    Hidalgo, Francisco; Noguez, Cecilia; Olvera de La Cruz, Monica

    2014-02-01

    Using time-perturbed density functional theory the optical activity of metal-thiolate compounds formed by highly symmetric Ag and Au nanoparticles (NPs) and a methyl-thiol molecule is studied after performing atomic optimizations and electronic calculations upon adsorption. Many different sites and orientations of the adsorbed molecule on icosahedral Ag and Au NPs of 55 atoms are considered. Upon molecular adsorption atomic distortions on Au NPs are induced while not on Ag, which causes higher molecular adsorption energies in Au than in Ag. Structural distortions and the specific molecular adsorption site and orientation result in chiral metal-thiolate NPs. Ag and Au compounds with similar chirality, according to Hausdorff chirality measurements, show different optical activity signatures, where circular dichroism spectra of Au NPs are more intense. These dissimilarities are attributed in part to the differences in the electronic density of states, which are a consequence of relativistic effects and the atomic distortion. It is concluded that the optical activity of Ag and Au compounds is due to different mechanisms, while in Au it is mainly due to the atomic distortion of the metallic NPs induced after molecular adsorption, in Ag it is defined by the adsorption site and molecular orientation with respect to the NP symmetry.

  12. Smart FBG-based FRP anchor

    NASA Astrophysics Data System (ADS)

    Zhou, Zhi; Zhang, Zhichun; Wang, Chuan; Ou, Jinping

    2006-03-01

    FRP ( Fiber Reinforced Polymer ) has become the popular material to alternate steel in civil engineering under harsh corrosion environment. But due to its low shear strength ability, the anchor for FRP is most important for its practical application. However, the strain state of the surface between FRP and anchor is not fully understood due to that there is no proper sensor to monitor the inner strain in the anchor by traditional method. In this paper, a new smart FBG-based FRP anchor is brought forward, and the inner strain distribution of FRP anchor has been monitored using FRP-OFBG sensors, a smart FBG-embedded FRP rebar, which is pre-embedded in the FRP rod and cast in the anchor. Based on the strain distribution information the bonding shear stress on the surface of FRP rod along the anchor can also be obtained. This method can supply important information for FRP anchor design and can also monitor the anchorage system, which is useful for the application of FRP in civil engineering. The experimental results also show that the smart FBG-based FRP anchor can give direct information of the load and damage of the FRP anchor.

  13. Unique (3,8)-connected lanthanide arenedisulfonate metal-organic frameworks containing benzimidazole-5,6-dicarboxylic acid co-ligand: Syntheses, structures and luminescence

    SciTech Connect

    Sun, Yan-Qiong; Liu, Qi; Zhong, Jie-Cen; Pan, Qun-Feng; Chen, Yi-Ping

    2013-10-15

    Two isostructural 3D lanthanide arenedisulfonate metal-organic frameworks (MOFs) [Ln(Hbidc)(nds){sub 0.5}(H{sub 2}O)]{sub n}(Ln=Eu(1), La(2)) have been successfully synthesized by the hydrothermal reaction of lanthanide oxide with 2,6-naphthalenedisulfonate sodium (Na{sub 2}nds) and an auxiliary ligand, 1H-benzimidazole-5,6-dicarboxylic acid (H{sub 3}bidc). The two complexes are both constructed from 2D [Ln(Hbidc)]{sup +} double layers pillared by nds{sup 2−} ligands to generate 3D (3, 8)-connected open-framework structures with 1D long narrow channels running along the a axis. From topological point of view, the 3D framework is a (3, 8)-connected tfz-d net. The weak interactions including N–H⋯O, O–H⋯O hydrogen bonds and π–π stacking are observed in 1. The 2D IR correlation spectroscopy was applied to study the molecular interactions induced by thermal perturbation. The emission spectra of 1 exhibit the characteristic transition of {sup 5}D{sub 0}→{sup 7}F{sub J}(J=0–4) of Eu(III). - Graphical abstract: Two isostructural 3D (3,8)-connected lanthanide arenedisulfonates were hydrothermally synthesized. The 2D IR correlation spectroscopy was applied to study the molecular interactions induced by thermal perturbation. Display Omitted - Highlights: • The first lanthanide arenedisulfonates incorporating fused-ring aromatic carboxylic acid. • Three-dimensional (3,8)-connected framework with tfz-d network topology. • The emission spectra of 1 exhibit the characteristic transition of {sup 5}D{sub 0}→{sup 7}F{sub J} (J=0–4) of Eu(III). • The 2D IR correlation spectroscopy was applied to study the molecular interactions.

  14. Five coordinate M(II)-diphenolate [M = Zn(II), Ni(II), and Cu(II)] Schiff base complexes exhibiting metal- and ligand-based redox chemistry.

    PubMed

    Franks, Mark; Gadzhieva, Anastasia; Ghandhi, Laura; Murrell, David; Blake, Alexander J; Davies, E Stephen; Lewis, William; Moro, Fabrizio; McMaster, Jonathan; Schröder, Martin

    2013-01-18

    Five-coordinate Zn(II), Ni(II), and Cu(II) complexes containing pentadentate N(3)O(2) Schiff base ligands [1A](2-) and [1B](2-) have been synthesized and characterized. X-ray crystallographic studies reveal five coordinate structures in which each metal ion is bound by two imine N-donors, two phenolate O-donors, and a single amine N-donor. Electron paramagnetic resonance (EPR) spectroscopic studies suggest that the N(3)O(2) coordination spheres of [Cu(1A)] and [Cu(1B)] are retained in CH(2)Cl(2) solution and solid-state superconducting quantum interference device (SQUID) magnetometric studies confirm that [Ni(1A)] and [Ni(1B)] adopt high spin (S = 1) configurations. Each complex exhibits two reversible oxidation processes between +0.05 and +0.64 V vs [Fc](+)/[Fc]. The products of one- and two-electron oxidations have been studied by UV/vis spectroelectrochemistry and by EPR spectroscopy which confirm that each oxidation process for the Zn(II) and Cu(II) complexes is ligand-based with sequential formation of mono- and bis-phenoxyl radical species. In contrast, the one-electron oxidation of the Ni(II) complexes generates Ni(III) products. This assignment is supported by spectroelectrochemical and EPR spectroscopic studies, density functional theory (DFT) calculations, and the single crystal X-ray structure of [Ni(1A)][BF(4)] which contains Ni in a five-coordinate distorted trigonal bipyramidal geometry. PMID:23297765

  15. Hybrid Coordination Networks Constructed from ɛ-Keggin-Type Polyoxometalates and Rigid Imidazole-Based Bridging Ligands as New Carriers for Noble-Metal Catalysts.

    PubMed

    Yang, Xiao-Jian; Sun, Meng; Zang, Hong-Ying; Ma, Yuan-Yuan; Feng, Xiao-Jia; Tan, Hua-Qiao; Wang, Yong-Hui; Li, Yang-Guang

    2016-03-18

    Three hybrid coordination networks that were constructed from ɛ-Keggin polyoxometalate building units and imidazole-based bridging ligands were prepared under hydrothermal conditions, that is, H[(Hbimb)2 (bimb){Zn4 PMo(V8) Mo(VI) 4 O40 }]⋅6 H2 O (1), [Zn(Hbimbp)(bimbp)3 {Zn4 PMo(V8) Mo(VI) 4 O40 }]⋅DMF⋅3.5 H2 O (2), and H[Zn2 (timb)2 (bimba)2 Cl2 {Zn4 PMo(V8) Mo(VI) 4 O40 }]⋅7 H2 O (3) (bimb=1,4-bis(1-imidazolyl)benzene, bimbp=4,4'-bis(imidazolyl)biphenyl, timb=1,3,5-tris(1-imidazolyl)benzene, bimba=3,5-bis(1-imidazolyl)benzenamine). All three compounds were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. The mixed valence of the Mo centers was analyzed by XPS spectroscopy and bond-valence sum calculations. In all three compounds, the ɛ-Keggin polyoxometalate (POM) units acted as nodes that were connected by rigid imidazole-based bridging ligands to form hybrid coordination networks. In compound 1, 1D zigzag chains extended to form a 3D supramolecular architecture through intermolecular hydrogen-bonding interactions. Compound 2 consisted of 2D curved sheets, whilst compound 3 contained chiral 2D networks. Because of the intrinsic reducing properties of ɛ-Keggin POM species, noble-metal nanoparticles were loaded onto these POM-based coordination networks. Thus, compounds 1-3 were successfully loaded with Ag nanoparticles, and the corresponding composite materials exhibited high catalytic activities for the reduction of 4-nitrophenol. PMID:26807960

  16. Four Zn(II)/Cd(II)-3-amino-1,2,4-triazolate frameworks constructed by in situ metal/ligand reactions: Structures and fluorescent properties

    SciTech Connect

    Chen Zilu; Li Xiaoling; Liang Fupei

    2008-08-15

    Four Cd(II) and Zn(II) complexes with the in situ-generated ligand of 3-amino-1,2,4-triazolate (AmTAZ{sup -}) were isolated from the solvothermal reactions of the corresponding Cd(II) or Zn(II) salts with 5-amino-1H-1,2,4-triazole-3-carboxylic acid (AmTAZAc). Their structures were determined by single-crystal X-ray diffraction analysis. [Zn(AmTAZ)(CH{sub 3}COO)] (1) presents a two-dimensional framework constructed from Zn(II) ions and {mu}{sub 3}-AmTAZ{sup -} ligands. A remarkable feature of [Zn{sub 4}(AmTAZ){sub 4}(SO{sub 4})(OH)(C{sub 2}O{sub 4}){sub 0.5}].2H{sub 2}O (2) is the construction of the building units of octagonal cylinders which interact with each other by sharing one face or overlapping, resulting in the formation of a three-dimensional framework with three kinds of 1D channels. [Cd(AmTAZ)Br] (3) crystallizes in a chiral space group P2{sub 1}2{sub 1}2{sub 1}, giving a homochiral three-dimensional framework with two types of helical channels (left- and right-handed). Different from the others, the 3-amino-1,2,4-triazole molecules in [Cd(AmTAZH)SO{sub 4}] (4) behave as neutral {mu}{sub 2}-2,4-bridges to connect the two-dimensional CdSO{sub 4} sheets into a three-dimensional framework. Of all, 2 and 3 display different fluorescent properties probably due to different metal ions, coordination environments and structural topologies. - Graphical abstract: The solvothermal reactions of Cd(II) and Zn(II) salts bearing different anions with 5-amino-1H-1,2,4-triazole-3-carboxylic acid (AmTAZAc) produced four Cd(II) and Zn(II) MOFs with the in situ-generated 3-amino-1,2,4-triazolate (AmTAZ{sup -}) ion as ligand, which display different structural topologies and fluorescent properties. Display Omitted.

  17. Comparative DNA binding abilities and phosphatase-like activities of mono-, di-, and trinuclear Ni(II) complexes: the influence of ligand denticity, metal-metal distance, and coordinating solvent/anion on kinetics studies.

    PubMed

    Bhardwaj, Vimal K; Singh, Ajnesh

    2014-10-01

    Six novel Ni(II) complexes, namely, [Ni2(HL(1))(OAc)2] (1), [Ni3L(1)2]·H2O·2CH3CN (2), [Ni2(L(2))(L(3))(CH3CN)] (3), [Ni2(L(2))2(H2O)2] (4), [Ni2(L(2))2(DMF)2]2·2H2O (5), and [Ni(HL(2))2]·H2O (6), were synthesized by reacting nitrophenol-based tripodal (H3L(1)) and dipodal (H2L(2)) Schiff base ligands with Ni(II) metal salts at ambient conditions. All the complexes were fully characterized with different spectroscopic techniques such as elemental analyses, IR, UV-vis spectroscopy, and electrospray ionization mass spectrometry. The solid-state structures of 2, 3, 5, and 6 were determined using single-crystal X-ray crystallography. The compounds 1, 3, 4, and 5 are dinuclear complexes where the two Ni(II) centers have octahedral geometry with bridging phenoxo groups. Compound 2 is a trinuclear complex with two different types of Ni(II) centers. In compound 3 one of the Ni(II) centers has a coordinated acetonitrile molecule, whereas in compound 4, a water molecule has occupied one coordination site of each Ni(II) center. In complex 5, the coordinated water of complex 4 was displaced by the dimethylformamide (DMF) during its crystallization. Complex 6 is mononuclear with two amine-bis(phenolate) ligands in scissorlike fashion around the Ni(II) metal center. The single crystals of 1 and 4 could not be obtained; however, from the spectroscopic data and physicochemical properties (electronic and redox properties) it was assumed that the structures of these complexes are quite similar to other analogues. DNA binding abilities and phosphatase-like activities of all characterized complexes were also investigated. The ligand denticity, coordinated anions/solvents (such as acetate, acetonitrile, water, and DMF), and cooperative action of two metal centers play a significant role in the phosphate ester bond cleavage of 2-hydroxypropyl-p-nitropenylphosphate by transesterification mechanism. Complex 3 exhibits highest activity among complexes 1-6 with 3.86 × 10(5) times greater rate enhancement than uncatalyzed reaction. PMID:25226493

  18. Metal-organic coordination polymers based on imidazolyl- and benzimidazolyl-containing 4,4‧-bipy type ligands

    NASA Astrophysics Data System (ADS)

    Jin, Guo-Xia; Ma, Jian-Ping; Dong, Yu-Bin

    2013-11-01

    Two new semirigid ligands 2,2'-bis(imidazol-1-ylmethyl)-4,4'-bis(4-pyridyl)biphenyl(L1) and 2,2'-bis(benzimidazol-1-ylmethyl)-4,4'-bis(4-pyridyl)biphenyl(L2) were designed and synthesized. Six new coordination compounds, {Cd(L1)Br2}n (1), {Cd(L1)(1,2-bdc)(H2O)ṡH2O}n (2), {Zn(L1) (1,3-bdc)ṡ2.7H2O}n (3), {Co(L1)(1,3-bdc)ṡH2O}n (4), (1,2-bdc = 1,2-benzenedicarboxylate, 1,3-bdc = 1,3-benzenedicarboxylate, {Cd(L2)2(NO3)2ṡ2H2O}n (5) and, [Ni(L2)2(H2O)2](ClO4)2ṡ3H2O (6) based on them were obtained and characterized by single-crystal X-ray diffraction methods. 1 is a 2D infinite spongy cushion-like network. In 2, two bridging 1,2-bdc anions chelate two neighboring Cd(II) atoms with their carboxylate groups to form a 1D double chain. 3 displays a 2D network in which the wavelike {Zn(1,3-bdc2-)}n chains are linked to each other by bidentate L1. 4 adopts a unique 3D framework, in which the coplanar {Co(1,3-bdc2-)}n chains are connected to each other through tridentate L1. 5 features a 1D double chain motif composed of a square bimetallic ring as the building block. 6 is mononuclear nickel complex. The photoluminescence properties of L1-L2, 1-3 and 5 were investigated, and all of them exhibit intense fluorescent emissions in the solid state at room temperature.

  19. Regulatory consideration of bioavailability for metals: simplification of input parameters for the chronic copper biotic ligand model.

    PubMed

    Peters, Adam; Merrington, Graham; de Schamphelaere, Karel; Delbeke, Katrien

    2011-07-01

    The chronic Cu biotic ligand model (CuBLM) provides a means by which the bioavailability of Cu can be taken into account in assessing the potential chronic risks posed by Cu at specific freshwater locations. One of the barriers to the widespread regulatory application of the CuBLM is the perceived complexity of the approach when compared to the current systems that are in place in many regulatory organizations. The CuBLM requires 10 measured input parameters, although some of these have a relatively limited influence on the predicted no-effect concentration (PNEC) for Cu. Simplification of the input requirements of the CuBLM is proposed by estimating the concentrations of the major ions Mg2+, Na+, K+, SO4(2-), Cl- , and alkalinity from Ca concentrations. A series of relationships between log10 (Ca, mg l(-1)) and log10 (major ion, mg l(-1)) was established from surface water monitoring data for Europe, and applied in the prediction of Cu PNEC values for some UK freshwater monitoring data. The use of default values for major ion concentrations was also considered, and both approaches were compared to the use of measured major ion concentrations. Both the use of fixed default major ion concentrations, and major ion concentrations estimated from Ca concentrations, provided Cu PNEC predictions which were in good agreement with the results of calculations using measured data. There is a slight loss of accuracy when using estimates of major ion concentrations compared to using measured concentration data, although to a lesser extent than when fixed default values are applied. The simplifications proposed provide a practical evidence-based methodology to facilitate the regulatory implementation of the CuBLM. PMID:21082669

  20. Development of a dipodal Schiff base ligand with N-imine and O-naphtholate donors: A potential chelator towards Cu(II) metal ion established through potentiometric and spectrophotometric studies

    NASA Astrophysics Data System (ADS)

    Baral, Minati; Gupta, Amit; Kanungo, B. K.

    2015-08-01

    A novel hydroxynaphthaldehyde derived Schiff base ligand N,N'-bis-[2-[(2-hydroxy-1-naphthyl)methyleneamino]ethyl]propanediamide (DOTA2HNAP) containing nitrogen and oxygen donor atoms has been developed. The lowest energy molecular structure of DOTA2HNAP and its complexes with Cu (II) metal ion were examined by molecular mechanics using MM+ force which later was re-optimized by semi-empirical method. The theoretical IR and UV spectra of the ligand were obtained using semi empirical/ZINDO/PM3 and were compared with the experimental ones. The coordinating ability of DOTA2HNAP with H+ and Cu(II) ions was investigated in 1:99 (DMSO: water) binary solvent mixture at 25±1°C by potentiometric and spectrophotometric method. The electronic spectra of the ligand show three distinct peaks (253nm, 320nm and 360nm) implicating existence of the Schiff base in quinone form that was well supported by theoretical spectral studies. Out of various complex species forming in solution, all the metal ions show higher stability of complexes when in 1:1 metal-ligand stoichiometry, binding through two N-imine and two O-naphtholate groups.

  1. GPI-anchored proteins and lipid rafts.

    PubMed

    Sangiorgio, Vanessa; Pitto, Marina; Palestini, Paola; Masserini, Massimo

    2004-07-01

    Several proteins are anchored to membranes via a post-translational lipid modification, the glycosylphosphatidylinositol (GPI) anchor. In mammals and other vertebrates, GPI-anchored proteins have been found in almost all tissues and cells examined. Several studies have provided significant insight into the functions of this ubiquitous modification. An intriguing relevant feature of GPI-anchored proteins is their association with lipid rafts, specialized regions of elevated cholesterol and sphingolipid content, that are present within most cell membranes. In addition to the structure and biosynthesis of the GPI-anchor, recent researches have focused on its molecular interaction with lipid rafts and the biological meaning of such