Science.gov

Sample records for metal organometallic chemistry

  1. Molecular metal catalysts on supports: organometallic chemistry meets surface science.

    PubMed

    Serna, Pedro; Gates, Bruce C

    2014-08-19

    -support bonding and structure, which identify the supports as ligands with electron-donor properties that influence reactivity and catalysis. Each of the catalyst design variables has been varied independently, illustrated by mononuclear and tetranuclear iridium on zeolite HY and on MgO and by isostructural rhodium and iridium (diethylene or dicarbonyl) complexes on these supports. The data provide examples resolving the roles of the catalyst design variables and place the catalysis science on a firm foundation of organometallic chemistry linked with surface science. Supported molecular catalysts offer the advantages of characterization in the absence of solvents and with surface-science methods that do not require ultrahigh vacuum. Families of supported metal complexes have been made by replacement of ligands with others from the gas phase. Spectroscopically identified catalytic reaction intermediates help to elucidate catalyst performance and guide design. The methods are illustrated for supported complexes and clusters of rhodium, iridium, osmium, and gold used to catalyze reactions of small molecules that facilitate identification of the ligands present during catalysis: alkene dimerization and hydrogenation, H-D exchange in the reaction of H2 with D2, and CO oxidation. The approach is illustrated with the discovery of a highly active and selective MgO-supported rhodium carbonyl dimer catalyst for hydrogenation of 1,3-butadiene to give butenes. PMID:25036259

  2. Organometallic Chemistry of Molybdenum.

    ERIC Educational Resources Information Center

    Lucas, C. Robert; Walsh, Kelly A.

    1987-01-01

    Suggests ways to avoid some of the problems students have learning the principles of organometallic chemistry. Provides a description of an experiment used in a third-year college chemistry laboratory on molybdenum. (TW)

  3. Multifunctionality of organometallic quinonoid metal complexes: surface chemistry, coordination polymers, and catalysts.

    PubMed

    Kim, Sang Bok; Pike, Robert D; Sweigart, Dwight A

    2013-11-19

    Quinonoid metal complexes have potential applications in surface chemistry, coordination polymers, and catalysts. Although quinonoid manganese tricarbonyl complexes have been used as secondary building units (SBUs) in the formation of novel metal-organometallic coordination networks and polymers, the potentially wider applications of these versatile linkers have not yet been recognized. In this Account, we focus on these diverse new applications of quinonoid metal complexes, and report on the variety of quinonoid metal complexes that we have synthesized. Through the use of [(η(6)-hydroquinone)Mn(CO)3](+), we are able to modify the surface of Fe3O4 and FePt nanoparticles (NPs). This process occurs either by the replacement of oleylamine with neutral [(η(5)-semiquinone)Mn(CO)3] at the NP surface, or by the binding of anionic [(η(4)-quinone)Mn(CO)3](-) upon further deprotonation of [(η(5)-semiquinone)Mn(CO)3] at the NP surface. We have demonstrated chemistry at the intersection of surface-modified NPs and coordination polymers through the growth of organometallic coordination polymers onto the surface modified Fe3O4 NPs. The resulting magnetic NP/organometallic coordination polymer hybrid material exhibited both the unique superparamagnetic behavior associated with Fe3O4 NPs and the paramagnetism attributable to the metal nodes, depending upon the magnetic range examined. By the use of functionalized [(η(5)-semiquinone)Mn(CO)3] complexes, we attained the formation of an organometallic monolayer on the surface of highly ordered pyrolitic graphite (HOPG). The resulting organometallic monolayer was not simply a random array of manganese atoms on the surface, but rather consisted of an alternating "up and down" spatial arrangement of Mn atoms extending from the HOPG surface due to hydrogen bonding of the quinonoid complexes. We also showed that the topology of metal atoms on the surface could be controlled through the use of quinonoid metal complexes. A quinonoid

  4. Patterns in Organometallic Chemistry with Application in Organic Synthesis.

    ERIC Educational Resources Information Center

    Schwartz, Jeffrey; Labinger, Jay A.

    1980-01-01

    Of interest in this discussion of organometallic complexes are stoichiometric or catalytic reagents for organic synthesis in the complex transformations observed during synthesis for transition metal organometallic complexes. Detailed are general reaction types from which the chemistry or many transition metal organometallic complexes can be…

  5. Organometallic Chemistry. Final Progress Report

    SciTech Connect

    2003-07-14

    The Gordon Research Conference (GRC) on Organometallic Chemistry was held at Salve Regina, Newport, Rhode Island, 7/21-26/02. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.

  6. Modules for Introducing Organometallic Reactions: A Bridge between Organic and Inorganic Chemistry

    ERIC Educational Resources Information Center

    Schaller, Chris P.; Graham, Kate J.; Johnson, Brian J.

    2015-01-01

    Transition metal organometallic reactions have become increasingly important in the synthesis of organic molecules. A new approach has been developed to introduce organometallic chemistry, along with organic and inorganic chemistry, at the foundational level. This change highlights applications of organometallic chemistry that have dramatically…

  7. Organometallic Chemistry and Catalysis in Industry.

    ERIC Educational Resources Information Center

    Parshall, George W.; Putscher, Richard E.

    1986-01-01

    Traces the growth in the industrial usage of organometallic chemistry from 1950 to 1977, pointing out that this growth involved the production of commodity chemicals. Indicates that one of the early successes of organometallic chemistry was the discovery of ethylene polymerization catalysts. (JN)

  8. 2012 ORGANOMETALLIC CHEMISTRY GRC/GRS, JULY 7-13, 2012

    SciTech Connect

    Hillhouse, Gregory

    2012-07-13

    The 2012 Organometallic Chemistry Gordon Research Conference will highlight new basic science and fundamental applications of organometallic chemistry in industrial, academic, and national lab settings. Scientific themes of the conference will include chemical synthesis, reactivity, catalysis, polymer chemistry, bonding, and theory that involve transition-metal (and main-group) interactions with organic moieties.

  9. Supported organometallic complexes: Surface chemistry, spectroscopy, and catalysis

    SciTech Connect

    Marks, T.J.

    1991-01-01

    Adsorbing organometallic molecules onto the surfaces of inorganic supports such as Al{sub 2}O{sub 3}, MgCl{sub 2}, SiO{sub 2}, etc. can result in dramatic enhancements in catalytic activity. The reasons for this and the structures of the resulting surface organometallic centers are not well understood. We have addressed this problem using actinide and early transition metal complexes as model adsorbates. Characterization tools include catalytic and stoichiometric reaction chemistry, reaction kinetics and isotopic labeling, quantitative poisoning studies, model solution chemistry, and a wide array of surface-sensitive spectroscopies such as CPMAS NMR, EPR, and UV-VIS as well as titration calorimetry. These chemical and physical experiments are closely coupled to model solution chemistry to provide maximum information yield. 4 refs., 2 figs.

  10. Organometallic chemistry: A new metathesis

    NASA Astrophysics Data System (ADS)

    Hennessy, Elisabeth T.; Jacobsen, Eric N.

    2016-08-01

    Carbonyls and alkenes, two of the most common functional groups in organic chemistry, generally do not react with one another. Now, a simple Lewis acid has been shown to catalyse metathesis between alkenes and ketones in a new carbonyl olefination reaction.

  11. Supported organometallic complexes: Surface chemistry, spectroscopy, and catalysis

    SciTech Connect

    Marks, T.J.

    1992-02-01

    The long-range goal of this project is to elucidate and understand the surface chemistry and catalytic properties of well-defined, highly-reactive organometallic molecules (principally based upon abundant actinide, lanthanide, and early transition elements) adsorbed on metal oxides and halides. The nature of the adsorbed species is probed by a battery of chemical and physicochemical techniques, to understand the nature of the molecular-surface coordination chemistry and how this can give rise to extremely high catalytic activity. A complementary objective is to delineate the scope and mechanisms of the heterogeneous catalytic reactions, as well as to relate them both conceptually and functionally to model systems generated in solution.

  12. Organometallic chemistry of bimetallic compounds

    SciTech Connect

    Casey, C.P.

    1991-07-01

    This report consists of six sections: heterobimetallic dihydrides, early-late transition metal heterobimetallic compounds, amphiphilic carbene complexes and hydroxycarbene complexes, diiron compounds with bridging hydrocarbon ligands, diphosphine chelates with natural bite angles near 120 degrees, and synthesis and reactions of M=M compounds. (WET)

  13. Some Tendencies in the Literature of Organometallic Chemistry

    ERIC Educational Resources Information Center

    Haiduc, Ionel

    1972-01-01

    A survey of the number of references published annually for individual elements or groups of elements suggests that the organometallic chemistry literature is approaching a phase of slower increase. (Author/NH)

  14. Metal alkoxides: templates for organometallic chemistry and catalysis. Final technical report on DE FG 02-86ER13570

    SciTech Connect

    Chisholm, Malcolm H.

    2002-11-01

    The physical properties and chemical reactivities of a series of alkoxide, fluoroalkoxide and thiolate compounds of molybdenum and tungsten having M{triple_bond}M or M{triple_bond}N bonds have been examined which reveal the influence of the pi-donor properties of the ligands: RO > R{sub f}O{approx}RS. Single-site metal alkoxide catalysts for the ring-opening polymerization of lactides have been prepared for the metals magnesium, zinc, and aluminum.

  15. A "Classic Papers" Approach to Teaching Undergraduate Organometallic Chemistry

    ERIC Educational Resources Information Center

    Duncan, Andrew P.; Johnson, Adam R.

    2007-01-01

    We have structured an upper-level undergraduate course in organometallic chemistry on a selection of "classic" publications in the field. This approach offers students a richly contextual introduction to many of the fundamental tenets of the discipline. After a brief introduction to the field led by the faculty, the students themselves are…

  16. Advanced polymer chemistry of organometallic anions

    SciTech Connect

    Chamberlin, R.M.; Abney, K.D.; Balaich, G.J.; Fino, S.A.

    1997-11-01

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of the project was to prepare and characterize new polymers incorporating cobalt dicarbollide. Specific goals were to prepare polymerizable cobalt dicarbollide monomers using the nucleophilic substitution route discovered in laboratories and to establish the reaction conditions required to form polymers from these complexes. This one-year project resulted in two publications (in press), and provided the foundation for further investigations into polymer synthesis and characterization using cobalt dicarbollide and other metallocarboranes. Interest in synthesizing organometallic polymers containing the cobalt bis(dicarbollide) anion is motivated by their possible application as cation exchange materials for the remediation of cesium-137 and strontium-90 from nuclear wastes.

  17. Half-metallicity in 2D organometallic honeycomb frameworks.

    PubMed

    Sun, Hao; Li, Bin; Zhao, Jin

    2016-10-26

    Half-metallic materials with a high Curie temperature (T C) have many potential applications in spintronics. Magnetic metal free two-dimensional (2D) half-metallic materials with a honeycomb structure contain graphene-like Dirac bands with π orbitals and show excellent aspects in transport properties. In this article, by investigating a series of 2D organometallic frameworks with a honeycomb structure using first principles calculations, we study the origin of forming half-metallicity in this kind of 2D organometallic framework. Our analysis shows that charge transfer and covalent bonding are two crucial factors in the formation of half-metallicity in organometallic frameworks. (i) Sufficient charge transfer from metal atoms to the molecules is essential to form the magnetic centers. (ii) These magnetic centers need to be connected through covalent bonding, which guarantee the strong ferromagnetic (FM) coupling. As examples, the organometallic frameworks composed by (1,3,5)-benzenetricarbonitrile (TCB) molecules with noble metals (Au, Ag, Cu) show half-metallic properties with T C as high as 325 K. In these organometallic frameworks, the strong electronegative cyano-groups (CN groups) drive the charge transfer from metal atoms to the TCB molecules, forming the local magnetic centers. These magnetic centers experience strong FM coupling through the d-p covalent bonding. We propose that most of the 2D organometallic frameworks composed by molecule-CN-noble metal honeycomb structures contain similar half metallicity. This is verified by replacing TCB molecules with other organic molecules. Although the TCB-noble metal organometallic framework has not yet been synthesized, we believe the development of synthesizing techniques and facility will enable the realization of them. Our study provides new insight into the 2D half-metallic material design for the potential applications in nanotechnology. PMID:27541575

  18. Supported organometallic complexes: Surface chemistry, spectroscopy, and catalysis. Progress report, February 1, 1991--January 31, 1992

    SciTech Connect

    Marks, T.J.

    1992-02-01

    The long-range goal of this project is to elucidate and understand the surface chemistry and catalytic properties of well-defined, highly-reactive organometallic molecules (principally based upon abundant actinide, lanthanide, and early transition elements) adsorbed on metal oxides and halides. The nature of the adsorbed species is probed by a battery of chemical and physicochemical techniques, to understand the nature of the molecular-surface coordination chemistry and how this can give rise to extremely high catalytic activity. A complementary objective is to delineate the scope and mechanisms of the heterogeneous catalytic reactions, as well as to relate them both conceptually and functionally to model systems generated in solution.

  19. 2011 Organometallic Chemistry (July 10-15, 2011, Salve Regina University, Newport, RI)

    SciTech Connect

    Dr. Emilio Bunel

    2011-07-15

    Organometallic chemistry has played and will continue to play a significant role in helping us understand the way bonds are made or broken in the presence of a transition metal complex. Current challenges range from the efficient exploitation of energy resources to the creative use of natural and artificial enzymes. Most of the new advances in the area are due to our extended understanding of processes at a molecular level due to new mechanistic studies, techniques to detect reaction intermediates and theory. The conference will bring the most recent advances in the field including nanocatalysis, surface organometallic chemistry, characterization techniques, new chemical reactivity and theoretical approaches along with applications to organic synthesis and the discovery of new materials. The Conference will bring together a collection of investigators who are at the forefront of their field, and will provide opportunities for junior scientists and graduate students to present their work in poster format and exchange ideas with leaders in the field. Six outstanding posters will be selected for short talks. The collegial atmosphere of this Conference, with programmed discussion sessions as well as opportunities for informal gatherings in the afternoons and evenings, provides an avenue for scientists from different disciplines to brainstorm and promotes cross-disciplinary collaborations in the various research areas represented. Graduate students and postdoctoral fellows should also consider participating in the Gordon Research Seminar on Organometallic Chemistry (July 9-10, same location) which is specially designed to promote interaction and discussion between junior scientists.

  20. Reactivity of seventeen- and nineteen-valence electron complexes in organometallic chemistry

    NASA Technical Reports Server (NTRS)

    Stiegman, Albert E.; Tyler, David R.

    1986-01-01

    A guideline to the reactivity of 17- and 19-valence electron species in organometallic chemistry is proposed which the authors believe will supersede all others. The thesis holds that the reactions of 17-electron metal radicals are associatively activated with reactions proceeding through a 19-valence electron species. The disparate reaction chemistry of the 17-electron metal radicals are unified in terms of this associative reaction pathway, and the intermediacy of 19-valence electron complexes in producing the observed products is discussed. It is suggested that related associatively activated pathways need to be considered in some reactions that are thought to occur by more conventional routes involving 16- and 18-electron intermediates. The basic reaction chemistry and electronic structures of these species are briefly discussed.

  1. Organometallic chemistry of bimetallic compounds. Progress report, January 1992--July 1995

    SciTech Connect

    Casey, C.P.

    1994-07-01

    Four main projects at the interface between organometallic chemistry and homogeneous catalysis were pursued. All were designed to give increased understanding of the mechanisms of organometallic reactions related to homogeneous and heterogeneous catalysis. In addition, a minor study involving {eta}{sup 5}-to {eta}{sup 1}-cyclopentadienyl ring slippage in catalysis was completed.

  2. Supported f-element organometallic complexes surface chemistry and catalysis: Technical progress report, March 15, 1987-December 28, 1987

    SciTech Connect

    Marks, T.J.; Burwell, R.L. Jr.

    1987-01-01

    The goal of this research program is to understand how the reactivity of organometallic molecules is dramatically altered by adsorption on inorganic supports such as ..gamma..-alumina, silica, magnesium chloride, etc. While the initial focus of this research concerned the catalytic properties of organoactinides adsorbed on alumina, the effort has now expanded in a number of new directions. These include new supports, new surface spectroscopic techniques, detailed studies of reaction kinetics, new metals, and new connections with solution chemistry.

  3. Supported organometallic complexes: Surface chemistry, spectroscopy, and catalysis

    SciTech Connect

    Marks, T.J.

    1990-02-01

    The goal of our program is to define those modes of interaction that take place between organometallic molecules and inorganic surfaces and, ultimately, to correlate various molecule-surface structures with catalytic properties.

  4. Mechanistic aspects of dinitrogen cleavage and hydrogenation to produce ammonia in catalysis and organometallic chemistry: relevance of metal hydride bonds and dihydrogen.

    PubMed

    Jia, Hong-Peng; Quadrelli, Elsje Alessandra

    2014-01-21

    Dinitrogen cleavage and hydrogenation by transition-metal centers to produce ammonia is central in industry and in Nature. After an introductory section on the thermodynamic and kinetic challenges linked to N2 splitting, this tutorial review discusses three major classes of transition-metal systems (homogeneous, heterogeneous and biological) capable of achieving dissociation and hydrogenation of dinitrogen. Molecular complexes, solid-state Haber-Bosch catalytic systems, silica-supported tantalum hydrides and nitrogenase will be discussed. Emphasis is focused on the reaction mechanisms operating in the process of dissociation and hydrogenation of dinitrogen, and in particular on the key role played by metal hydride bonds and by dihydrogen in such reactions. PMID:24108246

  5. Sulfur-bonded thiophenes in organometallic rhenium complexes and adsorption of isocyanides on gold

    SciTech Connect

    Robertson, M.J.

    1993-08-01

    This dissertation contains results of research conducted in two different areas: (1) organometallic synthesis and reactivity, and (2) organometallic surface chemistry. In the synthesis and reactivity studies, sulfur coordination of thiophene and benzo[b]thiophene to the metal center in organometallic rhenium complexes is examined. In the surface chemistry studies, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is used to analyze the adsorption of several isocyanides on the surface of gold powder. Results are compared and contrasted to known organometallic chemistry.

  6. An Organometallic Future in Green and Energy Chemistry?

    SciTech Connect

    Crabtree, Robert H

    2011-01-10

    The title topic is reviewed with selected examples taken from recent work, such as: the 'hydrogen borrowing' amine alkylation by alcohols; the dehydrogenative coupling of amine and alcohol to give amide; Ru complexes as solar cell photosensitizers; Ir organometallics as water oxidation catalyst precursors and as OLED emitters; as well as recent hydrogen storage strategies involving catalytic dehydrogenation of ammonia-borane and of organic heterocycles.

  7. Modular self-assembly, characterization, and host-guest chemistry of nanoscale organometallic architectures

    SciTech Connect

    Manna, J.; Kuehl, C.J.; Stang, P.J.; Muddiman, D.C.; Smith, R.D.

    1997-12-31

    The supramolecular synthesis and chemistry of organic macrocycles has been the focus of considerable study for over thirty years. In contrast, the chemistry of analogous inorganic and organometallic macrocycles is in it infancy; little is know about the stability, spectroscopic and physical properties, and chemistry of these species. We will report on the design of several unique supramolecular macrocycles and the characterization of these species by a range of spectroscopic techniques, including electrospray-ionization Fourier transform ion cyclotron resonance spectrometry. Preliminary data concerning the host-guest chemistry of these macrocycles will also be presented.

  8. Organometallic chemistry meets crystal engineering to give responsive crystalline materials.

    PubMed

    Bacchi, A; Pelagatti, P

    2016-01-25

    Dynamically porous crystalline materials have been obtained by engineering organometallic molecules. This feature article deals with organometallic wheel-and-axle compounds, molecules with two relatively bulky groups (wheels) connected by a linear spacer. The wheels are represented by half-sandwich Ru(ii) moieties, while the spacer can be covalent or supramolecular in character. Covalent spacers are obtained using divergent bidentate ligands connecting two [(arene)RuX2] groups. Supramolecular spacers are instead obtained by exploiting the dimerization of COOH or C(O)NH2 groups appended to N-based ligands. A careful choice of ligand functional groups and X ligands leads to the isolation of crystalline materials with remarkable host-guest properties, evidenced by the possibility of reversibly capturing/releasing volatile guests through heterogenous solid-gas reactions. Structural correlations between the crystalline arrangement of the apohost and the host-guest compounds allow us to envisage the structural path followed by the system during the exchange processes. PMID:26673552

  9. Probing the chemistry, electronic structure and redox energetics in pentavalent organometallic actinide complexes

    SciTech Connect

    Graves, Christopher R; Vaughn, Anthony E; Morris, David E; Kiplinger, Jaqueline L

    2008-01-01

    Complexes of the early actinides (Th-Pu) have gained considerable prominence in organometallic chemistry as they have been shown to undergo chemistries not observed with their transition- or lanthanide metal counterparts. Further, while bonding in f-element complexes has historically been considered to be ionic, the issue of covalence remains a subject of debate in the area of actinide science, and studies aimed at elucidating key bonding interactions with 5f-orbitals continue to garner attention. Towards this end, our interests have focused on the role that metal oxidation state plays in the structure, reactivity and spectral properties of organouranium complexes. We report our progress in the synthesis of substituted U{sup V}-imido complexes using various routes: (1) Direct oxidation of U{sup IV}-imido complexes with copper(I) salts; (2) Salt metathesis with U{sup V}-imido halides; (3) Protonolysis and insertion of an U{sup V}-imido alkyl or aryl complex with H-N{double_bond}CPh{sub 2} or N{triple_bond}C-Ph, respectively, to form a U{sup V}-imido ketimide complex. Further, we report and compare the crystallographic, electrochemical, spectroscopic and magnetic characterization of the pentavalent uranium (C{sub 5}Me{sub 5}){sub 2}U({double_bond}N-Ar)(Y) series (Y = OTf, SPh, C{triple_bond}C-Ph, NPh{sub 2}, OPh, N{double_bond}CPh{sub 2}) to further interrogate the molecular, electronic, and magnetic structures of this new class of uranium complexes.

  10. Organometallic chemistry of bimetallic compounds. Final progress report

    SciTech Connect

    Casey, C.P.

    1991-07-01

    This report consists of six sections: heterobimetallic dihydrides, early-late transition metal heterobimetallic compounds, amphiphilic carbene complexes and hydroxycarbene complexes, diiron compounds with bridging hydrocarbon ligands, diphosphine chelates with natural bite angles near 120 degrees, and synthesis and reactions of M=M compounds. (WET)

  11. 2001 Gordon Research Conference on Organometallic Chemistry. Final progress report [agenda and attendee list

    SciTech Connect

    Burns, Carol

    2001-07-27

    The Gordon Research Conference on Organometallic Chemistry was held at Salve Regina University, Newport, Rhode Island, July 22-27, 2001. The conference had 133 participants. The attendees represented the spectrum of endeavor in this field, coming from academia, industry, and government laboratories, and included US and foreign scientists, senior researchers, young investigators, and students. Emphasis was place on current unpublished research and discussion of the future target areas in this field. There was a conscious effort to stimulate lively discussion about the key issues in the field today. Time for formal presentations was limited in the interest of group discussions; poster sessions were held.

  12. Five-membered metallacycles of titanium and zirconium--attractive compounds for organometallic chemistry and catalysis.

    PubMed

    Rosenthal, Uwe; Burlakov, Vladimir V; Bach, Marc A; Beweries, Torsten

    2007-05-01

    In these days a renaissance of metallacycles as an increasingly important class of organometallic compounds for synthetic and catalytic applications is evident, making such very attractive for a plethora of investigations. Titanocene and zirconocene bis(trimethylsilyl)acetylene complexes, regarded as three-membered metallacycles (1-metallacyclopropenes), present a rich chemistry towards unsaturated molecules. By elimination of the alkyne these complexes form by reaction with unsaturated compounds five-membered titana- and zirconacycles, all of which are relevant to stoichiometric and catalytic C-C coupling and cleavage reactions of unsaturated molecules. PMID:17471397

  13. Mechanistic Studies at the Interface Between Organometallic Chemistry and Homogeneous Catalysis

    SciTech Connect

    Casey, Charles P

    2012-11-14

    Mechanistic Studies at the Interface Between Organometallic Chemistry and Homogeneous Catalysis Charles P. Casey, Principal Investigator Department of Chemistry, University of Wisconsin - Madison, Madison, Wisconsin 53706 Phone 608-262-0584 FAX: 608-262-7144 Email: casey@chem.wisc.edu http://www.chem.wisc.edu/main/people/faculty/casey.html Executive Summary. Our goal was to learn the intimate mechanistic details of reactions involved in homogeneous catalysis and to use the insight we gain to develop new and improved catalysts. Our work centered on the hydrogenation of polar functional groups such as aldehydes and ketones and on hydroformylation. Specifically, we concentrated on catalysts capable of simultaneously transferring hydride from a metal center and a proton from an acidic oxygen or nitrogen center to an aldehyde or ketone. An economical iron based catalyst was developed and patented. Better understanding of fundamental organometallic reactions and catalytic processes enabled design of energy and material efficient chemical processes. Our work contributed to the development of catalysts for the selective and mild hydrogenation of ketones and aldehydes; this will provide a modern green alternative to reductions by LiAlH4 and NaBH4, which require extensive work-up procedures and produce waste streams. (C5R4OH)Ru(CO)2H Hydrogenation Catalysts. Youval Shvo described a remarkable catalytic system in which the key intermediate (C5R4OH)Ru(CO)2H (1) has an electronically coupled acidic OH unit and a hydridic RuH unit. Our efforts centered on understanding and improving upon this important catalyst for reduction of aldehydes and ketones. Our mechanistic studies established that the reduction of aldehydes by 1 to produce alcohols and a diruthenium bridging hydride species occurs much more rapidly than regeneration of the ruthenium hydride from the diruthenium bridging hydride species. Our mechanistic studies require simultaneous transfer of hydride from ruthenium to

  14. Metal-organometallic polymers and frameworks derived from facially metalated arylcarboxylates

    NASA Astrophysics Data System (ADS)

    Kumalah Robinson, Sayon A.

    The interest in coordination polymers, also known as metal-organic frameworks, has risen drastically over the past 2 decades. In this time, the field has matured and given rise to a diverse range of crystalline structures possessing various functionalities. Coordination polymers are typically formed from the self assembly of metal ions which serve as nodes and organic ligands which act as bridges. By the careful selection of the organic ligand and the metal ion, the overall physical properties of the material may be tuned. In this work, the use of organometallic bridging ligands are explored using facially metalated aryl carboxylates ligands to synthesize metal-organometallic frameworks (MOMFs). Therefore, with the aim of synthesizing [CpM]+-functionalized (M = FeII, RuII; Cp = cyclopentadienyl) coordination polymers and metal organic frameworks, various [CpFe]+and [CpRu] + functionalized aryl carboxylates were synthesized and characterized. In particular, the [CpFe]+-functionalized benzoic, terephthalic and trimesic acids as well as the [CpRu]+-functionalized terephthalic acid were made. Using the [CpFe]+ complexes of the benzoic and terephthalic acid as bridging ligands, a number of 1D and 2D coordination polymers were synthesized. For instance, the reaction of [CpFe]+-functionalized benzoic acid with CdCl2 yielded the 1D chain of [Cd(benzoate)Cl 2]˙H2O whilst the reaction of [CpFe]+-functionalized terephthalic acid with Cu(NO3)2˙6H2O yielded a 2D square grid sheet. Using the [CpFe]+-functionalized terephthalic acid, a series of polymorphic, 3D metal-organometallic frameworks of the general formula [M3(terephthalate)4(mu-H2O)2(H 2O)2][NO3]2˙xsolvent (M = Co II, NiII ; solvent = EtOH, DMF, H2O) were synthesized and fully characterized. The polymorphic nature of these frameworks may be attributed to the different orientations that the [CpFe]+ moiety may adapt within the cavities in the 3D frameworks. The selectivity of the desolvated forms of the polymorphs for

  15. Organometallic Nanostructures of 1,4-DIBROMO-2,5-DIIODOBENZENE by Metal Ions Construction on Hopg Surface

    NASA Astrophysics Data System (ADS)

    Li, Wei; Wang, Zhongping; Leng, Xinli; Lu, Yan; Liu, Xiaoqing; Wang, Li

    2016-03-01

    Different organometallic nanostructures on highly oriented pyrolytic graphite (HOPG) have been synthesized by different metal ions coordinating with 1,4-Dibromo-2,5-diiodobenzene (C6H2Br2I2). Scanning tunneling microscopy (STM) images directly demonstrated the transformation of the nanostructure from self-assembled nanostructures formed by C6H2Br2I2 through halogen bond into organometallic network, formed by the dehalogenated C6H2Br2I2 molecules covalent bonded with metal ions. Moreover, by varying the concentrations of C6H2Br2I2 molecules or valence states of metal ions, organometallic structures with different shapes and sizes have been fabricated, which illustrates that the concentrations and valence states of the metal ions play important roles in the organometallic nanostructures.

  16. New Twists and Turns for Actinide Chemistry: Organometallic Infinite Coordination Polymers of Thorium Diazide.

    PubMed

    Monreal, Marisa J; Seaman, Lani A; Goff, George S; Michalczyk, Ryszard; Morris, David E; Scott, Brian L; Kiplinger, Jaqueline L

    2016-03-01

    Two organometallic 1D infinite coordination polymers and two organometallic monometallic complexes of thorium diazide have been synthesized and characterized. Steric control of these self-assembled arrays, which are dense in thorium and nitrogen, has also been demonstrated: infinite chains can be circumvented by using steric bulk either at the metallocene or with a donor ligand in the wedge. PMID:26865502

  17. Computational design of organometallic oligomers featuring 1,3-metal-carbon bonding and planar tetracoordinate carbon atoms.

    PubMed

    Zhao, Xue-Feng; Yuan, Cai-Xia; Wang, Xiang; Li, Jia-Jia; Wu, Yan-Bo; Wang, Xiaotai

    2016-01-15

    Density functional theory computations (B3LYP) have been used to explore the chemistry of titanium-aromatic carbon "edge complexes" with 1,3-metal-carbon (1,3-MC) bonding between Ti and planar tetracoordinate Cβ . The titanium-coordinated, end-capping chlorides are replaced with OH or SH groups to afford two series of difunctional monomers that can undergo condensation to form oxide- and sulfide-bridged oligomers. The sulfide-linked oligomers have less molecular strain and are more exergonic than the corresponding oxide-linked oligomers. The HOMO-LUMO gap of the oligomers varies with their composition and decreases with growing oligomer chain. This theoretical study is intended to enrich 1,3-MC bonding and planar tetracoordinate carbon chemistry and provide interesting ideas to experimentalists. Organometallic complexes with the TiE2 (E = OH and SH) decoration on the edge of aromatic hydrocarbons have been computationally designed, which feature 1,3-metal-carbon (1,3-MC) bonding between titanium and planar tetracoordinate β-carbon. Condensation of these difunctional monomers by eliminating small molecules (H2O and H2S) produce chain-like oligomers. The HOMO-LUMO gaps of the oligomers decreases with growing oligomer chain, a trend that suggests possible semiconductor properties for oligomers with longer chains. PMID:26399226

  18. Unusually Strong Long-Distance Metal-Metal Coupling in Bis(ferrocene)-Containing BOPHY: An Introduction to Organometallic BOPHYs.

    PubMed

    Rhoda, Hannah M; Chanawanno, Kullapa; King, Alexander J; Zatsikha, Yuriy V; Ziegler, Christopher J; Nemykin, Victor N

    2015-12-01

    The first organometallic BOPHY (BOPHY=bis(difluoroboron)-1,2-bis{(pyrrol-2-yl)methylene}hydrazine) containing two ferrocene substituents was prepared through a Knoevenagel condensation between tetramethyl substituted BOPHY and ferrocene carboxaldehyde. An unprecedentedly strong long-range (≈17.2 Å) metal-metal coupling in this new complex was investigated using electrochemical, spectroelectrochemical, and chemical oxidation methods. Electrochemical data is indicative of a 200 mV separation between the first and the second ferrocene-centered oxidation processes. Formation of the mixed-valence states and appearance and disappearance of two NIR bands were observed during stepwise oxidation of the first organometallic BOPHY. The electronic structure and the nature of the excited states in this new chromophore were studied by DFT and TDDFT calculations. PMID:26449288

  19. Supported organometallic complexes: Surface chemistry, spectroscopy, and catalysis. Progress report, March 15, 1988--July 14, 1989

    SciTech Connect

    Marks, T.J.

    1990-02-01

    The goal of our program is to define those modes of interaction that take place between organometallic molecules and inorganic surfaces and, ultimately, to correlate various molecule-surface structures with catalytic properties.

  20. Relating ionic liquids and polyethylene glycols to green chemistry, organometallic catalysis, and materials science

    NASA Astrophysics Data System (ADS)

    Klingshirn, Marc Allen

    The field of green chemistry has grown tremendously over the past years due to stricter environmental laws regulating the amount of toxic substances that are legally allowed into the environment. The objective of this work was to incorporate ILs and PEGs into gel type matrices and utilize them as solvent alternatives in hopes of helping advance the field of green chemistry and lowering environmental burden. Here, three new gel-type materials were studied. A PEG gel-silica sol composite and an IL-PEG gel were developed. Both materials were based on a cross-linked PEG hydrogel and its response to various inorganic salts. The new materials developed exhibited the same shrink-swell characteristics as the control PEG hydrogel, while the IL-PEG gel showed similar uptakes of linear alcohols from salt solutions. Additionally, when calcined, the PEG gel-silica sol composite was found to have unique morphologies that were dependent on PEG hydrogel concentration. The third material that was developed was a silica sol gel that was synthesized utilizing 1-butyl-3-methylimidazolium chloride as a (co)solvent. All previous work reported used ILs that had structures similar to surfactants that are traditionally used in creating high surface area materials. The work here presents a fundamental study of how short chained ILs can be used to produce high surface area materials and addresses questions such as how the IL orients itself within the matrix during the sol gel process. Another facet of the work involves the incorporation of ILs and PEGS into organometallic catalytic systems, specifically the hydroesterification of styrene and the copolymerization of styrene and carbon monoxide. The ILs' non-coordinating nature allows them to stabilize catalytically active charged species in addition to allowing for ease of catalyst recycling. The application of the presented work to the field of green chemistry includes the implementation of benign, non-volatile reaction media, specifically

  1. Determining the Quantum Efficiency for Activation of an Organometallic Photoinitiator for Cationic Polymerization: An Experiment for the Physical or Inorganic Chemistry Laboratory

    ERIC Educational Resources Information Center

    Hayes, David M.; Mahar, Maura; Schnabel, R. Chris; Shah, Paras; Lees, Alistair J.; Jakubek, Vladimir

    2007-01-01

    We present a new laboratory experiment on the photochemistry of organometallic [eta][superscript 5],[eta][superscript 6]-mixed-sandwich compounds, which is suitable for both the physical chemistry and inorganic chemistry laboratory. Specifically, students use 1,10-phenanthroline to trap the intermediate formed when…

  2. Organometallic neptunium(III) complexes.

    PubMed

    Dutkiewicz, Michał S; Farnaby, Joy H; Apostolidis, Christos; Colineau, Eric; Walter, Olaf; Magnani, Nicola; Gardiner, Michael G; Love, Jason B; Kaltsoyannis, Nikolas; Caciuffo, Roberto; Arnold, Polly L

    2016-08-01

    Studies of transuranic organometallic complexes provide a particularly valuable insight into covalent contributions to the metal-ligand bonding, in which the subtle differences between the transuranium actinide ions and their lighter lanthanide counterparts are of fundamental importance for the effective remediation of nuclear waste. Unlike the organometallic chemistry of uranium, which has focused strongly on U(III) and has seen some spectacular advances, that of the transuranics is significantly technically more challenging and has remained dormant. In the case of neptunium, it is limited mainly to Np(IV). Here we report the synthesis of three new Np(III) organometallic compounds and the characterization of their molecular and electronic structures. These studies suggest that Np(III) complexes could act as single-molecule magnets, and that the lower oxidation state of Np(II) is chemically accessible. In comparison with lanthanide analogues, significant d- and f-electron contributions to key Np(III) orbitals are observed, which shows that fundamental neptunium organometallic chemistry can provide new insights into the behaviour of f-elements. PMID:27442286

  3. Redox Chemistry in Thin Layers of Organometallic Complexes Prepared Using Ion Soft Landing

    SciTech Connect

    Peng, Wen-Ping; Johnson, Grant E.; Fortmeyer, Ivy C.; Wang, Peng; Hadjar, Omar; Cooks, Robert G.; Laskin, Julia

    2011-01-01

    Soft landing (SL) of mass-selected ions is used to introduce catalytically-active metal complexes complete with organic ligands into the gas phase and then to transfer them as ions onto an inert surface. This is part of an effort to prepare materials with defined active sites and thus achieve molecular design of surfaces in a highly controlled way. Solution-phase electrochemical studies have shown that VIVO(salen) reacts in the presence of acid to form VVO(salen)+ and the deoxygenated VIII(salen)+ complex -- a key intermediate in the four electron reduction of O2 by vanadium-salen. In this work, the VVO(salen)+ and [NiII(salen)+H]+ complexes were generated by electrospray ionization and mass-selected before being deposited into an inert fluorinated self-assembled monolayer (FSAM) surface on gold. A time dependence study after ion deposition showed loss of O from VVO(salen)+ forming VIII(salen)+ over a four-day period, indicating a slow interfacial reduction process. Similar results were obtained when other protonated molecules were co-deposited with VVO(salen)+ on the FSAM surface. In all these experiments oxidation of the VIII(salen)+ product occurred upon exposure to oxygen or to air. The cyclic regeneration of VVO(salen)+ upon exposure to molecular oxygen and its subsequent reduction to VIII(salen)+ in vacuum completes the catalytic cycle of O2 reduction by the immobilized vanadium-salen species. Moreover, our results represent the first evidence of formation of reactive organometallic complexes on substrates in the absence of solvent. Remarkably, deoxygenation of the oxo-vanadium complex, previously observed only in highly acidic non-aqueous solvents, occurs on the surface in the UHV environment using an acid which is deposited into the inert monolayer. This acid can be a protonated metal complex, e.g. [NiII(salen)+H]+ or an organic acid such as protonated diaminododecane.

  4. The solid-state synthesis of metal nanoparticles from organometallic precursors.

    PubMed

    Wostek-Wojciechowska, Dorota; Jeszka, Jeremiasz K; Amiens, Catherine; Chaudret, Bruno; Lecante, Pierre

    2005-07-01

    Nanoparticles (NPs), average size of 2-5 nm, of ruthenium, cobalt, and rhodium have been prepared by an original method, namely the solid-state decomposition under dihydrogen of an organometallic precursor either dispersed in polymer films or directly as nanocrystals. The NPs dispersion, size, and morphology are investigated by transmission electron microscopy, and their structure by wide angle X-ray scattering. Infrared spectroscopy, after adsorption of carbon monoxide on the metal NPs surfaces, evidences a nonoxidized surface of high reactivity. PMID:15914154

  5. Organometallic Radiopharmaceuticals

    NASA Astrophysics Data System (ADS)

    Alberto, Roger

    Although molecular imaging agents have to be synthesized ultimately from aqueous solutions, organometallic complexes are becoming more and more important as flexible yet kinetically stable building blocks for radiopharmaceutical drug discovery. The diversity of ligands, targets, and targeting molecules related to these complexes is an essential base for finding novel, noninvasive imaging agents to diagnose and eventually treat widespread diseases such as cancer. This review article covers the most important findings toward these objectives accomplished during the past 3-4 years. The two major available organometallic building blocks will be discussed in the beginning together with constraints for market introduction as imposed by science and industry. Since targeting radiopharmaceuticals are a major focus of current research in molecular imaging, attempts toward so-called technetium essential radiopharmaceuticals will be briefly touched in the beginning followed by the main discussion about the labeling of targeting molecules such as folic acid, nucleosides, vitamins, carbohydrates, and fatty acids. At the end, some new strategies for drug discovery will be introduced together with results from organometallic chemistry in water. The majority of the new results have been achieved with the [99mTc(OH2)3(CO)3]+ complex which will, though not exclusively, be a focus of this review.

  6. Distinctive Reaction Pathways at Base Metals in High-Spin Organometallic Catalysts.

    PubMed

    Holland, Patrick L

    2015-06-16

    Inexpensive "base" metals are more affordable and sustainable than precious metals and also offer opportunities to discover new mechanisms for selective catalytic reactions. Base metal complexes can have high-spin electronic configurations that are rare in precious metal complexes. This Account describes some concepts relevant to high-spin organometallic complexes, focusing on our recent work with β-diketiminate complexes of iron and cobalt. Even though high-spin organometallic complexes have some unfamiliar spectroscopic properties, they can be studied using NMR spectroscopy as well as techniques that focus on the magnetism brought about by the unpaired electrons. Understanding the mechanisms of reactions using these complexes can be complicated, because complexes with a high-spin electronic configuration may need to change spin states to avoid high barriers for reaction. These spin-state changes can be rapid, and the ability of an excited spin state to "cut through" the barrier for a reaction can lead to spin acceleration. These concepts, originally developed by Poli, Shaik, Schwarz, and Harvey, are applied here to the fundamental organometallic reaction of β-hydride elimination (BHE). Experimentally validated density-functional calculations show spin acceleration in BHE using three-coordinate iron(II) and cobalt(II) complexes. A square-planar transition state is particularly beneficial for accelerating BHE when a high-spin iron(II) complex goes from an S = 2 ground state to an S = 1 transition state or when a high-spin cobalt(II) complex goes from an S = 3/2 ground state to an S = 1/2 transition state. The relative energies of the spin states can be controlled with the choice of the supporting ligand. Using an appropriate ligand, isomerization of 1-alkenes to their Z-2 isomers can be catalyzed in high yields using the cobalt(II) alkyl complexes as catalysts. Though an earlier paper attributed the regioselectivity and stereoselectivity to the preferred geometry

  7. The design of a bipodal bis(pentafluorophenoxy)aluminate supported on silica as an activator for ethylene polymerization using surface organometallic chemistry.

    PubMed

    Sauter, Dominique W; Popoff, Nicolas; Bashir, Muhammad Ahsan; Szeto, Kai C; Gauvin, Régis M; Delevoye, Laurent; Taoufik, Mostafa; Boisson, Christophe

    2016-04-01

    A new class of well-defined activating supports for olefin polymerization was obtained via the surface organometallic chemistry approach. High activities in slurry polymerization of ethylene along with industrial-grade physical properties of the resulting polyethylene were obtained when these activators were combined with metallocene complexes in the presence of triisobutylaluminium. PMID:26899986

  8. Nanoscaled tin dioxide films processed from organotin-based hybrid materials: an organometallic route toward metal oxide gas sensors.

    PubMed

    Renard, Laetitia; Babot, Odile; Saadaoui, Hassan; Fuess, Hartmut; Brötz, Joachim; Gurlo, Aleksander; Arveux, Emmanuel; Klein, Andreas; Toupance, Thierry

    2012-11-01

    Nanocrystalline tin dioxide (SnO(2)) ultra-thin films were obtained employing a straightforward solution-based route that involves the calcination of bridged polystannoxane films processed by the sol-gel process from bis(triprop-1-ynylstannyl)alkylene and -arylene precursors. These films have been thoroughly characterized by FTIR, contact angle measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force (AFM) and scanning electron (SEM) microscopies. Annealing at a high temperature gave 30-35 nm thick cassiterite SnO(2) films with a mean crystallite size ranging from 4 to 7 nm depending on the nature of the organic linker in the distannylated compound used as a precursor. In the presence of H(2) and CO gases, these layers led to highly sensitive, reversible and reproducible responses. The sensing properties were discussed in regard to the crystallinity and porosity of the sensing body that can be tuned by the nature of the precursor employed. Organometallic chemistry combined with the sol-gel process therefore offers new possibilities toward metal oxide nanostructures for the reproducible and sensitive detection of combustible and toxic gases. PMID:23011110

  9. Quantum Monte Carlo study of charged transition-metal organometallic cluster systems

    NASA Astrophysics Data System (ADS)

    Tokar, Kamil; Derian, Rene; Stich, Ivan

    2015-03-01

    Using accurate fixed-node quantum Monte Carlo (QMC) methods we study 1D clusters formed by transition metal atoms separated by benzene molecules (TMBz), both positively and negatively charged. TMBz are among the most important π-bonded organometallics, which, however, often require charged states for experimental studies. We have performed a systematic study of ground-sate spin multiplets, ionization potentials, electron affinities, and dissociation energies of vanadium-benzene cationic and anionic half- and full-sandwiches. By comparison of QMC and DFT results, we find a very strong impact of electronic correlation on properties of these systems, such as dissociation energies, where ~1 eV energy corrections are found. In particular, the anions are unstable at the DFT level and are stabilized only at the QMC level after sophisticated optimization of the trial wavefunction. Supported by APVV-0207-11 and VEGA (2/0007/12) projects.

  10. CLUSTER CHEMISTRY

    SciTech Connect

    Muetterties, Earl L.

    1980-05-01

    Metal cluster chemistry is one of the most rapidly developing areas of inorganic and organometallic chemistry. Prior to 1960 only a few metal clusters were well characterized. However, shortly after the early development of boron cluster chemistry, the field of metal cluster chemistry began to grow at a very rapid rate and a structural and a qualitative theoretical understanding of clusters came quickly. Analyzed here is the chemistry and the general significance of clusters with particular emphasis on the cluster research within my group. The importance of coordinately unsaturated, very reactive metal clusters is the major subject of discussion.

  11. Probing the chemistry, electronic structure and redox energetics in organometallic pentavalent uranium complexes.

    PubMed

    Graves, Christopher R; Vaughn, Anthony E; Schelter, Eric J; Scott, Brian L; Thompson, Joe D; Morris, David E; Kiplinger, Jaqueline L

    2008-12-15

    A series of organometallic pentavalent uranium complexes of the general formula (C(5)Me(5))(2)U(=N-2,6-(i)Pr(2)-C(6)H(3))(Y) (Y = monoanionic, non-halide ligand) have been prepared using a variety of routes. Utilizing the direct oxidation of (C(5)Me(5))(2)U(=N-2,6-(i)Pr(2)-C(6)H(3))(THF) (2) with the appropriate copper(I) salt yielded the triflate (Y = OTf (OSO(2)CF(3)), 11), thiolate (Y = SPh, 12), and acetylide (Y = C[triple bond]CPh, 13) complexes, while a salt metathesis route between the U(V)-imido (C(5)Me(5))(2)U(=N-2,6-(i)Pr(2)-C(6)H(3))(I) (10) and various alkali salts gave the diphenylamide (Y = NPh(2), 14), aryloxide (Y = OPh, 15), alkyl (Y = Me, 16), and aryl (Y = Ph, 17) complexes. Paired with 13, the isolation of 16 and 17 shows that U(V) can support the full range of carbon anions (sp, sp(2), and sp(3)), and these are, to the best of our knowledge, the first examples of pentavalent uranium complexes with anionic carbon moieties other than carbocyclic (C(5)R(5), C(7)H(7), C(8)H(8)) ligands. Finally, both protonolysis and insertion pathways afforded the U(V)-imido ketimide complex (C(5)Me(5))(2)U(=N-2,6-(i)Pr(2)-C(6)H(3))(N=CPh(2)) (18). The complexes have been isolated in good yield and characterized using various combinations of (1)H NMR spectroscopy, elemental analysis, mass spectrometry, single crystal X-ray diffraction, cyclic voltammetry, UV-visible-NIR absorption spectroscopy, and magnetic susceptibility measurements. All (C(5)Me(5))(2)U(=N-Ar)(X) (X = F, Cl, Br, I) and (C(5)Me(5))(2)U(=N-Ar)(Y) complexes exhibit U(VI)/U(V) and U(V)/U(IV) redox couples by voltammetry. The potential separation between these couples remains essentially constant at approximately 1.50 V, but both processes shift in tandem in potential by approximately 700 mV across the series of X/Y ligands. No significant differences between mu(eff) values or temperature dependencies in the magnetic susceptibility were observed for these complexes regardless of the identity of the

  12. Organometallic Probe for the Electronics of Base-Stabilized Group 11 Metal Cations.

    PubMed

    Braunschweig, Holger; Ewing, William C; Kramer, Thomas; Mattock, James D; Vargas, Alfredo; Werner, Christine

    2015-08-24

    A number of trimetalloborides have been synthesized through the reactions of base-stabilized coinage metal chlorides with a dimanganaborylene lithium salt in the hope of using this organometallic platform to compare and evaluate the electronics of these popular coinage metal fragments. The adducts of Cu(I), Ag(I), and Au(I) ions, stabilized by tricyclohexylphosphine (PCy3), N-1,3-bis(4-methylphenyl)imidazol-2-ylidene (ITol), or 1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene (CAAC), with [{Cp(CO)2Mn}2B](-) were studied spectroscopically, structurally, and computationally. The geometries of the adducts fall into two classes, one symmetric and one asymmetric, each relying on the combined characteristics of both the metal and ligand. The energetic factors proposed as the causes of the structural differences were investigated by ETS-NOCV (extended transition state-natural orbitals for chemical valence) analysis, which showed the final geometry to be controlled by the competition between the tendency of the coinage metal to adopt a higher or lower coordination number and the willingness of the cationic fragment to participate in back-bonding interactions. PMID:26178571

  13. Entrapment of an organometallic complex within a metal: a concept for heterogeneous catalysis.

    PubMed

    Yosef, Itzik; Abu-Reziq, Raed; Avnir, David

    2008-09-10

    A novel family of composite materials, organically doped metals, has been recently introduced. Here, we demonstrate their use as a new platform for heterogeneous catalysis, namely the doping of a metal with a catalytic organometallic complex. Specifically, a rhodium(I) catalyst, (RhCl(COD)(Ph2P(C6H4SO3Na))), ([Rh]), was physically entrapped within silver, thus creating a new type of catalytic material: [Rh]@Ag. Several aspects were demonstrated with the development of this heterogeneous catalyst: a metal can be used as a support for heterogenizing a homogeneous catalyst; the homogeneous catalyst is stabilized by the entrapment within the metal; the products of the composite catalyst are different compared to those obtained from the homogeneous one; and the adsorption of [Rh] on the surface of Ag and its entrapment are very different processes only the latter provided appreciable catalytic activity. Thus, while homogeneous [Rh] was entirely destroyed after converting styrene to ethylbenzne at 50%, [Rh]@Ag remained active after effecting the same reaction to a yield of 85% (compared to only 7% for [Rh] adsorbed on Ag), and while homogeneous [Rh] hydrogenated diphenylacetylene to bibenzyl (and was completely deactivated after one cycle) with no trace of cis-stilbene, [Rh]@Ag afforded that compound as the main product and could be reused. PMID:18702492

  14. High-conductive organometallic molecular wires with delocalized electron systems strongly coupled to metal electrodes.

    PubMed

    Schwarz, Florian; Kastlunger, Georg; Lissel, Franziska; Riel, Heike; Venkatesan, Koushik; Berke, Heinz; Stadler, Robert; Lörtscher, Emanuel

    2014-10-01

    Besides active, functional molecular building blocks such as diodes or switches, passive components, for example, molecular wires, are required to realize molecular-scale electronics. Incorporating metal centers in the molecular backbone enables the molecular energy levels to be tuned in respect to the Fermi energy of the electrodes. Furthermore, by using more than one metal center and sp-bridging ligands, a strongly delocalized electron system is formed between these metallic "dopants", facilitating transport along the molecular backbone. Here, we study the influence of molecule-metal coupling on charge transport of dinuclear X(PP)2FeC4Fe(PP)2X molecular wires (PP = Et2PCH2CH2PEt2); X = CN (1), NCS (2), NCSe (3), C4SnMe3 (4), and C2SnMe3 (5) under ultrahigh vacuum and variable temperature conditions. In contrast to 1, which showed unstable junctions at very low conductance (8.1 × 10(-7) G0), 4 formed a Au-C4FeC4FeC4-Au junction 4' after SnMe3 extrusion, which revealed a conductance of 8.9 × 10(-3) G0, 3 orders of magnitude higher than for 2 (7.9 × 10(-6) G0) and 2 orders of magnitude higher than for 3 (3.8 × 10(-4) G0). Density functional theory (DFT) confirmed the experimental trend in the conductance for the various anchoring motifs. The strong hybridization of molecular and metal states found in the C-Au coupling case enables the delocalized electronic system of the organometallic Fe2 backbone to be extended over the molecule-metal interfaces to the metal electrodes to establish high-conductive molecular wires. PMID:25233125

  15. Method of Continuous Variations: Applications of Job Plots to the Study of Molecular Associations in Organometallic Chemistry[**

    PubMed Central

    Renny, Joseph S.; Tomasevich, Laura L.; Tallmadge, Evan H.; Collum, David B.

    2014-01-01

    Applications of the method of continuous variations—MCV or the Method of Job—to problems of interest to organometallic chemists are described. MCV provides qualitative and quantitative insights into the stoichiometries underlying association of m molecules of A and n molecules of B to form AmBn. Applications to complex ensembles probe associations that form metal clusters and aggregates. Job plots in which reaction rates are monitored provide relative stoichiometries in rate-limiting transition structures. In a specialized variant, ligand- or solvent-dependent reaction rates are dissected into contributions in both the ground states and transition states, which affords insights into the full reaction coordinate from a single Job plot. Gaps in the literature are identified and critiqued. PMID:24166797

  16. Metal-carbonyl organometallic polymers, PFpP, as resists for high-resolution positive and negative electron beam lithography.

    PubMed

    Zhang, J; Cao, K; Wang, X S; Cui, B

    2015-12-25

    Metal-containing resists for electron beam lithography (EBL) are attracting attention owing to their high dry etching resistance and possibility for directly patterning metal-containing nanostructures. The newly developed organometallic metal carbonyl polymers, PFpP, can function as EBL resists with strong etching resistance. One significant feature of the PFpP resist is its high resolution. Line arrays with line-widths as narrow as 17 nm have been created. The resist can also be used in positive tone. PMID:26481609

  17. Advances in organometallic synthesis with mechanochemical methods.

    PubMed

    Rightmire, Nicholas R; Hanusa, Timothy P

    2016-02-14

    Solvent-based syntheses have long been normative in all areas of chemistry, although mechanochemical methods (specifically grinding and milling) have been used to good effect for decades in organic, and to a lesser but growing extent, inorganic coordination chemistry. Organometallic synthesis, in contrast, represents a relatively underdeveloped area for mechanochemical research, and the potential benefits are considerable. From access to new classes of unsolvated complexes, to control over stoichiometries that have not been observed in solution routes, mechanochemical (or 'M-chem') approaches have much to offer the synthetic chemist. It has already become clear that removing the solvent from an organometallic reaction can change reaction pathways considerably, so that prediction of the outcome is not always straightforward. This Perspective reviews recent developments in the field, and describes equipment that can be used in organometallic synthesis. Synthetic chemists are encouraged to add mechanochemical methods to their repertoire in the search for new and highly reactive metal complexes and novel types of organometallic transformations. PMID:26763151

  18. Preparation of nanocrystalline metal oxides and intermetallic phases by controlled thermolysis of organometallic coordination polymers

    NASA Astrophysics Data System (ADS)

    Rehbein, Marcus; Epple, Matthias; Fischer, R. Dieter

    2000-06-01

    Organometallic coordination polymers of the super-Prussian blue type [(Me 3Sn) nM(CN) 6] (Me=CH 3; n=3, 4; M=Fe, Co, Ru) were subjected to thermolysis in different atmospheres (air, argon, hydrogen/nitrogen). In air, oxides were found: Fe 2O 3/SnO 2 (crystalline and nanocrystalline), Co 2SnO 4 and RuO 2. In argon and in hydrogen, the intermetallic phases FeSn 2, CoSn 2, Ru 3Sn 7 and Fe 3SnC were obtained. A detailed mechanistic study was carried out using thermogravimetry (TG), X-ray diffraction (XRD), X-ray absorption spectroscopy (EXAFS) at Fe, Co, Ru and Sn K-edges, infrared spectroscopy (IR) and elemental analysis. Below 250°C, Me 3SnCN and (CN) 2 are released, whereas above 250°C oxidation or pyrolysis leads to the corresponding oxides or intermetallic phases. Polymeric cyanides containing at least two metals have turned out to be suitable precursors to prepare well-defined oxides and intermetallic phases at comparatively low temperature.

  19. Magnetically-induced electric polarization in an organo-metallic magnet

    SciTech Connect

    Zapf, W S; Fabris, F W; Balakirev, F F; Francoual, S M; Kenzelmann, M; Chen, Y

    2009-01-01

    The coupling between magnetic order and ferroelectricity has been under intense investigation in a wide range of transition metal oxides. The strongest coupling is obtained in so-called magnetically induced multiferroics where ferroelectricity arises directly from magnetic order that breaks inversion symmetry. However, it has been difficult to find non-oxide based materials in which these effects occur. Here we present a study of copper dimethyl sulfoxide dichloride (CDC), an organometallic quantum magnet containing S =1/1 Cu spins, in which a switchable electric polarization arises from field-tuned magnetic order. Fast magnetic field pulses allow us to perform sensitive measurements of the electric polarization and demonstrate that the electric state is present only if the magnetic order is non-collinear. Furthermore, we show that the electric polarization can be switched in a stunning hysteretic fashion. Because the magnetic order in CDC is mediated by large organic molecules, our study shows that magnetoelectric interactions can exist in this important class of materials, opening the road to designing magnetoelectrics and multiferroics using large molecules as building blocks. Further, we demonstrate that CDC undergoes a magnetoelectric quantum phase transition -the first of its kind, where both ferroelectric and magnetic order emerge simultaneously as a function of magnetic field at very low temperatures.

  20. Surface chemistry of liquid metals

    NASA Technical Reports Server (NTRS)

    Mann, J. Adin, Jr.; Peebles, Henry; Peebles, Diamond; Rye, Robert; Yost, Fred

    1993-01-01

    The fundamental surface chemistry of the behavior of liquid metals spreading on a solid substrate is not at all well understood. Each of these questions involves knowing the details of the structure of interfaces and their dynamics. For example the structure of a monolayer of tin oxide on pure liquid tin is unknown. This is in contrast to the relatively large amount of data available on the structure of copper oxide monolayers on solid, pure copper. However, since liquid tin has a vapor pressure below 10(exp -10)torr for a reasonable temperature range above its melting point, it is possible to use the techniques of surface science to study the geometric, electronic and vibrational structures of these monolayers. In addition, certain techniques developed by surface chemists for the study of liquid systems can be applied to the ultra-high vacuum environment. In particular we have shown that light scattering spectroscopy can be used to study the surface tension tensor of these interfaces. The tin oxide layer in particular is very interesting in that the monolayer is rigid but admits of bending. Ellipsometric microscopy allows the visualization of monolayer thick films and show whether island formation occurs at various levels of dosing.

  1. Organometallic single source precursors for chemical vapor deposition of metal chalcogenides

    NASA Astrophysics Data System (ADS)

    Seidler, Dean Jerry

    The group 14--16 compounds with the general formula (Bn2SnE)3, (Bn3Sn)2E, and Bn 2Sn(EBn)2, where E = S or Se, were synthesized and investigated as potential single-source precursors for the preparation of tin chalcogenides. Each precursor was pyrolyzed under an inert atmosphere. Decomposition took place at relatively mild conditions (<400°C). The cyclic molecules, (Bn2SnS)3 and (Bn2SnSe)3, produced tin sulfide and tin selenide, respectively. The samples were XRD phase pure, and combustion analysis indicated less than 1% carbon present in the final product. The acyclic precursors, (Bn3Sn)2S and (Bn 3Sn)2Se, yielded a mixture of the tin chalcogenide and elemental tin with carbon content <1%. The pyrolysis of Bn2Sn(SBn) 2 and Bn2Sn(SeBn)2 produced SnS2 and SnSe2, respectively, with carbon contamination <3%. The only volatile by-product detected from the pyrolysis of these compounds was bibenzyl, indicating all of the tin and chalcogen were left behind in the solid state product. Solid solutions could be generated by combining (Bn 2SnS)3 and (Bn2SnSe)3, and pyrolyzing the mixture. Combinations of Bn2Sn(SBn)2 and Bn 2Sn(SeBn)2 yielded products with some solid solution character; however, some phase separation was indicated in the XRD patterns. Bn3SnSBn and (tert-Bu2SnS)2 were pyrolyzed to produce bulk samples of SnS and also used as single-source precursors for the chemical vapor deposition of thin films of SnS on glass and halite substrates. The composition and morphology of the products, both as bulk materials and thin films, were influenced by the structure of the organometallic precursor, the nature of the leaving group attached to the metal (or chalcogen), and the nature of the film substrate.

  2. Electron beam chemistry produces high purity metals

    NASA Technical Reports Server (NTRS)

    Philipp, W. H.; May, C. E.; Marsik, S. J.; Lad, R. A.

    1972-01-01

    Application of radiation chemistry for deposition of metals by irradiation of aqueous solutions with high energy electrons is presented. Design of reaction vessel for irradiation of solution is illustrated. Features of radiochemical technique and procedures followed are described.

  3. Organometallic Chemistry of Carbon Dioxide. Final Report for June 1, 1986 - March 31, 2002

    SciTech Connect

    Gibson, D. H.

    2002-09-26

    Research focused on C{sub 1} transition metal complexes that are relevant to CO{sub 2} activation and fixation. First, we prepared and studied new metallocarboxylic acids, a class of compounds proposed as intermediates in the Water Gas Shift reaction and CO{sub 2} reductions, and the corresponding metallocarboxylate anions. Next, we prepared and structurally characterized a large number of CO{sub 2}-bridged bimetallic compounds (models for metal surface-bound CO{sub 2}) and established structure-spectra correlations for the three general types of compounds identified. The next phase involved the synthesis and studies of putative catalytic intermediates derived from rhenium and ruthenium polypyridyl complexes in order to establish their fundamental reaction characteristics. Finally, we progressed to the design of a possible catalytic sequence which could account for C{sub 2} products formed in ruthenium-catalyzed CO{sub 2} reductions and to the synthesis, characterization and studies of the reactions of expected intermediates in the catalytic sequence.

  4. Separations chemistry of toxic metals

    SciTech Connect

    Smith, P.; Barr, M.; Barrans, R.

    1996-04-01

    Sequestering and removing toxic metal ions from their surroundings is an increasingly active area of research and is gaining importance in light of current environmental contamination problems both within the DOE complex and externally. One method of separating metal ions is to complex them to a molecule (a ligand or chelator) which exhibits specific binding affinity for a toxic metal, even in the presence of other more benign metals. This approach makes use of the sometimes subtle differences between toxic and non-toxic metals resulting from variations in size, charge and shape. For example, toxic metals such as chromium, arsenic, and technetium exist in the environment as oxyanions, negatively charged species with a characteristic tetrahedral shape. Other toxic metals such as actinides and heavy metals are positively charged spheres with specific affinities for particular donor atoms such as oxygen (for actinides) and nitrogen (for heavy metals). In most cases the toxic metals are found in the presence of much larger quantities of less toxic metals such as sodium, calcium and iron. The selectivity of the chelators is critical to the goal of removing the toxic metals from their less toxic counterparts. The approach was to build a ligand framework that complements the unique characteristics of the toxic metal (size, charge and shape) while minimizing interactions with non-toxic metals. The authors have designed ligands exhibiting specificity for the target metals; they have synthesized, characterized and tested these ligands; and they have shown that they exhibit the proposed selectivity and cooperative binding effects.

  5. High-efficiency organometallic vapor phase epitaxy AlGaAs/GaAs monolithic cascade solar cell using metal interconnects

    SciTech Connect

    Ludowise, M.J.; LaRue, R.A.; Borden, P.G.; Gregory, P.E.; Dietze, W.T.

    1982-09-15

    A two-junction solar cell has been fabricated using an Al/sub 0.30/Ga/sub 0.70/As (1.82 eV) tap cell and a GaAs (1.43 eV) bottom cell. A processed metal interconnect is used to connect the two cells together in series. An efficiency of 21.5% at 980 mW/cm/sup 2/ has been measured in a solar simulator with an open circuit voltage of 2.35 V, a short circuit current of 118.6 mA/cm/sup 2/, and a fill factor of 0.76. An efficiency of 22% has been measured under 130 AM3 sun in a solar tracking concentrator. Organometallic vapor phase epitaxy is used to grow the entire nine-layer device.

  6. THE COORDINATION CHEMISTRY OF METAL SURFACES

    SciTech Connect

    Muetterties, Earl L.

    1980-10-01

    In coordinately unsaturated molecular metal complexes, carbon-hydrogen bonds of the peripheral ligands may, if the stereochemistry allows, closely approach a metal center so as to develop a three-center two-electron bond between the carbon, the hydrogen, and the metal atoms, C-H-M. In some instances, the interaction .is followed by a scission of the C-H bond whereby the metal is effectively oxidized and discrete M-H and M-C {sigma} bonds are forrned. This class of metal-hydrogen-carbon interactions and reactions is shown to be a common phenomenon in metal surface chemistry. Ultra high vacuum studies of nickel and platinum with simple organic molecules like olefins, and arenes are described. These surface chemistry studies were done as a function of surface crystallography and surface composition. The discussion is largely limited to the chemistry of methyl isocyanide, acetonitrile, benzene and toluene. Molecular orbital calculations are presented that support the experimental identification of the importance of C-H-M metal bonding for metal surfaces.

  7. Medicinal Radiopharmaceutical Chemistry of Metal Radiopharmaceuticals

    NASA Astrophysics Data System (ADS)

    Saw, Maung Maung

    2012-06-01

    Metal complexes have been used as medicinal compounds. Metals have advantageous features over organic compounds. Significant applications of metal complexes are in the field of nuclear medicine. Radiopharmaceuticals are drugs containing radioisotopes used for diagnostic and therapeutic purposes. The generalized targeting strategy for molecular imaging probe consists of three essential parts: (i) reporter unit or payload, (ii) carrier, and (iii) targeting system. Medicinal radiopharmaceutical chemistry pays special consideration to radioisotopes, as a reporter unit for diagnostic application or as a payload for therapeutic application. Targeting is achieved by a few approaches but the most common is the bifunctional chelator approach. While designing a radiopharmaceutical, a range of issues needs to be considered including properties of metal radioisotopes, bifunctional chelators, linkers, and targeting molecules. Designing radiopharmaceuticals requires consideration of two key words: "compounds of biological interest" and "fit for intended use." The ultimate goal is the development of new diagnostic methods and treatment. Diagnostic metal radiopharmaceuticals are used for SPECT and PET applications. Technetium chemistry constitutes a major portion of SPECT and gallium chemistry constitutes a major portion of PET. Therapeutic radiopharmaceuticals can be constructed by using alpha-, beta minus-, or Auger electron-emitting radiometals. Special uses of medicinal radiopharmaceuticals include internal radiation therapy, brachytherapy, immunoPET, radioimmunotherapy, and peptide receptor radionuclide imaging and therapy.

  8. Theoretical approaches to metal chemistry

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W.; Langhoff, Stephen R.; Partridge, Harry; Halicioglu, Timur; Taylor, Peter R.

    1987-01-01

    Theoretical calculations on metals ranging from very accurate ab initio studies of diatomic and triatomic systems to model studies of larger clusters are presented. Recent improvements in the representation of one-particle and n-particle spaces have made possible the prediction that Al2 has a 3Pi(u) ground state, even though the 3Sigma(-)g state lies within 200/cm. Results suggest that cluster geometry varies dramatically with cluster size, and that rather large clusters are required before the bulk structure becomes optimal. Al cluster studies show that three-body terms are needed for quantitative agreement with ab initio calculations.

  9. Bioinorganic Chemistry of the Alkali Metal Ions.

    PubMed

    Kim, Youngsam; Nguyen, Thuy-Tien T; Churchill, David G

    2016-01-01

    The common Group 1 alkali metals are indeed ubiquitous on earth, in the oceans and in biological systems. In this introductory chapter, concepts involving aqueous chemistry and aspects of general coordination chemistry and oxygen atom donor chemistry are introduced. Also, there are nuclear isotopes of importance. A general discussion of Group 1 begins from the prevalence of the ions, and from a comparison of their ionic radii and ionization energies. While oxygen and water molecule binding have the most relevance to biology and in forming a detailed understanding between the elements, there is a wide range of basic chemistry that is potentially important, especially with respect to biological chelation and synthetic multi-dentate ligand design. The elements are widely distributed in life forms, in the terrestrial environment and in the oceans. The details about the workings in animal, as well as plant life are presented in this volume. Important biometallic aspects of human health and medicine are introduced as well. Seeing as the elements are widely present in biology, various particular endogenous molecules and enzymatic systems can be studied. Sodium and potassium are by far the most important and central elements for consideration. Aspects of lithium, rubidium, cesium and francium chemistry are also included; they help in making important comparisons related to the coordination chemistry of Na(+) and K(+). Physical methods are also introduced. PMID:26860297

  10. Organometallic molecular wires as versatile modules for energy-level alignment of the metal-molecule-metal junction.

    PubMed

    Sugimoto, Kaho; Tanaka, Yuya; Fujii, Shintaro; Tada, Tomofumi; Kiguchi, Manabu; Akita, Munetaka

    2016-04-30

    The organometallic Ru molecular wires 1-3 Ru(PR3)4(C[triple bond, length as m-dash]CC5H5N)2 [(PR3)4 = (dppe)2 (1), [P(OMe3)]4 (2), and (dmpe)2 (3)] show significantly higher conductance compared to their organic counterpart, 1,4-dipyridyl butadiyne (4). CV and UV-Vis measurements and DFT calculations suggest that the high-lying HOMOs of the Ru wires are the key factor for the high conductance. PMID:26996138

  11. 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.

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

    DOEpatents

    Giolando, Dean M.

    2003-09-30

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

  13. Introducing deep eutectic solvents to polar organometallic chemistry: chemoselective addition of organolithium and Grignard reagents to ketones in air.

    PubMed

    Vidal, Cristian; García-Álvarez, Joaquín; Hernán-Gómez, Alberto; Kennedy, Alan R; Hevia, Eva

    2014-06-01

    Despite their enormous synthetic relevance, the use of polar organolithium and Grignard reagents is greatly limited by their requirements of low temperatures in order to control their reactivity as well as the need of dry organic solvents and inert atmosphere protocols to avoid their fast decomposition. Breaking new ground on the applications of these commodity organometallics in synthesis under more environmentally friendly conditions, this work introduces deep eutetic solvents (DESs) as a green alternative media to carry out chemoselective additions of ketones in air at room temperature. Comparing their reactivities in DES with those observed in pure water suggest that a kinetic activation of the alkylating reagents is taking place, favoring nucleophilic addition over the competitive hydrolysis, which can be rationalized through formation of halide-rich magnesiate or lithiate species. PMID:24771680

  14. N-heterocyclic carbene metal complexes as bio-organometallic antimicrobial and anticancer drugs.

    PubMed

    Patil, Siddappa A; Patil, Shivaputra A; Patil, Renukadevi; Keri, Rangappa S; Budagumpi, Srinivasa; Balakrishna, Geetha R; Tacke, Matthias

    2015-01-01

    Late transition metal complexes that bear N-heterocyclic carbene (NHC) ligands have seen a speedy growth in their use as both, metal-based drug candidates and potentially active homogeneous catalysts in a plethora of C-C and C-N bond forming reactions. This review article focuses on the recent developments and advances in preparation and characterization of NHC-metal complexes (metal: silver, gold, copper, palladium, nickel and ruthenium) and their biomedical applications. Their design, syntheses and characterization have been reviewed and correlated to their antimicrobial and anticancer efficacies. All these initial discoveries help validate the great potential of NHC-metal derivatives as a class of effective antimicrobial and anticancer agents. PMID:26144266

  15. Science Update: Inorganic Chemistry.

    ERIC Educational Resources Information Center

    Rawls, Rebecca

    1981-01-01

    Describes areas of inorganic chemistry which have changed dramatically in the past year or two, including photochemistry, electrochemistry, organometallic complexes, inorganic reaction theory, and solid state chemistry. (DS)

  16. The Surface Chemistry of Metal Chalcogenide Nanocrystals

    NASA Astrophysics Data System (ADS)

    Anderson, Nicholas Charles

    The surface chemistry of metal chalcogenide nanocrystals is explored through several interrelated analytical investigations. After a brief discussion of the nanocrystal history and applications, molecular orbital theory is used to describe the electronic properties of semiconductors, and how these materials behave on the nanoscale. Quantum confinement plays a major role in dictating the optical properties of metal chalcogenide nanocrystals, however surface states also have an equally significant contribution to the electronic properties of nanocrystals due to the high surface area to volume ratio of nanoscale semiconductors. Controlling surface chemistry is essential to functionalizing these materials for biological imaging and photovoltaic device applications. To better understand the surface chemistry of semiconducting nanocrystals, three competing surface chemistry models are presented: 1.) The TOPO model, 2.) the Non-stoichiometric model, and 3.) the Neutral Fragment model. Both the non-stoichiometric and neutral fragment models accurately describe the behavior of metal chalcogenide nanocrystals. These models rely on the covalent bond classification system, which divides ligands into three classes: 1.) X-type, 1-electron donating ligands that balance charge with excess metal at the nanocrystal surface, 2.) L-type, 2-electron donors that bind metal sites, and 3.) Z-type, 2-electron acceptors that bind chalcogenide sites. Each of these ligand classes is explored in detail to better understand the surface chemistry of metal chalcogenide nanocrystals. First, chloride-terminated, tri-n-butylphosphine (Bu 3P) bound CdSe nanocrystals were prepared by cleaving carboxylate ligands from CdSe nanocrystals with chlorotrimethylsilane in Bu3P solution. 1H and 31P{1H} nuclear magnetic resonance spectra of the isolated nanocrystals allowed assignment of distinct signals from several free and bound species, including surface-bound Bu3P and [Bu3P-H]+[Cl]- ligands as well as a Bu

  17. From carbanions to organometallic compounds: quantification of metal ion effects on nucleophilic reactivities.

    PubMed

    Corral-Bautista, Francisco; Klier, Lydia; Knochel, Paul; Mayr, Herbert

    2015-10-12

    The influence of the metal on the nucleophilic reactivities of indenyl metal compounds was quantitatively determined by kinetic investigations of their reactions with benzhydrylium ions (Ar2 CH(+) ) and structurally related quinone methides. With the correlation equation log k2 =sN (N+E), it can be derived that the ionic indenyl alkali compounds are 10(18) to 10(24) times more reactive (depending on the reference electrophile) than the corresponding indenyltrimethylsilane. PMID:25951612

  18. Chiral chemistry of metal-camphorate frameworks.

    PubMed

    Gu, Zhi-Gang; Zhan, Caihong; Zhang, Jian; Bu, Xianhui

    2016-06-01

    This critical review presents the various synthetic approaches and chiral chemistry of metal-camphorate frameworks (MCamFs), which are homochiral metal-organic frameworks (MOFs) constructed from a camphorate ligand. The interest in this unique subset of homochiral MOFs is derived from the many interesting chiral features for both materials and life sciences, such as asymmetrical synthesis or crystallization, homochiral structural design, chiral induction, absolute helical control and ligand handedness. Additionally, we discuss the potential applications of homochiral MCamFs. This review will be of interest to researchers attempting to design other homochiral MOFs and those engaged in the extension of MOFs for applications such as chiral recognition, enantiomer separation, asymmetric catalysis, nonlinear sensors and devices. PMID:27021070

  19. Organometallic neptunium(III) complexes

    NASA Astrophysics Data System (ADS)

    Dutkiewicz, Michał S.; Farnaby, Joy H.; Apostolidis, Christos; Colineau, Eric; Walter, Olaf; Magnani, Nicola; Gardiner, Michael G.; Love, Jason B.; Kaltsoyannis, Nikolas; Caciuffo, Roberto; Arnold, Polly L.

    2016-08-01

    Studies of transuranic organometallic complexes provide a particularly valuable insight into covalent contributions to the metal–ligand bonding, in which the subtle differences between the transuranium actinide ions and their lighter lanthanide counterparts are of fundamental importance for the effective remediation of nuclear waste. Unlike the organometallic chemistry of uranium, which has focused strongly on UIII and has seen some spectacular advances, that of the transuranics is significantly technically more challenging and has remained dormant. In the case of neptunium, it is limited mainly to NpIV. Here we report the synthesis of three new NpIII organometallic compounds and the characterization of their molecular and electronic structures. These studies suggest that NpIII complexes could act as single-molecule magnets, and that the lower oxidation state of NpII is chemically accessible. In comparison with lanthanide analogues, significant d- and f-electron contributions to key NpIII orbitals are observed, which shows that fundamental neptunium organometallic chemistry can provide new insights into the behaviour of f-elements.

  20. Metals in the mesosphere: chemistry and change

    NASA Astrophysics Data System (ADS)

    Plane, John; Marsh, Daniel; Höffner, Josef; Janches, Diego; Dawkins, Erin; Gomez-Martin, Juan Carlos; Bones, David; Feng, Wuhu; Chipperfield, Martyn

    2016-07-01

    The meteoric metal layers (e.g. Na, Fe, K and Ca) - which form as a result of the ablation of incoming meteors - act as unique tracers for chemical and dynamical processes that occur within the upper mesosphere/lower thermosphere region. This presentation examines whether these metal layers are sensitive indicators of longer-term changes within the upper atmosphere. Output from the Whole Atmosphere Community Climate Model (WACCM) is used to assess the response of the Na, K and Fe layers across a 50-year period (1955-2005), while both model and observational data (satellite and lidar) is used to assess the response of the Na and K layers to the 11-year solar cycle extending between 2004-2013. On short time-scales, the K layer exhibits a very different seasonal behaviour compared to the other metals. This unusual behaviour is also exhibited at longer time-scales (both the 11-yr solar cycle and 50-yr periods); K displays a much more pronounced response to atmospheric changes at a 50-yr time scale than either Na or Fe. Underpinning this modelling work are two new laboratory systems developed at Leeds. First, a time-of-flight mass spectrometer with laser photo-ionization has been used to study the reactions of neutral metallic compounds in the gas phase which are not detectable by conventional spectroscopic probes. This has enabled significant advances in Na layer chemistry to be made. The second is a flowing afterglow/laser ablation experiment which has been used to study the dissociative recombination of metallic ions such as FeO ^{+} and CaO ^{+} with electrons; these processes are particularly important for modelling the phenomenon of sporadic metal layers.

  1. Transition-Metal-Free Cross-Coupling of Indium Organometallics with Chromene and Isochroman Acetals Mediated by BF3·OEt2.

    PubMed

    Gil-Negrete, José M; Pérez Sestelo, José; Sarandeses, Luis A

    2016-09-01

    A transition-metal-free coupling of triorganoindium reagents with benzopyranyl acetals mediated by a Lewis acid has been developed. The reaction of R3In with chromene and isochroman acetals in the presence of BF3·OEt2 afforded 2-substituted chromenes and 1-substituted isochromans, respectively, in good yields. The reactions proceed with a variety of triorganoindium reagents (aryl, heteroaryl, alkynyl, alkenyl, alkyl) using only 50 mol % of the organometallic, thus demonstrating the efficiency of these species. Preliminary mechanistic studies indicate the formation of an oxocarbenium ion intermediate in the presence of the Lewis acid. PMID:27530143

  2. EFFECT OF BIOSOLIDS APPLICATION ON SOIL METAL CHEMISTRY AND PHYTOAVAILABILITY

    EPA Science Inventory

    Addition of biosolids to soils increases the environmental loading of toxic metals (Cd, Zn, Cu, Ni, Pb, etc.) and alters the chemistry and phytoavailability of these metals. This alteration in phytoavailability associated with biosolids amended soil was recognized and utilized ...

  3. High-valent organometallic copper and palladium in catalysis.

    PubMed

    Hickman, Amanda J; Sanford, Melanie S

    2012-04-12

    Copper and palladium catalysts are critically important in numerous commercial chemical processes. Improvements in the activity, selectivity and scope of these catalysts could drastically reduce the environmental impact, and increase the sustainability, of chemical reactions. One rapidly developing strategy for achieving these goals is to use 'high-valent' organometallic copper and palladium intermediates in catalysis. Here we describe recent advances involving both the fundamental chemistry and the applications of these high-valent metal complexes in numerous synthetically useful catalytic transformations. PMID:22498623

  4. Risks associated with the transfer of toxic organo-metallic mercury from soils into the terrestrial feed chain.

    PubMed

    Henriques, Bruno; Rodrigues, S M; Coelho, C; Cruz, N; Duarte, A C; Römkens, P F A M; Pereira, E

    2013-09-01

    Although the transfer of organo-metallic mercury (OrgHg) in aquatic food webs has long been studied, it has only been recently recognized that there is also accumulation in terrestrial systems. There is still however little information about the exposure of grazing animals to OrgHg from soils and feed as well as on risks of exposure to animal and humans. In this study we collected 78 soil samples and 40 plant samples (Lolium perenne and Brassica juncea) from agricultural fields near a contaminated industrial area and evaluated the soil-to-plant transfer of Hg as well as subsequent trophic transfer. Inorganic Hg (IHg) concentrations ranged from 0.080 to 210mgkg(-1) d.w. in soils, from 0.010 to 84mgkg(-1) d.w. in roots and from 0.020 to 6.9mgkg(-1) d.w. in shoots. OrgHg concentrations in soils varied between 0.20 and 130μgkg(-1) d.w. representing on average 0.13% of the total Hg (THg). In root and shoot samples OrgHg comprised on average 0.58% (roots) and 0.66% (shoots) of THg. Average bioaccumulation factors (BAFs) for OrgHg in relation to soil concentrations were 3.3 (for roots) and 1.5 (for shoots). The daily intake (DI) of THg in 33 sampling sites exceeded the acceptable daily intake (ADI) of THg of both cows (ADI=1.4mgd(-1)) and sheep (ADI=0.28mgd(-1)), in view of food safety associated with THg in animal kidneys. Estimated DI of OrgHg for grazing animals were up to 220μgd(-1) (for cows) and up to 33μgd(-1) (for sheep). This study suggested that solely monitoring the levels of THg in soils and feed may not allow to adequately taking into account accumulation of OrgHg in feed crops and properly address risks associated with OrgHg exposure for animals and humans. Hence, the inclusion of limits for OrgHg in feed quality and food safety legislation is advised. PMID:23917441

  5. Coordination Chemistry of [Co(acac)2 ] with N-Doped Graphene: Implications for Oxygen Reduction Reaction Reactivity of Organometallic Co-O4 -N Species.

    PubMed

    Han, Jongwoo; Sa, Young Jin; Shim, Yeonjun; Choi, Min; Park, Noejung; Joo, Sang Hoon; Park, Sungjin

    2015-10-19

    Hybridization of organometallic complexes with graphene-based materials can give rise to enhanced catalytic performance. Understanding the chemical structures within hybrid materials is of primary importance. In this work, archetypical hybrid materials are synthesized by the reaction of an organometallic complex, [Co(II) (acac)2 ] (acac=acetylacetonate), with N-doped graphene-based materials at room temperature. Experimental characterization of the hybrid materials and theoretical calculations reveal that the organometallic cobalt-containing species is coordinated to heterocyclic groups in N-doped graphene as well as to its parental acac ligands. The hybrid material shows high electrocatalytic activity for the oxygen reduction reaction (ORR) in alkaline media, and superior durability and methanol tolerance to a Pt/C catalyst. Based on the chemical structures and ORR experiments, the catalytically active species is identified as a Co-O4 -N structure. PMID:26331625

  6. Transition-metal organometallic compounds as cocatalysts in olefin polymerization with MgCl{sub 2}-supported catalysts

    SciTech Connect

    Galimberti, M.; Piemontesi, F.; Giannini, U.; Albizzati, E.

    1993-12-06

    Zirconium tetrabenzyl was used as the cocatalyst in olefin polymerization together with MgCl{sub 2}-supported titanium catalysts. Its behavior was compared with those of aluminum and titanium organometallic compounds. In propylene polymerization performed with a MgCl{sub 2}/TiCl{sub 4} catalyst containing ethyl benzoate as the internal donor and with tetrabenzylzirconium as the cocatalyst, a polypropylene with 93 as its isostatic index was obtained, without the need of any external donor. They present a tentative explanation, based on the study of the interaction between the different components of the catalytic system.

  7. Organometallic Polymers.

    ERIC Educational Resources Information Center

    Carraher, Charles E., Jr.

    1981-01-01

    Reactions utilized to incorporate a metal-containing moiety into a polymer chain (addition, condensation, and coordination) are considered, emphasizing that these reactions also apply to smaller molecules. (JN)

  8. Outer-Sphere Electrophilic Fluorination of Organometallic Complexes.

    PubMed

    Milner, Lucy M; Pridmore, Natalie E; Whitwood, Adrian C; Lynam, Jason M; Slattery, John M

    2015-08-26

    Organofluorine chemistry plays a key role in materials science, pharmaceuticals, agrochemicals, and medical imaging. However, the formation of new carbon-fluorine bonds with controlled regiochemistry and functional group tolerance is synthetically challenging. The use of metal complexes to promote fluorination reactions is of great current interest, but even state-of-the-art approaches are limited in their substrate scope, often require activated substrates, or do not allow access to desirable functionality, such as alkenyl C(sp(2))-F or chiral C(sp(3))-F centers. Here, we report the formation of new alkenyl and alkyl C-F bonds in the coordination sphere of ruthenium via an unprecedented outer-sphere electrophilic fluorination mechanism. The organometallic species involved are derived from nonactivated substrates (pyridine and terminal alkynes), and C-F bond formation occurs with full regio- and diastereoselectivity. The fluorinated ligands that are formed are retained at the metal, which allows subsequent metal-mediated reactivity. PMID:26270894

  9. (Mechanistic examination of organometallic electron transfer reactions: Annual report, 1989)

    SciTech Connect

    Not Available

    1989-01-01

    Our mechanistic examination of electron transfer reactions between organometallic complexes has required data from our stopped-flow infrared spectrophotometer that was constructed in the first year. Our research on organometallic electron transfer reaction mechanisms was recognized by an invitation to the Symposium on Organometallic Reaction Mechanisms at the National ACS meeting in Miami. We have obtained a reasonable understanding of the electron transfer reactions between metal cations and anions and between metal carbonyl anions and metal carbonyl dimers. In addition we have begun to obtain data on the outer sphere electron transfer between metal carbonyl anions and coordination complexes and on reactions involving cluster anions.

  10. [Mechanistic examination of organometallic electron transfer reactions: Annual report, 1989

    SciTech Connect

    Not Available

    1989-12-31

    Our mechanistic examination of electron transfer reactions between organometallic complexes has required data from our stopped-flow infrared spectrophotometer that was constructed in the first year. Our research on organometallic electron transfer reaction mechanisms was recognized by an invitation to the Symposium on Organometallic Reaction Mechanisms at the National ACS meeting in Miami. We have obtained a reasonable understanding of the electron transfer reactions between metal cations and anions and between metal carbonyl anions and metal carbonyl dimers. In addition we have begun to obtain data on the outer sphere electron transfer between metal carbonyl anions and coordination complexes and on reactions involving cluster anions.

  11. An Alternative Approach to the Teaching of Systematic Transition Metal Chemistry.

    ERIC Educational Resources Information Center

    Hathaway, Brian

    1979-01-01

    Presents an alternative approach to teaching Systematic Transition Metal Chemistry with the transition metal chemistry skeleton features of interest. The "skeleton" is intended as a guide to predicting the chemistry of a selected compound. (Author/SA)

  12. Science Update: Inorganic Chemistry

    ERIC Educational Resources Information Center

    Rawls, Rebecca

    1978-01-01

    This first in a series of articles describing the state of the art of various branches of chemistry reviews inorganic chemistry, including bioinorganic, photochemistry, organometallic, and solid state chemistries. (SL)

  13. Chemistry of soluble β-diketiminatoalkaline-earth metal complexes with M-X bonds (M=Mg, Ca, Sr; X=OH, Halides, H).

    PubMed

    Sarish, Sankaranarayana Pillai; Nembenna, Sharanappa; Nagendran, Selvarajan; Roesky, Herbert W

    2011-03-15

    Victor Grignard's Nobel Prize-winning preparation of organomagnesium halides (Grignard reagents) marked the formal beginning of organometallic chemistry with alkaline earth metals. Further development of this invaluable synthetic route, RX+Mg→RMgX, with the heavier alkaline earth metals (Ca and Sr) was hampered by limitations in synthetic methodologies. Moreover, the lack of suitable ligands for stabilizing the reactive target molecules, particularly with the more electropositive Ca and Sr, was another obstacle. The absence in the literature, until just recently, of fundamental alkaline earth metal complexes with M-H, M-F, and M-OH (where M is the Group 2 metal Mg, Ca, or Sr) bonds amenable for organometallic reactions is remarkable. The progress in isolating various unstable compounds of p-block elements with β-diketiminate ligands was recently applied to Group 2 chemistry. The monoanionic β-diketiminate ligands are versatile tools for addressing synthetic challenges, as amply demonstrated with alkaline earth complexes: the synthesis and structural characterization of soluble β-diketiminatocalcium hydroxide, β-diketiminatostrontium hydroxide, and β-diketiminatocalcium fluoride are just a few examples of our contribution to this area of research. To advance the chemistry beyond synthesis, we have investigated the reactivity and potential for applications of these species, for example, through the demonstration of dip coating surfaces with CaCO(3) and CaF(2) with solutions of the calcium hydroxide and calcium fluoride complexes, respectively. In this Account, we summarize some recent developments in alkaline earth metal complex chemistry, particularly of Mg, Ca, and Sr, through the utilization of β-diketiminate ligands. We focus on results generated in our laboratory but give due mention to work from other groups as well. We also highlight the closely related chemistry of the Group 12 element Zn, as well as the important chemistry developed by other groups

  14. Polymeric, Metallic, and Other Glasses in Introductory Chemistry

    ERIC Educational Resources Information Center

    Hawkes, Stephen J.

    2008-01-01

    Non-ceramic glasses are not adequately discussed in introductory chemistry. Such glasses include polycarbonate, which many corrective lenses are made of, amber, enamel, gelatin, hard candy, coal, refrigerated glycerol, and metallic glasses that have been marketed in recent decades. What is usually discussed in elementary texts is siliceous glass,…

  15. Omar Yaghi on Chemistry and Metal Organic Frameworks

    SciTech Connect

    Omar Yaghi

    2012-07-23

    In this edited version of the hour long talk, Omar Yaghi, director of the Molecular Foundry, sat down in conversation with Jeff Miller, head of Public Affairs, on July 11th, 2012 to discuss his fascination with the hidden world of chemistry and his work on Metal Organic Frameworks.

  16. Omar Yaghi on Chemistry and Metal Organic Frameworks

    ScienceCinema

    Omar Yaghi

    2013-06-24

    In this edited version of the hour long talk, Omar Yaghi, director of the Molecular Foundry, sat down in conversation with Jeff Miller, head of Public Affairs, on July 11th, 2012 to discuss his fascination with the hidden world of chemistry and his work on Metal Organic Frameworks.

  17. Contribution of radiation chemistry to the study of metal clusters.

    PubMed

    Belloni, J

    1998-11-01

    Radiation chemistry dates from the discovery of radioactivity one century ago by H. Becquerel and P. and M. Curie. The complex phenomena induced by ionizing radiation have been explained progressively. At present, the methodology of radiation chemistry, particularly in the pulsed mode, provides a powerful means to study not only the early processes after the energy absorption, but more generally a broad diversity of chemical and biochemical reaction mechanisms. Among them, the new area of metal cluster chemistry illustrates how radiation chemistry contributed to this field in suggesting fruitful original concepts, in guiding and controlling specific syntheses, and in the detailed elaboration of the mechanisms of complex and long-unsolved processes, such as the dynamics of nucleation, electron transfer catalysis and photographic development. PMID:9806605

  18. Reactivity of Gold Complexes towards Elementary Organometallic Reactions.

    PubMed

    Joost, Maximilian; Amgoune, Abderrahmane; Bourissou, Didier

    2015-12-01

    For a while, the reactivity of gold complexes was largely dominated by their Lewis acid behavior. In contrast to the other transition metals, the elementary steps of organometallic chemistry-oxidative addition, reductive elimination, transmetallation, migratory insertion-have scarcely been studied in the case of gold or even remained unprecedented until recently. However, within the last few years, the ability of gold complexes to undergo these fundamental reactions has been unambiguously demonstrated, and the reactivity of gold complexes was shown to extend well beyond π-activation. In this Review, the main achievements described in this area are presented in a historical context. Particular emphasis is set on mechanistic studies and structure determination of key intermediates. The electronic and structural parameters delineating the reactivity of gold complexes are discussed, as well as the remaining challenges. PMID:26768342

  19. Ab Initio Calculations Applied to Problems in Metal Ion Chemistry

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Partridge, Harry; Arnold, James O. (Technical Monitor)

    1994-01-01

    Electronic structure calculations can provide accurate spectroscopic data (such as molecular structures) vibrational frequencies, binding energies, etc.) that have been very useful in explaining trends in experimental data and in identifying incorrect experimental measurements. In addition, ab initio calculations. have given considerable insight into the many interactions that make the chemistry of transition metal systems so diverse. In this review we focus on cases where calculations and experiment have been used to solve interesting chemical problems involving metal ions. The examples include cases where theory was used to differentiate between disparate experimental values and cases where theory was used to explain unexpected experimental results.

  20. The Renaissance of Metal-Pyrimidine Nucleobase Coordination Chemistry.

    PubMed

    Lippert, Bernhard; Sanz Miguel, Pablo J

    2016-08-16

    The significance of metal ions for the function and properties of DNA and RNA, long seen primarily under biological aspects and medicinal uses, has recently gained a renewed momentum. This is a consequence of the advent of novel applications in the fields of materials science, biotechnology, and analytical sensor chemistry that relate to the designed incorporation of transition metal ions into nucleic acid base pairs. Ag(+) and Hg(2+) ions, binding to pyrimidine (pym) nucleobases, represent major players in this development. Interestingly, these metal ions were the ones that some 60 years ago started the field! At the same time, the mentioned metal ions had demonstrated a "special relationship" with the pym nucleobases cytosine, thymine, and uracil! Parallel work conducted with oligonucleotides and model nucleobases fostered numerous significant details of these interactions, in particular when X-ray crystallography was involved, correcting earlier views occasionally. Our own activities during the past three to four decades have focused on, among others, the coordination chemistry of transition and main-group metal ions with pym model nucleobases, with an emphasis on Pt(II) and Pd(II). It has always been our goal to deduce, if possible, the potential relevance of our findings for biological processes. It is interesting to put our data, in particular for trans-a2Pt(II) (a = NH3 or amine), into perspective with those of other metal ions, notably Ag(+) and Hg(2+). Irrespective of major differences in kinetics and lability/inertness between d(8) and d(10) metal ions, there is also a lot of similarity in structural aspects as a result of the preferred linear coordination geometry of these species. Moreover, the apparent clustering of metal ions to the pym nucleobases, which is presumably essential for the formation of nanoclusters on oligonucleotide scaffolds, is impressively reflected in model systems, as are reasons for inter-nucleobase cross-links containing more

  1. A primer on trace metal-sediment chemistry

    USGS Publications Warehouse

    Horowitz, Arthur J.

    1985-01-01

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

  2. Molecular dynamics simulation of organometallic reaction dynamics, and, Enhancing achievement in chemistry for African American students through innovations in pedagogy aligned with supporting assessment and curriculum and integrated under an alternative research paradigm

    NASA Astrophysics Data System (ADS)

    Mebane, Sheryl Dee

    Part I. Molecular dynamics simulation of organometallic reaction dynamics. To study the interplay of solute and solvent dynamics, large-scale molecular dynamics simulations were employed. Lennard-Jones and electrostatic models of potential energies from solvent-only studies were combined with solute potentials generated from ab-initio calculations. Radial distribution functions and other measures revealed the polar solvent's response to solute dynamics following CO dissociation. In future studies, the time-scale for solvent coordination will be confirmed with ultrafast spectroscopy data. Part II. Enhancing achievement in chemistry for African American students through innovations in pedagogy aligned with supporting assessment and curriculum and integrated under an alternative research paradigm. Much progress has been made in the area of research in education that focuses on teaching and learning in science. Much effort has also centered on documenting and exploring the disparity in academic achievement between underrepresented minority students and students comprising a majority in academic circles. However, few research projects have probed educational inequities in the context of mainstream science education. In order to enrich this research area and to better reach underserved learning communities, the educational experience of African American students in an ethnically and academically diverse high school science class has been examined throughout one, largely successful, academic year. The bulk of data gathered during the study was obtained through several qualitative research methods and was interpreted using research literature that offered fresh theoretical perspectives on equity that may better support effective action.

  3. Non-metallocene organometallic complexes and related methods and systems

    DOEpatents

    Agapie, Theodor; Golisz, Suzanne Rose; Tofan, Daniel; Bercaw, John E.

    2010-12-07

    A non-metallocene organometallic complex comprising a tridentate ligand and a metal bonded to a tridentate ligand, wherein two substituted aryl groups in the tridentate ligand are connected to a cyclic group at the ortho position via semi-rigid ring-ring linkages, and selected so to provide the resulting non-metallocene organometallic complex with a C.sub.S geometry, a C.sub.1 geometry, a C.sub.2 geometry or a C.sub.2v geometry. Method for performing olefin polymerization with a non-metallocene organometallic complex as a catalyst, related catalytic systems, tridentate ligand and method for providing a non-metallocene organometallic complex.

  4. Chemistry and Properties of Complex Intermetallics from Metallic Fluxes

    SciTech Connect

    Kanatzidis, Mercouri G.

    2015-03-28

    This project investigated the reaction chemistry and synthesis of new intermetallic materials with complex compositions and structures using metallic fluxes as solvents. It was found that the metallic fluxes offer several key advantages in facilitating the formation and crystal growth of new materials. The fluxes mostly explored were liquid aluminum, gallium and indium. The main purpose of this project was to exploit the potential of metallic fluxes as high temperature solvent for materials discovery in the broad class of intermetallics. This work opened new paths to compound formation. We discovered many new Si (or Ge)-based compounds with novel structures, bonding and physicochemical properties. We created new insights about the reaction chemistry that is responsible for stabilizing the new materials. We also studied the structural and compositional relationships to understand their properties. We investigated the use of Group-13 metals Al, Ga and In as solvents and have generated a wide variety of new results including several new ternary and quaternary materials with fascinating structures and properties as well as new insights as to how these systems are stabilized in the fluxes. The project focused on reactions of metals from the rare earth element family in combination with transition metals with Si and Ge. For example molten gallium has serves both as a reactive and non-reactive solvent in the preparation and crystallization of intermetallics in the system RE/M/Ga/Ge(Si). Molten indium behaves similarly in that it too is an excellent reaction medium, but it gives compounds that are different from those obtained from gallium. Some of the new phase identified in the aluminide class are complex phases and may be present in many advanced Al-matrix alloys. Such phases play a key role in determining (either beneficially or detrimentally) the mechanical properties of advanced Al-matrix alloys. This project enhanced our basic knowledge of the solid state chemistry

  5. The Systematic Study of the Organotransition Metal Compounds.

    ERIC Educational Resources Information Center

    Carriedo, Gabino A.

    1990-01-01

    Discussed is an extension of the conventional method for studying the organometallic chemistry of transition metals that may be useful to show how the various existing types of low-valence complexes can be constructed. This method allows students to design new types of complexes that may still be nonexistent. (CW)

  6. Surface modification, organometallic and polyaryl polymer coatings, and flame spray technologies for preventing corrosion of metals. Final report

    SciTech Connect

    Sugama, T.

    1995-07-01

    To improve adherent properties of electrogalvanized steel (EGS) to polymeric topcoats, the surfaces of EGS were modified by polyelectrolyte-modified zinc phosphating solution. The electrochemical reaction between phosphating solution and EGS led to the complete coverage with fully grown hopeite crystals after only 5 sec treatment, thereby improving adhesion to topcoating and providing protection of EGS against corrosion. To evaluate the ability of polyphenylene sulfide (PPS) polyaryl thermoplastic coatings to protect zinc phosphate (Zn{center_dot}Ph)treated steels from corrosion in a wet, harsh environment ( 1.0 wt % H{sub 2}SO{sub 4}, 3.0 wt % NaCl and 96.0 wt % water at temperatures from 25{degrees} to 200{degree}C), we exposed them in an autoclave to attempt heating-cooling cyclic fatigue tests (1 cycle = 12 hr at 200{degrees}C + 12 hr at 25{degrees}C) up to 90 times. The major chemical reaction at the interface between the PPS and Zn in the Zn-Ph layer during cycling led to the formation of ZnS reaction product, which enhanced the Zn-Ph-to-PPS adhesive bond; correspondingly, there were no signs of peeling and separation of the coating after 90 cycles. organometallosiloxane polymer (OMSP) was synthesized through the hydrolysis-condensation reaction of the mixed precursor solutions of the N-[3-(triethoxysily)propyl]-4,5,-dihydroimidazole and {Beta}-trimethoxysilylethyl-2-pyridine sols in liquor medium and the metal alkoxides and metallocene dichloride dissolved in water or tetrahydrofurane. The OMSP films (thickness, 0. 5 to 1. 0 {mu}m) deposited by simple dip-withdrawing coating methods to aluminum alloys displayed the impedance of > 10{sup 6} ohm-cm {sup 2} after exposure for 40 days in 0.5 N NaCl solution at 25{degrees}C and the 3000 hr-salt spray resistance. Using a flame spray coating process, the methacrylic acid-modified polyethylene copolymer was overlaid onto cold rolled steel surfaces.

  7. Quantum Chemistry for Surface Segregation in Metal Alloys

    SciTech Connect

    Sholl, David

    2006-08-31

    Metal alloys are vital materials for the fabrication of high-flux, high-selectivity hydrogen separation membranes. A phenomenon that occurs in alloys that does not arise in pure metals is surface segregation, where the composition of the surface differs from the bulk composition. Little is known about the strength of surface segregation in the alloys usually considered for hydrogen membranes. Despite this lack of knowledge, surface segregation may play a decisive role in the ability of appropriately chosen alloys to be resistant to chemical poisoning, since membrane poisoning is controlled by surface chemistry. The aim of this Phase I project is to develop quantum chemistry approaches to assess surface segregation in a prototypical hydrogen membrane alloy, fcc Pd{sub 75}Cu{sub 25}. This alloy is known experimentally to have favorable surface properties as a poison resistant H{sub 2} purification membrane (Kamakoti et al., Science 307 (2005) 569-573), but previous efforts at modeling surfaces of this alloy have ignored the possible role of surface segregation (Alfonso et al., Surf. Sci. 546 (2003) 12-26).

  8. Modulation of human osteoblasts by metal surface chemistry.

    PubMed

    Hofstetter, Wilhelm; Sehr, Harald; de Wild, Michael; Portenier, Jeannette; Gobrecht, Jens; Hunziker, Ernst B

    2013-08-01

    The use of metal implants in dental and orthopedic surgery is continuously expanding and highly successful. While today longevity and load-bearing capacity of the implants fulfill the expectations of the patients, acceleration of osseointegration would be of particular benefit to shorten the period of convalescence. To further clarify the options to accelerate the kinetics of osseointegration, within this study, the osteogenic properties of structurally identical surfaces with different metal coatings were investigated. To assess the development and function of primary human osteoblasts on metal surfaces, cell viability, differentiation, and gene expression were determined. Titanium surfaces were used as positive, and surfaces coated with gold were used as negative controls. Little differences in the cellular parameters tested for were found when the cells were grown on titanium discs sputter coated with titanium, zirconium, niobium, tantalum, gold, and chromium. Cell number, activity of cell layer-associated alkaline phosphatase (ALP), and levels of transcripts encoding COL1A1 and BGLAP did not vary significantly in dependence of the surface chemistry. Treatment of the cell cultures with 1,25(OH)2 D3 /Dex, however, significantly increased ALP activity and BGLAP messenger RNA levels. The data demonstrate that the metal layer coated onto the titanium discs exerted little modulatory effects on cell behavior. It is suggested that the microenvironment regulated by the peri-implant tissues is more effective in regulating the tissue response than is the material of the implant itself. PMID:23359530

  9. Exploration of Fluorine Chemistry at the Multidisciplinary Interface of Chemistry and Biology

    PubMed Central

    Ojima, Iwao

    2013-01-01

    Over the last three decades, my engagement in “fluorine chemistry” has evolved substantially, because of the multidisciplinary nature of the research programs. I began my research career as a synthetic chemist in organometallic chemistry and homogeneous catalysis directed toward organic synthesis. Then, I was brought into a very unique world of “fluorine chemistry” in the end of 1970s. I started exploring the interface of fluorine chemistry and transition metal homogeneous catalysis first, which was followed by amino acids, peptides, and peptidomimetics for medicinal chemistry. Since then, I have been exploring the interfaces of fluorine chemistry and multidisciplinary fields of research involving medicinal chemistry, chemical biology, cancer biology and molecular imaging. This perspective intends to cover my fruitful endeavor in the exploration of fluorine chemistry at the multidisciplinary interface of chemistry and biology in a chronological order to show the evolution of my research interest and strategy. PMID:23614876

  10. Syntheses and characterization of dichlorozirconium porphyrin complexes and their novel organometallic derivatives. X-ray structure of Zr(TPP)Cl[sub 2](THF)

    SciTech Connect

    Heejoon Kim; Dongmok Whang; Kimoon Kim ); Youngkyu Do )

    1993-02-03

    The chemistry of early transition metal porphyrin complexes, especially, that of the second- and third-row metal complexes has not been developed much due in part to their high oxophilicity. The authors have been interested in exploring zirconium and hafnium porphyrin complexes because they may show a rich organometallic chemistry as zirconocene derivatives do. The key entry to the organometallic zirconium porphyrin complexes would be Zr(porphyrin)Cl[sub 2], analogous to ZrCp[sub 2]Cl[sub 2]. The dichloride complex may be converted to organometallic [sigma]-complexes such as dialkyl complexes by the reactions with alkyllithium or Grignard reagents. It may also form organometallic [tau]-complexes by replacing the two chlorides with a cyclooctatetraenyl dianion or a dicarbollide dianion. Indeed, the authors have succeeded in preparing Zr(por)Cl[sub 2] (por = OEP, TPP) and their organometallic derivatives Zr(TPP)Me[sub 2] and Zr(OEP)([eta][sup 5]-C[sub 2]B[sub 9]H[sub 11]). They have presented the preliminary results on their syntheses and characterization by spectroscopy but have been unable to grow X-ray-quality crystals of either of the organometallic complexes until recently. When they finished the structural characterization of Zr(OEP)([eta][sup 5]C[sub 2]B[sub 9]H[sub 11]) by X-ray crystallography, however, Arnold and co-workers published the synthesis and characterization of Zr(OEP)Cl[sub 2] and several organometallic complexes derived from it, including Zr(OEP)(CH[sub 2]SiMe[sub 3])[sub 2] and Zr(OEP)([eta][sup 5]-C[sub 2]B[sub 9]H[sub 11]). Here they present their results on the syntheses and characterization of Zr(por)Cl[sub 2] (por = OEP, TPP), Zr(TPP)Me[sub 2], and Zr(OEP)([eta][sup 5]-C[sub 2]B[sub 9]H[sub 11]) and the X-ray structure of Zr(TPP)Cl[sub 2](THF). 22 refs., 2 tabs.

  11. Detection of toxic organometallic complexes in wastewaters using algal assays.

    PubMed

    Wong, S L; Nakamoto, L; Wainwright, J F

    1997-05-01

    Chlorella (a unicellular green alga) and Cladophora (a filamentous alga) were used in algal assays to identify the presence and toxicity of organometallic complexes in four industrial wastewaters. Toxicities of inorganic Pb and organometallic compounds (trimethyl, tetramethyl and tetraethyl leads, cacodylic acid and Cu-picolinate) were examined, using algal cells grown in 10% BBM solution. Inorganic Pb and organometallic compounds altered the fine structure of Chlorella cells in a distinguishable manner. X-ray microanalysis revealed that organometallic compounds accumulated in the neutral lipids of Cladophora cells. By applying the above techniques to the wastewater assays, two of the four wastewaters tested were found to contain organometallic complexes. Wastewater from a chemical company contained only traces of organo-Cu, but one mining effluent contained significant quantities of organo-Cu and organo-Pb, and traces of organo-Cr and organo-Tl (thallium). These studies suggest that X-ray microanalysis of algae may be a useful tool in identifying aquatic systems contaminated with metals and organometallic compounds. PMID:9175500

  12. Surface chemistry of the atomic layer deposition of metals and group III oxides

    NASA Astrophysics Data System (ADS)

    Goldstein, David Nathan

    Atomic Layer Deposition (ALD) is a thin-film growth technique offering precise control of film thickness and the ability to coat high-aspect-ratio features such as trenches and nanopowders. Unlike other film growth techniques, ALD does not require harsh processing conditions and is not limited by line-of-sight deposition. Emerging applications for ALD materials include semiconductor devices, gas sensors, and water-diffusion barriers. The chemistry behind ALD involves understanding how the precursors interact with surfaces to deposit the desired material. All ALD precursors need to be stable on the substrate to ensure self-limiting behavior yet reactive enough to be easily removed with the second reagent. Recent precursor development has provided many volatile organometallic compounds for most of the periodic table. As the number of precursors increases, proper precursor choice becomes crucial. This is because the film properties, growth rates, and growth temperature vary widely between the precursors. Many of the above traits can be predicted with knowledge of the precursor reaction mechanisms. This thesis aims to link surface reaction mechanisms to observed growth and nucleation trends in metal and oxide ALD systems. The first portion of this thesis explores the mechanisms of two ALD oxide systems. First, I examine the mechanism of ALD alumina with ozone. Ozone is used as an oxidant in the semiconductor industry because the deposited Al 2O3 films possess better insulating properties and ozone is easier to purge from a vacuum system. FT-IR analysis reveals a complicated array of surface intermediates such as formate, carbonate, and methoxy groups that form during Al2O3 growth with ozone. Next, a new method to deposit thin films of Ga2O3 is introduced. Gallium oxide is a transparent conducting oxide that needs expensive solid precursors to be deposited by ALD. I show that trimethylgallium is a good high-temperature ALD precursor that deposits films of Ga2O 3 with

  13. Electrophilic Metal Alkyl Chemistry in New Ligand Environments

    SciTech Connect

    Jordan, Richard F.

    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.

  14. EFFECT OF BIOSOLIDS APPLICATION ON SOIL METAL CHEMISTRY AND PHYTOAVAILABILITY (LAKE BUENA VISTA, FL)

    EPA Science Inventory

    Addition of biosolids to soils increases the environmental loading of toxic metals (Cd, Zn, Cu, Ni, Pb, etc.) and alters the chemistry and phytoavailability of these metals. This alteration in phytoavailability associated with biosolids amended soil was recognized and utilized ...

  15. Organometallic electrochemistry based on electrolytes containing weakly-coordinating fluoroarylborate anions.

    PubMed

    Geiger, William E; Barrière, Frédéric

    2010-07-20

    -deficient organometallic compounds are subject to nucleophilic attack by the traditional family of electrolyte anions. With a view to testing the scope of the much less nucleophililic WCAs in providing a benign electrolyte anion for the generation of organometallic cation radicals, we carried out a series of studies on transition metal sandwich and half-sandwich compounds. The model compounds were chosen both for their fundamental importance and because their radical cations had been neither isolated nor spectrally characterized, despite many previous electrochemical investigations with traditional anions. The oxidation of prototypical organometallic compounds, such as the sandwich-structured ruthenocene and the piano-stool structured Cr(eta(6)-C(6)H(6))(CO)(3), Mn(eta(5)-C(5)H(5))(CO)(3), Re(eta(5)-C(5)H(5))(CO)(3), and Co(eta(5)-C(5)H(5))(CO)(2), gave the first definitive in situ characterization of their radical cations. In several cases, the kinetic stabilization of the anodic products allowed the identification of dimers or unique dimer radicals having weak metal-metal bonds and provided new preparative options for organometallic systems. In terms of thermodynamic effects, the lower ion-pairing abilities of WCAs and their good solubility in a broad range of solvents, including those of lower polarity, permitted a systematic study that yielded an integrated model of how to use solvent-electrolyte combinations to manipulate the E(1/2) differences of compounds undergoing multiple electron-transfer reactions. Although the efficacy of WCA-based electrolytes in organometallic anodic chemistry is now established, WCAs might further expand applications of organic redox chemistry. Other WCAs, including those derived from carboranes and fluorinated alkoxyaluminates, merit additional studies. PMID:20345126

  16. The Chemistry of Metal-Rich Hot Neptunes

    NASA Astrophysics Data System (ADS)

    Moses, Julianne I.; Richardson, M. R.; Madhusudhan, N.; Line, M. R.; Visscher, C.; Fortney, J. J.

    2012-10-01

    Neptune-mass planets with very high metallicities (100-3000 times solar) will exhibit an interesting continuum of atmospheric compositions in between the so-called “hot Neptune” and “Super Earth” exoplanet categories. If its metallicity is only slightly enhanced over solar, a Neptune-mass planet would have a photospheric composition similar to that predicted for any hydrogen-dominated, Jupiter-mass planet possessing a similar thermal structure and experiencing a similar incident stellar flux. Hydrogen-poor Super Earths, on the other hand, could have a variety of atmospheric compositions (e.g., Schaefer et al. 2011, arXiv:1108.4660), ranging from H2O-, CO2-, or N2-dominated atmospheres, to more exotic high-temperature SiO and metal-rich atmospheres, depending on the planet’s mass, evolutionary history, incident stellar flux, and effective temperature. A Neptune-mass planet can become metal rich through efficient hydrogen escape (e.g., for less-massive, close-in planets) or through inefficient accretion of H2, as has been suggested for our own solar-system “ice giant” Neptune, where carbon is enriched by 40-70 times solar (e.g., Karkoschka and Tomasko 2011, Icarus 211, 780) and oxygen may be enriched as much as 440 times solar (e.g., Lodders and Fegley 1994, Icarus 112, 368). We explore the predicted equilibrium and disequilibrium chemistry of generic hot Neptunes with metallicities varying from 1-3000 times solar and discuss observational consequences. The models are applied to the case of GJ 436b, where we find that methane will be the dominant carbon carrier until very high metallicities, near 2000x solar, at which point the planet can have roughly equal proportions of CO, H2, and CO2, with methane becoming a more minor constituent. We compare our model results with Spitzer infrared secondary-eclipse data for GJ436b. This work was supported by the NASA PATM program.

  17. The crystal chemistry of inorganic metal borohydrides and their relation to metal oxides.

    PubMed

    Černý, Radovan; Schouwink, Pascal

    2015-12-01

    The crystal structures of inorganic homoleptic metal borohydrides are analysed with respect to their structural prototypes found amongst metal oxides in the inorganic databases such as Pearson's Crystal Data [Villars & Cenzual (2015). Pearson's Crystal Data. Crystal Structure Database for Inorganic Compounds, Release 2014/2015, ASM International, Materials Park, Ohio, USA]. The coordination polyhedra around the cations and the borohydride anion are determined, and constitute the basis of the structural systematics underlying metal borohydride chemistry in various frameworks and variants of ionic packing, including complex anions and the packing of neutral molecules in the crystal. Underlying nets are determined by topology analysis using the program TOPOS [Blatov (2006). IUCr CompComm. Newsl. 7, 4-38]. It is found that the Pauling rules for ionic crystals apply to all non-molecular borohydride crystal structures, and that the latter can often be derived by simple deformation of the close-packed anionic lattices c.c.p. and h.c.p., by partially removing anions and filling tetrahedral or octahedral sites. The deviation from an ideal close packing is facilitated in metal borohydrides with respect to the oxide due to geometrical and electronic considerations of the BH4(-) anion (tetrahedral shape, polarizability). This review on crystal chemistry of borohydrides and their similarity to oxides is a contribution which should serve materials engineers as a roadmap to design new materials, synthetic chemists in their search for promising compounds to be prepared, and materials scientists in understanding the properties of novel materials. PMID:26634719

  18. Rational design of an organometallic glutathione transferase inhibitor

    SciTech Connect

    Ang, W.H.; Parker, L.J.; De Luca, A.; Juillerat-Jeanneret, L.; Morton, C.J.; LoBello, M.; Parker, M.W.; Dyson, P.J.

    2010-08-17

    A hybrid organic-inorganic (organometallic) inhibitor was designed to target glutathione transferases. The metal center is used to direct protein binding, while the organic moiety acts as the active-site inhibitor. The mechanism of inhibition was studied using a range of biophysical and biochemical methods.

  19. Molecular switches in carbon-rich organometallic compounds: Theoretical aspects

    NASA Astrophysics Data System (ADS)

    Costuas, Karine

    2015-01-01

    Organometallic complexes associated with an appropriate choice of ancillary ligands reveal to have a wide range of physical properties leading to promising applications when incorporated in nano-size devices. The challenge is to design innovative multifunctional compounds based on redox active carbon-rich organometallics associated with spin carriers and/or photochromic units. A multidisciplinary approach in this area has proved to be efficient in a series a systems combining carbon-rich bridging ligands and redox metallic moieties. In this domain, the role of theoretical investigations based on quantum mechanics tools have a crucial role in rationalizing and in helping designing systems possessing target properties.

  20. Molecular switches in carbon-rich organometallic compounds: Theoretical aspects

    SciTech Connect

    Costuas, Karine

    2015-01-22

    Organometallic complexes associated with an appropriate choice of ancillary ligands reveal to have a wide range of physical properties leading to promising applications when incorporated in nano-size devices. The challenge is to design innovative multifunctional compounds based on redox active carbon-rich organometallics associated with spin carriers and/or photochromic units. A multidisciplinary approach in this area has proved to be efficient in a series a systems combining carbon-rich bridging ligands and redox metallic moieties. In this domain, the role of theoretical investigations based on quantum mechanics tools have a crucial role in rationalizing and in helping designing systems possessing target properties.

  1. Group 9 organometallic compounds for therapeutic and bioanalytical applications.

    PubMed

    Ma, Dik-Lung; Chan, Daniel Shiu-Hin; Leung, Chung-Hang

    2014-12-16

    CONSPECTUS: Compared with organic small molecules, metal complexes offer several distinct advantages as therapeutic agents or biomolecular probes. Carbon atoms are typically limited to linear, trigonal planar, or tetrahedral geometries, with a maximum of two enantiomers being formed if four different substituents are attached to a single carbon. In contrast, an octahedral metal center with six different substituents can display up to 30 different stereoisomers. While platinum- and ruthenium-based anticancer agents have attracted significant attention in the realm of inorganic medicinal chemistry over the past few decades, group 9 complexes (i.e., iridium and rhodium) have garnered increased attention in therapeutic and bioanalytical applications due to their adjustable reactivity (from kinetically liable to substitutionally inert), high water solubility, stability to air and moisture, and relative ease of synthesis. In this Account, we describe our efforts in the development of group 9 organometallic compounds of general form [M(C(∧)N)2(N(∧)N)] (where M = Ir, Rh) as therapeutic agents against distinct biomolecular targets and as luminescent probes for the construction of oligonucleotide-based assays for a diverse range of analytes. Earlier studies by researchers had focused on organometallic iridium(III) and rhodium(III) half-sandwich complexes that show promising anticancer activity, although their precise mechanisms of action still remain unknown. More recently, kinetically-inert group 9 complexes have arisen as fascinating alternatives to organic small molecules for the specific targeting of enzyme activity. Research in our laboratory has shown that cyclometalated octahedral rhodium(III) complexes were active against Janus kinase 2 (JAK2) or NEDD8-activating enzyme (NAE) activity, or against NO production leading to antivasculogenic activity in cellulo. At the same time, recent interest in the development of small molecules as modulators of protein

  2. Combinatorial sythesis of organometallic materials

    DOEpatents

    Schultz, Peter G.; Xiang, Xiaodong; Goldwasser, Isy

    2002-07-16

    Methods and apparatus for the preparation and use of a substrate having an array of diverse materials in predefined regions thereon. A substrate having an array of diverse materials thereon is generally prepared by delivering components of materials to predefined regions on a substrate, and simultaneously reacting the components to form at least two materials. Materials which can be prepared using the methods and apparatus of the present invention include, for example, covalent network solids, ionic solids and molecular solids. More particularly, materials which can be prepared using the methods and apparatus of the present invention include, for example, inorganic materials, intermetallic materials, metal alloys, ceramic materials, organic materials, organometallic materials, non-biological organic polymers, composite materials (e.g., inorganic composites, organic composites, or combinations thereof), etc. Once prepared, these materials can be screened for useful properties including, for example, electrical, thermal, mechanical, morphological, optical, magnetic, chemical, or other properties. Thus, the present invention provides methods for the parallel synthesis and analysis of novel materials having useful properties.

  3. Organometallics Roundtable 2011

    SciTech Connect

    Gladysz, John A.; Ball, Zachary T.; Bertrand, Guy; Blum, Suzanne A.; Dong, Vy M.; Dorta, Reto; Hahn, F. Ekkehardt; Humphrey, Mark; Jones, William D.; Klosin, Jerzy; Manners, Ian; Marks, Tobin J.; Mayer, James M.; Rieger, Bernhard; Ritter, Joachim C.; Sattelberger, Alfred P.; Schomaker, Jennifer M.; Wing-Wah Yam, Vivian

    2012-01-09

    We are living in an era of unprecedented change in academic, industrial, and government-based research worldwide, and navigating these rough waters requires "all hands on deck". Toward this end, Organometallics has assembled a panel of seventeen experts who share their thoughts on a variety of matters of importance to our field. In constituting this panel, an attempt was made to secure representation from a number of countries and career stages, as well as from industry. We were fortunate that so many busy experts could take the time to spend with us. The following pages constitute an edited transcript of the panel discussion held on August 29, 2011, which was structured around the 10 questions summarized in the side bar and repeated below.

  4. Ultrafast studies of organometallic photochemistry: The mechanism of carbon-hydrogen bond activation in solution

    SciTech Connect

    Bromberg, S.E.

    1998-05-01

    When certain organometallic compounds are photoexcited in room temperature alkane solution, they are able to break or activate the C-H bonds of the solvent. Understanding this potentially practical reaction requires a detailed knowledge of the entire reaction mechanism. Because of the dynamic nature of chemical reactions, time-resolved spectroscopy is commonly employed to follow the important events that take place as reactants are converted to products. For the organometallic reactions examined here, the electronic/structural characteristics of the chemical systems along with the time scales for the key steps in the reaction make ultrafast UV/Vis and IR spectroscopy along with nanosecond Step-Scan FTIR spectroscopy the ideal techniques to use for this study. An initial study of the photophysics of (non-activating) model metal carbonyls centering on the photodissociation of M(CO){sub 6} (M = Cr, W, Mo) was carried out in alkane solutions using ultrafast IR spectroscopy. Next, picosecond UV/vis studies of the C-H bond activation reaction of Cp{sup *}M(CO){sub 2} (M = Rh, Ir), conducted in room temperature alkane solution, are described in an effort to investigate the origin of the low quantum yield for bond cleavage ({approximately}1%). To monitor the chemistry that takes place in the reaction after CO is lost, a system with higher quantum yield is required. The reaction of Tp{sup *}Rh(CO){sub 2} (Tp{sup *} = HB-Pz{sub 3}{sup *}, Pz{sup *} = 3,5-dimethylpyrazolyl) in alkanes has a quantum yield of {approximately}30%, making time resolved spectroscopic measurements possible. From ultrafast IR experiments, two subsequently formed intermediates were observed. The nature of these intermediates are discussed and the first comprehensive reaction mechanism for a photochemical C-H activating organometallic complex is presented.

  5. Technetium chemistry

    SciTech Connect

    Burns, C.; Bryan, J.; Cotton, F.; Ott, K.; Kubas, G.; Haefner, S.; Barrera, J.; Hall, K.; Burrell, A.

    1996-04-01

    Technetium chemistry is a young and developing field. Despite the limited knowledge of its chemistry, technetium is the workhorse for nuclear medicine. Technetium is also a significant environmental concern because it is formed as a byproduct of nuclear weapons production and fission-power generators. Development of new technetium radio-pharmaceuticals and effective environmental control depends strongly upon knowledge of basic technetium chemistry. The authors performed research into the basic coordination and organometallic chemistry of technetium and used this knowledge to address nuclear medicine and environmental applications. This is the final report of a three-year Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL).

  6. Soft metal thiol chemistry is not involved in the transport of arsenite by the Ars pump.

    PubMed Central

    Chen, Y; Dey, S; Rosen, B P

    1996-01-01

    The single cysteine in the ArsB protein subunit of the arsenite resistance pump was changed to serine and alanine residues. Resistance in cells expressing the two mutant arsB genes was the same as in the wild type, and the serine substitution had no effect on the arsenite transport properties. These results eliminate possible thiol chemistry in translocation. Thus, the pump uses soft metal chemistry for metalloactivation and nonmetal chemistry for oxyanion transport. PMID:8550532

  7. Zintl cluster chemistry in the alkali-metal-gallium systems

    SciTech Connect

    Henning, R.

    1998-03-27

    Previous research into the alkali-metal-gallium systems has revealed a large variety of networked gallium deltahedra. The clusters are analogues to borane clusters and follow the same electronic requirements of 2n+2 skeletal electrons for closo-deltahedra. This work has focused on compounds that do not follow the typical electron counting rules. The first isolated gallium cluster was found in Cs{sub 8}Ga{sub 11}. The geometry of the Ga{sub 11}{sup 7{minus}} unit is not deltahedral but can be described as a penta-capped trigonal prism. The reduction of the charge from a closo-Ga{sub 11}{sup 13{minus}} to Ga{sub 11}{sup 7{minus}} is believed to be the driving force of the distortion. The compound is paramagnetic because of an extra electron but incorporation of a halide atom into the structure captures the unpaired electron and forms a diamagnetic compound. A second isolated cluster has been found in Na{sub 10}Ga{sub 10}Ni where the tetra-capped trigonal prismatic gallium is centered by nickel. Stabilization of the cluster occurs through Ni-Ga bonding. A simple two-dimensional network occurs in the binary K{sub 2}Ga{sub 3} Octahedra are connected through four waist atoms to form a layered structure with the potassium atoms sitting between the layers. Na{sub 30.5}Ga{sub 60{minus}x}Ag{sub x} is nonstoichiometric and needs only a small amount of silver to form (x {approximately} 2--6). The structure is composed of three different clusters which are interconnected to form a three-dimensional structure. The RbGa{sub 3{minus}x}Au{sub x} system is also nonstoichiometric with a three-dimensional structure composed of Ga{sub 8} dodecahedra and four-bonded gallium atoms. Unlike Na{sub 30.5}Ga{sub 60{minus}x}Ag{sub x}, the RbGa{sub 3} binary is also stable. The binary is formally a Zintl phase but the ternary is not. Some chemistry in the alkali-metal-indium system also has been explored. A new potassium-indium binary is discussed but the structure has not been completely

  8. Chemistry of Two-Dimensional Transition Metal Carbides (MXenes)

    NASA Astrophysics Data System (ADS)

    Mashtalir, Olha

    With consumer trends pushing toward smaller, faster, more flexible, multitasking devices, researchers striving to meet these needs have targeted two-dimensional (2D) materials---and graphene in particular---as holding the most promise for use in advanced applications. But in 2011, a significant interest has been triggered by a newly discovered family of novel 2D materials---layered transitional metal carbides and carbonitrides, named MXenes. Those compounds were of general formula Mn+1 XnTx, where M stands for metal atom, X is C and/or N, n = 1, 2 or 3, and Tx represents surface groups. Being initially suggested as a material for electrical energy storage systems, MXenes' properties and their potential applications have not been explored. This work is the first complete study of MXenes' chemistry that sheds light on the chemical composition, structure and properties of these novel materials and possible routes of its modification. The research was focused on 2D titanium carbide, Ti3C2Tx, chosen as the representative of the MXene family. The kinetic study of Ti 3C2Tx synthesis discovered the main synthesis parameters, viz. temperature, time and particle size, that affect the etching process and define the quality of final product. MXenes were found to be able to spontaneously accommodate various ions and small organic molecules between the layers leading to preopening of the structure. A major challenge of large scale production of delaminated, atomically thin 2D MXene layers was solved with two delamination techniques involving dimethyl sulfoxide and isopropyl amine pre-intercalation followed by sonication in water. Ti3C2Tx was also found to possess adsorptive and photocatalytic properties, revealing its potential for environmental applications. It also showed limited stability in water and in the presence of oxygen, providing important practical information on proper handling and storage of MXene materials. Completion of this work allowed the performance of energy

  9. Filtrates & Residues: Hemoglobinometry--A Biochemistry Experiment that Utilizes the Principles of Transition Metal Chemistry.

    ERIC Educational Resources Information Center

    Giuliano, Vincenzo; Rieck, John Paul

    1987-01-01

    Describes a chemistry experiment dealing with hemoglobinometry that can apply to transition metal chemistry, colorimetry, and biochemistry. Provides a detailed description of the experimental procedure, including discussions of the preparation of the cyanide reagent, colorimetric measurements, and waste disposal and treatment. (TW)

  10. In –Situ Spectroscopic Investigation of Immobilized Organometallic Catalysts

    SciTech Connect

    Davis, Robert, J.

    2007-11-14

    Immobilized organometallic catalysts, in principle, can give high rates and selectivities like homogeneous catalysts with the ease of separation enjoyed by heterogeneous catalysts. However, the science of immobilized organometallics has not been developed because the field lies at the interface between the homogeneous and heterogeneous catalysis communities. By assembling an interdisciplinary research team that can probe all aspects of immobilized organometallic catalyst design, the entire reacting system can be considered, where the transition metal complex, the complex-support interface and the properties of the support can all be considered simultaneously from both experimental and theoretical points of view. Researchers at Georgia Tech and the University of Virginia are studying the fundamental principles that can be used to understand and design future classes of immobilized organometallic catalysts. In the framework of the overall collaborative project with Georgia Tech, our work focused on (a) the X-ray absorption spectroscopy of an immobilized Pd-SCS-O complex (b) the mode of metal leaching from supported Pd catalysts during Heck catalysis and (c) the mode of deactivation of Jacobsen’s Co-salen catalysts during the hydrolytic kinetic resolution of terminal epoxides. Catalysts containing supported Pd pincer complexes, functionalized supports containing mercapto and amine groups, and oligomeric Co-salen catalysts were synthesized at Georgia Tech and sent to the University of Virginia. Incorporation of Pd onto several different kinds of supports (silica, mercapto-functionalized silica, zeolite Y) was performed at the University of Virginia.

  11. Selective Organic and Organometallic Reactions in Water-Soluble Host-Guest Supramolecular Systems

    SciTech Connect

    Pluth, Michael D.; Raymond, Kenneth N.; Bergman, Robert G.

    2008-02-16

    Inspired by the efficiency and selectivity of enzymes, synthetic chemists have designed and prepared a wide range of host molecules that can bind smaller molecules with their cavities; this area has become known as 'supramolecular' or 'host-guest' chemistry. Pioneered by Lehn, Cram, Pedersen, and Breslow, and followed up by a large number of more recent investigators, it has been found that the chemical environment in each assembly - defined by the size, shape, charge, and functional group availability - greatly influences the guest-binding characteristics of these compounds. In contrast to the large number of binding studies that have been carried out in this area, the exploration of chemistry - especially catalytic chemistry - that can take place inside supramolecular host cavities is still in its infancy. For example, until the work described here was carried out, very few examples of organometallic reactivity inside supramolecular hosts were known, especially in water solution. For that reason, our group and the group directed by Kenneth Raymond decided to take advantage of our complementary expertise and attempt to carry out metal-mediated C-H bond activation reactions in water-soluble supramolecular systems. This article begins by providing background from the Raymond group in supramolecular coordination chemistry and the Bergman group in C-H bond activation. It goes on to report the results of our combined efforts in supramolecular C-H activation reactions, followed by extensions of this work into a wider range of intracavity transformations.

  12. [Development of new synthetic method using organometallic complexes and an application toward natural product synthesis].

    PubMed

    Mori, Miwako

    2005-01-01

    Recently, many organometallic complexes, such as palladium, nickel, ruthenium, titanium complexes and others, were used for synthetic organic chemistry. We have developed many novel synthetic methods using these organometallic complexes for synthetic organic chemistry. As the organometallic complexes, nickel, chromium, molybdenum, ruthenium, zirconium, titanium, and palladium complexes, were used. Furthermore, bimetallic complexes having silicon-tin and silicon-zirconium bonds were investigated. On the other hand, utilization of gases in synthetic organic chemistry has been also developed. 1 atm pressure of gases such as CO, CO(2), N(2), ethylene and acetylene, could be used and the reaction procedure is very simple, that a balloon filled with a gas is connected on the top of the flask. Using our novel synthetic methods, we have synthesized many natural products and biologically active substances, such as cephalotaxin, mesembrine, tubifoline, strychnine, stemoamide, lycopodine, pumiliotoxin C, beta-lactam, carbapenam and benzodiazepinone derivatives. PMID:15635281

  13. An Advanced Organometallic Lab Experiment with Biological Implications: Synthesis and Characterization of Fe[subscript 2](µ-S[subscript 2])(C0)[subscript 6

    ERIC Educational Resources Information Center

    Barrett, Jacob; Spentzos, Ariana; Works, Carmen

    2015-01-01

    The organometallic complex Fe[subscript 2](µ-S[subscript 2])(CO)[subscript 6] has interesting biological implications. The concepts of bio-organometallic chemistry are rarely discussed at the undergraduate level, but this experiment can start such a conversation and, in addition, teach valuable synthetic techniques. The lab experiment takes a…

  14. From Metalloproteins to Coordination Chemistry: A Learning Exercise to Teach Transition Metal Chemistry

    ERIC Educational Resources Information Center

    Reglinski, John; Graham, Duncan; Kennedy, Alan R.; Gibson, Lorraine T.

    2004-01-01

    An exercise is organized to reinforce the fundamental rules of coordination chemistry through a biological study of metalloproteins. The work, which is divided into four well-defined activities, involves a major application of computer databases to address chemical problems.

  15. Production of metals and compounds by radiation chemistry

    NASA Technical Reports Server (NTRS)

    Marsik, S. J.; Philipp, W. H.

    1969-01-01

    Preparation of metals and compounds by radiation induced chemical reactions involves irradiation of metal salt solutions with high energy electrons. This technique offers a method for the preparation of high purity metals with minimum contamination from the container material or the cover gas.

  16. First-Principles Molecular Dynamics Studies of Organometallic Complexes and Homogeneous Catalytic Processes.

    PubMed

    Vidossich, Pietro; Lledós, Agustí; Ujaque, Gregori

    2016-06-21

    Computational chemistry is a valuable aid to complement experimental studies of organometallic systems and their reactivity. It allows probing mechanistic hypotheses and investigating molecular structures, shedding light on the behavior and properties of molecular assemblies at the atomic scale. When approaching a chemical problem, the computational chemist has to decide on the theoretical approach needed to describe electron/nuclear interactions and the composition of the model used to approximate the actual system. Both factors determine the reliability of the modeling study. The community dedicated much effort to developing and improving the performance and accuracy of theoretical approaches for electronic structure calculations, on which the description of (inter)atomic interactions rely. Here, the importance of the model system used in computational studies is highlighted through examples from our recent research focused on organometallic systems and homogeneous catalytic processes. We show how the inclusion of explicit solvent allows the characterization of molecular events that would otherwise not be accessible in reduced model systems (clusters). These include the stabilization of nascent charged fragments via microscopic solvation (notably, hydrogen bonding), transfer of charge (protons) between distant fragments mediated by solvent molecules, and solvent coordination to unsaturated metal centers. Furthermore, when weak interactions are involved, we show how conformational and solvation properties of organometallic complexes are also affected by the explicit inclusion of solvent molecules. Such extended model systems may be treated under periodic boundary conditions, thus removing the cluster/continuum (or vacuum) boundary, and require a statistical mechanics simulation technique to sample the accessible configurational space. First-principles molecular dynamics, in which atomic forces are computed from electronic structure calculations (namely, density

  17. Spectroscopy of Organometallic Radicals

    SciTech Connect

    Morse, Michael D.

    2015-12-14

    In this grant, we have been mainly concerned with characterization of the chemical bond between transition metals and carbon, although some work has also been directed toward understanding the bonding between transition metals and other main group elements. We have also undertaken some studies on the actinide metals, U and Th.

  18. Polymeric Micelle-Mediated Delivery of DNA-Targeting Organometallic Complexes for Resistant Ovarian Cancer Treatment.

    PubMed

    Duan, Xiaopin; Liu, Demin; Chan, Christina; Lin, Wenbin

    2015-08-26

    Three half-sandwich iridium and ruthenium organometallic complexes with high cytotoxicity are synthesized, and their anticancer mechanisms are elucidated. The organometallic complexes can interact with DNA through coordination or intercalation, thereby inducing apoptosis and inhibiting proliferation of resistant cancer cells. The organometallic complexes are then incorporated into polymeric micelles through the polymer-metal coordination between poly(ethylene glycol)-b-poly(glutamic acid) [PEG-b-P(Glu)] and organometallic complexes to further enhance their anticancer effects as a result of the enhanced permeability and retention effect. The micelles with particle sizes of ≈60 nm are more efficiently internalized by cancer cells than the corresponding complexes, and selectively dissociate and release organometallic anticancer agents within late endosomes and lysosomes, thereby enhancing drug delivery to the nuclei of cancer cells and facilitating their interactions with DNA. Thus, the micelles display higher antitumor activity than the organometallic complexes alone with a lack of the systemic toxicity in a mouse xenograft model of cisplatin-resistant human ovarian cancer. These results suggest that the polymeric micelles carrying anticancer organometallic complexes provide a promising platform for the treatment of resistant ovarian cancer and other hard-to-treat solid tumors. PMID:25963931

  19. Defect Chemistry and Plasmon Physics of Colloidal Metal Oxide Nanocrystals

    SciTech Connect

    Lounis, SD; Runnerstrorm, EL; Llordes, A; Milliron, DJ

    2014-05-01

    Plasmonic nanocrystals of highly doped metal oxides have seen rapid development in the past decade and represent a class of materials with unique optoelectronic properties. In this Perspective, we discuss doping mechanisms in metal oxides and the accompanying physics of free carrier scattering, both of which have implications in determining the properties of localized surface plasmon resonances (LSPRs) in these nanocrystals. The balance between activation and compensation of dopants limits the free carrier concentration of the most common metal oxides, placing a ceiling on the LSPR frequency. Furthermore, because of ionized impurity scattering of the oscillating plasma by dopant ions, scattering must be treated in a fundamentally different way in semiconductor metal oxide materials when compared with conventional metals. Though these effects are well-understood in bulk metal oxides, further study is needed to understand their manifestation in nanocrystals and corresponding impact on plasmonic properties, and to develop materials that surpass current limitations in free carrier concentration.

  20. Analytical chemistry methods for metallic core components: Revision March 1985

    SciTech Connect

    Not Available

    1985-03-01

    This standard provides analytical chemistry methods for the analysis of alloys used to fabricate core components. These alloys are 302, 308, 316, 316-Ti, and 321 stainless steels and 600 and 718 Inconels and they may include other 300-series stainless steels.

  1. Unveiling the chemistry behind the green synthesis of metal nanoparticles.

    PubMed

    Santos, Sónia A O; Pinto, Ricardo J B; Rocha, Sílvia M; Marques, Paula A A P; Pascoal Neto, Carlos; Silvestre, Armando J D; Freire, Carmen S R

    2014-09-01

    Nanobiotechnology has emerged as a fundamental domain in modern science, and metallic nanoparticles (NPs) are one of the largest classes of NPs studied because of their wide spectrum of possible applications in several fields. The use of plant extracts as reducing and stabilizing agents in their synthesis is an interesting and reliable alternative to conventional methodologies. However, the role of the different components of such extracts in the reduction/stabilization of metal ions has not yet been understood clearly. Here we studied the behavior of the main components of a Eucalyptus globulus Labill. bark aqueous extract during metal-ion reduction followed by advanced chromatographic techniques, which allowed us to establish their specific role in the process. The obtained results showed that phenolic compounds, particularly galloyl derivatives, are mainly responsible for the metal-ion reduction, whereas sugars are essentially involved in the stabilization of the NPs. PMID:25088383

  2. The Heat Capacity of Metals: A Physical Chemistry Experiment.

    ERIC Educational Resources Information Center

    Shigeishi, R. A.

    1979-01-01

    Presented here are improvements in the original design of an introductory statistical thermodynamics experiment with the result that heat capacities of metals are routinely obtained within ten percent of literature values. (BB)

  3. Synthesis and chemistry of cationic d sup 0 metal alkyl complexes

    SciTech Connect

    Jordan, R.F.

    1990-01-01

    The long term goals of this project are to design and synthesize highly unsaturated, electrophilic metal complexes and to explore their use as catalysts, reagents, and/or model systems for olefin polymerization and C-H activation chemistry. During the 1990 budget year we have focused our attention on (i) the ligand C-H activation chemistry of Cp{sub 2}Zr(CH{sub 3})(THF){sup +} and related cationic, d{sup o} Zr alkyl complexes, and (ii) the synthesis of new classes of group 4 metal alkyl complexes with non-Cp{sub 2}M ligand environments.

  4. New applications of Ziegler-Natta organometallic catalysts

    SciTech Connect

    Noskova, N.H.; Sokol'skii, D.V.

    1983-05-01

    The composition of Ziegler-Natta organometallic catalysts was discussed. These catalysts were found to be a set of definite complexes, including a polynuclear cluster complex, in dynamic equilibrium with each other. New applications were found for Ziegler-Natta catalysts, specifically, use for the mild activation of alkanes, reduction of carbon monoxide, and positional isomerization of unconjugated dienes into conjugated analogs which are promising in metal complex catalysis.

  5. Generation, Characterization, and Tunable Reactivity of Organometallic Fragments Bound to a Protein Ligand.

    PubMed

    Key, Hanna M; Clark, Douglas S; Hartwig, John F

    2015-07-01

    Organotransition metal complexes catalyze important synthetic transformations, and the development of these systems has rested on the detailed understanding of the structures and elementary reactions of discrete organometallic complexes bound to organic ligands. One strategy for the creation of new organometallic systems is to exploit the intricate and highly structured ligands found in natural metalloproteins. We report the preparation and characterization of discrete rhodium and iridium fragments bound site-specifically in a κ(2)-fashion to the protein carbonic anhydrase as a ligand. The reactions of apo human carbonic anhydrase with [Rh(nbd)2]BF4 or [M(CO)2(acac)] (M=Rh, Ir) form proteins containing Rh or Ir with organometallic ligands. A colorimetric assay was developed to quantify rapidly the metal occupancy at the native metal-binding site, and (15)N-(1)H NMR spectroscopy was used to establish the amino acids to which the metal is bound. IR spectroscopy and EXAFS revealed the presence and number of carbonyl ligands and the number total ligands, while UV-vis spectroscopy provided a signature to readily identify species that had been fully characterized. Exploiting these methods, we observed fundamental stoichiometric reactions of the artificial organometallic site of this protein, including reactions that simultaneously form and cleave metal-carbon bonds. The preparation and reactivity of these artificial organometallic proteins demonstrate the potential to study a new genre of organometallic complexes for which the rates and outcomes of organometallic reactions can be controlled by genetic manipulation of the protein scaffold. PMID:26020584

  6. Convergent study of Ru-ligand interactions through QTAIM, ELF, NBO molecular descriptors and TDDFT analysis of organometallic dyes

    NASA Astrophysics Data System (ADS)

    Sánchez-Coronilla, Antonio; Sánchez-Márquez, Jesús; Zorrilla, David; Martín, Elisa I.; de los Santos, Desireé M.; Navas, Javier; Fernández-Lorenzo, Concha; Alcántara, Rodrigo; Martín-Calleja, Joaquín

    2014-08-01

    We report a theoretical study of a series of Ru complexes of interest in dye-sensitised solar cells, in organic light-emitting diodes, and in the war against cancer. Other metal centres, such as Cr, Co, Ni, Rh, Pd, and Pt, have been included for comparison purposes. The metal-ligand trends in organometallic chemistry for those compounds are shown synergistically by using three molecular descriptors: quantum theory of atoms in molecules (QTAIM), electron localisation function (ELF) and second-order perturbation theory analysis of the natural bond orbital (NBO). The metal-ligand bond order is addressed through both delocalisation index (DI) of QTAIM and fluctuation index (λ) of ELF. Correlation between DI and λ for Ru-N bond in those complexes is introduced for the first time. Electron transfer and stability was also assessed by the second-order perturbation theory analysis of the NBO. Electron transfer from the lone pair NBO of the ligands toward the antibonding lone pair NBO of the metal plays a relevant role in stabilising the complexes, providing useful insights into understanding the effect of the 'expanded ligand' principle in supramolecular chemistry. Finally, absorption wavelengths associated to the metal-to-ligand charge transfer transitions and the highest occupied molecular orbital (HOMO)--lowest unoccupied molecular orbital (LUMO) characteristics were studied by time-dependent density functional theory.

  7. Use of ionic liquids as coordination ligands for organometallic catalysts

    DOEpatents

    Li, Zaiwei; Tang, Yongchun; Cheng; Jihong

    2009-11-10

    Aspects of the present invention relate to compositions and methods for the use of ionic liquids with dissolved metal compounds as catalysts for a variety of chemical reactions. Ionic liquids are salts that generally are liquids at room temperature, and are capable of dissolving a many types of compounds that are relatively insoluble in aqueous or organic solvent systems. Specifically, ionic liquids may dissolve metal compounds to produce homogeneous and heterogeneous organometallic catalysts. One industrially-important chemical reaction that may be catalyzed by metal-containing ionic liquid catalysts is the conversion of methane to methanol.

  8. Biogenic synthesis of metallic nanoparticles and prospects toward green chemistry.

    PubMed

    Adil, Syed Farooq; Assal, Mohamed E; Khan, Mujeeb; Al-Warthan, Abdulrahman; Siddiqui, Mohammed Rafiq H; Liz-Marzán, Luis M

    2015-06-01

    The immense importance of nanoparticles and their applications is a strong motivation for exploring new synthetic techniques. However, due to strict regulations that manage the potential environmental impacts greener alternatives for conventional synthesis are the focus of intense research. In the scope of this perspective, a concise discussion about the use of green reducing and stabilizing agents toward the preparation of metal nanoparticles is presented. Reports on the synthesis of noble metal nanoparticles using plant extracts, ascorbic acid and sodium citrate as green reagents are summarized and discussed, pointing toward an urgent need of understanding the mechanistic aspects of the involved reactions. PMID:25633046

  9. Recovering ferromagnetic metal surfaces to fully exploit chemistry in molecular spintronics

    NASA Astrophysics Data System (ADS)

    Galbiati, Marta; Delprat, Sophie; Mattera, Michele; Mañas-Valero, Samuel; Forment-Aliaga, Alicia; Tatay, Sergio; Deranlot, Cyrile; Seneor, Pierre; Mattana, Richard; Petroff, Frédéric

    2015-05-01

    Organic spintronics is a new emerging field that promises to offer the full potential of chemistry to spintronics, as for example high versatility through chemical engineering and simple low cost processing. However, one key challenge that remains to be unlocked for further applications is the high incompatibility between spintronics key materials such as high Curie temperature Co, Ni, Fe (and their alloys) and wet chemistry. Indeed, the transition metal proneness to oxidation has so far hampered the integration of wet chemistry processes into the development of room temperature organic spintronics devices. As a result, they had mainly to rely on high vacuum physical processes, restraining the choice of available organic materials to a small set of sublimable molecules. In this letter, focusing on cobalt as an example, we show a wet chemistry method to easily and selectively recover a metallic surface from an air exposed oxidized surface for further integration into spintronics devices. The oxide etching process, using a glycolic acid based solution, proceeds without increasing the surface roughness and allows the retrieval of an oxygen-free chemically active cobalt layer. This unlocks the full potential of wet chemistry processes towards room temperature molecular spintronics with transition metals electrodes. We demonstrate this by the grafting of alkylthiols self-assembled monolayers on recovered oxidized cobalt surfaces.

  10. Wildfires and water chemistry: effect of metals associated with wood ash.

    PubMed

    Cerrato, José M; Blake, Johanna M; Hirani, Chris; Clark, Alexander L; Ali, Abdul-Mehdi S; Artyushkova, Kateryna; Peterson, Eric; Bixby, Rebecca J

    2016-08-10

    The reactivity of metals associated with ash from wood collected from the Valles Caldera National Preserve, Jemez Mountains, New Mexico, was assessed through a series of laboratory experiments. Microscopy, spectroscopy, diffraction, and aqueous chemistry measurements were integrated to determine the chemical composition of wood ash and its effect on water chemistry. Climate change has caused dramatic impacts and stresses that have resulted in large-scale increases in wildfire activity in semi-arid areas of the world. Metals and other constituents associated with wildfire ash can be transported by storm event runoff and negatively affect the water quality in streams and rivers. Differences among ash from six tree species based on total concentrations of metals such as Ca, Al, Mg, Fe, and Mn were identified using non-metric multidimensional analysis. Metal-bearing carbonate and oxide phases were quantified by X-ray diffraction analyses and X-ray spectroscopy analyses. These metal-bearing carbonate phases were readily dissolved in the first 30 minutes of reaction with 18 MΩ water and 10 mM HCO3(-) in laboratory batch experiments which resulted in the release of metals and carbonates in the ash, causing water alkalinity to increase. However, metal concentrations decreased over the course of the experiment, suggesting that metals re-adsorb to ash. Our results suggest that the dissolution of metal-bearing carbonate and oxide phases in ash and metal re-adsorption to ash are relevant processes affecting water chemistry after wildfire events. These results have important implications to better understand the impact of wildfire events on water quality. PMID:27457586

  11. Valence-Bond Concepts in Coordination Chemistry and the Nature of Metal-Metal Bonds.

    ERIC Educational Resources Information Center

    Pauling, Linus; Herman, Zelek S.

    1984-01-01

    Discusses the valence-bond method, applying it to some coordination compounds of metals, especially those involving metal-metal bonds. Suggests that transition metals can form as many as nine covalent bonds, permitting valence-theory to be extended to transition metal compounds in a more effective way than has been possible before. (JN)

  12. Coloring a Superabsorbent Polymer with Metal Ions: An Undergraduate Chemistry Experiment

    ERIC Educational Resources Information Center

    Yaung, Jing-Fun; Chen, Yueh-Huey

    2009-01-01

    A novel undergraduate chemistry experiment involving superabsorbent polymers commonly used in diapers and other personal care products is described. Students observe the removal of divalent transition-metal ions from aqueous solutions by the polymers. With the procedures provided, students are able to color the superabsorbent polymers with metal…

  13. Quantitative Ultrasound-Assisted Extraction for Trace-Metal Determination: An Experiment for Analytical Chemistry

    ERIC Educational Resources Information Center

    Lavilla, Isela; Costas, Marta; Pena-Pereira, Francisco; Gil, Sandra; Bendicho, Carlos

    2011-01-01

    Ultrasound-assisted extraction (UAE) is introduced to upper-level analytical chemistry students as a simple strategy focused on sample preparation for trace-metal determination in biological tissues. Nickel extraction in seafood samples and quantification by electrothermal atomic absorption spectrometry (ETAAS) are carried out by a team of four…

  14. Selective Bifunctional Modification of a Non-catenated Metal-Organic Framework Material via 'Click' Chemistry

    SciTech Connect

    Gadzikwa, Tendai; Farha, Omar K.; Malliakas, Christos D.; Kanatzidis, Mercouri G.; Hupp, Joseph T.; Nguyen, SonBinh T.; NWU

    2009-12-01

    A noncatenated, Zn-based metal-organic framework (MOF) material bearing silyl-protected acetylenes was constructed and postsynthetically modified using 'click' chemistry. Using a solvent-based, selective deprotection strategy, two different organic azides were 'clicked' onto the MOF crystals, resulting in a porous material whose internal and external surfaces are differently functionalized.

  15. Lithium metal doped electrodes for lithium-ion rechargeable chemistry

    DOEpatents

    Liu, Gao; Battaglia, Vince; Wang, Lei

    2016-09-13

    An embodiment of the invention combines the superior performance of a polyvinylidene difluoride (PVDF) or polyethyleneoxide (POE) binder, the strong binding force of a styrene-butadiene (SBR) binder, and a source of lithium ions in the form of solid lithium metal powder (SLMP) to form an electrode system that has improved performance as compared to PVDF/SBR binder based electrodes. This invention will provide a new way to achieve improved results at a much reduced cost.

  16. Prebiotic coordination chemistry: The potential role of transition-metal complexes in the chemical evolution

    NASA Technical Reports Server (NTRS)

    Beck, M.

    1979-01-01

    In approaching the extremely involved and complex problem of the origin of life, consideration of the coordination chemistry appeared not only as a possibility but as a necessity. The first model experiments appear to be promising because of prebiotic-type synthesis by means of transition-metal complexes. It is especially significant that in some instances various types of vitally important substances (nucleic bases, amino acids) are formed simultaneously. There is ground to hope that systematic studies in this field will clarify the role of transition-metal complexes in the organizatorial phase of chemical evolution. It is obvious that researchers working in the fields of the chemistry of cyano and carbonyl complexes, and of the catalytic effect of transition-metal complexes are best suited to study these aspects of the attractive and interesting problem of the origin of life.

  17. The surface chemistry of metal-organic frameworks.

    PubMed

    McGuire, Christina V; Forgan, Ross S

    2015-03-28

    Metal-organic frameworks (MOFs) have received particular attention over the last 20 years as a result of their attractive properties offering potential applications in a number of areas. Typically, these characteristics are tuned by functionalisation of the bulk of the MOF material itself. This Feature Article focuses instead on modification of MOF particles at their surfaces only, which can also offer control over the bulk properties of the material. The differing surface modification techniques available to the synthetic chemist will be discussed, with a focus on the effect of surface modification of MOFs on their fundamental properties and application in adsorption, catalysis, drug delivery and other areas. PMID:25116412

  18. Two-Center/Three-Electron Sigma Half-Bonds in Main Group and Transition Metal Chemistry.

    PubMed

    Berry, John F

    2016-01-19

    First proposed in a classic Linus Pauling paper, the two-center/three-electron (2c/3e) σ half-bond challenges the extremes of what may or may not be considered a chemical bond. Two electrons occupying a σ bonding orbital and one electron occupying the antibonding σ* orbital results in bond orders of ∼0.5 that are characteristic of metastable and exotic species, epitomized in the fleetingly stable He2(+) ion. In this Account, I describe the use of coordination chemistry to stabilize such fugacious three-electron bonded species at disparate ends of the periodic table. A recent emphasis in the chemistry of metal-metal bonds has been to prepare compounds with extremely short metal-metal distances and high metal-metal bond orders. But similar chemistry can be used to explore metal-metal bond orders less than one, including 2c/3e half-bonds. Bimetallic compounds in the Ni2(II,III) and Pd2(II,III) oxidation states were originally examined in the 1980s, but the evidence collected at that time suggested that they did not contain 2c/3e σ bonds. Both classes of compounds have been re-examined using EPR spectroscopy and modern computational methods that show the unpaired electron of each compound to occupy a M-M σ* orbital, consistent with 2c/3e Ni-Ni and Pd-Pd σ half-bonds. Elsewhere on the periodic table, a seemingly unrelated compound containing a trigonal bipyramidal Cu3S2 core caused a stir, leaving prominent theorists at odds with one another as to whether the compound contains a S-S bond. Due to my previous experience with 2c/3e metal-metal bonds, I suggested that the Cu3S2 compound could contain a 2c/3e S-S σ half-bond in the previously unknown oxidation state of S2(3-). By use of the Cambridge Database, a number of other known compounds were identified as potentially containing S2(3-) ligands, including a noteworthy set of cyclopentadienyl-supported compounds possessing diamond-shaped Ni2E2 units with E = S, Se, and Te. These compounds were subjected to

  19. Fundamental organometallic reactions: Applications on the CYBER 205

    NASA Technical Reports Server (NTRS)

    Rappe, A. K.

    1984-01-01

    Two of the most challenging problems of Organometallic chemistry (loosely defined) are pollution control with the large space velocities needed and nitrogen fixation, a process so capably done by nature and so relatively poorly done by man (industry). For a computational chemist these problems are on the fringe of what is possible with conventional computers (large models needed and accurate energetics required). A summary of the algorithmic modification needed to address these problems on a vector processor such as the CYBER 205 and a sketch of findings to date on deNOx catalysis and nitrogen fixation are presented.

  20. Atom-Precise Organometallic Zinc Clusters.

    PubMed

    Banh, Hung; Dilchert, Katharina; Schulz, Christine; Gemel, Christian; Seidel, Rüdiger W; Gautier, Régis; Kahlal, Samia; Saillard, Jean-Yves; Fischer, Roland A

    2016-03-01

    The bottom-up synthesis of organometallic zinc clusters is described. The cation {[Zn10 ](Cp*)6 Me}(+) (1) is obtained by reacting [Zn2 Cp*2 ] with [FeCp2 ][BAr4 (F) ] in the presence of ZnMe2 . In the presence of suitable ligands, the high reactivity of 1 enables the controlled abstraction of single Zn units, providing access to the lower-nuclearity clusters {[Zn9 ](Cp*)6 } (2) and {[Zn8 ](Cp*)5 ((t) BuNC)3 }(+) (3). According to DFT calculations, 1 and 2 can be described as closed-shell species that are electron-deficient in terms of the Wade-Mingos rules because the apical ZnCp* units that constitute the cluster cage do not have three, but only one, frontier orbitals available for cluster bonding. Zinc behaves flexibly in building the skeletal metal-metal bonds, sometimes providing one major frontier orbital (like Group 11 metals) and sometimes providing three frontier orbitals (like Group 13 elements). PMID:26846901

  1. Experimental studies of the chemistry of metal clusters

    SciTech Connect

    Parks, E.K.; Riley, S.J.

    1988-01-01

    The procedures for studying chemical reactions of metal clusters in a continuous-flow reactor are described, and examples of such studies are given. Experiments to be discussed include kinetics and thermodynamics measurements, and determination of the composition of clusters saturated with various adsorbate reagents. Specific systems to be covered include the reaction of iron clusters with ammonia and with hydrogen, the reaction of nickel clusters with hydrogen and with ammonia, and the reaction of platinum clusters with ethylene. The last two reactions are characterized by complex, multi-step processes that lead to adsorbate decomposition and hydrogen desorption from the clusters. Methods for probing these processes will be discussed. 26 refs., 8 figs.

  2. Metal-dithiocarbamate complexes: chemistry and biological activity.

    PubMed

    Hogarth, Graeme

    2012-10-01

    Dithiocarbamates are highly versatile mono-anionic chelating ligands which form stable complexes with all the transition elements and also the majority of main group, lanthanide and actinide elements. They are easily prepared from primary or secondary amines and depending upon the nature of the cation can show good solubility in water or organic solvents. They are related to the thiuram disulfides by a one-electron redox process (followed by dimerisation via sulfur-sulfur bond formation) which is easily carried out upon addition of iodide or ferric salts. Dithiocarbamates are lipophilic and generally bind to metals in a symmetrical chelate fashion but examples of other coordination modes are known, the monodentate and anisobidentate modes being most prevalent. They are planar sterically non-demanding ligands which can be electronically tuned by judicious choice of substituents. They stabilize metals in a wide range of oxidation states, this being attributed to the existence of soft dithiocarbamate and hard thioureide resonance forms, the latter formally resulting from delocalization of the nitrogen lone pair onto the sulfurs, and consequently their complexes tend to have a rich electrochemistry. Tetraethyl thiuramdisulfide (disulfiram or antabuse) has been used as a drug since the 1950s but it is only recently that dithiocarbamate complexes have been explored within the medicinal domain. Over the past two decades anti-cancer activity has been noted for gold and copper complexes, technetium and copper complexes have been used in PET-imaging, dithiocarbamates have been used to treat acute cadmium poisoning and copper complexes also have been investigated as SOD inhibitors. PMID:22931592

  3. Direct synthesis of organometallics V. Direct synthesis of isopropylcyclopentadienyl M(I) compounds of Ga, Tl, Mn and Cu via metal vapour cocondensation, and their spectroscopic characterization

    NASA Astrophysics Data System (ADS)

    Tacke, Matthias; Teuber, Roland

    1997-06-01

    The cocondensation of metal atoms of Ga, Tl, Cu and Mn with 6,6-dimethylfulvene leads to the formation of Cp iM(I) derivatives (Cp i = C 5H 4CHMe 2) which need — in the case of Cu and Mn — trimethylphosphite as a co-ligand to fill up their coordination sphere. It is remarkable that the synthesis of the thermolabile Cp iGa(I) is possible by using the newly developed cocondensation vessel with a cooled internal drain. The species is stable in solution up to -30°C and is therefore characterized by its 71Ga NMR and MS spectrum and the following reactions. The reaction is believed to pass through a metal fulvene complex in a first step, which is characterized for Ga by quantum mechanical methods. For the gallium case a tucked-in η 6 bonding mode with formation of Ga(II), instead of coordination to an η 5 cylopentadienyl or η 4 fulvene, is observed. ? Following the formation of this first intermediate, a complete mechanism is developed by using semiempirical calculations. The resulting geometries and reaction enthalpies are discussed in comparison with the reaction of tin atoms with the fulvene, which ends in the formation of ansa-stannocene. In contrast to this reaction, the cocondensation of cobalt atoms with 6,6-dimethylfulvene in the presence of trimethylphosphite ends in the formation of CoH(P(OMe) 3) 4 instead of a half-sandwich complex.

  4. Optimizing chemistry of bulk metallic glasses for improved thermal stability

    NASA Astrophysics Data System (ADS)

    Dulikravich, G. S.; Egorov, I. N.; Colaco, M. J.

    2008-10-01

    Thermo-mechanical-physical properties of bulk metallic glasses (BMGs) depend strongly on the concentrations of each of the chemical elements in a given alloy. The proposed methodology for simultaneously optimizing these multiple properties by accurately determining proper concentrations of each of the alloying elements is based on the use of computational algorithms rather than on traditional experimentation, expert experience and intuition. Specifically, the proposed BMG design method combines an advanced stochastic multi-objective evolutionary optimization algorithm based on self-adapting response surface methodology and an existing database of experimentally evaluated BMG properties. During the iterative computational design procedure, a relatively small number of new BMGs need to be manufactured and experimentally evaluated for their properties in order to continuously verify the accuracy of the entire design methodology. Concentrations of the most important alloying elements can be predicted so that new BMGs have multiple properties optimized in a Pareto sense. This design concept was verified for superalloys using strictly experimental data. Thus, the key innovation here lies in arriving at the BMG compositions which will have the highest glass forming ability by utilizing an advanced multi-objective optimization algorithm while requiring a minimum number of BMGs to be manufactured and tested in order to verify the predicted performance of the predicted BMG compositions.

  5. EPR study of the onset of long-range order in the 2D organo-metallic magnet Cu(pyz)2(pyo)2(PF6)2

    SciTech Connect

    Mcdonald, Ross D; Ayala - Valenzuela, Oscar E; Singleton, John; Goddard, Paul A; Franke, I; Manson, J. L.

    2011-01-14

    The spin (S) 1/2 two-dimensional (2D) square-lattice quantum Heisenberg antiferromagnet system has long been interesting to theoretical physicists due to the variety of transitions that can arise. Moreover, the role of S = 1/2 fluctuations on a square lattice in the mechanism for cuprate superconductivity is hotly debated. Low dimensional metal-organic magnets, such as Cu(pyz){sub 2}(pyo){sub 2}(PF{sub 6}){sub 2}, offer the possibility to readily control the exchange parameters in a 20 system by changing chemical composition, thus creating spin architectures with desirable properties 'to order'. For a perfectly 20 system, long range magnetic order would not occur at finite temperature. However, in the metal-organic systems, interlayer coupling gives rise to a finite Neel temperature. For these quasi-2D systems the ordering temperature is dominated by the weakest (the interlayer) exchange interaction, whereas the saturation magnetic field is dominated by the strongest exchange interactions, thus providing a means of estimating the spatial exchange anisotropy in the system. It should be noted that the more 2D the system, the wider the temperature (T) range, T{sub N} < T < J/k{sub B}, over which magnetic fluctuations dominate. As evident by the ratio of magnetic saturation field, H{sub sat} {approx} 30 T, to the Neel temperature, T{sub N} = 1.72 K, Cu(pyz){sub 2}(pyo){sub 2}(PF{sub 6}){sub 2} is a good example of a 2D system with the anisotropy between inplane and interplane exchange interactions being of the order of 10{sup 3}.

  6. Bonds Between Metal Atoms: A New Mode of Transition Metal Chemistry.

    ERIC Educational Resources Information Center

    Cotton, F. Albert; Chisholm, Malcolm H.

    1982-01-01

    Discusses polynuclear metal clusters (containing two or more metal atoms bonded to one another as well as to nonmetallic elements), including their formation and applications. Studies of bonds between metal atoms reveal superconductors, organic-reaction catalysts, and photosensitive complexes that may play a role in solar energy. (JN)

  7. Development of degradative techniques for coal chemistry based on ether cleavage reactions and metal arene chemistry

    SciTech Connect

    Lemke, D.W.

    1988-01-01

    The degradation of C-O and C-C bonds have been examined using model compounds that are similar in structure to those found in coal and other natural products. The conditions to maximize ether cleavage and minimize the formation of undesirable side products were determined by varying the concentration of reagents, temperature, and reaction time. 2-Phenoxynaphthalene (1) and 1-methoxypyrene (2) were the compounds examined. The optimum conditions demonstrated complete disappearance of 1 and 2, mass recoveries were above 84%, and the formation of reduced dimers in less than 10 mole % yield. The possibility of cleaving a C-C bond by a (3+2) cycloaddition and subsequent cycloreversion reactions was examined by treating a variety of dipolarphiles with deprotonated (({eta}{sup 6}-arene)FeCp){sup +} complexes (arene = hexamethylbenzene or tetralin) Azides and ozone were found to add quantitatively to the metal-arene complexes. Upon decomplexation of the ring, moderated yields of benzyl substituted products were isolated. The mechanism of this reaction is yet unknown but is postulated to occur by direct nucleophilic addition of the complex anion to the most electropositive atom of the dipolarphile. Chemical and electrochemical oxidation techniques were applied to the deprotonated (({eta}{sup 6}-arene)FeCp){sup +} complexes. Only minor yields of benzylic oxidation products were observed.

  8. Organometallic Polymeric Conductors

    NASA Technical Reports Server (NTRS)

    1997-01-01

    For aerospace applications, the use of polymers can result in tremendous weight savings over metals. Suitable polymeric materials for some applications like EMI shielding, spacecraft grounding, and charge dissipation must combine high electrical conductivity with long-term environmental stability, good processability, and good mechanical properties. Recently, other investigators have reported hybrid films made from an electrically conductive polymer combined with insulating polymers. In all of these instances, the films were prepared by infiltrating an insulating polymer with a precursor for a conductive polymer (either polypyrrole or polythiophene), and oxidatively polymerizing the precursor in situ. The resulting composite films have good electrical conductivity, while overcoming the brittleness inherent in most conductive polymers. The highest conductivities reported (approximately 4/Scm) were achieved with polythiophene in a polystyrene host polymer. The best films using a polyamide as base polymer were four orders of magnitude less conductive than the polystyrene films. The authors suggested that this was because polyimides were unable to swell sufficiently for infiltration of monomer as in the polystyrene. It was not clear, however, if the different conductivities obtained were merely the result of differing oxidation conditions. Oxidation time, temperature and oxidant concentration varied widely among the studies.

  9. Surface chemistry : a non-negligible parameter in determining optical properties of small colloidal metal nanoparticles.

    SciTech Connect

    Sun, Y.; Gray, S. K.; Peng, S.

    2011-01-01

    Surface chemistry can become pronounced in determining the optical properties of colloidal metal nanoparticles as the nanoparticles become so small (diameters <20 nm) that the surface atoms, which can undergo chemical interactions with the environment, represent a significant fraction of the total number of atoms although this effect is often ignored. For instance, formation of chemical bonds between surface atoms of small metal nanoparticles and capping molecules that help stabilize the nanoparticles can reduce the density of conduction band electrons in the surface layer of metal atoms. This reduced electron density consequently influences the frequency-dependent dielectric constant of the metal atoms in the surface layer and, for sufficiently high surface to volume ratios, the overall surface plasmon resonance (SPR) absorption spectrum. The important role of surface chemistry is highlighted here by carefully analyzing the classical Mie theory and a multi-layer model is presented to produce more accurate predictions by considering the chemically reduced density of conduction band electrons in the outer shell of metal atoms in nanoparticles. Calculated absorption spectra of small Ag nanoparticles quantitatively agree with the experimental results for our monodispersed Ag nanoparticles synthesized via a well-defined chemical reduction process, revealing an exceptional size-dependence of absorption peak positions: the peaks first blue-shift followed by a turnover and a dramatic red-shift as the particle size decreases. A comprehensive understanding of the relationship between surface chemistry and optical properties is beneficial to exploit new applications of small colloidal metal nanoparticles, such as colorimetric sensing, electrochromic devices, and surface enhanced spectroscopies.

  10. Tuning exchange interactions in organometallic semiconductors

    NASA Astrophysics Data System (ADS)

    Rawat, Naveen; Manning, Lane W.; Hua, Kim-Ngan; Headrick, Randall L.; Cherian, Judy G.; Bishop, Michael M.; McGill, Stephen A.; Furis, Madalina I.

    2015-09-01

    Organic semiconductors are emerging as a leading area of research as they are expected to overcome limitations of inorganic semiconductor devices for certain applications where low cost manufacturing, device transparency in the visible range or mechanical flexibility are more important than fast switching times. Solution processing methods produce thin films with millimeter sized crystalline grains at very low cost manufacturing prices, ideally suited for optical spectroscopy investigations of long range many-body effects in organic systems. To this end, we synthesized an entire family of organosoluble 3-d transition metal Pc's and successfully employed a novel solution-based pen-writing deposition technique to fabricate long range ordered thin films of mixtures of metal-free (H2Pc) molecule and organometallic phthalocyanines (MPc's). Our previous studies on the parent MPc crystalline thin films identified different electronic states mediating exchange interactions in these materials. This understanding of spin-dependent exchange interaction between delocalized π-electrons with unpaired d spins enabled the further tuning of these interactions by mixing CoPc and H2Pc in different ratios ranging from 1:1 to 1000:1 H2Pc:MPc. The magnitude of the exchange is also tunable as a function of the average distance between unpaired spins in these materials. Furthermore, high magnetic field (B < 25T) MCD and magneto-photoluminescence show evidence of spin-polarized band-edge excitons in the same materials.

  11. Photoredox Catalysis Unlocks Single-Electron Elementary Steps in Transition Metal Catalyzed Cross-Coupling

    PubMed Central

    2016-01-01

    Since initial reports, cross-coupling technologies employing photoredox catalysts to access novel reactivity have developed with increasing pace. In this Outlook, prominent examples from the recent literature are organized on the basis of the elementary transformation enabled by photoredox catalysis and are discussed in the context of relevant historical precedent in stoichiometric organometallic chemistry. This treatment allows mechanistic similarities inherent to odd-electron transition metal reactivity to be generalized to a set of lessons for future reaction development. PMID:27280163

  12. Structural modifications due to interface chemistry at metal-nitride interfaces

    PubMed Central

    Yadav, S. K.; Shao, S.; Wang, J.; Liu, X.-Y.

    2015-01-01

    Based on accurate first principles density functional theory (DFT) calculations, an unusual phenomenon of interfacial structural modifications, due to the interface chemistry influence is identified at two metal-nitride interfaces with strong metal-nitrogen affinity, Al/TiN {111} and Al/VN {111} interfaces. It is shown that at such interfaces, a faulted stacking structure is energetically preferred on the Al side of the interface. And both intrinsic and extrinsic stacking fault energies in the vicinity Al layers are negligibly small. However, such phenomenon does not occur in Pt/TiN and Pt/VN interfaces because of the weak Pt-N affinity. Corresponding to structural energies of metal-nitride interfaces, the linear elasticity analysis predicts characteristics of interfacial misfit dislocations at metal-nitride interfaces. PMID:26611639

  13. Some aspects of metallic ion chemistry and dynamics in the mesosphere and thermosphere

    NASA Technical Reports Server (NTRS)

    Mathews, J. D.

    1987-01-01

    The relationship between the formation of sporadic layers of metallic ion and the dumping of these ions into the upper mesosphere is discussed in terms of the tidal wind, classical (i.e., windshear) and other more complex, perhaps highly nonlinear layer formation mechanisms, and a possible circulation mechanism for these ions. Optical, incoherent scatter radar, rocket, and satellite derived evidence for various layer formation mechanisms and for the metallic ion circulation system is reviewed. The results of simple one dimensional numerical model calculations of sporadic E and intermediate layer formation are presented along with suggestions for more advanced models of intense or blanketing sporadic E. The flux of metallic ions dumped by the tidal wind system into the mesosphere is estimated and compared with estimates of total particle flux of meteoric origin. Possible effects of the metallic ion flux and of meteoric dust on D region ion chemistry are discussed.

  14. Structural modifications due to interface chemistry at metal-nitride interfaces

    SciTech Connect

    Yadav, S. K.; Shao, S.; Wang, J.; Liu, X. -Y.

    2015-11-27

    Based on accurate first principles density functional theory (DFT) calculations, an unusual phenomenon of interfacial structural modifications, due to the interface chemistry influence is identified at two metal-nitride interfaces with strong metal-nitrogen affinity, Al/TiN {111} and Al/VN {111} interfaces. It is shown that at such interfaces, a faulted stacking structure is energetically preferred on the Al side of the interface. And both intrinsic and extrinsic stacking fault energies in the vicinity Al layers are negligibly small. However, such phenomenon does not occur in Pt/TiN and Pt/VN interfaces because of the weak Pt-N affinity. As a result, corresponding to structural energies of metal-nitride interfaces, the linear elasticity analysis predicts characteristics of interfacial misfit dislocations at metal-nitride interfaces.

  15. Structural modifications due to interface chemistry at metal-nitride interfaces

    DOE PAGESBeta

    Yadav, S. K.; Shao, S.; Wang, J.; Liu, X. -Y.

    2015-11-27

    Based on accurate first principles density functional theory (DFT) calculations, an unusual phenomenon of interfacial structural modifications, due to the interface chemistry influence is identified at two metal-nitride interfaces with strong metal-nitrogen affinity, Al/TiN {111} and Al/VN {111} interfaces. It is shown that at such interfaces, a faulted stacking structure is energetically preferred on the Al side of the interface. And both intrinsic and extrinsic stacking fault energies in the vicinity Al layers are negligibly small. However, such phenomenon does not occur in Pt/TiN and Pt/VN interfaces because of the weak Pt-N affinity. As a result, corresponding to structural energiesmore » of metal-nitride interfaces, the linear elasticity analysis predicts characteristics of interfacial misfit dislocations at metal-nitride interfaces.« less

  16. Redox chemistry and metal-insulator transitions intertwined in a nano-porous material

    NASA Astrophysics Data System (ADS)

    Maximoff, Sergey N.; Smit, Berend

    2014-06-01

    Metal-organic frameworks are nano-porous adsorbents of relevance to gas separation and catalysis, and separation of oxygen from air is essential to diverse industrial applications. The ferrous salt of 2,5-dihydroxy-terephthalic acid, a metal-organic framework of the MOF74 family, can selectively adsorb oxygen in a manner that defies the classical picture: adsorption sites either do or do not share electrons over a long range. Here we propose, and then justify phenomenologically and computationally, a mechanism. Charge-transfer-mediated adsorption of electron acceptor oxygen molecules in the metal-organic framework, which is a quasi-one-dimensional electron-donor semiconductor, drives and is driven by quasi-one-dimensional metal-insulator-metal transitions that localize or delocalize the quasi-one-dimensional electrons. This mechanism agrees with the empirical evidence, and predicts a class of nano-porous semiconductors or metals and potential adsorbents and catalysts in which chemistry and metal-insulator-metal transitions intertwine.

  17. Organometallic Polymeric Conductors

    NASA Technical Reports Server (NTRS)

    Youngs, Wiley J.

    1997-01-01

    For aerospace applications, the use of polymers can result in tremendous weight savings over metals. Suitable polymeric materials for some applications like EMI shielding, spacecraft grounding, and charge dissipation must combine high electrical conductivity with long-term environmental stability, good processability, and good mechanical properties. Recently, other investigators have reported hybrid films made from an electrically conductive polymer combined with insulating polymers. In all of these instances, the films were prepared by infiltrating an insulating polymer with a precursor for a conductive polymer (either polypyrrole or polythiophene), and oxidatively polymerizing the precursor in situ. The resulting composite films have good electrical conductivity, while overcoming the brittleness inherent in most conductive polymers. Many aerospace applications require a combination of properties. Thus, hybrid films made from polyimides or other engineering resins are of primary interest, but only if conductivities on the same order as those obtained with a polystyrene base could be obtained. Hence, a series of experiments was performed to optimize the conductivity of polyimide-based composite films. The polyimide base chosen for this study was Kapton. 3-MethylThiophene (3MT) was used for the conductive phase. Three processing variables were identified for producing these composite films, namely time, temperature, and oxidant concentration for the in situ oxidation. Statistically designed experiments were used to examine the effects of these variables and synergistic/interactive effects among variables on the electrical conductivity and mechanical strength of the films. Multiple linear regression analysis of the tensile data revealed that temperature and time have the greatest effect on maximum stress. The response surface of maximum stress vs. temperature and time (for oxidant concentration at 1.2 M) is shown. Conductivity of the composite films was measured for

  18. Exploring Undergraduates' Understanding of Transition Metals Chemistry with the Use of Cognitive and Confidence Measures

    ERIC Educational Resources Information Center

    Sreenivasulu, Bellam; Subramaniam, R.

    2014-01-01

    Compared to studies on school students' understanding of various topics in the sciences, studies involving university students have received relatively less attention in the science education literature. In this study, we investigated university students' understanding of transition metals chemistry, a topic in inorganic chemistry, which…

  19. Capturing snapshots of post-synthetic metallation chemistry in metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Bloch, Witold M.; Burgun, Alexandre; Coghlan, Campbell J.; Lee, Richmond; Coote, Michelle L.; Doonan, Christian J.; Sumby, Christopher J.

    2014-10-01

    Post-synthetic metallation is employed strategically to imbue metal-organic frameworks (MOFs) with enhanced performance characteristics. However, obtaining precise structural information for metal-centred reactions that take place within the pores of these materials has remained an elusive goal, because of issues with high symmetry in certain MOFs, lower initial crystallinity for some chemically robust MOFs, and the reduction in crystallinity that can result from carrying out post-synthetic reactions on parent crystals. Here, we report a new three-dimensional MOF possessing pore cavities that are lined with vacant di-pyrazole groups poised for post-synthetic metallation. These metallations occur quantitatively without appreciable loss of crystallinity, thereby enabling examination of the products by single-crystal X-ray diffraction. To illustrate the potential of this platform to garner fundamental insight into metal-catalysed reactions in porous solids we use single-crystal X-ray diffraction studies to structurally elucidate the reaction products of consecutive oxidative addition and methyl migration steps that occur within the pores of the Rh-metallated MOF, 1·[Rh(CO)2][Rh(CO)2Cl2].

  20. Immobilization of two organometallic complexes into a single cage to construct protein-based microcompartments.

    PubMed

    Maity, Basudev; Fukumori, Kazuki; Abe, Satoshi; Ueno, Takafumi

    2016-04-01

    Natural protein-based microcompartments containing multiple enzymes promote cascade reactions within cells. We use the apo-ferritin protein cage to mimic such biocompartments by immobilizing two organometallic Ir and Pd complexes into the single protein cage. Precise locations of the metals and their accumulation mechanism were studied by X-ray crystallography. PMID:27021005

  1. Development of Li-Metal Battery Cell Chemistries at NASA Glenn Research Center

    NASA Technical Reports Server (NTRS)

    Lvovich, Vadim F.

    2015-01-01

    State-of-the-Art lithium-ion battery technology is limited by specific energy and thus not sufficiently advanced to support the energy storage necessary for aerospace needs, such as all-electric aircraft and many deep space NASA exploration missions. In response to this technological gap, our research team at NASA Glenn Research Center has been active in formulating concepts and developing testing hardware and components for Li-metal battery cell chemistries. Lithium metal anodes combined with advanced cathode materials could provide up to five times the specific energy versus state-of-the-art lithium-ion cells (1000 Whkg versus 200 Whkg). Although Lithium metal anodes offer very high theoretical capacity, they have not been shown to successfully operate reversibly.

  2. Methyl Complexes of the Transition Metals.

    PubMed

    Campos, Jesús; López-Serrano, Joaquín; Peloso, Riccardo; Carmona, Ernesto

    2016-05-01

    Organometallic chemistry can be considered as a wide area of knowledge that combines concepts of classic organic chemistry, that is, based essentially on carbon, with molecular inorganic chemistry, especially with coordination compounds. Transition-metal methyl complexes probably represent the simplest and most fundamental way to view how these two major areas of chemistry combine and merge into novel species with intriguing features in terms of reactivity, structure, and bonding. Citing more than 500 bibliographic references, this review aims to offer a concise view of recent advances in the field of transition-metal complexes containing M-CH3 fragments. Taking into account the impressive amount of data that are continuously provided by organometallic chemists in this area, this review is mainly focused on results of the last five years. After a panoramic overview on M-CH3 compounds of Groups 3 to 11, which includes the most recent landmark findings in this area, two further sections are dedicated to methyl-bridged complexes and reactivity. PMID:26991740

  3. Tabletop Extreme Ultraviolet Spectroscopy of Element-Specific Organometallic Photophysics

    NASA Astrophysics Data System (ADS)

    Vura-Weis, Josh

    High-harmonic extreme ultraviolet (XUV) spectroscopy has the potential to provide the elemental, oxidation-state, and spin-state specificity of core-level spectroscopy with the convenience and ultrafast time resolution of tabletop laser sources. We will show that M-edge spectroscopy of first-row transition metal complexes (3p -->3d excitation) is a sensitive probe of the electronic structure of organometallic complexes in solution. Furthermore, this technique can be used to determine the relaxation dynamics of these molecules in the first few femtoseconds to nanoseconds after photoexcitation.

  4. Exploring Undergraduates' Understanding of Transition Metals Chemistry with the use of Cognitive and Confidence Measures

    NASA Astrophysics Data System (ADS)

    Sreenivasulu, Bellam; Subramaniam, R.

    2014-12-01

    Compared to studies on school students' understanding of various topics in the sciences, studies involving university students have received relatively less attention in the science education literature. In this study, we investigated university students' understanding of transition metals chemistry, a topic in inorganic chemistry, which has been only scarcely explored in the science education literature. A four-tier diagnostic instrument was used. The instrument comprises 25 questions, and each question has an answer tier, a confidence rating for this tier, a reason tier and a confidence rating for this tier. Versions of the instrument were refined iteratively during the preliminary and pilot phases of the study. This study reports on the results obtained from the main phase of the study, using a sample of 140 students. Overall, the diagnostic test was difficult for the students. The students had a mean score of 38 %, based on correct responses for both answer and reason tiers for the questions. It was accompanied by a mean confidence of only 3.49 out of 6 (that is, 58.2 %) for the whole test. The results indicate that transition metals chemistry is a difficult topic for the students. Twenty-four alternative conceptions have been identified in this study, including some indication of their strengths. Some implications of the study are discussed.

  5. New Molecular Architecture for Electrically Conducting Materials Based on Unsymmetrical Organometallic-Dithiolene Complexes

    NASA Astrophysics Data System (ADS)

    Kubo, Kazuya; Kato, Reizo

    New molecular architecture for highly conducting molecular materials was developed with use of unsymmetrical organometallic-dithiolene complexes. The new architecture has various advantages including easy modification of their molecular and electronic features. Organometallic complexes based on unsymmetrical Au(III)-dithiolene complexes [(ppy)Au(C8H4S8 or C8H4S6O2)] were prepared for new cationic components of molecular conductors. These unsymmetrical organometallic complexes can provide various cation radical salts [(ppy)Au(S-S)]2[anion][solvent] n (S-S = C8H4S8 or C8H4S6O2, anion = PF6 -, BF4 -, AsF6 -, TaF6 -, solvent = PhCl, n = 0-0.5) by constant current electrolysis of their benzonitrile or chlorobenzene solutions containing (Bu4N)(anion) as electrolyte. [(ppy)Au(C8H4S8)]2[PF6] under pressure is the first molecular metal based on the organometallic component. In this review, principle of the molecular architecture based on the unsymmetrical organometallic-dithiolene complexes and physical properties of their cation radical salts are discussed.

  6. Combinatorial screening of inorganic and organometallic materials

    DOEpatents

    Schultz, Peter G.; Xiang, Xiaodong; Goldwasser, Isy

    2002-01-01

    Methods and apparatus for the preparation and use of a substrate having an array of diverse materials in predefined regions thereon. A substrate having an array of diverse materials thereon is generally prepared by delivering components of materials to predefined regions on a substrate, and simultaneously reacting the components to form at least two materials. Materials which can be prepared using the methods and apparatus of the present invention include, for example, covalent network solids, ionic solids and molecular solids. More particularly, materials which can be prepared using the methods and apparatus of the present invention include, for example, inorganic materials, intermetallic materials, metal alloys, ceramic materials, organic materials, organometallic materials, non-biological organic polymers, composite materials (e.g., inorganic composites, organic composites, or combinations thereof), etc. Once prepared, these materials can be screened for useful properties including, for example, electrical, thermal, mechanical, morphological, optical, magnetic, chemical, or other properties. Thus, the present invention provides methods for the parallel synthesis and analysis of novel materials having useful properties.

  7. Organic or organometallic template mediated clay synthesis

    SciTech Connect

    Gregar, K.C.; Winans, R.E.; Botto, R.E.

    1992-12-31

    A method is given for incorporating diverse varieties of intercalants or templates directly during hydrothermal synthesis of clays such as hectorite or montmorillonite-type layer-silicate clays. For a hectorite layer-silicate clay, refluxing a gel of silica sol, magnesium hydroxide sol and LiF for 2 days with an organic or organometallic intercalant or template results in crystalline products containing either (a) organic dye molecules such as ethyl violet and methyl green, (b) dye molecules such as alcian blue based on a Cu(II)-phthalocyannine complex, or (c) transition metal complexes such as Ru(II)phenanthroline and Co(III)sepulchrate or (d) water-soluble porphyrins and metalloporphyrins. Montmorillonite-type clays are made by the method taught by US patent No. 3,887,454 issued to Hickson, June 13, 1975; however, a variety of intercalants or templates may be introduced. The intercalants or templates should have water-solubility, positive charge, and thermal stability under moderately basic (pH 9-10) aqueous reflux conditions or hydrothermal pressurized conditions for the montmorillonite-type clays.

  8. Organic or organometallic template mediated clay synthesis

    DOEpatents

    Gregar, K.C.; Winans, R.E.; Botto, R.E.

    1994-05-03

    A method is described for incorporating diverse varieties of intercalates or templates directly during hydrothermal synthesis of clays such as hectorite or montmorillonite-type layer-silicate clays. For a hectorite layer-silicate clay, refluxing a gel of silica sol, magnesium hydroxide sol and lithium fluoride for two days in the presence of an organic or organometallic intercalate or template results in crystalline products containing either (a) organic dye molecules such as ethyl violet and methyl green, (b) dye molecules such as alcian blue that are based on a Cu(II)-phthalocyannine complex, or (c) transition metal complexes such as Ru(II)phenanthroline and Co(III)sepulchrate or (d) water-soluble porphyrins and metalloporphyrins. Montmorillonite-type clays are made by the method taught by U.S. Pat. No. 3,887,454 issued to Hickson, Jun. 13, 1975; however, a variety of intercalates or templates may be introduced. The intercalates or templates should have (i) water-solubility, (ii) positive charge, and (iii) thermal stability under moderately basic (pH 9-10) aqueous reflux conditions or hydrothermal pressurized conditions for the montmorillonite-type clays. 22 figures.

  9. Organic or organometallic template mediated clay synthesis

    DOEpatents

    Gregar, Kathleen C.; Winans, Randall E.; Botto, Robert E.

    1994-01-01

    A method for incorporating diverse Varieties of intercalants or templates directly during hydrothermal synthesis of clays such as hectorite or montmorillonite-type layer-silicate clays. For a hectorite layer-silicate clay, refluxing a gel of silica sol, magnesium hydroxide sol and lithium fluoride for two days in the presence of an organic or organometallic intercalant or template results in crystalline products containing either (a) organic dye molecules such as ethyl violet and methyl green, (b) dye molecules such as alcian blue that are based on a Cu(II)-phthalocyannine complex, or (c) transition metal complexes such as Ru(II)phenanthroline and Co(III)sepulchrate or (d) water-soluble porphyrins and metalloporphyrins. Montmorillonite-type clays are made by the method taught by U.S. Pat. No. 3,887,454 issued to Hickson, Jun. 13, 1975; however, a variety of intercalants or templates may be introduced. The intercalants or templates should have (i) water-solubility, (ii) positive charge, and (iii) thermal stability under moderately basic (pH 9-10) aqueous reflux conditions or hydrothermal pressurized conditions for the montmorillonite-type clays.

  10. Nonsteroidal Anti-inflammatory-Organometallic Anticancer Compounds.

    PubMed

    Păunescu, Emilia; McArthur, Sarah; Soudani, Mylène; Scopelliti, Rosario; Dyson, Paul J

    2016-02-15

    Compounds that combine metal-based drugs with covalently linked targeted organic agents have been shown, in some instances, to exhibit superior anticancer properties compared to the individual counterparts. Within this framework, we prepared a series of organometallic ruthenium(II)- and osmium(II)-p-cymene complexes modified with the nonsteroidal anti-inflammatory drugs (NSAIDs) indomethacin and diclofenac. The NSAIDs are attached to the organometallic moieties via monodentate (pyridine/phosphine) or bidentate (bipyridine) ligands, affording piano-stool Ru(II) and Os(II) arene complexes of general formula [M(η(6)-p-cymene)Cl2(N)], where N is a pyridine-based ligand, {2-(2-(1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indol-3-yl)acetoxy)ethyl-3-(pyridin-3-yl)propanoate} or {2-(2-(2-((2,6-dichlorophenyl)amino)phenyl)acetoxy)ethyl-3-(pyridin-3-yl)propanoate}, [M(η(6)-p-cymene)Cl2(P)], where P is a phosphine ligand, {2-(2-(1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indol-3-yl)acetoxy)ethyl-4-(diphenylphosphanyl)benzoate} or {2-(2-(2-((2,6-dichlorophenyl)amino)phenyl)acetoxy)ethyl-4-(diphenylphosphanyl)benzoate, and [M(η(6)-p-cymene)Cl(N,N')][Cl], where N,N' is a bipyridine-based ligand, (4'-methyl-[2,2'-bipyridin]-4-yl)methyl-2-(1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indol-3-yl)acetate), (4'-methyl-[2,2'-bipyridin]-4-yl)methyl-2-(2-((2,6-dichlorophenyl)amino)phenyl)acetate), (bis(2-(2-(1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indol-3-yl)acetoxy)ethyl)[2,2'-bipyridine]-5,5'-dicarboxylate), or (bis(2-(2-(2-((2,6-dichlorophenyl)amino)phenyl)acetoxy)ethyl)[2,2'-bipyridine]-5,5'-dicarboxylate). The antiproliferative properties of the complexes were assessed in human ovarian cancer cells (A2780 and A2780cisR, the latter being resistant to cisplatin) and nontumorigenic human embryonic kidney (HEK-293) cells. Some of the complexes are considerably more cytotoxic than the original drugs and also display significant cancer cell selectivity. PMID:26824462

  11. CHEMISTRY OF SO{sub 2} ON MODEL METAL AND OXIDE CATALYSTS: PHOTOEMISSION AND XANES STUDIES

    SciTech Connect

    RODRIGUEZ,J.A.; JIRSAK,T.; CHATURVEDI,S.; HRBEK,J.; FREITAG,A.; LARESE,J.Z.

    2000-07-09

    High-resolution synchrotron based photoemission and x-ray absorption spectroscopy have been used to study the interaction of SO{sub 2} with a series of metals and oxides. The chemistry of SO{sub 2} on metal surfaces is rich. At low coverages, the molecule fully decomposes into atomic S and O. At large coverages, the formation of SO{sub 3} and SO{sub 4} takes place. The following sequence was found for the reactivity of the metals towards SO{sub 2}: Pt {approx} Rh < Ru < Mo << Zn, Sn, Cs. Alloying can be useful for reducing the chemical affinity of a metal for SO{sub 2} and controlling S poisoning. Pd atoms bonded to Rh and Pt atoms bonded to Sn interact weakly with SO{sub 2}. In general, SO{sub 2} mainly reacts with the O centers of metal oxides. SO{sub 4} is formed on CeO{sub 2} and SO{sub 3} on ZnO. On these systems there is no decomposition of SO{sub 2}. Dissociation of the molecule is observed after introducing a large amount of Ce{sup 3+} sites in ceria, or after depositing Cu or alkali metals on the oxide surfaces. These promote the catalytic activity of the oxides during the destruction of SO{sub 2}.

  12. Synthesis of Some "Cobaloxime" Derivatives: A Demonstration of "Umpolung" in the Reactivity of an Organometallic Complex

    NASA Astrophysics Data System (ADS)

    Jameson, Donald L.; Grzybowski, Joseph J.; Hammels, Deb E.; Castellano, Ronald K.; Hoke, Molly E.; Freed, Kimberly; Basquill, Sean; Mendel, Angela; Shoemaker, William J.

    1998-04-01

    This article describes a four-reaction sequence for the synthesis of two organometallic "cobaloxime" derivatives. The concept of "Umpolung" or reversal of reactivity is demonstrated in the preparation of complexes. The complex Co(dmgH)2(4-t-BuPy)Et is formed by the reaction of a cobalt (I) intermediate (cobalt in the role of nucleophile) with ethyl iodide. The complex Co(dmgH)2(4-t-BuPy)Ph is formed by the reaction of PhMgBr with a cobalt (III) intermediate (cobalt in the role of electrophile). All the products contain cobalt in the diamagnetic +3 oxidation state and are readily characterized by proton and carbon NMR. The four reaction sequence may be completed in two 4-hour lab periods. Cobaloximes are well known as model complexes for Vitamin B-12 and the experiment exposes students to aspects of classical coordination chemistry, organometallic chemistry and bioinorganic chemistry. The experiment also illustrates an important reactivity parallel between organic and organometallic chemistry.

  13. Molecular Surface Chemistry by Metal Single Crystals and Nanoparticles from Vacuum to High Pressure.

    SciTech Connect

    Somorjai, Gabor A.; Park, Jeong Y.

    2008-04-05

    Model systems for studying molecular surface chemistry have evolved from single crystal surfaces at low pressure to colloidal nanoparticles at high pressure. Low pressure surface structure studies of platinum single crystals using molecular beam surface scattering and low energy electron diffraction techniques probe the unique activity of defects, steps and kinks at the surface for dissociation reactions (H-H, C-H, C-C, O{double_bond}O bonds). High-pressure investigations of platinum single crystals using sum frequency generation vibrational spectroscopy have revealed the presence and the nature of reaction intermediates. High pressure scanning tunneling microscopy of platinum single crystal surfaces showed adsorbate mobility during a catalytic reaction. Nanoparticle systems are used to determine the role of metal-oxide interfaces, site blocking and the role of surface structures in reactive surface chemistry. The size, shape and composition of nanoparticles play important roles in determining reaction activity and selectivity.

  14. Preparation of highly reactive metal powders: preparation, characterization, and chemistry of iron, cobalt, nickel, palladium, and platinum microparticles

    SciTech Connect

    Kavaliunas, A.V.; Taylor, A.; Rieke, R.D.

    1983-01-01

    Anhydrous metal halides of iron cobalt, nickel, palladium, and platinum are readily reduced in glyme or tetra-hydro-furan (THF) with lithium in the presence of a small amount of naphthalene and yield finely divided, black metal powders of exceptional reactivity. Metal powders of Fe and Co react with C/sub 6/F/sub 5/X (X = Br, I) to yield solvated M(C/sub 6/F/sub 5/)/sub 2/ and MX/sub 2/. Powders of palladium and platinum react with C/sub 6/F/sub 5/I to yield solvated M(C/sub 6/F/sub 5/)I (M = Pd, Pt). Nickel powder reacts with C/sub 6/F/sub 5/I to yield the solvated species Ni(C/sub 6/F/sub 5/)/sub 2/ and NiI/sub 2/, however, with C/sub 6/F/sub 5/Br the product is solvated Ni(C/sub 6/F/sub 5/)Br. In most cases the metal powders are sufficiently reactive that a stoichiometric amount of C/sub 6/F/sub 5/X to the metal powder is used. The coordinated ether of all of these organometallic compounds is exceptionally labile and is displaced with a variety of ligands: phosphines, amines, sulfides, isocyanides, diolefins, and carbon monoxide. Many of the resultant compounds are novel and most are obtained in high yields. Palladium metal powder to which has been added 2,2'-bipyridine (bpy) reacts with iodobenzene to yield Pd(C/sub 6/H/sub 5/)I(bpy). Surface analyses including ESCA (electron spectroscopy) and BET were performed on the highly reactive Ni, Pt, and Pd metal powders. 32 references, 4 tables.

  15. Improved Modeling of Transition Metals, Applications to Catalysis and Technetium Chemistry

    SciTech Connect

    Cundari, T. R.

    2004-03-05

    There is considerable impetus for identification of aqueous OM catalysts as water is the ultimate ''green'' solvent. In collaboration with researchers at Ames Lab, we investigated effective fragment and Monte Carlo techniques for aqueous-phase hydroformylation (HyF). The Rh of the HyF catalyst is weakly aquated, in contrast to the hydride of the Rh-H bond. As the insertion of the olefin C=C into Rh-H determines the linear-to-branched aldehyde ratio, it is reasonable to infer that solvent plays an important role in regiochemistry. Studies on aqueous-phase organometallic catalysis were complemented in studies of the gas-phase reaction. A Rh-carbonyl-phosphine catalyst was investigated. Two of the most important implications of this research include (a) pseudorotation among five-coordinate intermediates is significant in HyF, and (b) CO insertion is the rate-determining step. The latter is in contrast to experimental deductions, highlighting the need for more accurate modeling. To this end, we undertook studies of (a) experimentally relevant PR{sub 3} co-ligands (PMe{sub 3}, PPh{sub 3}, P(p-PhSO{sub 3{sup -}}){sub 3}, etc.), and (b) HyF of propene. For the propylene research, simulations indicated that the linear: branched aldehyde ratio (linear is more desirable) is determined by thermodynamic discrimination of two distinct pathways. Other projects include a theory-experiment study of C-H activation by early transition metal systems, which establishes that weakly-bound adducts play a key role in activity selectivity. By extension, more selective catalysts for functionalization of methane (major component of natural gas) will require better understanding of these adducts, which are greatly affected by steric interactions with the ligands. In the de novo design of Tc complexes, we constructed (and are now testing) a coupled quantum mechanics-molecular mechanics protocol. Initial research shows it to be capable of accurately predicting structure ''from scratch

  16. 103Rh NMR spectroscopy and its application to rhodium chemistry.

    PubMed

    Ernsting, Jan Meine; Gaemers, Sander; Elsevier, Cornelis J

    2004-09-01

    Rhodium is used for a number of large processes that rely on homogeneous rhodium-catalyzed reactions, for instance rhodium-catalyzed hydroformylation of alkenes, carbonylation of methanol to acetic acid and hydrodesulfurization of thiophene derivatives (in crude oil). Many laboratory applications in organometallic chemistry and catalysis involve organorhodium chemistry and a wealth of rhodium coordination compounds is known. For these and other areas, 103Rh NMR spectroscopy appears to be a very useful analytical tool. In this review, most of the literature concerning 103Rh NMR spectroscopy published from 1989 up to and including 2003 has been covered. After an introduction to several experimental methods for the detection of the insensitive 103Rh nucleus, a discussion of factors affecting the transition metal chemical shift is given. Computational aspects and calculations of chemical shifts are also briefly addressed. Next, the application of 103Rh NMR in coordination and organometallic chemistry is elaborated in more detail by highlighting recent developments in measurement and interpretation of 103Rh NMR data, in relation to rhodium-assisted reactions and homogeneous catalysis. The dependence of the 103Rh chemical shift on the ligands at rhodium in the first coordination sphere, on the complex geometry, oxidation state, temperature, solvent and concentration is treated. Several classes of compounds and special cases such as chiral rhodium compounds are reviewed. Finally, a section on scalar coupling to rhodium is provided. PMID:15307053

  17. Transition metal oxides deposited on rhodium and platinum: Surface chemistry and catalysis

    SciTech Connect

    Boffa, A B

    1994-07-01

    The surface chemistry and catalytic reactivity of transition metal oxides deposited on Rh and Pt substrates has been examined in order to establish the role of oxide-metal interactions in influencing catalytic activity. The oxides investigated included titanium oxide (TiOx), vanadium oxide (VOx), iron oxide (FeOx), zirconium oxide (ZrOx), niobium oxide (NbOx), tantalum oxide (TaOx), and tungsten oxide (WOx). The techniques used to characterize the sample included AES, XPS, LEED, TPD, ISS, and STM. After characterization of the surface in UHV, the sample was enclosed in an atmospheric reaction cell to measure the influence of the oxide deposits on the catalytic activity of the pure metal for CO and CO{sub 2} hydrogenation. The oxide deposits were found to strongly enhance the reactivity of the Rh foil. The rates of methane formation were promoted by up to 15 fold with the maximum in rate enhancement occurring at oxide coverages of approximately 0.5 ML. TiOx TaOx, and NbOx were the most effective promoters and were stable in the highest oxidation states during both reactions (compared to VOx, WOx, and FeOx). The trend in promoter effectiveness was attributed to the direct relationship between oxidation state and Lewis acidity. Bonding at the metal oxide/metal interface between the oxygen end of adsorbed CO and the Lewis acidic oxide was postulated to facilitate C-O bond dissociation and subsequent hydrogenation. 192 refs.

  18. Bringing inorganic chemistry to life with inspiration from R. J. P. Williams.

    PubMed

    Hill, H Allen O; Sadler, Peter J

    2016-03-01

    Our appreciation of the scholarly ideas and thinking of Bob Williams is illustrated here by a few of the areas in which he inspired us. His journey to bring inorganic chemistry to life began with an early interest in analytical chemistry, rationalising the relative stabilities of metal coordination complexes (The Irving-Williams Series), and elucidating the organometallic redox chemistry of vitamin B12. He (and Vallee) recognised that metal ions are in energised (entatic) states in proteins and enzymes, which themselves are dynamic structures of rods and springs. He played a key role in helping Rosenberg to pave the road toward the clinic for the anticancer drug cisplatin. He believed that evolution is not just dependent on DNA, but also on the metallome. Organisms and the environment are one system: does DNA code directly for all the essential elements of life? PMID:26841789

  19. Automated building of organometallic complexes from 3D fragments.

    PubMed

    Foscato, Marco; Venkatraman, Vishwesh; Occhipinti, Giovanni; Alsberg, Bjørn K; Jensen, Vidar R

    2014-07-28

    A method for the automated construction of three-dimensional (3D) molecular models of organometallic species in design studies is described. Molecular structure fragments derived from crystallographic structures and accurate molecular-level calculations are used as 3D building blocks in the construction of multiple molecular models of analogous compounds. The method allows for precise control of stereochemistry and geometrical features that may otherwise be very challenging, or even impossible, to achieve with commonly available generators of 3D chemical structures. The new method was tested in the construction of three sets of active or metastable organometallic species of catalytic reactions in the homogeneous phase. The performance of the method was compared with those of commonly available methods for automated generation of 3D models, demonstrating higher accuracy of the prepared 3D models in general, and, in particular, a much wider range with respect to the kind of chemical structures that can be built automatically, with capabilities far beyond standard organic and main-group chemistry. PMID:24998944

  20. Porewater chemistry in a treatment wetland: links to metal retention and release

    NASA Astrophysics Data System (ADS)

    Vadas, T. M.; Zhang, J.

    2011-12-01

    Constructed wetlands are gaining increased support for treatment of nonpoint source pollutants. A subsurface flow wetland treating runoff from an agricultural milkhouse floor and roof drainage has been monitored for metal removal. Influent dissolved concentrations from 5 to 30 ppb Cu and 60 to 800 ppb Zn were observed. Effluent concentrations of Zn were always lower from about 3 to 60 ppb Zn, however, Cu was typically around 10 ppb, and much larger at certain points in time, up to 95 ppb Cu. The results were similar in vegetated and non-vegetated wetlands, suggesting abiotic chemistry or microbial activity is controlling metal mobility. Porewater samples were taken using soil moisture lysimeters during both non-storm and storm events to examine metal and related chemistry with depth and distance in the wetland. Under non storm conditions, Cu and Zn average porewater concentrations were 64 and 250 ppb, respectively and did not vary much along the length of the wetland. During a storm event, Zn concentrations in the porewater initially increased near the inlet shortly after a storm, but typically decreased along the length and depth of the wetland to less than 60 ppb. Observed porewater Cu concentrations also increased near the inlet in some cases up to 700 ppb, but dropped rapidly with distance to less than 30 ppb near the middle of the wetland and increased again near the outlet. The dissolved Fe and Mn concentrations follow nearly opposite trends as Cu, increasing and then decreasing along the length of the wetland, suggesting possibly different roles in controlling Cu retention in each stage of the wetland, either co-precipitation with Cu initially, or reductive dissolution and release of Cu in later stages. An understanding of what controls metal retention and release is relevant to optimizing future design parameters of these wetlands.

  1. Chemistry Notes

    ERIC Educational Resources Information Center

    School Science Review, 1972

    1972-01-01

    Thirteen ideas are presented that may be of use to chemistry teachers. Topics covered include vitamin C, industrial chemistry, electrical conductivity, electrolysis, alkali metals, vibration modes infra-red, dynamic equilibrium, and some new demonstrations in gaseous combinations. (PS)

  2. Partitioning of metals in different binding phases of tropical estuarine sediments: importance of metal chemistry.

    PubMed

    Chakraborty, Parthasarathi; Chakraborty, Sucharita; Vudamala, Krushna; Sarkar, Arindam; Nath, B Nagender

    2016-02-01

    Distribution of metals in different binding phases of estuarine sediments provides chemically significant description of metal-sediment interactions. This study describes the influences of ligand field stabilization energy (LFSE), Jahn-Teller effect, and water exchange rate (k-w) on metal distribution in different binding phases of estuarine sediments. It was found that Cu had highest affinity for organic binding phases in the studied sediments followed by Ni and Pb. However, Pb showed strong association with Fe/Mn oxide phases followed by Ni and Cu. Faster k-w of Cu (II) (1 × 10(9) s(-1)) increased the rate of complex formation of Cu(2+) ion with ligand in the organic phases. The Cu-ligand (from organic phase) complexes gained extra stability by the Jahn-Teller effect. The combined effects of these two phenomena and high ionic potential increased the association of Cu with the organic phases of the sediments than Ni and Pb. The smaller ionic radii of Ni(2+) (0.72 Å) than Pb(2+) (1.20 Å) increase the stability of Ni-ligand complexes in the organic phase of the sediments. High LFSE of Ni(II) (compared with Pb(2+) ions) also make Ni-organic complexes increasingly stable than Pb. High k-w (7 × 10(9) s(-1)) of Pb did not help it to associate with organic phases in the sediments. The high concentration of Pb in the Fe/Mn oxyhydroxide binding phase was probably due to co-precipitation of Pb(2+) and Fe(3+). High surface area or site availability for Pb(2+) ion on Fe oxyhydroxide phase was probably responsible for the high concentration of Pb in Fe/Mn oxyhydroxide phase. Increasing concentrations of Cu in organic phases with the increasing Cu loading suggest that enough binding sites were available for Cu in the organic binding phases of the sediments. This study also describes the influence of nature of sedimentary organic carbon (terrestrial and marine derived OC) in controlling these metal distribution and speciation in marine sediment. PMID:26490921

  3. Physical chemistry of the organic analog of metal metal eutectic and monotectic alloys

    NASA Astrophysics Data System (ADS)

    Rai, U. S.; Rai, R. N.

    1998-01-01

    The phase diagram of an organic analog of a metal-metal system involving succinonitrile (SCN) and carbontetrabromide (CTB) shows the formation of a eutectic (0.996 mole fraction of SCN) and a monotectic (0.040 mole fraction of SCN) with a wide range of miscibility gap in the system. The consolute temperature is 111.5°C above the monotectic horizontal. The growth data, determined by measuring the rate of movement of solid-liquid interface in a capillary, at different undercooling (Δ T) suggest that they obey the parabolic law, v= u(Δ T) n, where v is the linear velocity of crystallization and u and n are constants depending on the nature of materials involved. Using enthalpy of fusion of the pure components, the eutectic and the monotectic, entropy of fusion, Jackson's roughness parameter, interfacial energy, size of the critical nucleus and excess thermodynamic functions were calculated. While microstructural investigations of pure components give dendritic microstructures, those of eutectic and monotectic give characteristic lamellar structures.

  4. Electrically Conductive, Corrosion-Resistant Coatings Through Defect Chemistry for Metallic Interconnects

    SciTech Connect

    Anil V. Virkar

    2006-12-31

    The principal objective of this work was to develop oxidation protective coatings for metallic interconnect based on a defect chemistry approach. It was reasoned that the effectiveness of a coating is dictated by oxygen permeation kinetics; the slower the permeation kinetics, the better the protection. All protective coating materials investigated to date are either perovskites or spinels containing metals exhibiting multiple valence states (Co, Fe, Mn, Cr, etc.). As a result, all of these oxides exhibit a reasonable level of electronic conductivity; typically at least about {approx}0.05 S/cm at 800 C. For a 5 micron coating, this equates to a maximum {approx}0.025 {Omega}cm{sup 2} area specific resistance due to the coating. This suggests that the coating should be based on oxygen ion conductivity (the lower the better) and not on electronic conductivity. Measurements of ionic conductivity of prospective coating materials were conducted using Hebb-Wagner method. It was demonstrated that special precautions need to be taken to measure oxygen ion conductivity in these materials with very low oxygen vacancy concentration. A model for oxidation under a protective coating is presented. Defect chemistry based approach was developed such that by suitably doping, oxygen vacancy concentration was suppressed, thus suppressing oxygen ion transport and increasing effectiveness of the coating. For the cathode side, the best coating material identified was LaMnO{sub 3} with Ti dopant on the Mn site (LTM). It was observed that LTM is more than 20 times as effective as Mn-containing spinels. On the anode side, LaCrO3 doped with Nb on the Cr site (LNC) was the material identified. Extensive oxidation kinetics studies were conducted on metallic alloy foils with coating {approx}1 micron in thickness. From these studies, it was projected that a 5 micron coating would be sufficient to ensure 40,000 h life.

  5. Flat Chern band in a two-dimensional organometallic framework.

    PubMed

    Liu, Zheng; Wang, Zheng-Fei; Mei, Jia-Wei; Wu, Yong-Shi; Liu, Feng

    2013-03-01

    By combining exotic band dispersion with nontrivial band topology, an interesting type of band structure, namely, the flat Chern band, has recently been proposed to spawn high-temperature fractional quantum Hall states. Despite the proposal of several theoretical lattice models, however, it remains doubtful whether such a "romance of flatland" could exist in a real material. Here, we present a first-principles design of a two-dimensional indium-phenylene organometallic framework that realizes a nearly flat Chern band right around the Fermi level by combining lattice geometry, spin-orbit coupling, and ferromagnetism. An effective four-band model is constructed to reproduce the first-principles results. Our design, in addition, provides a general strategy to synthesize topologically nontrivial materials by virtue of organic chemistry and nanotechnology. PMID:23521279

  6. Flat Chern Band in a Two-Dimensional Organometallic Framework

    NASA Astrophysics Data System (ADS)

    Liu, Zheng; Wang, Zheng-Fei; Mei, Jia-Wei; Wu, Yong-Shi; Liu, Feng

    2013-03-01

    By combining exotic band dispersion with nontrivial band topology, an interesting type of band structure, namely, the flat Chern band, has recently been proposed to spawn high-temperature fractional quantum Hall states. Despite the proposal of several theoretical lattice models, however, it remains doubtful whether such a “romance of flatland” could exist in a real material. Here, we present a first-principles design of a two-dimensional indium-phenylene organometallic framework that realizes a nearly flat Chern band right around the Fermi level by combining lattice geometry, spin-orbit coupling, and ferromagnetism. An effective four-band model is constructed to reproduce the first-principles results. Our design, in addition, provides a general strategy to synthesize topologically nontrivial materials by virtue of organic chemistry and nanotechnology.

  7. Flat Chern Band in a Two-Dimensional Organometallic Framework

    NASA Astrophysics Data System (ADS)

    Liu, Zheng; Wang, Zheng-Fei; Mei, Jia-Wei; Wu, Yong-Shi; Liu, Feng

    2013-03-01

    By combining exotic band dispersion with nontrivial band topology, an interesting type of band, namely the flat chern band (FCB), has recently been proposed, in which carriers experience strong Coulomb interaction as well as topological frustration that in together spawn unprecedented topological strongly-correlated electronic states, such as high-temperature fractional quantum hall state. Despite the proposal of several theoretical lattice models, however, it remains a doubt whether such a ``romance of flatland'' could exist in a real material. Here, we present a first-principles design to realize a nearly FCB right around the Fermi level in a two-dimensional (2D) Indium-Phenylene Organometallic Framework (IPOF). Our design in addition provides a general strategy to synthesize topologically nontrivial materials in virtue of organic chemistry and nanotechnology. Supported by DOE-BES and ARL

  8. Reliable Electronic Structure Calculations for Heavy Element Chemistry: Molecules Containing Actinides, Lanthanides, and Transition Metals

    SciTech Connect

    Marino, Maria, M.; Ermler, Walter C

    2006-01-27

    It is now possible to calculate many properties including the energetics (total bond dissociation energies or heats of formation) of molecules containing light elements to high accuracy by using correlation-consistent basis sets, coupled cluster theory and including additive corrections for core-valence and relativistic effects and careful treatment of the zero point energy. We propose to develop software for ab initio electronic structure calculations based on molecular orbital theory and density functional theory with the proper treatment of relativistic effects to study complexes of heavy elements in order to assist in understanding and predicting the chemistry of the actinides, lanthanides, and heavy transition metals, molecules critical to DOE missions including environmental management. The proposed work will focus on the development of these electronic structure methods and their implementation in software on advanced massively parallel processor (MPP) computer architectures capable of multi-tens of teraflops to petaflops. The core of the software will be developed within the NWChem and Columbus software suites. We propose to make the software broadly available so that other scientists can use these tools to address the complex environmental problems facing the Department of Energy's nuclear production sites as well as other waste sites in the Nation. Our implementation of relativistic quantum chemical methods for massively parallel computers will enable us to simulate the behavior of heavy-element compounds at the same type of level currently available for light-element compounds. In addition, this work will enable us to provide better methods for benchmarks of the additive energetic schemes currently available for light atom compounds. The theoretical and computational methodology so developed will be an invaluable supplement to current, very expensive experimental studies of the actinides, lanthanides, and radioactive heavy transition metal elements

  9. Dependence of bonding interactions in Layered Double Hydroxides on metal cation chemistry

    NASA Astrophysics Data System (ADS)

    Shamim, Mostofa; Dana, Kausik

    2016-12-01

    The evolution of various Infrared bands of Layered Double Hydroxides (LDH) with variable Zn:Al ratio was analyzed to correlate it with the changes in octahedral metal cation chemistry, interlayer carbonate anion and hydroxyl content of LDH. The synthesized phase-pure LDHs were crystallized as hexagonal 2H polytype with a Manasseite structure. The broad and asymmetric hydroxyl stretching region (2400-4000 cm-1) can be deconvoluted into four different bands. With increase in Zn2+:Al3+ metal ratio, the peak position of stretching frequencies of Al3+sbnd OH and carbonate-bridged hydroxyl (water) decrease almost linearly. Individual band's peak position and area under the curve have been successfully correlated with the carbonate and hydroxyl content of LDH. Due to lowering of symmetry of the carbonate anion, the IR-inactive peak νCsbnd O, symm at 1064 cm-1 becomes IR active. The peak position of metal-oxygen bands and carbonate bending modes are practically unaffected by the Zn2+:Al3+ ratio but the area under the individual M-O bands shows a direct correlation.

  10. Metal-support bonds in supported metal catalysts

    SciTech Connect

    Gates, B.C.

    1990-01-01

    This research project, now in its third year, is an investigation of the synthesis, structure, and bonding of a family of metal complexes, clusters, and particles on the surfaces of high-area metal oxide supports. The focus is the structure of the metal-support interface. Surface species have been prepared by synthetic organometallic chemistry on the support surfaces. The organometallic precursors are complexes of W, Re, Os, Ir, and Pt, including W(CO){sub 6}, HRe(CO){sub 5}, Re{sub 2}(CO){sub 10}, H{sub 3}Re{sub 3}(CO){sub 12}, H{sub 2}Os(CO){sub 4}, Ir({eta}{sup 3}-C{sub 3}H{sub 5}){sub 3}, and Pt({eta}{sup 3}-C{sub 3}H{sub 5}){sub 2}. The supports are primarily MgO and {gamma}-Al{sub 2}O{sub 3}. The surface species have been characterized by infrared and EXAFS spectroscopies, among other techniques. 7 refs., 5 figs., 4 tabs.

  11. Heavy metal coordination chemistry in mercaptides and enzymes studied by TDPAC

    NASA Astrophysics Data System (ADS)

    Butz, T.

    1993-03-01

    Time differential perturbed angular correlation (TDPAC) studies of the coordination chemistry of the heavy metal atoms Cd and Hg via the nuclear quadrupole interaction are presented for the following systems; (i) mercury complexes with mercaptides, polymers with thiol groups, and ferrocenethiols. Mercury has a strong tendency to form linear or almost linear bonds with sulfur ligands. Evidence for 1,3-dithia-2-mercura[3]ferrocenophane formation is presented. (ii)111mCd-derivatives of the small electron transport proteins azurin, including a his 117gly mutant, and stellacyanin. The titration of the his 117gly mutant of azurin with imidazole was monitored in situ. (iii)111mCd- and199mHg-derivatives of the multi-Cu enzymes ascorbate oxidase and laccase. Reconstitution probabilities for Hg-reconstitution will be given as well as information on selective depletion and blocking of Cu-sites.

  12. Inorganic Chemistry Solutions to Semiconductor Nanocrystal Problems

    SciTech Connect

    Alvarado, Samuel R.; Guo, Yijun; Ruberu, T. Purnima A.; Tavasoli, Elham; Vela, Javier

    2014-03-15

    The optoelectronic and chemical properties of semiconductor nanocrystals heavily depend on their composition, size, shape and internal structure, surface functionality, etc. Available strategies to alter these properties through traditional colloidal syntheses and ligand exchange methods place a premium on specific reaction conditions and surfactant combinations. In this invited review, we apply a molecular-level understanding of chemical precursor reactivity to reliably control the morphology, composition and intimate architecture (core/shell vs. alloyed) of semiconductor nanocrystals. We also describe our work aimed at achieving highly selective, low-temperature photochemical methods for the synthesis of semiconductor–metal and semiconductor–metal oxide photocatalytic nanocomposites. In addition, we describe our work on surface modification of semiconductor nanocrystal quantum dots using new approaches and methods that bypass ligand exchange, retaining the nanocrystal's native ligands and original optical properties, as well as on spectroscopic methods of characterization useful in determining surface ligand organization and chemistry. Using recent examples from our group and collaborators, we demonstrate how these efforts have lead to faster, wider and more systematic application of semiconductor nanocrystal-based materials to biological imaging and tracking, and to photocatalysis of unconventional substrates. We believe techniques and methods borrowed from inorganic chemistry (including coordination, organometallic and solid state chemistry) have much to offer in reaching a better understanding of the synthesis, functionalization and real-life application of such exciting materials as semiconductor nanocrystals (quantum dots, rods, tetrapods, etc.).

  13. The Construction of Metal-Organic Framework with Active Backbones by the Utilization of Reticular Chemistry

    NASA Astrophysics Data System (ADS)

    Choi, Eunwoo

    With the principles of reticular chemistry, metal-organic frameworks with ultra-high porosity, chiral-recognition unit as a chiral stationary phase, metalloporhyrins for enhanced hydrogen adsorption and an intrinsic conductivity to form porous conductors, have been prepared. This dissertation presents how the principles of reticular chemistry were utilized to achieve in the preparations of metal-organic frameworks with a large surface area and active backbones. Through the simple isoreticular (having the same framework topology) expansion from MOF-177 composed with 1,3,5-tris(4'-carboxyphenyl-)benzene (BTB3-) as the strut; MOF-200 was prepared with 4,4',4"-(benzene-1,3,5-triyl-tris(benzene-4,1-diy1))tribenzoic acid an extension from BTB3- by a phenylene unit to yield one of the most porous MOFs with a Langmuir surface area of 10,400 m2. and the lowest density of 0.22 cm3.g-1. A successful thermal polymerization reaction at 325 °C inside of the pores of highly porous MOF, MOF-177, was performed and verified the integrity of the MOF structure even after the thermal reaction. 1,4-Diphenylbutadiyne that is known to polymerize upon heating to form a conjugated backbone was impregnated via solution-diffusion into MOF-177 and then subsequently polymerized by heat to form polymer impregnated MOF-177. Characterization was carried out using powder X-ray diffraction and volumetric sorption analyzer. MOF-1020 with a linear quaterphenyl dicarboxylate-based strut was designed to contain a chiral bisbinaphthyl crown-ether moiety for alkyl ammonium resolution was precisely placed into a Zn4O(CO2)6-based cubic MOF structure. Unfortunately, the chiral resolution was not achieved due to the sensitivity and the pore environment of MOF-1020. However, an interesting phenomenon was observed, where the loss of crystallinity occurs upon solvent removal while the crystallites remain shiny and crystalline, but it readily is restored upon re-solvation of the crystallites. This rare

  14. Chemistry Rocks: Redox Chemistry as a Geologic Tool.

    ERIC Educational Resources Information Center

    Burns, Mary Sue

    2001-01-01

    Applies chemistry to earth science, uses rocks in chemistry laboratories, and teaches about transition metal chemistry, oxidation states, and oxidation-reduction reactions from firsthand experiences. (YDS)

  15. Noninvasive Fluid Level Sensor for Organometallic Sources

    NASA Technical Reports Server (NTRS)

    Gerdes, W.

    1986-01-01

    Two ultrasonic methods available for measuring level of organometallic liquid in stainless-steel (or other homogeneous solid) container. Methods require no disassembly or weighing of container. Commercially available ultrasonic flaw detectors, some of which have digital readouts and computer interfaces, used in techniques. Both methods used in crystal growth to determine level of liquids contained in sealed, opaque containers.

  16. Organometallic Salts Generate Optical Second Harmonics

    NASA Technical Reports Server (NTRS)

    Marder, Seth R.; Perry, Joseph W.

    1991-01-01

    Series of organometallic salts exhibit large second-order dielectric susceptibilities, as evidenced by generation of second harmonics when illuminated at visible and near-infrared wavelengths. Investigations of these and related compounds continue with view toward development of materials for use as optical second-harmonic generators, electro-optical modulators, optical switches, piezoelectric sensors, and parametric crystals.

  17. Organometallic catalysts for primary phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    Walsh, Fraser

    1987-01-01

    A continuing effort by the U.S. Department of Energy to improve the competitiveness of the phosphoric acid fuel cell by improving cell performance and/or reducing cell cost is discussed. Cathode improvement, both in performance and cost, available through the use of a class of organometallic cathode catalysts, the tetraazaannulenes (TAAs), was investigated. A new mixed catalyst was identified which provides improved cathode performance without the need for the use of a noble metal. This mixed catalyst was tested under load for 1000 hr. in full cell at 160 to 200 C in phosphoric acid H3PO4, and was shown to provide stable performance. The mixed catalyst contains an organometallic to catalyze electroreduction of oxygen to hydrogen peroxide and a metal to catalyze further electroreduction of the hydrogen peroxide to water. Cathodes containing an exemplar mixed catalyst (e.g., Co bisphenyl TAA/Mn) operate at approximately 650 mV vs DHE in 160 C, 85% H3PO4 with oxygen as reactant. In developing this mixed catalyst, a broad spectrum of TAAs were prepared, tested in half-cell and in a rotating ring-disk electrode system. TAAs found to facilitate the production of hydrogen peroxide in electroreduction were shown to be preferred TAAs for use in the mixed catalyst. Manganese (Mn) was identified as a preferred metal because it is capable of catalyzing hydrogen peroxide electroreduction, is lower in cost and is of less strategic importance than platinum, the cathode catalyst normally used in the fuel cell.

  18. Organometallic catalysts for primary phosphoric acid fuel cells

    NASA Astrophysics Data System (ADS)

    Walsh, Fraser

    1987-03-01

    A continuing effort by the U.S. Department of Energy to improve the competitiveness of the phosphoric acid fuel cell by improving cell performance and/or reducing cell cost is discussed. Cathode improvement, both in performance and cost, available through the use of a class of organometallic cathode catalysts, the tetraazaannulenes (TAAs), was investigated. A new mixed catalyst was identified which provides improved cathode performance without the need for the use of a noble metal. This mixed catalyst was tested under load for 1000 hr. in full cell at 160 to 200 C in phosphoric acid H3PO4, and was shown to provide stable performance. The mixed catalyst contains an organometallic to catalyze electroreduction of oxygen to hydrogen peroxide and a metal to catalyze further electroreduction of the hydrogen peroxide to water. Cathodes containing an exemplar mixed catalyst (e.g., Co bisphenyl TAA/Mn) operate at approximately 650 mV vs DHE in 160 C, 85% H3PO4 with oxygen as reactant. In developing this mixed catalyst, a broad spectrum of TAAs were prepared, tested in half-cell and in a rotating ring-disk electrode system. TAAs found to facilitate the production of hydrogen peroxide in electroreduction were shown to be preferred TAAs for use in the mixed catalyst. Manganese (Mn) was identified as a preferred metal because it is capable of catalyzing hydrogen peroxide electroreduction, is lower in cost and is of less strategic importance than platinum, the cathode catalyst normally used in the fuel cell.

  19. Synthesis and chemistry of cationic d sup 0 metal alkyl complexes

    SciTech Connect

    Jordan, R.F.

    1991-01-01

    The objective of this project is to develop new types of electrophilic metal alkyl complexes for catalytic C-H activation and olefin polymerization chemistry, and associated fundamental mechanistic studies. We have focused our efforts on four classes of early metal alkyl complexes: (1) cationic group 4 Cp{sub 2}M(R){sup +} complexes (1) which are active species in Cp{sub 2}MX{sub 2}-based Ziegler-Natta olefin polymerization catalyst systems and which catalyze productive C-H activation reactions of heterocycles, (2) neutral (dicarbollide)(Cp*)M(R) complexes (2) which are structurally are electronically very similar to 1, (3) half-sandwich complexes CpM(R){sub 2}(L){sub n}{sup +} which are highly coordinatively and electronically unsaturated, and (4) new group 5 (dicarbollide)(Cp)MR{sub 2} and (dicarbollide){sub 2} MR complexes which are more unsaturated than group 5 Cp{sub 2}M systems due to incorporation of the dicarbollide ligand.

  20. Chemistry Notes.

    ERIC Educational Resources Information Center

    School Science Review, 1982

    1982-01-01

    Presents background information, laboratory procedures, classroom materials/activities, and experiments for chemistry. Topics include superheavy elements, polarizing power and chemistry of alkali metals, particulate carbon from combustion, tips for the chemistry laboratory, interesting/colorful experiments, behavior of bismuth (III) iodine, and…

  1. Major-ion and selected trace-metal chemistry of the Biscayne Aquifer, Southeast Florida

    USGS Publications Warehouse

    Radell, M.J.; Katz, B.G.

    1991-01-01

    The major-ion and selected trace-metal chemistry of the Biscayne aquifer was characterized as part of the Florida Ground-Water Quality Monitoring Network Program, a multiagency cooperative effort concerned with delineating baseline water quality for major aquifer systems in the State. The Biscayne aquifer is unconfined and serves as the sole source of drinking water for more than 3 million people in southeast Florida. The Biscayne aquifer consists of highly permeable interbedded limestone and sandstone of Pleistocene and Pliocene age underlying most of Dade and Broward Counties and parts of Palm Beach and Monroe Counties. The high permeability is largely caused by extensive carbonate dissolution. Water sampled from 189 wells tapping the Biscayne aquifer was predominantly a calcium bicarbonate type with some mixed types occurring in coastal areas and near major canals. Major - ion is areally uniform throughout the aquifer. According to nonparametric statistical tests of major ions and dissolved solids, the concentrations of calcium, sodium, bicarbonate, and dissolved solids increased significantly with well depth ( 0.05 significance level ), probably a result of less circulation at depth. Potassium and nitrate concentrations decreased significantly with depth. Although the source of recharge to the aquifer varies seasonally, there was no statistical difference in the concentration of major ions in pared water samples from 27 shallow wells collected during wet and dry seasons. Median concentrations for barium, chromium, copper, lead, and manganese were below maximum or secondary maximum contaminant levels set by the US Environmental Protection Agency. The median iron concentration only slightly exceeded the secondary maximum contaminant level. The concentration of barium was significantly related (0.05 significance level) to calcium and bicarbonate concentration. No distinct areal pattern or vertical distribution of the selected trace metals was evident in water from

  2. Ozone in sea water. Part 1: Chemistry; Part 2: Corrosion of metals

    SciTech Connect

    Wyllie, W.E. II; Brown, B.E.; Duquette, D.J.

    1995-12-01

    Ozonation of sea water for biofouling control is being utilized in desalination processes, heat exchange systems, as well as in salt water aquariums. The chemistry of ozone in sea water is much more complex than in fresh water due to the high concentration of easily oxidizable, ozone-demanding species and the formation of secondary oxidants. The major secondary oxidant is bromine in the form of hypobromite and hypobromous acid (BrO{sup {minus}}/HOBr) which are formed by oxidation of the bromide ion (Br{sup {minus}}), naturally found in sea water in concentrations of 65 mg/L. HOBr can react again with ozone to return Br{sup {minus}}, resulting in accelerated decomposition of ozone, or to form bromate (BrO{sub 3}{sup {minus}}) The BrO ion is known to interfere with the measurement of residual ozone in sea water, so it is important that the feed gas conditions, solution pH, and the hypobromous and bromate concentrations be reported to quantify the amount of ozone introduced into a system. In 0.5 N NaCl and sea water solutions, ozone appears to stabilize the passivity of passivating metals, but susceptibility to crevice corrosion appears to increase in the same environments. The effect of BrO{sup {minus}}/HOBr on the corrosion of metals in sea water is believed to be similar to chlorine and ozone, in that it acts as a strong oxidizer. However, it is not certain whether BrO{sup {minus}}/HOBr and BrO{sub 3}{sup {minus}} have any damaging effects on protective metal films.

  3. Organometallic synthesis, reactivity and catalysis in the solid state using well-defined single-site species

    PubMed Central

    Pike, Sebastian D.; Weller, Andrew S.

    2015-01-01

    Acting as a bridge between the heterogeneous and homogeneous realms, the use of discrete, well-defined, solid-state organometallic complexes for synthesis and catalysis is a remarkably undeveloped field. Here, we present a review of this topic, focusing on describing the key transformations that can be observed at a transition-metal centre, as well as the use of well-defined organometallic complexes in the solid state as catalysts. There is a particular focus upon gas–solid reactivity/catalysis and single-crystal-to-single-crystal transformations. PMID:25666064

  4. Molecular tectonics: heterometallic coordination networks based on a Pt(II) organometallic metallatecton.

    PubMed

    Zigon, Nicolas; Kyritsakas, Nathalie; Hosseini, Mir Wais

    2015-08-28

    Combinations of a neutral organometallic tecton based on a square planar Pt(ii) complex bearing two triphenylphosphine groups and two 4-ethynylpyridyl coordinating moieties in trans positions, with various metal halides (MX2, M = Co(ii), Ni(ii), Cd(ii), X = Cl(-) or Br(-)) lead to the formation of 2D grid type heterobimetallic coordination networks in the crystalline phase. PMID:26204438

  5. Progress toward cascade cells made by OM-VPE. [organometallic vapor phase epitaxy

    NASA Technical Reports Server (NTRS)

    Borden, P. G.; Larue, R. A.; Ludowise, M. J.

    1982-01-01

    Organometallic Vapor Phase Epitaxy (COM-VPE) was used to make a sophisticated monolithic cascade cell, with a peak AMO efficiency of 16.6%, not corrected for 14% grid coverage. The cell has 9 epitaxial layers. The top cell is 1.35 microns thick with a 0.1 micron thich emitter. Both cells are heteroface n-p structures. The cascade cell uses metal interconnects. Details of growth and processing are described.

  6. Organometallic Antitumour Agents with Alternative Modes of Action

    NASA Astrophysics Data System (ADS)

    Casini, Angela; Hartinger, Christian G.; Nazarov, Alexey A.; Dyson, Paul J.

    The therapeutic index of drugs that target DNA, a ubiquitous target present in nearly all cells, is low. Nevertheless, DNA has remained the primary target for medicinal chemists developing metal-based anticancer drugs, although DNA has been essentially abandoned in favour of non-genomic targets by medicinal chemists developing organic drugs. A number of organometallic drugs that target proteins/enzymes have been developed and these compounds, based on ruthenium, osmium and gold, are described in this chapter. Targets include cathepsin B, thioredoxin reductases, multidrug resistance protein (Pgp), glutathione S-transferases and kinases. It is found that compounds that inhibit these various targets are active against metastatic tumours, or tumours that are resistant to classical DNA damaging agents such as cisplatin, and therefore offer considerable potential in clinical applications.

  7. The Discovery-Oriented Approach to Organic Chemistry. 7. Rearrangement of "trans"-Stilbene Oxide with Bismuth Trifluoromethanesulfonate and Other Metal Triflates: A Microscale Green Organic Chemistry Laboratory Experiment

    ERIC Educational Resources Information Center

    Christensen, James E.; Huddle, Matthew G.; Rogers, Jamie L.; Yung, Herbie; Mohan, Ram S.

    2008-01-01

    Although green chemistry principles are increasingly stressed in the undergraduate curriculum, there are only a few lab experiments wherein the toxicity of reagents is taken into consideration in the design of the experiment. We report a microscale green organic chemistry laboratory experiment that illustrates the utility of metal triflates,…

  8. Creating a Discovery Platform for Confined-Space Chemistry and Materials: Metal-Organic Frameworks.

    SciTech Connect

    Allendorf, Mark D.; Greathouse, Jeffery A.; Simmons, Blake

    2008-09-01

    Metal organic frameworks (MOF) are a recently discovered class of nanoporous, defect-free crystalline materials that enable rational design and exploration of porous materials at the molecular level. MOFs have tunable monolithic pore sizes and cavity environments due to their crystalline nature, yielding properties exceeding those of most other porous materials. These include: the lowest known density (91% free space); highest surface area; tunable photoluminescence; selective molecular adsorption; and methane sorption rivaling gas cylinders. These properties are achieved by coupling inorganic metal complexes such as ZnO4 with tunable organic ligands that serve as struts, allowing facile manipulation of pore size and surface area through reactant selection. MOFs thus provide a discovery platform for generating both new understanding of chemistry in confined spaces and novel sensors and devices based on their unique properties. At the outset of this project in FY06, virtually nothing was known about how to couple MOFs to substrates and the science of MOF properties and how to tune them was in its infancy. An integrated approach was needed to establish the required knowledge base for nanoscale design and develop methodologies integrate MOFs with other materials. This report summarizes the key accomplishments of this project, which include creation of a new class of radiation detection materials based on MOFs, luminescent MOFs for chemical detection, use of MOFs as templates to create nanoparticles of hydrogen storage materials, MOF coatings for stress-based chemical detection using microcantilevers, and %22flexible%22 force fields that account for structural changes in MOFs that occur upon molecular adsorption/desorption. Eight journal articles, twenty presentations at scientific conferences, and two patent applications resulted from the work. The project created a basis for continuing development of MOFs for many Sandia applications and succeeded in securing %242

  9. Mechanistic study of organometallic vapor phase epitaxy

    SciTech Connect

    Stringfellow, G.B.

    1990-12-31

    Only AsH{sub 3} and PH{sub 3} have been used as the group V source molecules for organometallic vapor phase epitaxy (OMVPE) of III/V semiconductors until recently, since they have been the only precursors yielding device quality materials. This paper reviews recent work on the pyrolysis of individual organometallic molecules, with emphasis on the group V sources, including: (1) the methylarsines, di- and tri-methylarsine, (2) the ethylarsines, mono-, di-, and tri-ethylarsine, and (3) the singly substituted tertiarybutyl arsine and phosphine molecules. The pyrolysis and growth reactions occurring when both group III and group V precursors are present simultaneously, i.e., the reactions occuring during OMVPE growth of several III/V semiconductors, are also briefly reviewed.

  10. Mechanistic study of organometallic vapor phase epitaxy

    SciTech Connect

    Stringfellow, G.B.

    1990-01-01

    Only AsH{sub 3} and PH{sub 3} have been used as the group V source molecules for organometallic vapor phase epitaxy (OMVPE) of III/V semiconductors until recently, since they have been the only precursors yielding device quality materials. This paper reviews recent work on the pyrolysis of individual organometallic molecules, with emphasis on the group V sources, including: (1) the methylarsines, di- and tri-methylarsine, (2) the ethylarsines, mono-, di-, and tri-ethylarsine, and (3) the singly substituted tertiarybutyl arsine and phosphine molecules. The pyrolysis and growth reactions occurring when both group III and group V precursors are present simultaneously, i.e., the reactions occuring during OMVPE growth of several III/V semiconductors, are also briefly reviewed.

  11. Bioinspired heme, heme/nonheme diiron, heme/copper, and inorganic NOx chemistry: *NO((g)) oxidation, peroxynitrite-metal chemistry, and *NO((g)) reductive coupling.

    PubMed

    Schopfer, Mark P; Wang, Jun; Karlin, Kenneth D

    2010-07-19

    The focus of this Forum Article highlights work from our own laboratories and those of others in the area of biochemical and biologically inspired inorganic chemistry dealing with nitric oxide [nitrogen monoxide, *NO((g))] and its biological roles and reactions. The latter focus is on (i) oxidation of *NO((g)) to nitrate by nitric oxide dioxygenases (NODs) and (ii) reductive coupling of two molecules of *NO((g)) to give N(2)O(g). In the former case, NODs are described, and the highlighting of possible peroxynitrite/heme intermediates and the consequences of this are given by a discussion of recent works with myoglobin and a synthetic heme model system for NOD action. Summaries of recent copper complex chemistries with *NO((g)) and O(2)(g), leading to peroxynitrite species, are given. The coverage of biological reductive coupling of *NO((g)) deals with bacterial nitric oxide reductases (NORs) with heme/nonheme diiron active sites and on heme/copper oxidases such as cytochrome c oxidase, which can mediate the same chemistry. Recently designed protein and synthetic model compounds (heme/nonheme/diiron or heme/copper) as functional mimics are discussed in some detail. We also highlight examples from the chemical literature, not necessarily involving biologically relevant metal ions, that describe the oxidation of *NO((g)) to nitrate (or nitrite) and possible peroxynitrite intermediates or reductive coupling of *NO((g)) to give nitrous oxide. PMID:20666386

  12. Surface functionalization of two-dimensional metal chalcogenides by Lewis acid–base chemistry

    NASA Astrophysics Data System (ADS)

    Lei, Sidong; Wang, Xifan; Li, Bo; Kang, Jiahao; He, Yongmin; George, Antony; Ge, Liehui; Gong, Yongji; Dong, Pei; Jin, Zehua; Brunetto, Gustavo; Chen, Weibing; Lin, Zuan-Tao; Baines, Robert; Galvão, Douglas S.; Lou, Jun; Barrera, Enrique; Banerjee, Kaustav; Vajtai, Robert; Ajayan, Pulickel

    2016-05-01

    Precise control of the electronic surface states of two-dimensional (2D) materials could improve their versatility and widen their applicability in electronics and sensing. To this end, chemical surface functionalization has been used to adjust the electronic properties of 2D materials. So far, however, chemical functionalization has relied on lattice defects and physisorption methods that inevitably modify the topological characteristics of the atomic layers. Here we make use of the lone pair electrons found in most of 2D metal chalcogenides and report a functionalization method via a Lewis acid–base reaction that does not alter the host structure. Atomic layers of n-type InSe react with Ti4+ to form planar p-type [Ti4+n(InSe)] coordination complexes. Using this strategy, we fabricate planar p–n junctions on 2D InSe with improved rectification and photovoltaic properties, without requiring heterostructure growth procedures or device fabrication processes. We also show that this functionalization approach works with other Lewis acids (such as B3+, Al3+ and Sn4+) and can be applied to other 2D materials (for example MoS2, MoSe2). Finally, we show that it is possible to use Lewis acid–base chemistry as a bridge to connect molecules to 2D atomic layers and fabricate a proof-of-principle dye-sensitized photosensing device.

  13. Surface functionalization of two-dimensional metal chalcogenides by Lewis acid-base chemistry.

    PubMed

    Lei, Sidong; Wang, Xifan; Li, Bo; Kang, Jiahao; He, Yongmin; George, Antony; Ge, Liehui; Gong, Yongji; Dong, Pei; Jin, Zehua; Brunetto, Gustavo; Chen, Weibing; Lin, Zuan-Tao; Baines, Robert; Galvão, Douglas S; Lou, Jun; Barrera, Enrique; Banerjee, Kaustav; Vajtai, Robert; Ajayan, Pulickel

    2016-05-01

    Precise control of the electronic surface states of two-dimensional (2D) materials could improve their versatility and widen their applicability in electronics and sensing. To this end, chemical surface functionalization has been used to adjust the electronic properties of 2D materials. So far, however, chemical functionalization has relied on lattice defects and physisorption methods that inevitably modify the topological characteristics of the atomic layers. Here we make use of the lone pair electrons found in most of 2D metal chalcogenides and report a functionalization method via a Lewis acid-base reaction that does not alter the host structure. Atomic layers of n-type InSe react with Ti(4+) to form planar p-type [Ti(4+)n(InSe)] coordination complexes. Using this strategy, we fabricate planar p-n junctions on 2D InSe with improved rectification and photovoltaic properties, without requiring heterostructure growth procedures or device fabrication processes. We also show that this functionalization approach works with other Lewis acids (such as B(3+), Al(3+) and Sn(4+)) and can be applied to other 2D materials (for example MoS2, MoSe2). Finally, we show that it is possible to use Lewis acid-base chemistry as a bridge to connect molecules to 2D atomic layers and fabricate a proof-of-principle dye-sensitized photosensing device. PMID:26828848

  14. Gas-phase chemistry of transition-metal ions with alkanes: do initial electrostatic interaction control final product distributions

    SciTech Connect

    Hankinson, D.J.; Allison, J.

    1987-09-24

    There are features of the dynamics of gas-phase ion/molecule reactions that make them unique when compared to neutral/neutral reactions and solution processes. Exceedingly rich and complex chemistry can be observed in gas-phase systems in which a reactant is charged, due, in part, to the relatively long lifetime of the ion/molecule complex that is initially formed. Here possible correlations between final reaction products and geometry-specific complexes that are initially formed are discussed. The chemistry under study is that for univalent first-row transition-metal ions with n-butane, in which cleavage of C-H and C-C bonds is observed for some metals.

  15. Investigation of organometallic reaction mechanisms with one and two dimensional vibrational spectroscopy

    SciTech Connect

    Cahoon, James Francis

    2008-12-01

    One and two dimensional time-resolved vibrational spectroscopy has been used to investigate the elementary reactions of several prototypical organometallic complexes in room temperature solution. The electron transfer and ligand substitution reactions of photogenerated 17-electron organometallic radicals CpW(CO)3 and CpFe(CO)2 have been examined with one dimensional spectroscopy on the picosecond through microsecond time-scales, revealing the importance of caging effects and odd-electron intermediates in these reactions. Similarly, an investigation of the photophysics of the simple Fischer carbene complex Cr(CO)5[CMe(OMe)] showed that this class of molecule undergoes an unusual molecular rearrangement on the picosecond time-scale, briefly forming a metal-ketene complex. Although time-resolved spectroscopy has long been used for these types of photoinitiated reactions, the advent of two dimensional vibrational spectroscopy (2D-IR) opens the possibility to examine the ultrafast dynamics of molecules under thermal equilibrium conditions. Using this method, the picosecond fluxional rearrangements of the model metal carbonyl Fe(CO)5 have been examined, revealing the mechanism, time-scale, and transition state of the fluxional reaction. The success of this experiment demonstrates that 2D-IR is a powerful technique to examine the thermally-driven, ultrafast rearrangements of organometallic molecules in solution.

  16. A comprehensive review on biosorption of heavy metals by algal biomass: materials, performances, chemistry, and modeling simulation tools.

    PubMed

    He, Jinsong; Chen, J Paul

    2014-05-01

    Heavy metals contamination has become a global issue of concern due to their higher toxicities, nature of non-biodegradability, high capabilities in bioaccumulation in human body and food chain, and carcinogenicities to humans. A series of researches demonstrate that biosorption is a promising technology for removal of heavy metals from aqueous solutions. Algae serve as good biosorbents due to their abundance in seawater and fresh water, cost-effectiveness, reusability and high metal sorption capacities. This article provides a comprehensive review of recent findings on performances, applications and chemistry of algae (e.g., brown, green and red algae, modified algae and the derivatives) for sequestration of heavy metals. Biosorption kinetics and equilibrium models are reviewed. The mechanisms for biosorption are presented. Biosorption is a complicated process involving ion-exchange, complexation and coordination. Finally the theoretical simulation tools for biosorption equilibrium and kinetics are presented so that the readers can use them for further studies. PMID:24630371

  17. The performance of semilocal and hybrid density functionals in 3d transition-metal chemistry

    NASA Astrophysics Data System (ADS)

    Furche, Filipp; Perdew, John P.

    2006-01-01

    We investigate the performance of contemporary semilocal and hybrid density functionals for bond energetics, structures, dipole moments, and harmonic frequencies of 3d transition-metal (TM) compounds by comparison with gas-phase experiments. Special attention is given to the nonempirical metageneralized gradient approximation (meta-GGA) of Tao, Perdew, Staroverov, and Scuseria (TPSS) [Phys. Rev. Lett. 91, 146401 (2003)], which has been implemented in TURBOMOLE for the present work. Trends and error patterns for classes of homologous compounds are analyzed, including dimers, monohydrides, mononitrides, monoxides, monofluorides, polyatomic oxides and halogenides, carbonyls, and complexes with organic π ligands such as benzene and cyclopentadienyl. Weakly bound systems such as Ca2, Mn2, and Zn2 are discussed. We propose a reference set of reaction energies for benchmark purposes. Our all-electron results with quadruple zeta valence basis sets validate semilocal density-functional theory as the workhorse of computational TM chemistry. Typical errors in bond energies are substantially larger than in (organic) main group chemistry, however. The Becke-Perdew'86 [Phys. Rev. A 38, 3098 (1988); Phys. Rev. B 33, 8822 (1986)] GGA and the TPSS meta-GGA have the best price/performance ratio, while the TPSS hybrid functional achieves a slightly lower mean absolute error in bond energies. The popular Becke three-parameter hybrid B3LYP underbinds significantly and tends to overestimate bond distances; we give a possible explanation for this. We further show that hybrid mixing does not reduce the width of the error distribution on our reference set. The error of a functional for the s-d transfer energy of a TM atom does not predict its error for TM bond energies and bond lengths. For semilocal functionals, self-interaction error in one- and three-electron bonds appears to be a major source of error in TM reaction energies. Nevertheless, TPSS predicts the correct ground

  18. Use of column V alkyls in organometallic vapor phase epitaxy (OMVPE)

    NASA Technical Reports Server (NTRS)

    Ludowise, M. J.; Cooper, C. B., III

    1982-01-01

    The use of the column V-trialkyls trimethylarsenic (TMAs) and trimethylantimony (TMSb) for the organometallic vapor phase epitaxy (OM-VPE) of III-V compound semiconductors is reviewed. A general discussion of the interaction chemistry of common Group III and Group V reactants is presented. The practical application of TMSb and TMAs for OM-VPE is demonstrated using the growth of GaSb, GaAs(1-y)Sb(y), Al(x)Ga(1-x)Sb, and Ga(1-x)In(x)As as examples.

  19. Cytotoxic properties of a new organometallic platinum(II) complex and its gold(I) heterobimetallic derivatives.

    PubMed

    Serratrice, Maria; Maiore, Laura; Zucca, Antonio; Stoccoro, Sergio; Landini, Ida; Mini, Enrico; Massai, Lara; Ferraro, Giarita; Merlino, Antonello; Messori, Luigi; Cinellu, Maria Agostina

    2016-01-14

    A novel platinum(ii) organometallic complex, [Pt(pbi)(Me)(DMSO)], bearing the 2-(2'-pyridyl)-benzimidazole (pbiH) ligand, was synthesized and fully characterized. Interestingly, the reaction of this organometallic platinum(ii) complex with two distinct gold(i) phosphane compounds afforded the corresponding heterobimetallic derivatives with the pbi ligand bridging the two metal centers. The antiproliferative properties in vitro of [Pt(pbi)(Me)(DMSO)] and its gold(i) derivatives as well as those of the known coordination platinum(ii) and palladium(ii) complexes with the same ligand, of the general formula [MCl2(pbiH)], were comparatively evaluated against A2780 cancer cells, either sensitive or resistant to cisplatin. A superior biological activity of the organometallic compound clearly emerged compared to the corresponding platinum(ii) complex; the antiproliferative effects are further enhanced upon attaching the gold(i) triphenylphosphine moiety to the organometallic Pt compound. Remarkably, these novel metal species are able to overcome nearly complete resistance to cisplatin. Significant mechanistic insight into the study compounds was gained after investigating their reactions with a few representative biomolecules by electrospray mass spectrometry and X-ray crystallography. The obtained results are comprehensively discussed. PMID:26609781

  20. The extreme chemistry of multiple stellar populations in the metal-poor globular cluster NGC 4833

    NASA Astrophysics Data System (ADS)

    Carretta, E.; Bragaglia, A.; Gratton, R. G.; D'Orazi, V.; Lucatello, S.; Momany, Y.; Sollima, A.; Bellazzini, M.; Catanzaro, G.; Leone, F.

    2014-04-01

    Our FLAMES survey of Na-O anticorrelation in globular clusters (GCs) is extended to NGC 4833, a metal-poor GC with a long blue tail on the horizontal branch (HB). We present the abundance analysis for a large sample of 78 red giants based on UVES and GIRAFFE spectra acquired at the ESO-VLT. We derived abundances of Na, O, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Ba, La, and Nd. This is the first extensive study of this cluster from high resolution spectroscopy. On the scale of our survey, the metallicity of NGC 4833 is [Fe/H] = -2.015 ± 0.004 ± 0.084 dex (rms = 0.014 dex) from 12 stars observed with UVES, where the first error is from statistics and the second one refers to the systematic effects. The iron abundance in NGC 4833 is homogeneous at better than 6%. On the other hand, the light elements involved in proton-capture reactions at high temperature show the large star-to-star variations observed in almost all GCs studied so far. The Na-O anticorrelation in NGC 4833 is quite extended, as expected from the high temperatures reached by stars on the HB, and NGC 4833 contains a conspicuous fraction of stars with extreme [O/Na] ratios. More striking is the finding that large star-to-star variations are also seen for Mg, which spans a range of more than 0.5 dex in this GC. Depletions in Mg are correlated to the abundances of O and anti-correlated with Na, Al, and Si abundances. This pattern suggests the action of nuclear processing at unusually high temperatures, producing the extreme chemistry observed in the stellar generations of NGC 4833. These extreme changes are also seen in giants of the much more massive GCs M 54 and ω Cen, and our conclusion is that NGC 4833 has probably lost a conspicuous fraction of its original mass due to bulge shocking, as also indicated by its orbit. Based on observations collected at ESO telescopes under programmes 083.D-0208 and 68.D-0265.Full Tables 2, 6-11 are only available at the CDS via anonymous ftp to http

  1. Environmental Chemistry as Focus in the Undergraduate Curriculum

    NASA Astrophysics Data System (ADS)

    Chittenden, D. M.; Draganjac, M. E.; Wyatt, W. V.

    1995-10-01

    Several of the Arkansas State University chemistry faculty have elected to make environmental chemistry a focus of the laboratory experience to teach basic principles in instrumentation, physical chemistry, and inorganic chemistry courses. Additionally, in the undergraduate research laboratory required for a BS degree, they have mentored students in environmentally relevant projects. The instrumentation involved in these undergraduate experiences were the Varian Spectra250+ with GTA-97 graphite furnace atomic absorption (GFAA) spectrometer and the Seiko TG/DTA320 Thermal Analyzer. TGA methods are currently used in physical chemistry and inorganic chemistry as stand-alone experiments to introduce the technique to the students. In the physical chemistry laboratory, students use the TGA curve to explain mass loss and predict final product. Samples in this initial year included CuSO4(5 hydrate), FeSO4(7 hydrate), CaC2O4(2 hydrate), and metal carbonates; the behavior of all these compounds is well documented. See figure. Students in the inorganic chemistry laboratory were required to determine the number of waters of hydration, and explain decomposition including the thermicity of the process. Currently, an integrated inorganic lab experience is being developed based on the chemistry of selected metal polysulfide complexes (environmentally important as models for hydrodesulfurization catalysts). The TGA/DTA methods will be used to study the decomposition of the polysulfide. The decomposition product will be further characterized by powder X-ray diffraction techniques. The TGA/DTA has been used in Special Problems in Chemistry--the research experience--to study the thermal stability of an organometallic polymer semi-conductor and to study the vapor transport of chromium oxides in the Cr/O/H2O system. The GFAA became fully operational as the instrumentation course was beginning in the fall of 1994. The graphite furnace mode was demonstrated to the Instrumentation

  2. Lead toxicity to Lemna minor predicted using a metal speciation chemistry approach.

    PubMed

    Antunes, Paula M C; Kreager, Nancy J

    2014-10-01

    In the present study, predictive measures for Pb toxicity and Lemna minor were developed from bioassays with 7 surface waters having varied chemistries (0.5-12.5 mg/L dissolved organic carbon, pH of 5.4-8.3, and water hardness of 8-266 mg/L CaCO3 ). As expected based on water quality, 10%, 20%, and 50% inhibitory concentration (IC10, IC20, and IC50, respectively) values expressed as percent net root elongation (%NRE) varied widely (e.g., IC20s ranging from 306 nM to >6920 nM total dissolved Pb), with unbounded values limited by Pb solubility. In considering chemical speciation, %NRE variability was better explained when both Pb hydroxides and the free lead ion were defined as bioavailable (i.e., f{OH} ) and colloidal Fe(III)(OH)3 precipitates were permitted to form and sorb metals (using FeOx as the binding phase). Although cause and effect could not be established because of covariance with alkalinity (p = 0.08), water hardness correlated strongly (r(2)  = 0.998, p < 0.0001) with the concentration of total Pb in true solution ([Pb]T_True solution ). Using these correlations as the basis for predictions (i.e., [Pb]T_True solution vs water hardness and %NRE vs f{OH} ), IC20 and IC50 values produced were within a factor of 2.9 times and 2.2 times those measured, respectively. The results provide much needed effect data for L. minor and highlight the importance of chemical speciation in Pb-based risk assessments for aquatic macrophytes. PMID:25044009

  3. Influence of soil chemistry on metal and bioessential element concentrations in nymphal and adult periodical cicadas (Magicicada spp.)

    USGS Publications Warehouse

    Robinson, G.R., Jr.; Sibrell, P.L.; Boughton, C.J.; Yang, L.H.

    2007-01-01

    Metal and bioessential element concentrations were measured in three species of 17-year periodical cicadas (Magicicada spp.) to determine how cicada tissue chemistry is affected by soil chemistry, measure the bioavailability of metals from both uncontaminated and lead-arsenate-pesticide contaminated soils, and assess the potential risks of observed metal contamination for wildlife. Periodical cicada nymphs feed on root xylem fluids for 13 or 17??years of underground development. The nymphs then emerge synchronously at high densities, before leaving their nymphal keratin exoskeleton and molting into their adult form. Cicadas are an important food source for birds and animals during emergence events, and influence nutrient cycles in woodland ecosystems. Nymphal exoskeletons and whole adult cicadas were sampled in Clarke and Frederick Counties, Virginia and Berkeley and Jefferson Counties, West Virginia during the Brood X emergence in May and June, 2004. Elements, such as Al, Fe, and Pb, are strongly enriched in the nymphal exoskeleton relative to the adult body; Cu and Zn are enriched in bodies. Concentrations of Fe and Pb, when normalized to relatively inert soil constituents such as Al and Ce, are similar in both the molt exoskeleton and their host soil, implying that passive assimilation through prolonged soil contact (adhesion or adsorption) might control these metal concentrations. Normalized concentrations of bioessential elements, such as S, P, K, Ca, Mn, Cu, Zn, and Mo, and chalcophile (sulfur-loving) elements, such as As, Se, and Au, indicate strong enrichment in cicada tissues relative to soil, implying selective absorption and retention by xylem fluids, the cicada nymphs themselves, or both. Element enrichment patterns in cicada tissues are similar to enrichment patterns observed in xylem fluids from tree roots. Chalcophile elements and heavy metals accumulate in keratin-rich tissues and may bind to sulfhydryl groups. Metal concentrations in the nymphal

  4. Synthesis and Small Molecule Exchange Studies of a Magnesium Bisformate Metal-Organic Framework: An Experiment in Host-Guest Chemistry for the Undergraduate Laboratory

    ERIC Educational Resources Information Center

    Rood, Jeffrey A.; Henderson, Kenneth W.

    2013-01-01

    concepts of host-guest chemistry and size exclusion in porous metal-organic frameworks (MOFs). The experiment has been successfully carried out in both introductory and advanced-level inorganic chemistry laboratories. Students synthesized the porous MOF, alpha-Mg[subscript…

  5. Exploration geochemical technique for the determination of preconcentrated organometallic halides by ICP-AES

    USGS Publications Warehouse

    Motooka, J.M.

    1988-01-01

    An atomic absorption extraction technique which is widely used in geochemical exploration for the determination of Ag, As, Au, Bi, Cd, Cu, Mo, Pb, Sb, and Zn has been modified and adapted to a simultaneous inductively coupled plasma-atomic emission instrument. the experimental and operating parameters are described for the preconcentration of the metals into their organometallic halides and for the determination of the metals. Lower limits of determination are equal to or improved over those for flame atomic absorption (except Au) and ICP results are very similar to the accepted AA values, with precision for the ICP data in excess of that necessary for exploration purposes.

  6. Metal-organic frameworks for analytical chemistry: from sample collection to chromatographic separation.

    PubMed

    Gu, Zhi-Yuan; Yang, Cheng-Xiong; Chang, Na; Yan, Xiu-Ping

    2012-05-15

    In modern analytical chemistry researchers pursue novel materials to meet analytical challenges such as improvements in sensitivity, selectivity, and detection limit. Metal-organic frameworks (MOFs) are an emerging class of microporous materials, and their unusual properties such as high surface area, good thermal stability, uniform structured nanoscale cavities, and the availability of in-pore functionality and outer-surface modification are attractive for diverse analytical applications. This Account summarizes our research on the analytical applications of MOFs ranging from sampling to chromatographic separation. MOFs have been either directly used or engineered to meet the demands of various analytical applications. Bulk MOFs with microsized crystals are convenient sorbents for direct application to in-field sampling and solid-phase extraction. Quartz tubes packed with MOF-5 have shown excellent stability, adsorption efficiency, and reproducibility for in-field sampling and trapping of atmospheric formaldehyde. The 2D copper(II) isonicotinate packed microcolumn has demonstrated large enhancement factors and good shape- and size-selectivity when applied to on-line solid-phase extraction of polycyclic aromatic hydrocarbons in water samples. We have explored the molecular sieving effect of MOFs for the efficient enrichment of peptides with simultaneous exclusion of proteins from biological fluids. These results show promise for the future of MOFs in peptidomics research. Moreover, nanosized MOFs and engineered thin films of MOFs are promising materials as novel coatings for solid-phase microextraction. We have developed an in situ hydrothermal growth approach to fabricate thin films of MOF-199 on etched stainless steel wire for solid-phase microextraction of volatile benzene homologues with large enhancement factors and wide linearity. Their high thermal stability and easy-to-engineer nanocrystals make MOFs attractive as new stationary phases to fabricate MOF

  7. Electron configuration and correlation effects in organometallic molecules from constraint density functional theory

    NASA Astrophysics Data System (ADS)

    Nawa, Kenji; Nakamura, Kohji; Akiyama, Toru; Ito, Tomonori; Weinert, Michael

    2015-03-01

    Interest in single organometallic molecule and that adsorbed on solid surfaces has rapidly increased because of possible novel applications. For molecules with transition metals (TMs), the d-electron configuration is an essential aspect of their electronic and magnetic properties, and correlation effects can not be excluded. Here, we investigate systematically the electron configuration and correlation effects for prototypical organometallic molecules of tridimensional metallocene (TMCp2) and planer phthalocyanine (TMPc). Calculations were carried out based on the constraint density functional theory (DFT) by using the full-potential linearized augmented plane wave method that incorporates an on-site Coulomb interaction correction + U . We find that these correlation effects play a key role in determining the ground state of the electron configuration for the organometallic molecules. The calculated ground states of TMCp2, where TM =Cr, Mn, Fe, Co, and Ni, obtained by constraint DFT with +U reproduce the experimentally determined structures of 3E2 g , 6A1 g , 1A1 g , 2E1 g , and 3A2 g , respectively. Results for the TMPc will be also presented.

  8. Chemistry of the Most Metal-poor Stars in the Bulge and the z ≳ 10 Universe

    NASA Astrophysics Data System (ADS)

    Casey, Andrew R.; Schlaufman, Kevin C.

    2015-08-01

    Metal-poor stars in the Milky Way are local relics of the epoch of the first stars and the first galaxies. However, a low metallicity does not prove that a star formed in this ancient era, as metal-poor stars form over a range of redshift in different environments. Theoretical models of Milky Way formation have shown that at constant metallicity, the oldest stars are those closest to the center of the Galaxy on the most tightly bound orbits. For that reason, the most metal-poor stars in the bulge of the Milky Way provide excellent tracers of the chemistry of the high-redshift universe. We report the dynamics and detailed chemical abundances of three stars in the bulge with [{Fe}/{{H}}]≲ -2.7, two of which are the most metal-poor stars in the bulge in the literature. We find that with the exception of scandium, all three stars follow the abundance trends identified previously for metal-poor halo stars. These three stars have the lowest [Sc ii/Fe] abundances yet seen in α-enhanced giant stars in the Galaxy. Moreover, all three stars are outliers in the otherwise tight [Sc ii/Fe]-[Ti ii/Fe] relation observed among metal-poor halo stars. Theoretical models predict that there is a 30% chance that at least one of these stars formed at z≳ 15, while there is a 70% chance that at least one formed at 10≲ z≲ 15. These observations imply that by z˜ 10, the progenitor galaxies of the Milky Way had both reached [{Fe}/{{H}}]˜ -3.0 and established the abundance pattern observed in extremely metal-poor stars. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  9. Synthesis and properties of novel, electroactive organometallic polymers

    SciTech Connect

    Not Available

    1987-01-01

    The object of this research is to synthesize a number of organometallic polymers based on 1,8-dimetallocenylnaphthalene (1) as a monomeric structural unit, and to examine the physical properties of these substances, especially their electrical conductance. In such polymers contiguous metallocene units are held face-to-face in a columnar array, so that conduction, in the partially oxidized material can in principal be achieved through {pi}-orbital interaction of neighboring metallocene units. The author has shown that low molecular weight polymers, based on 1 (M=Fe or Ru) can be prepared by palladium catalyzed coupling of ferrocenylzinc halides with 1,8-diiodonaphthalene, and now propose to define reaction conditions for the preparation of much higher molecular weight polymers. The synthesis of analogous polymers incorporating cobalt and nickel, through the use of cobaltocene and nickelocene in the coupling reaction, will also be examined. Other mixed metal polymeric systems, in which two transition metals alternate along the chain, may be preparable from 1,8-bis(cyclopentadienyl)naphthalene 3, recently synthesized in our laboratories. The preparation of 3 should also provide and opportunity for the synthesis of unique polymeric systems based on linear dimeric, trigonal trimeric and tetrahedral tetrameric cyclopentadienylmetal complexes. These syntheses will be examined. Finally, the application of the coupling-polymerization reaction to 1,4-dihalobenzenes will also be examined. 34 refs., 3 figs.

  10. Dominance of interface chemistry over the bulk properties in determining the electronic structure of epitaxial metal/perovskite oxide heterojunctions

    SciTech Connect

    Chambers, Scott A.; Du, Yingge; Gu, Meng; Droubay, Timothy C.; Hepplestone, Steven; Sushko, Petr

    2015-06-09

    We show that despite very similar crystallographic properties and work function values in the bulk, epitaxial Fe and Cr metallizations on Nb:SrTiO3(001) generate completely different heterojunction electronic properties. Cr is Ohmic whereas Fe forms a Schottky barrier with a barrier height of 0.50 eV. This contrast arises because of differences in interface chemistry. In contrast to Cr [Chambers, S. A. et al., Adv. Mater. 2013, 25, 4001.], Fe exhibits a +2 oxidation state and occupies Ti sites in the perovskite lattice, resulting in negligible charge transfer to Ti, upward band bending, and Schottky barrier formation. The differences between Cr and Fe are understood by performing first-principles calculations of the energetics of defect formation which corroborate the observed interface chemistry and structure.

  11. Transuranic organometallics: The next generation

    SciTech Connect

    Zwick, B.D.; Sattelberger, A.P.; Avens, L.R.

    1990-01-01

    Neptunium and plutonium metal react cleanly with 3/2 equiv. I{sub 2} in aprotic ligating solvents, L, such as tetrahydrofuran (THF), pyridine (Py), and dimethylsulfoxide (DMSO) to give the triiodide complexes as tetrasolvates, AnI{sub 3}(L){sub 4} (An = Np, L = THF (1)); An = Pu, L = THF (2a), Py (2b), and DMSO (2c). These triiodide complexes are convenient precursors to new transuranic compounds. Reaction of the triiodide complexes 1 and 2a hexane with 3 equiv. of sodium bis(trimethylsilyl)amide give the volatile, solvate-free tris(silylamide) complexes, An(N(SiMe{sub 3}){sub 2}){sub 3} (An = Np, 3; An = Pu, 4). The silylamide complexes 3 and 4 undergo rapid reaction in hexane upon stoichiometric addition of HO-2,6-(t-C{sub 4}H{sub 9}){sub 2}C{sub 6}H{sub 3} to give the aryl oxide complexes An(O-2,6-(t-C{sub 4}H{sub 9}){sub 2}C{sub 6}H{sub 3}){sub 3} (An = Np, 5; An = Pu, 6). Preliminary investigations suggest that the aryl oxide complexes 5 and 6 react with lithium bis(trimethylsilyl)methanide, Li{sup +} CH(SiMe{sub 3}){sub 2}, in hexane to give the homoleptic alkyl complexes An(CH(SiMe{sub 3}){sub 2}){sub 3} (An = Np, 7; An = Pu, 8). The homoleptic silylamide, aryl oxide, and alkyl complexes are the first to be reported for transuranic elements. 17 refs.

  12. A Titanium-Organic Framework as an Exemplar of Combining the Chemistry of Metal- and Covalent-Organic Frameworks.

    PubMed

    Nguyen, Ha L; Gándara, Felipe; Furukawa, Hiroyasu; Doan, Tan L H; Cordova, Kyle E; Yaghi, Omar M

    2016-04-01

    A crystalline material with a two-dimensional structure, termed metal-organic framework-901 (MOF-901), was prepared using a strategy that combines the chemistry of MOFs and covalent-organic frameworks (COFs). This strategy involves in situ generation of an amine-functionalized titanium oxo cluster, Ti6O6(OCH3)6(AB)6 (AB = 4-aminobenzoate), which was linked with benzene-1,4-dialdehyde using imine condensation reactions, typical of COFs. The crystal structure of MOF-901 is composed of hexagonal porous layers that are likely stacked in staggered conformation (hxl topology). This MOF represents the first example of combining metal cluster chemistry with dynamic organic covalent bond formation to give a new crystalline, extended framework of titanium metal, which is rarely used in MOFs. The incorporation of Ti(IV) units made MOF-901 useful in the photocatalyzed polymerization of methyl methacrylate (MMA). The resulting polyMMA product was obtained with a high-number-average molar mass (26 850 g mol(-1)) and low polydispersity index (1.6), which in many respects are better than those achieved by the commercially available photocatalyst (P-25 TiO2). Additionally, the catalyst can be isolated, reused, and recycled with no loss in performance. PMID:26998612

  13. The biological chemistry of the transition metal "transportome" of Cupriavidus metallidurans.

    PubMed

    Nies, Dietrich H

    2016-05-01

    This review tries to illuminate how the bacterium Cupriavidus metallidurans CH34 is able to allocate essential transition metal cations to their target proteins although these metals have similar charge-to-surface ratios and chemical features, exert toxic effects, compete with each other, and occur in the bacterial environment over a huge range of concentrations and speciations. Central to this ability is the "transportome", the totality of all interacting metal import and export systems, which, as an emergent feature, transforms the environmental metal content and speciation into the cellular metal mélange. In a kinetic flow equilibrium resulting from controlled uptake and efflux reactions, the periplasmic and cytoplasmic metal content is adjusted in a way that minimizes toxic effects. A central core function of the transportome is to shape the metal ion composition using high-rate and low-specificity reactions to avoid time and/or energy-requiring metal discrimination reactions. This core is augmented by metal-specific channels that may even deliver metals all the way from outside of the cell to the cytoplasm. This review begins with a description of the basic chemical features of transition metal cations and the biochemical consequences of these attributes, and which transition metals are available to C. metallidurans. It then illustrates how the environment influences the metal content and speciation, and how the transportome adjusts this metal content. It concludes with an outlook on the fate of metals in the cytoplasm. By generalization, insights coming from C. metallidurans shed light on multiple transition metal homoeostatic mechanisms in all kinds of bacteria including pathogenic species, where the "battle" for metals is an important part of the host-pathogen interaction. PMID:27065183

  14. Chemistry and thermal history of metal particles in Luna 20 soils.

    NASA Technical Reports Server (NTRS)

    Goldstein, J. I.; Blau, P. J.

    1973-01-01

    Individual metal particles from Luna 20 thin sections 521, 513 and 514 as well as several small metallic inclusions in silicate particles from Luna 20 thin sections 501 and 502 were examined using optical microscopy and the electron microprobe. All the metallic particles and inclusions analyzed are of meteoritic Co-Ni content as are most of the metallic particles from the Fra Mauro and the Apollo 16 highlands sites. It is proposed that most of the metal at these 3 sites had its origin in the meteoritic projectiles that bombarded and accumulated in the early lunar crust. It is apparent that the metallic particles and some of the metallic inclusions in the Luna 20 soil have been subjected to reheating on the moon and this process has removed any evidence of the original meteoritic microstructure of the metal.

  15. SYNTHESIS OF NEW WATER-SOLUBLE METAL-BINDING POLYMERS: COMBINATORIAL CHEMISTRY APPROACH

    EPA Science Inventory

    A variety of metals that require removal and concentration exist in DOE waste, ground, or process waters. These can include, for example, RCRA metals such as mercury in mixed waste, valuable metals such as copper in acid mine drainage, actinides in plutonium processing facilities...

  16. The corrosion behavior of Alloy 52 weld metal in cyclic hydrogenated and oxygenated water chemistry in high temperature aqueous environment

    NASA Astrophysics Data System (ADS)

    Xu, Jian; Shoji, Tetsuo

    2015-06-01

    The corrosion behavior of Alloy 52 weld metal in cyclic hydrogenated and oxygenated water chemistry in high temperature water is studied by in situ monitoring corrosion potential (Ecorr), contact electric resistance (CER) and electrochemical impedance measurements (EIS), and ex situ scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. The Ecorr and film resistance show large change when the environment is changed from hydrogenated water to oxygenated water and changeable with changing environment while the morphology and composition only show obvious distinction in the first cycle. The main factor controlling the electric/electrochemical properties of the oxide film is Ecorr.

  17. The chemistry of rhenium and tungsten porphyrin complexes in low oxidation states. Synthesis and characterization of rhenium and tungsten porphyrin dimers containing metal-metal multiple bonds

    SciTech Connect

    Collmann, J.P.; Garner, J.M.; Woo, L.K. )

    1989-10-11

    The coordination chemistry of rhenium and tungsten porphyrin complexes in low oxidation states is presented. W{sup IV}(Por)(Cl){sub 2}, W{sup II}(Por)(H{sub 5}C{sub 6}C{identical to}CC{sub 6}H{sub 5}) and W{sup II}(OEP)(PEt{sub 3}){sub 2} complexes (Por = 5,10,15,20-tetra(4-tolyl)porphyrin (TTP) or 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP) dianions) were found to be similar to the analogous molybdenum porphyrin complexes by spectroscopic and magnetic measurements. UV-visible and vibrational spectroscopies indicate that these oxidations occur at the metal-metal bond rather than the porphyrin ligand.

  18. Surface chemistry, microstructure and friction properties of some ferrous-base metallic glasses at temperatures to 750 C

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1982-01-01

    X-ray photoelectron spectroscopy analysis, transmission electron microscopy, diffraction studies, and sliding friction experiments were conducted with ferrous-base metallic glasses in sliding contact with aluminum oxide at temperatures from room to 750 C in a vacuum of 30 nPa. The results indicate that there is a significant temperature influence on the friction properties, surface chemistry, and microstructure of metallic glasses. The relative concentrations of the various constituents at the surface of the sputtered specimens were very different from the normal bulk compositions. Contaminants can come from the bulk of the material to the surface upon heating and impart boric oxide and silicon oxide at 350 C and boron nitride above 500 C. The coefficient of friction increased with increasing temperature to 350 C. Above 500 C the coefficient of friction decreased rapidly. The segregation of contaminants may be responsible for the friction behavior.

  19. Organometallic Complexes Anchored to Conductive Carbon for Electrocatalytic Oxidation of Methane at Low Temperature.

    PubMed

    Joglekar, Madhura; Nguyen, Vinh; Pylypenko, Svitlana; Ngo, Chilan; Li, Quanning; O'Reilly, Matthew E; Gray, Tristan S; Hubbard, William A; Gunnoe, T Brent; Herring, Andrew M; Trewyn, Brian G

    2016-01-13

    Low-temperature direct methane fuel cells (DMEFCs) offer the opportunity to substantially improve the efficiency of energy production from natural gas. This study focuses on the development of well-defined platinum organometallic complexes covalently anchored to ordered mesoporous carbon (OMC) for electrochemical oxidation of methane in a proton exchange membrane fuel cell at 80 °C. A maximum normalized power of 403 μW/mg Pt was obtained, which was 5 times higher than the power obtained from a modern commercial catalyst and 2 orders of magnitude greater than that from a Pt black catalyst. The observed differences in catalytic activities for oxidation of methane are linked to the chemistry of the tethered catalysts, determined by X-ray photoelectron spectroscopy. The chemistry/activity relationships demonstrate a tangible path for the design of electrocatalytic systems for C-H bond activation that afford superior performance in DMEFC for potential commercial applications. PMID:26492385

  20. The effects of metallicity, UV radiation and non-equilibrium chemistry in high-resolution simulations of galaxies

    NASA Astrophysics Data System (ADS)

    Richings, A. J.; Schaye, Joop

    2016-05-01

    We present a series of hydrodynamic simulations of isolated galaxies with stellar mass of 109 M⊙. The models use a resolution of 750 M⊙ per particle and include a treatment for the full non-equilibrium chemical evolution of ions and molecules (157 species in total), along with gas cooling rates computed self-consistently using the non-equilibrium abundances. We compare these to simulations evolved using cooling rates calculated assuming chemical (including ionization) equilibrium, and we consider a wide range of metallicities and UV radiation fields, including a local prescription for self-shielding by gas and dust. We find higher star formation rates and stronger outflows at higher metallicity and for weaker radiation fields, as gas can more easily cool to a cold (few hundred Kelvin) star-forming phase under such conditions. Contrary to variations in the metallicity and the radiation field, non-equilibrium chemistry generally has no strong effect on the total star formation rates or outflow properties. However, it is important for modelling molecular outflows. For example, the mass of H2 outflowing with velocities {>}50 {km} {s}^{-1} is enhanced by a factor ˜20 in non-equilibrium. We also compute the observable line emission from C II and CO. Both are stronger at higher metallicity, while C II and CO emission are higher for stronger and weaker radiation fields, respectively. We find that C II is generally unaffected by non-equilibrium chemistry. However, emission from CO varies by a factor of ˜2-4. This has implications for the mean XCO conversion factor between CO emission and H2 column density, which we find is lowered by up to a factor ˜2.3 in non-equilibrium, and for the fraction of CO-dark molecular gas.

  1. Chemistry and pharmacological properties of some natural and synthetic antioxidants for heavy metal toxicity.

    PubMed

    Flora, S J S; Shrivastava, Rupal; Mittal, Megha

    2013-01-01

    Heavy metals are known to cause oxidative deterioration of bio-molecules by initiating free radical mediated chain reaction resulting in lipid per-oxidation, protein oxidation and oxidation of nucleic acid like DNA and RNA. The development of effective dual functioning antioxidants, possessing both metal-chelating and free radical-scavenging properties should bring into play. Administration of natural and synthetic antioxidants like, quercetin, catechin, taurine, captopril, gallic acid, melatonin, N-acetyl cysteine, α- lipoic acid and others have been recognized in the disease prevention and clinical recovery against heavy metal intoxication. These antioxidants affect biological systems not only through direct quenching of free radicals but also via chelation of toxic metal(s). These antioxidants also, have the capacity to enhance cellular antioxidant defense mechanism by regenerating endogenous antioxidants, such as glutathione and vitamin C and E. They also influence cellular signaling and trigger redox sensitive regulatory pathways. The reactivity of antioxidants in protecting against heavy metal induced oxidative stress depends upon their structural properties, their partitioning abilities between hydrophilic and lipophilic environment and their hydrogen donation antioxidant properties. Herein, we review the structural, biochemical and pharmacological properties of selected antioxidants with particular reference to their ability to (i) chelate heavy metals from its complex (ii) ameliorate free radical (iii) terminate heavy metal induced free radical chain reaction (iv) regenerate endogenous antioxidants and, (v) excretion of metal without its redistribution. PMID:24206124

  2. Simulation and testing of a vertical organometallic vapor phase epitaxy reactor

    NASA Astrophysics Data System (ADS)

    Sani, R. A.; Barmawi, M.; Mindara, J. Y.

    1998-02-01

    The purpose of the study is to design a single wafer vertical organo-metallic vapor phase epitaxy (OMVPE) reactor which gives a uniform deposition around the symmetry axis. The vertical reactor under the consideration consist of a diffuser and a system of coaxial cylinders to laminarize the flow which may lead to a uniform deposition without rotating the susceptor. The simulation shows that for a susceptor with a radius of 2.5 cm, a uniformity can be achieved in a region of a radius of 2 cm within 1% for certain operating condition. The result is compared with the experimental measurement of TiO2 deposition from TTIP.

  3. Polyhydrides of Platinum Group Metals: Nonclassical Interactions and σ-Bond Activation Reactions.

    PubMed

    Esteruelas, Miguel A; López, Ana M; Oliván, Montserrat

    2016-08-10

    The preparation, structure, dynamic behavior in solution, and reactivity of polyhydride complexes of platinum group metals, described during the last three decades, are contextualized from both organometallic and coordination chemistry points of view. These compounds, which contain dihydrogen, elongated dihydrogen, compressed dihydride, and classical dihydride ligands promote the activation of B-H, C-H, Si-H, N-H, O-H, C-C, C-N, and C-F, among other σ-bonds. In this review, it is shown that, unlike other more mature areas, the chemistry of polyhydrides offers new exciting conceptual challenges and at the same time the possibility of interacting with other fields including the conversion and storage of regenerative energy, organic synthetic chemistry, drug design, and material science. This wide range of possible interactions foresees promising advances in the near future. PMID:27268136

  4. Benzene Adsorption on (110) Surfaces of Transition Metals: Role of van der Waals Interaction and Substrate Chemistry

    NASA Astrophysics Data System (ADS)

    Matos, Jeronimo; Yildirim, Handan; Kara, Abdelkader

    2014-03-01

    The characteristics of Benzene adsorption on metals and their alloy surfaces, and the interface features have been the subject of many experimental and theoretical studies. With the availability of the new vdW functionals, we revisit this organic molecule/metal system to assess the influence of vdW interactions on the adsorption as well as to examine the performance of these vdW functionals. We will present the adsorption geometries, adsorption energies and heights, the characteristics of interface electronic structure, and the charge transfer for Benzene adsorption on the (110) surfaces of seven transition metals; Au, Ag, Cu, Pd, Pt, Rh, and Ni. The calculations are carried out using PBE and vdW-DF family functionals implemented in the VASP package. We will provide comparisons with the available experimental and theoretical studies on the adsorption geometries and energies, and the effect introduced by varying surface chemistries. We will also provide comparisons with the recent study for Benzene adsorption on the (111) surfaces of the same metal substrates . This work is funded by the U.S. Department of Energy Basic Energy Science under Contract No DE-FG02-11ER16243.

  5. Influences of Mn(II) and V(IV) on Bacterial Surface Chemistry and Metal Reactivity

    NASA Astrophysics Data System (ADS)

    French, S.; Fakra, S.; Glasauer, S.

    2009-05-01

    Microorganisms in terrestrial and marine environments are typically bathed in solutions that contain a range of metal ions, toxic and beneficial. Bacteria such as Shewanella putrefaciens CN32 are metabolically versatile in their respiration, and the reductive dissolution of widely dispersed metals such as Fe(III), Mn(IV), or V(V) can present unique challenges if nearby bodies of water are used for irrigation or drinking. In redox transition zones, dissimilatory metal reduction (DMR) by bacteria can lead to generation of high concentrations of soluble metals. It has been shown that metals will associate with negatively charged bacterial membranes, and the mechanisms of metal reduction are well defined for many species of bacteria. The interaction of metals with the cell wall during DMR is, however, not well documented; very little is known about the interaction of respired transition metals with membrane lipids. Furthermore, bacterial surfaces tend to change in response to their immediate environments. Variations in conditions such as oxygen or metal presence may affect surface component composition, including availability of metal reactive sites. Our research seeks to characterize the biochemical nature of metal-membrane interactions, as well as identify the unique changes at the cell surface that arise as a result of metal presence in their environments. We have utilized scanning transmission X-ray microscopy (STXM) to examine the dynamics of soluble Mn(II) and V(IV) interactions with purified bacterial membranes rather than whole cells. This prevents intracellular interferences, and allows for near edge X-ray absorption fine structure (NEXAFS) spectroscopic analyses of cell surface and surface-associated components. NEXAFS spectra for carbon, nitrogen, and oxygen edges indicate that Mn(II) and V(IV) induce biological modifications of the cell membrane in both aerobic and anaerobic conditions. These changes depend not only on the metal, but also on the presence of

  6. Switching on Elusive Organometallic Mechanisms with Photoredox Catalysis

    PubMed Central

    Terrett, Jack A.; Cuthbertson, James D.; Shurtleff, Valerie W.; MacMillan, David W. C.

    2015-01-01

    Transition metal-catalyzed cross-coupling reactions have become one of the most utilized carbon–carbon and carbon–heteroatom bond-forming reactions in chemical synthesis. More recently, nickel catalysis has been shown to participate in a wide variety of C–C bond forming reactions, most notably Negishi, Suzuki–Miyaura, Stille, Kumada, and Hiyama couplings1,2. Despite the tremendous advances in C–C fragment couplings, the ability to forge C–O bonds in a general fashion via nickel catalysis has been largely unsuccessful. The challenge for nickel-mediated alcohol couplings has been the mechanistic requirement for the critical C–O bond forming step (formally known as the reductive elimination step) to occur via a Ni(III) alkoxide intermediate. In this manuscript, we demonstrate that visible light-excited photoredox catalysts can modulate the preferred oxidation states of nickel alkoxides in an operative catalytic cycle, thereby providing transient access to Ni(III) species that readily participate in reductive elimination. Using this synergistic merger of photoredox and nickel catalysis, we have developed a highly efficient and general carbon–oxygen coupling reaction using abundant alcohols and aryl bromides. More significantly, we have developed a general strategy to “switch on” important yet elusive organometallic mechanisms via oxidation state modulations using only weak light and single-electron transfer (SET) catalysts. PMID:26266976

  7. High-sensitivity molecular organometallic resist for EUV (MORE)

    NASA Astrophysics Data System (ADS)

    Passarelli, James; Murphy, Michael; Del Re, Ryan; Sortland, Miriam; Dousharm, Levi; Vockenhuber, Michaela; Ekinci, Yasin; Neisser, Mark; Freedman, Daniel A.; Brainard, Robert L.

    2015-03-01

    We have developed organometallic carboxylate compounds [RnM(O2CR')2] capable of acting as negativetone EUV resists. Overall, the best and fastest resists contain antimony, are pentavalent and the carboxylate group contains a polymerizable olefin (e.g. acrylate, methacrylate or styrenecarboxylate). Evidence suggests that high sensitivity is achieved through the polymerization of olefins in the exposed region. We have performed a systematic sensitivity study of molecules of the type RnM(O2CR')2 where we have studied seven R groups, four main group metals (M), and three polymerizable carboxylate groups (O2CR'). We found that the greatest predictor of sensitivity of the RnSb(O2CR')2 resists is their level of polymerizable olefins. We mathematically define the polymerizable olefin loading (POL) as the ratio of the number of olefins vs. the number of non-hydrogen atoms. Linear and log plots of Emax vs. POL for a variety of molecules of the type R3Sb(O2CR')2 lend insight into the behaviour of these resists.

  8. Switching on elusive organometallic mechanisms with photoredox catalysis.

    PubMed

    Terrett, Jack A; Cuthbertson, James D; Shurtleff, Valerie W; MacMillan, David W C

    2015-08-20

    Transition-metal-catalysed cross-coupling reactions have become one of the most used carbon-carbon and carbon-heteroatom bond-forming reactions in chemical synthesis. Recently, nickel catalysis has been shown to participate in a wide variety of C-C bond-forming reactions, most notably Negishi, Suzuki-Miyaura, Stille, Kumada and Hiyama couplings. Despite the tremendous advances in C-C fragment couplings, the ability to forge C-O bonds in a general fashion via nickel catalysis has been largely unsuccessful. The challenge for nickel-mediated alcohol couplings has been the mechanistic requirement for the critical C-O bond-forming step (formally known as the reductive elimination step) to occur via a Ni(III) alkoxide intermediate. Here we demonstrate that visible-light-excited photoredox catalysts can modulate the preferred oxidation states of nickel alkoxides in an operative catalytic cycle, thereby providing transient access to Ni(III) species that readily participate in reductive elimination. Using this synergistic merger of photoredox and nickel catalysis, we have developed a highly efficient and general carbon-oxygen coupling reaction using abundant alcohols and aryl bromides. More notably, we have developed a general strategy to 'switch on' important yet elusive organometallic mechanisms via oxidation state modulations using only weak light and single-electron-transfer catalysts. PMID:26266976

  9. Coordination of dibensothiophenes and corannulenes to organometallic ruthenium (II) fragments

    SciTech Connect

    Vecchi, Paul Anthony

    2005-05-01

    This dissertation contains five papers in the format required for journal publication which describe (in part) my research accomplishments as a graduate student at Iowa State University. This work can be broadly categorized as the binding of weakly-coordinating ligands to cationic organometallic ruthenium fragments, and consists of two main areas of study. Chapters 2-4 are investigations into factors that influence the binding of dibenzothiophenes to {l_brace}Cp'Ru(CO){sub 2}{r_brace}{sup +} fragments, where Cp' = {eta}{sup 5}-C{sub 5}H{sub 5} (Cp) and {eta}{sup 5}-C{sub 5}Me{sub 5} (Cp*). Chapters 5 and 6 present the synthesis and structural characterization of complexes containing corannulene buckybowls that are {eta}{sup 6}-coordinated to {l_brace}Cp*Ru{r_brace}{sup +} fragments. The first chapter contains a brief description of the difficulty in lowering sulfur levels in diesel fuel along with a review of corannulene derivatives and their metal complexes. After the final paper is a short summary of the work herein (Chapter 7). Each chapter is independent, and all equations, schemes, figures, tables, references, and appendices in this dissertation pertain only to the chapter in which they appear.

  10. Organometallic carboxylate resists for extreme ultraviolet with high sensitivity

    NASA Astrophysics Data System (ADS)

    Passarelli, James; Murphy, Michael; Re, Ryan Del; Sortland, Miriam; Hotalen, Jodi; Dousharm, Levi; Fallica, Roberto; Ekinci, Yasin; Neisser, Mark; Freedman, Daniel A.; Brainard, Robert L.

    2015-10-01

    We have developed organometallic carboxylate compounds [RnM)] capable of acting as negative-tone extreme ultraviolet (EUV) resists. The most sensitive of these resists contain antimony, three R-groups and two carboxylate groups, and carboxylate groups with polymerizable olefins (e.g., acrylate, methacrylate, or styrenecarboxylate). Evidence suggests that high sensitivity is achieved through the polymerization of olefins in the exposed region. We have performed a systematic sensitivity study of the molecules of the type RnM) where we have studied seven R groups, four main group metals (M), and three polymerizable carboxylate groups (O2CR‧). The sensitivity of these resists was evaluated using Emax or dose to maximum resist thickness after exposure and development. We found that the greatest predictor of sensitivity of the RnSb) resists is their level of polymerizable olefins. We mathematically define the polymerizable olefin loading (POL) as the ratio of the number of olefins versus the number of nonhydrogen atoms. Linear and log plots of Emax versus POL for a variety of molecules of the type R3Sb) lend insight into the behavior of these resists.

  11. Record Multiphoton Absorption Cross-Sections by Dendrimer Organometalation.

    PubMed

    Simpson, Peter V; Watson, Laurance A; Barlow, Adam; Wang, Genmiao; Cifuentes, Marie P; Humphrey, Mark G

    2016-02-12

    Large increases in molecular two-photon absorption, the onset of measurable molecular three-photon absorption, and record molecular four-photon absorption in organic π-delocalizable frameworks are achieved by incorporation of bis(diphosphine)ruthenium units with alkynyl linkages. The resultant ruthenium alkynyl-containing dendrimers exhibit strong multiphoton absorption activity through the biological and telecommunications windows in the near-infrared region. The ligated ruthenium units significantly enhance solubility and introduce fully reversible redox switchability to the optical properties. Increasing the ruthenium content leads to substantial increases in multiphoton absorption properties without any loss of optical transparency. This significant improvement in multiphoton absorption performance by incorporation of the organometallic units into the organic π-framework is maintained when the relevant parameters are scaled by molecular weights or number of delocalizable π-electrons. The four-photon absorption cross-section of the most metal-rich dendrimer is an order of magnitude greater than the previous record value. PMID:26797727

  12. Switching on elusive organometallic mechanisms with photoredox catalysis

    NASA Astrophysics Data System (ADS)

    Terrett, Jack A.; Cuthbertson, James D.; Shurtleff, Valerie W.; MacMillan, David W. C.

    2015-08-01

    Transition-metal-catalysed cross-coupling reactions have become one of the most used carbon-carbon and carbon-heteroatom bond-forming reactions in chemical synthesis. Recently, nickel catalysis has been shown to participate in a wide variety of C-C bond-forming reactions, most notably Negishi, Suzuki-Miyaura, Stille, Kumada and Hiyama couplings. Despite the tremendous advances in C-C fragment couplings, the ability to forge C-O bonds in a general fashion via nickel catalysis has been largely unsuccessful. The challenge for nickel-mediated alcohol couplings has been the mechanistic requirement for the critical C-O bond-forming step (formally known as the reductive elimination step) to occur via a Ni(III) alkoxide intermediate. Here we demonstrate that visible-light-excited photoredox catalysts can modulate the preferred oxidation states of nickel alkoxides in an operative catalytic cycle, thereby providing transient access to Ni(III) species that readily participate in reductive elimination. Using this synergistic merger of photoredox and nickel catalysis, we have developed a highly efficient and general carbon-oxygen coupling reaction using abundant alcohols and aryl bromides. More notably, we have developed a general strategy to `switch on' important yet elusive organometallic mechanisms via oxidation state modulations using only weak light and single-electron-transfer catalysts.

  13. Difficulties in Interpreting Alkali Metal Trends at the Senior Chemistry Level.

    ERIC Educational Resources Information Center

    de Berg, Kevin

    2001-01-01

    Explores the reasons for the differences in alkali metal reactivity in water in terms of thermodynamics rather than ionization trends. Shows that differences in alkali metal reactivity with water are more appropriately explained in terms of the kinetics of the reactions. (MM)

  14. ALTERATION OF SOIL METAL CHEMISTRY AND PHYTOAVAILABILITY ASSOCIATED WITH BIOSOLIDS APPLICATION (ABSTRACT)

    EPA Science Inventory

    Biosolids are a complex mixture which contain both inorganic and organic adsorbents. Thus, addition of biosolids to soil not only increases the environmental loading of toxic metals (Cd, Zn, Cu, Ni, Pb, etc.) it alters the phytoavailability of these metals. This reduction in ph...

  15. PbO2: from semi-metal to transparent conducting oxide by defect chemistry control.

    PubMed

    Walsh, Aron; Kehoe, Aoife B; Temple, Douglas J; Watson, Graeme W; Scanlon, David O

    2013-01-18

    Lead dioxide has been studied for over 150 years as a component of the lead-acid battery. Based on first-principles calculations, we predict that by tuning the concentration of electrons in the material, through control of the defect chemistry, PbO(2) can be rendered from black to optically transparent, thus opening up applications in the field of optoelectronics. PMID:23205392

  16. Structural and Magnetic Diversity in Alkali-Metal Manganate Chemistry: Evaluating Donor and Alkali-Metal Effects in Co-complexation Processes.

    PubMed

    Uzelac, Marina; Borilovic, Ivana; Amores, Marco; Cadenbach, Thomas; Kennedy, Alan R; Aromí, Guillem; Hevia, Eva

    2016-03-24

    By exploring co-complexation reactions between the manganese alkyl Mn(CH2SiMe3)2 and the heavier alkali-metal alkyls M(CH2SiMe3) (M=Na, K) in a benzene/hexane solvent mixture and in some cases adding Lewis donors (bidentate TMEDA, 1,4-dioxane, and 1,4-diazabicyclo[2,2,2] octane (DABCO)) has produced a new family of alkali-metal tris(alkyl) manganates. The influences that the alkali metal and the donor solvent impose on the structures and magnetic properties of these ates have been assessed by a combination of X-ray, SQUID magnetization measurements, and EPR spectroscopy. These studies uncover a diverse structural chemistry ranging from discrete monomers [(TMEDA)2 MMn(CH2SiMe3)3] (M=Na, 3; M=K, 4) to dimers [{KMn(CH2SiMe3)3 ⋅C6 H6}2] (2) and [{NaMn(CH2SiMe3)3}2 (dioxane)7] (5); and to more complex supramolecular networks [{NaMn(CH2SiMe3)3}∞] (1) and [{Na2Mn2 (CH2SiMe3)6 (DABCO)2}∞] (7)). Interestingly, the identity of the alkali metal exerts a significant effect in the reactions of 1 and 2 with 1,4-dioxane, as 1 produces coordination adduct 5, while 2 forms heteroleptic [{(dioxane)6K2Mn2 (CH2SiMe3)4(O(CH2)2OCH=CH2)2}∞] (6) containing two alkoxide-vinyl anions resulting from α-metalation and ring opening of dioxane. Compounds 6 and 7, containing two spin carriers, exhibit antiferromagnetic coupling of their S=5/2 moments with varying intensity depending on the nature of the exchange pathways. PMID:26916525

  17. TRACE ELEMENT CHEMISTRY IN RESIDUAL-TREATED SOIL: KEY CONCEPTS AND METAL BIOAVAILABILITY

    EPA Science Inventory

    Trace element solubility and availability in land-applied residuals is governed by fundamental chemical reactions between metal constituents, soil, and residual components. Iron, aluminum, and manganese oxides; organic matter; and phosphates, carbonates, and sulfides are importan...

  18. A Bioanalytical Chemistry Experiment for Undergraduate Students: Biosensors Based on Metal Nanoparticles

    ERIC Educational Resources Information Center

    Niagi, John; Warner, John; Andreesco, Silvana

    2007-01-01

    The study describes the development of new biosensors based on metal nanoparticles because of its high surface area and large binding ability. The adopted procedure is extremely simple and versatile and can be used in various applications of electrochemistry.

  19. Transition metal complexes of phyllobilins - a new realm of bioinorganic chemistry.

    PubMed

    Li, Chengjie; Kräutler, Bernhard

    2015-06-14

    Natural cyclic tetrapyrroles feature outstanding capacity for binding transition metal ions, furnishing Nature with the important metallo-porphyrinoid 'Pigments of Life', such as heme, chlorophyll (Chl) and vitamin B12. In contrast, linear tetrapyrroles are not generally ascribed a biologically relevant ability for metal-binding. Indeed, when heme or Chl are degraded to natural linear tetrapyrroles, their central Fe- or Mg-ions are set free. Some linear tetrapyrroles are, however, effective multi-dentate ligands and their transition metal complexes have remarkable chemical properties. The focus of this short review is centred on such complexes of the linear tetrapyrroles derived from natural Chl-breakdown, called phyllobilins. These natural bilin-type compounds are massively produced in Nature and in highly visible processes. Colourless non-fluorescing Chl-catabolites (NCCs) and the related dioxobilin-type NCCs, which typically accumulate in leaves as 'final' products of Chl-breakdown, show low affinity for transition metal-ions. However, NCCs are oxidized in leaves to give less saturated coloured phyllobilins, such as yellow or pink Chl-catabolites (YCCs or PiCCs). YCCs and PiCCs are ligands for various biologically relevant transition metal-ions, such as Zn(ii)-, Ni(ii)- and Cu(ii)-ions. Complexation of Zn(ii)- and Cd(ii)-ions by the effectively tridentate PiCC produces blue metal-complexes that exhibit an intense red fluorescence, thus providing a tool for the sensitive detection of these metal ions. Outlined here are fundamental aspects of structure and metal coordination of phyllobilins, including a comparison with the corresponding properties of bilins. This knowledge may be valuable in the quest of finding possible biological roles of the phyllobilins. Thanks to their capacity for metal-ion coordination, phyllobilins could, e.g., be involved in heavy-metal transport and detoxification, and some of their metal-complexes could act as sensitizers for singlet

  20. Transition metal complexes of phyllobilins – a new realm of bioinorganic chemistry

    PubMed Central

    Li, Chengjie

    2015-01-01

    Natural cyclic tetrapyrroles feature outstanding capacity for binding transition metal ions, furnishing Nature with the important metallo-porphyrinoid ‘Pigments of Life’, such as heme, chlorophyll (Chl) and vitamin B12. In contrast, linear tetrapyrroles are not generally ascribed a biologically relevant ability for metal-binding. Indeed, when heme or Chl are degraded to natural linear tetrapyrroles, their central Fe- or Mg-ions are set free. Some linear tetrapyrroles are, however, effective multi-dentate ligands and their transition metal complexes have remarkable chemical properties. The focus of this short review is centred on such complexes of the linear tetrapyrroles derived from natural Chl-breakdown, called phyllobilins. These natural bilin-type compounds are massively produced in Nature and in highly visible processes. Colourless non-fluorescing Chl-catabolites (NCCs) and the related dioxobilin-type NCCs, which typically accumulate in leaves as ‘final’ products of Chl-breakdown, show low affinity for transition metal-ions. However, NCCs are oxidized in leaves to give less saturated coloured phyllobilins, such as yellow or pink Chl-catabolites (YCCs or PiCCs). YCCs and PiCCs are ligands for various biologically relevant transition metal-ions, such as Zn(ii)-, Ni(ii)- and Cu(ii)-ions. Complexation of Zn(ii)- and Cd(ii)-ions by the effectively tridentate PiCC produces blue metal-complexes that exhibit an intense red fluorescence, thus providing a tool for the sensitive detection of these metal ions. Outlined here are fundamental aspects of structure and metal coordination of phyllobilins, including a comparison with the corresponding properties of bilins. This knowledge may be valuable in the quest of finding possible biological roles of the phyllobilins. Thanks to their capacity for metal-ion coordination, phyllobilins could, e.g., be involved in heavy-metal transport and detoxification, and some of their metal-complexes could act as sensitizers for

  1. New chemistry for the growth of first-row transition metal films by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Klesko, Joseph Peter

    Thin films containing first-row transition metals are widely used in microelectronic, photovoltaic, catalytic, and surface-coating applications. In particular, metallic films are essential for interconnects and seed, barrier, and capping layers in integrated circuitry. Traditional vapor deposition methods for film growth include PVD, CVD, or the use of plasma. However, these techniques lack the requisite precision for film growth at the nanoscale, and thus, are increasingly inadequate for many current and future applications. By contrast, ALD is the favored approach for depositing films with absolute surface conformality and thickness control on 3D architectures and in high aspect ratio features. However, the low-temperature chemical reduction of most first-row transition metal cations to their zero-valent state is very challenging due to their negative electrochemical potentials. A lack of strongly-reducing coreagents has rendered the thermal ALD of metallic films an intractable problem for many elements. Additionally, several established ALD processes for metal films are plagued by low growth rates, impurity incorporation, poor nucleation, high surface roughness, or the need for hazardous coreagents. Finally, stoichiometric control of ternary films grown by ALD is rare, but increasingly important, with emerging applications for metal borate films in catalysis and lithium ion batteries. The research herein is focused toward the development of new ALD processes for the broader application of metal, metal oxide, and metal borate thin films to future nanoscale technologies. These processes display self-limited growth and support the facile nucleation of smooth, continuous, high-purity films. Bis(trimethylsilyl) six-membered rings are employed as strongly-reducing organic coreagents for the ALD of titanium and antimony metal films. Additionally, new processes are developed for the growth of high-purity, low-resistivity cobalt and nickel metal films by exploiting the

  2. Controlling Surface Chemistry of Gallium Liquid Metal Alloys to Enhance their Fluidic Properties

    NASA Astrophysics Data System (ADS)

    Ilyas, Nahid; Cumby, Brad; Cook, Alexander; Durstock, Michael; Tabor, Christopher; Materials; Manufacturing Directorate Team

    Gallium liquid metal alloys (GaLMAs) are one of the key components of emerging technologies in reconfigurable electronics, such as tunable radio frequency antennas and electronic switches. Reversible flow of GaLMA in microchannels of these types of devices is hindered by the instantaneous formation of its oxide skin in ambient environment. The oxide film sticks to most surfaces leaving unwanted metallic residues that can cause undesired electronic properties. In this report, residue-free reversible flow of a binary alloy of gallium (eutectic gallium indium) is demonstrated via two types of surface modifications where the oxide film is either protected by an organic thin film or chemically removed. An interface modification layer (alkyl phosphonic acids) was introduced into the microfluidic system to modify the liquid metal surface and protect its oxide layer. Alternatively, an ion exchange membrane was utilized as a 'sponge-like' channel material to store and slowly release small amounts of HCl to react with the surface oxide of the liquid metal. Characterization of these interfaces at molecular level by surface spectroscopy and microscopy provided with mechanistic details for the interfacial interactions between the liquid metal surface and the channel materials.

  3. Shape-Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?

    PubMed Central

    Xia, Younan; Xiong, Yujie; Lim, Byungkwon; Skrabalak, Sara E.

    2009-01-01

    Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. The aim of this article is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Toward the end of this article, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take. PMID:19053095

  4. Two Principles of Reticular Chemistry Uncovered in a Metal-Organic Framework of Heterotritopic Linkers and Infinite Secondary Building Units.

    PubMed

    Catarineu, Noelle R; Schoedel, Alexander; Urban, Philipp; Morla, Maureen B; Trickett, Christopher A; Yaghi, Omar M

    2016-08-31

    Structural diversity of metal-organic frameworks (MOFs) has been largely limited to linkers with at most two different types of coordinating groups. MOFs constructed from linkers with three or more nonidentical coordinating groups have not been explored. Here, we report a robust and porous crystalline MOF, Zn3(PBSP)2 or MOF-910, constructed from a novel linker PBSP (phenylyne-1-benzoate, 3-benzosemiquinonate, 5-oxidopyridine) bearing three distinct types of coordinative functionality. The MOF adopts a complex and previously unreported topology termed tto. Our study suggests that simple, symmetric linkers are not a necessity for formation of crystalline extended structures and that new, more complex topologies are attainable with irregular, heterotopic linkers. This work illustrates two principles of reticular chemistry: first, selectivity for helical over straight rod secondary building units (SBUs) is achievable with polyheterotopic linkers, and second, the pitch of the resulting helical SBUs may be fine-tuned based on the metrics of the polyheterotopic linker. PMID:27517606

  5. Modification of graphene chemistry for metal nanoparticle growth: the effect of substrate selection

    NASA Astrophysics Data System (ADS)

    Zaniewski, Anna; Nemanich, Robert

    2014-03-01

    Graphene and metal nanoparticle composites are a promising class of materials with unique electronic, optical, and chemical properties. In this work, graphene is used as a reducing surface to grow metal nanoparticles out of solution-based metal precursors. The nanoparticle formation is found to strongly depend upon the graphene substrate selection. The studied substrates include silicon oxide, silicon, lithium niobate, and copper. Our results indicate that the chemical properties of graphene depend upon this selection. For example, for the same reaction times and concentration, the reduction of gold chloride to gold nanoparticles on graphene/lithium niobate results in 3% nanoparticle coverage compared to 20% coverage on graphene/silicon and 60% on graphene/copper. This work is supported through the National Science Foundation under Grant # DMR-1206935 .

  6. Cyclopentadienyl-ruthenium(II) and iron(II) organometallic compounds with carbohydrate derivative ligands as good colorectal anticancer agents.

    PubMed

    Florindo, Pedro R; Pereira, Diane M; Borralho, Pedro M; Rodrigues, Cecília M P; Piedade, M F M; Fernandes, Ana C

    2015-05-28

    New ruthenium(II) and iron(II) organometallic compounds of general formula [(η(5)-C5H5)M(PP)Lc][PF6], bearing carbohydrate derivative ligands (Lc), were prepared and fully characterized and the crystal structures of five of those compounds were determined by X-ray diffraction studies. Cell viability of colon cancer HCT116 cell line was determined for a total of 23 organometallic compounds and SAR's data analysis within this library showed an interesting dependency of the cytotoxic activity on the carbohydrate moiety, linker, phosphane coligands, and metal center. More importantly, two compounds, 14Ru and 18Ru, matched oxaliplatin IC50 (0.45 μM), the standard metallodrug used in CC chemotherapeutics, and our leading compound 14Ru was shown to be significantly more cytotoxic than oxaliplatin to HCT116 cells, triggering higher levels of caspase-3 and -7 activity and apoptosis in a dose-dependent manner. PMID:25923600

  7. 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.

  8. Friction and surface chemistry of some ferrous-base metallic glasses

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1982-01-01

    The friction properties of some ferrous-base metallic glasses were measured both in argon and in vacuum to a temperature of 350 C. The alloy surfaces were also analyzed with X-ray photoelectron spectroscopy to identify the compounds and elements present on the surface. The results of the investigation indicate that even when the surfaces of the amorphous alloys, or metallic glasses, are atomically clean, bulk contaminants such as boric oxide and silicon dioxide diffuse to the surfaces. Friction measurements in both argon and vacuum indicate that the alloys exhibit higher coefficients of friction in the crystalline state than they do in the amorphous state.

  9. Coordination Chemistry of Cyclic Disilylated Germylenes and Stannylenes with Group 11 Metals

    PubMed Central

    2014-01-01

    Reactions of Et3P adducts of bissilylated germylenes and stannylenes with gold, silver, and copper cyanides led to cyanogermyl or -stannyl complexes of the respective metals. In the course of the reaction the phosphine moved to the metal, while the cyanide migrated to the low-coordinate group 14 element. The respective gold complexes were found to be monomeric, whereas the silver and copper complexes exhibited a tendency to dimerize in the solid state. Attempts to abstract the phosphine ligand with B(C6F5)3 led only to the formation of adducts with the borane coordinating to the cyanide nitrogen atom. PMID:25550678

  10. Transition metal catalysis in the mitochondria of living cells.

    PubMed

    Tomás-Gamasa, María; Martínez-Calvo, Miguel; Couceiro, José R; Mascareñas, José L

    2016-01-01

    The development of transition metal catalysts capable of promoting non-natural transformations within living cells can open significant new avenues in chemical and cell biology. Unfortunately, the complexity of the cell makes it extremely difficult to translate standard organometallic chemistry to living environments. Therefore, progress in this field has been very slow, and many challenges, including the possibility of localizing active metal catalysts into specific subcellular sites or organelles, remain to be addressed. Herein, we report a designed ruthenium complex that accumulates preferentially inside the mitochondria of mammalian cells, while keeping its ability to react with exogenous substrates in a bioorthogonal way. Importantly, we show that the subcellular catalytic activity can be used for the confined release of fluorophores, and even allows selective functional alterations in the mitochondria by the localized transformation of inert precursors into uncouplers of the membrane potential. PMID:27600651

  11. Oxidation chemistry of chloric acid in NOx/SOx and air toxic metal removal from gas streams

    SciTech Connect

    Kaczur, J.J.

    1996-12-31

    Chloric acid, HClO{sub 3}, is a new oxidizer which has recently been shown to be an effective agent in the simultaneous removal of NOx and/or SOx from combustion flue gases and various chemical processes, including nitrations and metal pickling. Aqueous chloric acid readily reacts with NO and SO{sub 2} even in dilute solutions at ambient temperatures. Chlorine dioxide, ClO{sub 2}, is formed as a chemical intermediate in the solution phase oxidation reactions. The oxidation by-products of NO include NO{sub 2} and nitric acid. The ClO{sub 2} generated from the solution phase reactions also participates in gas phase oxidation reactions with NO and NO{sub 2}. The combined solution phase and fast gas phase reaction chemistries provide the means for creating a new type of high performance NOx/SOx removal process. Wet scrubber based pilot plant tests have demonstrated up to 99% removal of NO. Additional recent research work has shown that chloric acid is an effective reagent for the removal of air toxic metals, such as elemental mercury, which are present in the waste gas output streams from incinerators, hydrogen from mercury cell chlor-alkali plants, and flue gases of coal-fired power plants. Work in this area is being conducted by Argonne National Laboratories and Olin. This paper discusses the oxidation chemistry of chloric acid and its unique solution and gas phase reactions with NO, SO{sub 2}, and air toxics in wet scrubber type process equipment. 32 refs., 16 figs., 5 tabs.

  12. HARNESSING THE CHEMISTRY OF CO2

    SciTech Connect

    Louie, Janis

    2010-05-11

    Our research program is broadly focused on activating CO{sub 2} through the use of organic and organometallic based catalysts. Some of our methods have centered on annulation reactions of unsaturated hydrocarbons (and carbonyl substrates) to provide a diverse array of carbocycles and heterocycles. We use a combination of catalyst discovery and optimization in conjunction with classical physical organic chemistry to elucidate the key mechanistic features of the cycloaddition reactions such that the next big advances in catalyst development can be made. Key to all of our cycloaddition reactions is the use of a sterically hindered, electron donating N heterocyclic carbene (NHC) ligand, namely IPr (or SIPr), in conjunction with a low valent nickel pre-catalyst. The efficacy of this ligand is two-fold: (1) the high {delta}-donating ability of the NHC increases the nucleophilicity of the metal center which thereby facilitates interaction with the electrophilic carbonyl and (2) the steric hindrance prevents an otherwise competitive side reaction involving only the alkyne substrate. Such a system has allowed for the facile cycloaddition to prepare highly functionalized pyrones, pyridones, pyrans, as well as novel carbocycles. Importantly, all reactions proceed under extremely mild conditions (room temperature, atmospheric pressures, and short reaction times), require only catalytic amounts of Ni/NHC and readily available starting materials, and afford annulated products in excellent yields. Our current focus revolves around understanding the fundamental processes that govern these cycloadditions such that the next big advance in the cyclization chemistry of CO{sub 2} can be made. Concurrent to our annulation chemistry is our investigation of the potential for imidazolylidenes to function as thermally-actuated CO{sub 2} sequestering and delivery agents.

  13. Shape, metal abundance, chemistry, and origin of chondrules in the Renazzo (CR) chondrite

    SciTech Connect

    Ebel, D.S.; Weisberg, M.K.; Hertz, J.; Campbell, A.J.

    2009-03-31

    We used synchrotron X-ray microtomography to image in 3-dimensions (3D) eight whole chondrules in a {approx}1 cm{sup 3} piece of the Renazzo (CR) chondrite at {approx}17 {micro}m per volume element (voxel) edge. We report the first volumetric (3D) measurement of metal/silicate ratios in chondrules and quantify indices of chondrule sphericity. Volumetric metal abundances in whole chondrules range from 1 to 37 volume % in 8 measured chondrules and by inspection in tomography data. We show that metal abundances and metal grain locations in individual chondrules cannot be reliably obtained from single random 2D sections. Samples were physically cut to intersect representative chondrules multiple times and to verify 3D data. Detailed 2D chemical analysis combined with 3D data yield highly variable whole-chondrule Mg/Si ratios with a supra-chondritic mean value, yet the chemically diverse, independently formed chondrules are mutually complementary in preserving chondritic (solar) Fe/Si ratios in the aggregate CR chondrite. These results are consistent with localized chondrule formation and rapid accretion resulting in chondrule + matrix aggregates (meteorite parent bodies) that preserve the bulk chondritic composition of source regions.

  14. 'Unconventional' coordination chemistry by metal chelating fragments in a metalloprotein active site.

    PubMed

    Martin, David P; Blachly, Patrick G; Marts, Amy R; Woodruff, Tessa M; de Oliveira, César A F; McCammon, J Andrew; Tierney, David L; Cohen, Seth M

    2014-04-01

    The binding of three closely related chelators: 5-hydroxy-2-methyl-4H-pyran-4-thione (allothiomaltol, ATM), 3-hydroxy-2-methyl-4H-pyran-4-thione (thiomaltol, TM), and 3-hydroxy-4H-pyran-4-thione (thiopyromeconic acid, TPMA) to the active site of human carbonic anhydrase II (hCAII) has been investigated. Two of these ligands display a monodentate mode of coordination to the active site Zn(2+) ion in hCAII that is not recapitulated in model complexes of the enzyme active site. This unprecedented binding mode in the hCAII-thiomaltol complex has been characterized by both X-ray crystallography and X-ray spectroscopy. In addition, the steric restrictions of the active site force the ligands into a 'flattened' mode of coordination compared with inorganic model complexes. This change in geometry has been shown by density functional computations to significantly decrease the strength of the metal-ligand binding. Collectively, these data demonstrate that the mode of binding by small metal-binding groups can be significantly influenced by the protein active site. Diminishing the strength of the metal-ligand bond results in unconventional modes of metal coordination not found in typical coordination compounds or even carefully engineered active site models, and understanding these effects is critical to the rational design of inhibitors that target clinically relevant metalloproteins. PMID:24635441

  15. Metal Based Synthetic Strategies and the Examination of Structure Determining Factors in Alkaline Earth Metal Compounds

    NASA Astrophysics Data System (ADS)

    Takahashi, Yuriko

    Last decades have witnessed a large expansion of the organometallic heavier alkaline earth metal species. However, continued growth of this promising area of chemistry has been slowed by severe restrictions and limitations in viable synthetic methodologies leading to difficulties in preparing and characterizing the target compounds. There is clearly a need for the further development of synthetic methodologies and detailed structure function analysis that will promote the further advancement of organoalkaline earth metal chemistry in applications as diverse as materials chemistry and catalysis. This thesis work greatly extends the synthetic options currently available towards organoalkaline earth metal species by introducing redox transmetallation protolysis (RTP), a reaction based on the readily available Ph3Bi as a non-toxic transmetallation agent. Based on a straightforward one-pot procedure and work-up, Ph3Bi based RTP presents a powerful synthetic alternative for the facile preparation of a large variety of heavy alkaline earth metal compounds. The second part of the thesis explores the effect of secondary non covalent interactions on the coordination chemistry as well as thermal properties of a series of novel alkali, alkaline earth, rare earth as well as heterobimetallic alkali/alkaline earth fluoroalkoxides. These compounds showcase the significance of non-covalent M···F-C and agostic interactions on metal stabilization and structural features, providing critical input on ligand design for the design of advanced metal organic vapor deposition (MOCVD) precursor materials. This work also showcases the impact of M···F-C interactions over M---co-ligand coordination, a critical precursor design element as well.

  16. NOBLE METAL CHEMISTRY AND HYDROGEN GENERATION DURING SIMULATED DWPF MELTER FEED PREPARATION

    SciTech Connect

    Koopman, D

    2008-06-25

    Simulations of the Defense Waste Processing Facility (DWPF) Chemical Processing Cell vessels were performed with the primary purpose of producing melter feeds for the beaded frit program plus obtaining samples of simulated slurries containing high concentrations of noble metals for off-site analytical studies for the hydrogen program. Eight pairs of 22-L simulations were performed of the Sludge Receipt and Adjustment Tank (SRAT) and Slurry Mix Evaporator (SME) cycles. These sixteen simulations did not contain mercury. Six pairs were trimmed with a single noble metal (Ag, Pd, Rh, or Ru). One pair had all four noble metals, and one pair had no noble metals. One supporting 4-L simulation was completed with Ru and Hg. Several other 4-L supporting tests with mercury have not yet been performed. This report covers the calculations performed on SRNL analytical and process data related to the noble metals and hydrogen generation. It was originally envisioned as a supporting document for the off-site analytical studies. Significant new findings were made, and many previous hypotheses and findings were given additional support as summarized below. The timing of hydrogen generation events was reproduced very well within each of the eight pairs of runs, e.g. the onset of hydrogen, peak in hydrogen, etc. occurred at nearly identical times. Peak generation rates and total SRAT masses of CO{sub 2} and oxides of nitrogen were reproduced well. Comparable measures for hydrogen were reproduced with more variability, but still reasonably well. The extent of the reproducibility of the results validates the conclusions that were drawn from the data.

  17. Bioorganometallic Chemistry and Malaria

    NASA Astrophysics Data System (ADS)

    Biot, Christophe; Dive, Daniel

    This chapter summarizes recent developments in the design, synthesis, and structure-activity relationship studies of organometallic antimalarials. It begins with a general introduction to malaria and the biology of the parasite Plasmodium falciparum, with a focus on the heme detoxification system. Then, a number of metal complexes from the literature are reported for their antiplasmodial activity. The second half of the chapter deals with the serendipitous discovery of ferroquine, its mechanism(s) of action, and the failure to induce a resistance. Last, but not least, we suggest that the bioorganometallic approach offers the potential for the design of novel therapeutic agents.

  18. Separation and Identification of a Mixture of Group 6 Transition-Metal Carbonyl Compounds Using GC-MS in the General Chemistry Curriculum

    ERIC Educational Resources Information Center

    Fong, Lawrence K.

    2004-01-01

    Students in the general chemistry course are advised to scrutinize data obtained by gas chromatograph (GC) for segregation, and mass spectroscopy (MS) for recognizing combination of group 6 transition-metal carbonyl compounds. The GC-MS method arouses students' interest, as it can be applied to real-world situations, such as the routine…

  19. "Click" Chemistry: Application of Copper Metal in Cu-Catalyzed Azomethine Imine-Alkyne Cycloadditions.

    PubMed

    Pušavec Kirar, Eva; Grošelj, Uroš; Mirri, Giorgio; Požgan, Franc; Strle, Gregor; Štefane, Bogdan; Jovanovski, Vasko; Svete, Jurij

    2016-07-15

    A series of 16 copper-catalyzed azomethine imine-alkyne cycloaddition (CuAIAC) reactions between four pyrazolidinone-1-azomethine imines and four terminal ynones gave the corresponding fluorescent cycloadducts as bimane analogues in very high yields. The applicability of CuAIAC was demonstrated by the fluorescent labeling of functionalized polystyrene and by using Cu-C and Cu-Fe as catalysts. Experimental evidence, kinetic measurements, and correlation between a clean catalyst surface and the reaction rate are in agreement with a homotopic catalytic system with catalytic Cu(I)-acetylide formed from Cu(0) by "in situ" oxidation. The availability of azomethine imines, mild reaction conditions, simple workup, and scalability make CuAIAC a viable supplement to the Cu-catalyzed azide-alkyne cycloaddition reaction in "click" chemistry. PMID:27305104

  20. Chemistry at the dirac point of graphene

    NASA Astrophysics Data System (ADS)

    Sarkar, Santanu

    device mobility. To this end, we find that the organometallic hexahapto metal complexation chemistry of graphene, in which the graphene pi-band constructively hybridizes with the vacant d-orbitals of transition metals, allows the fabrication of field effect devices which retain a high degree of the mobility with enhanced on-off ratio. In summary, we find that the singular electronic structure of graphene at the Dirac point governs the chemical reactivity of graphene and this chemistry will play a vital role in propelling graphene to assume its role as the next generation electronic material beyond silicon.

  1. Radical S-Adenosyl-l-methionine Chemistry in the Synthesis of Hydrogenase and Nitrogenase Metal Cofactors*

    PubMed Central

    Byer, Amanda S.; Shepard, Eric M.; Peters, John W.; Broderick, Joan B.

    2015-01-01

    Nitrogenase, [FeFe]-hydrogenase, and [Fe]-hydrogenase enzymes perform catalysis at metal cofactors with biologically unusual non-protein ligands. The FeMo cofactor of nitrogenase has a MoFe7S9 cluster with a central carbon, whereas the H-cluster of [FeFe]-hydrogenase contains a 2Fe subcluster coordinated by cyanide and CO ligands as well as dithiomethylamine; the [Fe]-hydrogenase cofactor has CO and guanylylpyridinol ligands at a mononuclear iron site. Intriguingly, radical S-adenosyl-l-methionine enzymes are vital for the assembly of all three of these diverse cofactors. This minireview presents and discusses the current state of knowledge of the radical S-adenosylmethionine enzymes required for synthesis of these remarkable metal cofactors. PMID:25477518

  2. High-pressure chemistry of hydrogen in metals: in situ study of iron hydride.

    PubMed

    Badding, J V; Hemley, R J; Mao, H K

    1991-07-26

    Optical observations and x-ray diffraction measurements of the reaction between iron and hydrogen at high pressure to form iron hydride are described. The reaction is associated with a sudden pressure-induced expansion at 3.5 gigapascals of iron samples immersed in fluid hydrogen. Synchrotron x-ray diffraction measurements carried out to 62 gigapascals demonstrate that iron hydride has a double hexagonal close-packed structure, a cell volume up to 17% larger than pure iron, and a stoichiometry close to FeH. These results greatly extend the pressure range over which the technologically important iron-hydrogen phase diagram has been characterized and have implications for problems ranging from hydrogen degradation and embrittlement of ferrous metals to the presence of hydrogen in Earth's metallic core. PMID:17746396

  3. Metal mediated sol-gel chemistry of 1,2-Bis(triethoxysilyl)-ethene

    SciTech Connect

    Carpenter, J.P.; Yamanaka, S.A.; McClain, M.D.

    1996-10-01

    Ethenyl-bridged polysilsesquioxane xerogels and aerogels were formed from the sol-gel polymerization of 1,2-bis(triethoxysilyl)ethene. Gels were synthesized from the cis- and trans-isomers by both acid and base catalysis. While the trans-monomer exhibited relatively fast gelation times, the cis-monomer depending on the conditions either formed no gel of had very long gelation times. The addition of a coordinating metal such as Pd to the cis-monomer sol results in dramatically decreased gelation times. The addition of salts with noncoordinating metals did not significantly shorten the gelation times indicating that a template effect may be directing the polymerization of the cis-monomer. The ethenyl-bridged polysilsesquioxanes were characterized by solid state {sup 29}Si and {sup 13}C NMR, nitrogen sorption porosimetry, and transmission electron microscopy.

  4. Synthesis and chemistry of cationic d{sup 0} metal alkyl complexes. Progress report, July 1988--May 1991

    SciTech Connect

    Jordan, R.F.

    1991-12-31

    The objective of this project is to develop new types of electrophilic metal alkyl complexes for catalytic C-H activation and olefin polymerization chemistry, and associated fundamental mechanistic studies. We have focused our efforts on four classes of early metal alkyl complexes: (1) cationic group 4 Cp{sub 2}M(R){sup +} complexes (1) which are active species in Cp{sub 2}MX{sub 2}-based Ziegler-Natta olefin polymerization catalyst systems and which catalyze productive C-H activation reactions of heterocycles, (2) neutral (dicarbollide)(Cp*)M(R) complexes (2) which are structurally are electronically very similar to 1, (3) half-sandwich complexes CpM(R){sub 2}(L){sub n}{sup +} which are highly coordinatively and electronically unsaturated, and (4) new group 5 (dicarbollide)(Cp)MR{sub 2} and (dicarbollide){sub 2} MR complexes which are more unsaturated than group 5 Cp{sub 2}M systems due to incorporation of the dicarbollide ligand.

  5. Crystal chemistry and electronic structure of the metallic lithium ion conductor, LiNiN.

    PubMed

    Stoeva, Zlatka; Jäger, Bernd; Gomez, Ruben; Messaoudi, Sabri; Yahia, Mouna Ben; Rocquefelte, Xavier; Hix, Gary B; Wolf, Walter; Titman, Jeremy J; Gautier, Régis; Herzig, Peter; Gregory, Duncan H

    2007-02-21

    The layered ternary nitride LiNiN shows an interesting combination of fast Li+ ion diffusion and metallic behavior, properties which suggest potential applications as an electrode material in lithium ion batteries. A detailed investigation of the structure and properties of LiNiN using powder neutron diffraction, ab initio calculations, SQUID magnetometry, and solid-state NMR is described. Variable-temperature neutron diffraction demonstrates that LiNiN forms a variant of the parent Li3N structure in which Li+ ion vacancies are ordered within the [LiN] planes and with Ni exclusively occupying interlayer positions (at 280 K: hexagonal space group Pm2, a = 3.74304(5) A, c = 3.52542(6) A, Z = 1). Calculations suggest that LiNiN is a one-dimensional metal, as a result of the mixed pi- and sigma-bonding interactions between Ni and N along the c-axis. Solid-state 7Li NMR spectra are consistent with both fast Li+ motion and metallic behavior. PMID:17260984

  6. Chemistry of guanidinate-stabilised diboranes: transition-metal-catalysed dehydrocoupling and hydride abstraction.

    PubMed

    Wagner, Arne; Litters, Sebastian; Elias, Jana; Kaifer, Elisabeth; Himmel, Hans-Jörg

    2014-09-22

    Herein, we analyse the catalytic boron-boron dehydrocoupling reaction that leads from the base-stabilised diborane(6) [H2 B(hpp)]2 (hpp=1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate) to the base-stabilised diborane(4) [H2 B(hpp)]2 . A number of potential transition-metal precatalysts was studied, including transition-metal complexes of the product diborane(4). The synthesis and structural characterisation of two further examples of such complexes is presented. The best results for the dehydrocoupling reactions were obtained with precatalysts of Group 9 metals in the oxidation state of +I. The active catalyst is formed in situ through a multistep process that involves reduction of the precatalyst by the substrate [H2 B(hpp)]2 , and mechanistic investigations indicate that both heterogeneous and (slower) homogeneous reaction pathways play a role in the dehydrocoupling reaction. In addition, hydride abstraction from [H2 B(hpp)]2 and related diboranes is analysed and the possibility for subsequent deprotonation is discussed by probing the protic character of the cationic boron-hydrogen compounds with NMR spectroscopic analysis. PMID:25168516

  7. Suppressing molecular motions for enhanced room-temperature phosphorescence of metal-free organic materials

    PubMed Central

    Kwon, Min Sang; Yu, Youngchang; Coburn, Caleb; Phillips, Andrew W.; Chung, Kyeongwoon; Shanker, Apoorv; Jung, Jaehun; Kim, Gunho; Pipe, Kevin; Forrest, Stephen R.; Youk, Ji Ho; Gierschner, Johannes; Kim, Jinsang

    2015-01-01

    Metal-free organic phosphorescent materials are attractive alternatives to the predominantly used organometallic phosphors but are generally dimmer and are relatively rare, as, without heavy-metal atoms, spin–orbit coupling is less efficient and phosphorescence usually cannot compete with radiationless relaxation processes. Here we present a general design rule and a method to effectively reduce radiationless transitions and hence greatly enhance phosphorescence efficiency of metal-free organic materials in a variety of amorphous polymer matrices, based on the restriction of molecular motions in the proximity of embedded phosphors. Covalent cross-linking between phosphors and polymer matrices via Diels–Alder click chemistry is devised as a method. A sharp increase in phosphorescence quantum efficiency is observed in a variety of polymer matrices with this method, which is ca. two to five times higher than that of phosphor-doped polymer systems having no such covalent linkage. PMID:26626796

  8. Suppressing molecular motions for enhanced room-temperature phosphorescence of metal-free organic materials.

    PubMed

    Kwon, Min Sang; Yu, Youngchang; Coburn, Caleb; Phillips, Andrew W; Chung, Kyeongwoon; Shanker, Apoorv; Jung, Jaehun; Kim, Gunho; Pipe, Kevin; Forrest, Stephen R; Youk, Ji Ho; Gierschner, Johannes; Kim, Jinsang

    2015-01-01

    Metal-free organic phosphorescent materials are attractive alternatives to the predominantly used organometallic phosphors but are generally dimmer and are relatively rare, as, without heavy-metal atoms, spin-orbit coupling is less efficient and phosphorescence usually cannot compete with radiationless relaxation processes. Here we present a general design rule and a method to effectively reduce radiationless transitions and hence greatly enhance phosphorescence efficiency of metal-free organic materials in a variety of amorphous polymer matrices, based on the restriction of molecular motions in the proximity of embedded phosphors. Covalent cross-linking between phosphors and polymer matrices via Diels-Alder click chemistry is devised as a method. A sharp increase in phosphorescence quantum efficiency is observed in a variety of polymer matrices with this method, which is ca. two to five times higher than that of phosphor-doped polymer systems having no such covalent linkage. PMID:26626796

  9. Preparation of nanoparticles and organometallic compounds via the SMAD technique

    NASA Astrophysics Data System (ADS)

    Ponce, Audaldo A.

    The SMAD method is a versatile synthetic technique for preparation of organometallic compounds, colloids and nanostructured materials from metals and semiconductors. In this work we use this technique to prepare beta-diketonate complexes of Ba and Cu, nanoparticles of Fe-SiO and copper, and for first time nanoparticles of ionic salt-like compounds. The evaporation and cocondensation of Fe, SiO, and an organic solvent, produces nanoparticles of Fe-SiO that when heat treated and passivated, acquire a core-shell structure that protects the iron core from oxidation, preserving its magnetic properties. beta-Diketonate complexes of Ba and Cu have been prepared free of water and with a considerable purity. Moreover, a striking finding was the dependence of the reactivity of the copper particles with their size toward the formation of the beta-diketonate complex. Nanocrystalline particles of copper have been prepared, and their chemical and catalytic reactivity have been tested in the Ullman reaction and the hydrogenation of CO2 to form CH3OH. Their chemical reactivity in the Ullman reaction is proportional to their surface area, and more reactive that those found in literature, with a maximum yield of 90% biphenyl at 150°C after 6 h. for the Cu*/toluene sample. Their catalytic activity tested using nanocrystalline ZnO as a support, resulted in a maximum conversion of 80% from CO2 to CH3OH. Nanocrystalline LiF particles have been successfully prepared with surface areas of 230--520 m2/g and with crystallite size of 5--10 nm. These particles present resistance to sintering when heated from room temperature up to 200°C. These samples can be densified without crystallite growth.

  10. Rational Design of Polynuclear Organometallic Assemblies from a Simple Heteromultifunctional Ligand.

    PubMed

    Zhang, Long; Lin, Yue-Jian; Li, Zhen-Hua; Jin, Guo-Xin

    2015-10-28

    In modern coordination chemistry, supramolecular coordination complexes take advantage of ligand design to control the shapes and sizes of such architectures. Here we describe how to utilize starting building blocks and a multifunctional ligand to rationally design and synthesize different types of discrete assemblies. Using a hydroxamate ligand featuring two pair of chelating sites together with half-sandwich iridium and rhodium fragments, we were able to construct a series multinuclear organometallic macrocycles and cages through stepwise coordination-driven self-assembly. Experimental observations, supported by computational work, show that selective coordination modes were ascribed to the significant electronic density differences of the two chelating sites, (O,O') and (N,N'). The results underline the advantages of the discrimination between soft and hard binding sites, and suggest that hydroxamic acids can be used as a versatile class of facile multifunctional scaffold for the construction of novel two-dimensional and three-dimensional architectures. PMID:26440304

  11. Metal-sulfide mineral ores, Fenton chemistry and disease. Particle induced inflammatory stress response in lung cells

    SciTech Connect

    Harrington, Andrea D.; Smirnov, Alexander; Tsirka, Stella E.; Schoonen, Martin A. A.

    2014-07-10

    The inhalation of mineral particulates and other earth materials, such as coal, can initiate or enhance disease in humans. Workers in occupations with high particulate exposure, such as mining, are particularly at risk. The ability of a material to generate an inflammatory stress response (ISR), a measure of particle toxicity, is a useful tool in evaluating said exposure risk. ISR is defined as the upregulation of cellular reactive oxygen species (ROS) normalized to cell viability. This study compares the ISR of A549 human lung epithelial cells after exposure to well-characterized common metal-sulfide ore mineral separates. The evaluation of the deleterious nature of ore minerals is based on a range of particle loadings (serial dilutions of 0.002 m2/mL stock) and exposure periods (beginning at 30 min and measured systematically for up to 24 h). There is a wide range in ISR values generated by the ore minerals. The ISR values produced by the sphalerite samples are within the range of inert materials. Arsenopyrite generated a small ISR that was largely driven by cell death. Galena showed a similar, but more pronounced response. Copper-bearing ore minerals generated the greatest ISR, both by upregulating cellular ROS and generating substantial and sustained cell death. Chalcopyrite and bornite, both containing ferrous iron, generated the greatest ISR overall. Particles containing Fenton metals as major constituents produce the highest ISR, while other heavy metals mainly generate cell death. Furthermore, this study highlights the importance of evaluating the chemistry, oxidation states and structure of a material when assessing risk management.

  12. Metal-sulfide mineral ores, Fenton chemistry and disease. Particle induced inflammatory stress response in lung cells

    DOE PAGESBeta

    Harrington, Andrea D.; Smirnov, Alexander; Tsirka, Stella E.; Schoonen, Martin A. A.

    2014-07-10

    The inhalation of mineral particulates and other earth materials, such as coal, can initiate or enhance disease in humans. Workers in occupations with high particulate exposure, such as mining, are particularly at risk. The ability of a material to generate an inflammatory stress response (ISR), a measure of particle toxicity, is a useful tool in evaluating said exposure risk. ISR is defined as the upregulation of cellular reactive oxygen species (ROS) normalized to cell viability. This study compares the ISR of A549 human lung epithelial cells after exposure to well-characterized common metal-sulfide ore mineral separates. The evaluation of the deleteriousmore » nature of ore minerals is based on a range of particle loadings (serial dilutions of 0.002 m2/mL stock) and exposure periods (beginning at 30 min and measured systematically for up to 24 h). There is a wide range in ISR values generated by the ore minerals. The ISR values produced by the sphalerite samples are within the range of inert materials. Arsenopyrite generated a small ISR that was largely driven by cell death. Galena showed a similar, but more pronounced response. Copper-bearing ore minerals generated the greatest ISR, both by upregulating cellular ROS and generating substantial and sustained cell death. Chalcopyrite and bornite, both containing ferrous iron, generated the greatest ISR overall. Particles containing Fenton metals as major constituents produce the highest ISR, while other heavy metals mainly generate cell death. Furthermore, this study highlights the importance of evaluating the chemistry, oxidation states and structure of a material when assessing risk management.« less

  13. Metal-Sulfide Mineral Ores, Fenton Chemistry and Disease – Particle Induced Inflammatory Stress Response in Lung Cells

    PubMed Central

    Harrington, Andrea D.; Smirnov, Alexander; Tsirka, Stella E.; Schoonen, Martin A.A.

    2014-01-01

    The inhalation of mineral particulates and other earth materials, such as coal, can initiate or enhance disease in humans. Workers in occupations with high particulate exposure, such as mining, are particularly at risk. The ability of a material to generate an inflammatory stress response (ISR), a measure of particle toxicity, is a useful tool in evaluating said exposure risk. ISR is defined as the upregulation of cellular reactive oxygen species (ROS) normalized to cell viability. This study compares the ISR of A549 human lung epithelial cells after exposure to well-characterized common metal-sulfide ore mineral separates. The evaluation of the deleterious nature of ore minerals is based on a range of particle loadings (serial dilutions of 0.002 m2/mL stock) and exposure periods (beginning at 30 minutes and measured systematically for up to 24 hours). There is a wide range in ISR values generated by the ore minerals. The ISR values produced by the sphalerite samples are within the range of inert materials. Arsenopyrite generated a small ISR that was largely driven by cell death. Galena showed a similar, but more pronounced response. Copper-bearing ore minerals generated the greatest ISR, both by upregulating cellular ROS and generating substantial and sustained cell death. Chalcopyrite and bornite, both containing ferrous iron, generated the greatest ISR overall. Particles containing Fenton metals as major constituents produce the highest ISR, while other heavy metals mainly generate cell death. This study highlights the importance of evaluating the chemistry, oxidation states and structure of a material when assessing risk management. PMID:25107347

  14. Metal-sulfide mineral ores, Fenton chemistry and disease--particle induced inflammatory stress response in lung cells.

    PubMed

    Harrington, Andrea D; Smirnov, Alexander; Tsirka, Stella E; Schoonen, Martin A A

    2015-01-01

    The inhalation of mineral particulates and other earth materials, such as coal, can initiate or enhance disease in humans. Workers in occupations with high particulate exposure, such as mining, are particularly at risk. The ability of a material to generate an inflammatory stress response (ISR), a measure of particle toxicity, is a useful tool in evaluating said exposure risk. ISR is defined as the upregulation of cellular reactive oxygen species (ROS) normalized to cell viability. This study compares the ISR of A549 human lung epithelial cells after exposure to well-characterized common metal-sulfide ore mineral separates. The evaluation of the deleterious nature of ore minerals is based on a range of particle loadings (serial dilutions of 0.002m(2)/mL stock) and exposure periods (beginning at 30min and measured systematically for up to 24h). There is a wide range in ISR values generated by the ore minerals. The ISR values produced by the sphalerite samples are within the range of inert materials. Arsenopyrite generated a small ISR that was largely driven by cell death. Galena showed a similar, but more pronounced response. Copper-bearing ore minerals generated the greatest ISR, both by upregulating cellular ROS and generating substantial and sustained cell death. Chalcopyrite and bornite, both containing ferrous iron, generated the greatest ISR overall. Particles containing Fenton metals as major constituents produce the highest ISR, while other heavy metals mainly generate cell death. This study highlights the importance of evaluating the chemistry, oxidation states and structure of a material when assessing risk management. PMID:25107347

  15. New precursors and chemistry for the growth of transition metal films by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Knisley, Thomas Joseph

    The advancing complexity of advanced microelectronic devices is placing rigorous demands on currently used PVD and CVD deposition techniques. The ALD deposition method is proposed to meet the film thickness and conformality constraints needed by the semiconductor industry in future manufacturing processes. Unfortunately, there is a limited number of chemical precursors available that have high thermal stability, reactivity, and vapor pressure suitable for ALD film growth to occur. These properties collectively contribute to the lack of suitable transition metal precursors available for use in ALD. In this thesis, we report the discovery of a series of novel transition metal diazadienate precursors that promising properties deemed suitable for ALD. The volatility and thermal stability of the new transition metal diazadienyl compounds were studied by preparative sublimation and capillary tube melting point/decomposition experiments. Thermogravimetric analyses (TGA) demonstrate precursor residues of less than 4% at 500 °C. In addition, sublimation data, melting points, and decomposition temperatures for all complexes are presented. The manganese diazadienyl complex has the highest decomposition temperature of the series of complexes produced (325 °C). During preparative sublimations, the product recoveries of all transition metal diazadienyl complexes were greater than 92.0% with nonvolatile residues of less than 7.0%. This is an excellent indication that these complexes may be suitable candidates as metal precursors for ALD. Nickel nitride (NixN) films have been studied as an intermediate material for the formation of both nickel metal and nickel silicide using chemical vapor deposition. Herein, we describe the ALD growth of nickel nitride thin films from bis(1,4-di-tert-butyl-1,3-diazabutadiene) nickel(II) (Ni(tBu2DAD)2) and 1,1-dimethylhydrazine. An ALD window for the deposition of nickel nitride films on 500 nm thermal SiO2 substrates was observed between 225

  16. Control of interfacial chemistry and mechanical properties in metal/ceramic composites. Ph.D. Thesis

    SciTech Connect

    Wang, Hsin-Fu

    1994-12-31

    Evaluation of the mechanical properties of metal/ceramic interfaces (Ti/AI2O3) was accomplished by using four-point bending tests, nanoindentation tests and fiber pushout tests. At first, the interfacial fracture energy of composites with different applied bonding temperatures from 700 C to 1000 C and thickness of the metal interlayers were measured by four-point bending tests. The mixed mode interfacial fracture energy of the Ti/Al2O3 interface was found to increase with increasing bonding temperatures up to 950 C. There is increasing interdiffusion of the constituent atoms across the interfaces with increasing temperature as verified by X-ray mapping. Thus, a stronger chemical bond forms between the Ti and the Al2O3. Above this temperature, the interfacial fracture energy drops due to the formation of a continuous brittle intermetallic compound (Ti3Al) at the Ti/Al2O3 interface. Modification of the interface was achieved with a diffusion barrier consisting of a refractory metal and Y2O3 duplex coating prepared by r.f. sputtering methods. The diffusion barrier significantly reduces the diffusion of the constituent atoms and prevents the formation of a continuous Ti3Al reaction layer, thus maintaining the chemical integrity and stability at the Ti/Al2O3 interface. The interfacial fracture energy can be further reduced by providing thinner Ti interlayers. The contribution of the energy dissipation process to the interfacial fracture energy is due to plastic energy absorption in the Ti interlayer during the fracture process. The interfacial shear strength, interfacial frictional stress and mode II interfacial fracture energy of the fiber composites were obtained by performing the fiber pushout tests. Using the Atomic Force Microscope (AFM), the surface roughness and texture of the three different Al2O3 fibers were evaluated. Incorporation of the experimental data and the theory gives the calculated frictional coefficient to be 0.35.

  17. Latest approaches on green chemistry preconcentration methods for trace metal determination in seawater--a review.

    PubMed

    La Colla, Noelia Soledad; Domini, Claudia Elizabeth; Marcovecchio, Jorge Eduardo; Botté, Sandra Elizabeth

    2015-03-15

    Evaluation of trace metal levels in seawater samples is undertaken regularly by research groups all over the world, leading to a growing demand for techniques involving fewer toxic reagents, less time-consuming protocols and lower limits of detection. This review focuses on providing a brief but concise description of the latest methodologies developed to this end, outlining the advantages and disadvantages of the various protocols, chelating and dispersive agents and instruments used. Conclusions are drawn on the basis of the articles reviewed, highlighting improvements introduced in order to enhance the performance of the protocols. PMID:25532056

  18. On-Surface Observation of the Formation of Organometallic Complex in a Supramolecular Network

    NASA Astrophysics Data System (ADS)

    Li, Yibao; Cheng, Linxiu; Liu, Chunhua; Liu, Wei; Fan, Yulan; Fan, Xiaolin; Zeng, Qingdao

    2015-06-01

    The on-surface formation of organometallic monomers or oligomers, especially in supramolecular network, attracts an extensive interest for chemists and material scientist. In this work, we have investigated metal coordination between zinc (II) phthalocyanine (ZnPc) and 1, 3-di (4-pyridyl) propane (dipy-pra) in the 2, 6, 11-tricarboxydecyloxy-3, 7, 10-triundecyloxy triphenylene (asym-TTT) supramolecular template by means of scanning tunneling microscopy (STM) on highly oriented pyrolytic graphite (HOPG) substrate under ambient conditions. The experimental results demonstrate that every two ZnPc molecules in one nano-reactor connect with each other through one dipy-pra molecule by metal-coordination interaction. In this coordinating process, the template of asym-TTT supramolecular networks plays a significant role.

  19. On-Surface Observation of the Formation of Organometallic Complex in a Supramolecular Network

    PubMed Central

    Li, Yibao; Cheng, Linxiu; Liu, Chunhua; Liu, Wei; Fan, Yulan; Fan, Xiaolin; Zeng, Qingdao

    2015-01-01

    The on-surface formation of organometallic monomers or oligomers, especially in supramolecular network, attracts an extensive interest for chemists and material scientist. In this work, we have investigated metal coordination between zinc (II) phthalocyanine (ZnPc) and 1, 3-di (4-pyridyl) propane (dipy-pra) in the 2, 6, 11-tricarboxydecyloxy-3, 7, 10-triundecyloxy triphenylene (asym-TTT) supramolecular template by means of scanning tunneling microscopy (STM) on highly oriented pyrolytic graphite (HOPG) substrate under ambient conditions. The experimental results demonstrate that every two ZnPc molecules in one nano-reactor connect with each other through one dipy-pra molecule by metal-coordination interaction. In this coordinating process, the template of asym-TTT supramolecular networks plays a significant role. PMID:26061532

  20. On-Surface Observation of the Formation of Organometallic Complex in a Supramolecular Network.

    PubMed

    Li, Yibao; Cheng, Linxiu; Liu, Chunhua; Liu, Wei; Fan, Yulan; Fan, Xiaolin; Zeng, Qingdao

    2015-01-01

    The on-surface formation of organometallic monomers or oligomers, especially in supramolecular network, attracts an extensive interest for chemists and material scientist. In this work, we have investigated metal coordination between zinc (II) phthalocyanine (ZnPc) and 1, 3-di (4-pyridyl) propane (dipy-pra) in the 2, 6, 11-tricarboxydecyloxy-3, 7, 10-triundecyloxy triphenylene (asym-TTT) supramolecular template by means of scanning tunneling microscopy (STM) on highly oriented pyrolytic graphite (HOPG) substrate under ambient conditions. The experimental results demonstrate that every two ZnPc molecules in one nano-reactor connect with each other through one dipy-pra molecule by metal-coordination interaction. In this coordinating process, the template of asym-TTT supramolecular networks plays a significant role. PMID:26061532

  1. Computational Estimate of the Photophysical Capabilities of Four Series of Organometallic Iron(II) Complexes.

    PubMed

    Dixon, Isabelle M; Boissard, Gauthier; Whyte, Hannah; Alary, Fabienne; Heully, Jean-Louis

    2016-06-01

    In this study, we examine a large range of organometallic iron(II) complexes with the aim of computationally identifying the most promising ones in terms of photophysical properties. These complexes combine polypyridine, bis(phosphine), and carbon-bound ligands. Density functional theory has allowed us to establish a comparative Jablonski diagram displaying the lowest singlet, triplet, and quintet states. All of the proposed FeN5C or FeN3P2C complexes unfavorably possess a lowest triplet state of metal-centered (MC) nature. Among the FeN4C2 and FeN2P2C2 series, the carbene complexes display the least favorable excited-state distribution, also having a low-lying (3)MC state. Validating our design strategy, we are now able to propose seven iron(II) complexes displaying a lowest excited state of triplet metal-to-ligand charge-transfer nature. PMID:27228301

  2. A Selenium-Containing Diarylamido Pincer Ligand: Synthesis and Coordination Chemistry with Group 10 Metals.

    PubMed

    Charette, Bronte J; Ritch, Jamie S

    2016-06-20

    The synthesis of new bifunctional organoselenium diarylamine compounds RN(4-Me-2-SeMe-C6H3)2 (R = Me: 1; R = tert-butoxycarbonyl (Boc): 2; R = H: 3-H) via aryllithium chemistry is disclosed. Compound 1 serves as a Se,Se-bidentate neutral ligand toward Pd(II), forming the coordination complex {PdCl2[MeN(4-Me-2-SeMe-C6H3)2-κ(2)Se)]} (1-Pd) in reaction with [PdCl2(COD)] (COD = 1,5-cyclooctadiene), while the protio ligand 3-H forms tridentate pincer complexes [MCl(N(4-Me-2-SeMe-C6H3)2)] (M = Pd: 3-Pd; M = Pt: 3-Pt) with [MCl2(COD)] (M = Pd, Pt) in the presence of triethylamine. Complex 1-Pd does not undergo N-C cleavage at high temperature, unlike related alkylphosphine-bearing complexes. All compounds have been characterized by multinuclear ((1)H, (13)C, (77)Se) NMR spectroscopy, and crystal structures of 1, 1-Pd, 3-Pd, and 3-Pt are reported. Additionally, density functional theory calculations have been performed on the pincer complexes to contrast them with well-known analogues containing phosphine donor groups. PMID:27281450

  3. Modern Chemistry Techniques Applied to Metal Behavior and Chelation in Medical and Environmental Systems ? Final Report

    SciTech Connect

    Sutton, M; Andresen, B; Burastero, S R; Chiarappa-Zucca, M L; Chinn, S C; Coronado, P R; Gash, A E; Perkins, J; Sawvel, A M; Szechenyi, S C

    2005-02-03

    This report details the research and findings generated over the course of a 3-year research project funded by Lawrence Livermore National Laboratory (LLNL) Laboratory Directed Research and Development (LDRD). Originally tasked with studying beryllium chemistry and chelation for the treatment of Chronic Beryllium Disease and environmental remediation of beryllium-contaminated environments, this work has yielded results in beryllium and uranium solubility and speciation associated with toxicology; specific and effective chelation agents for beryllium, capable of lowering beryllium tissue burden and increasing urinary excretion in mice, and dissolution of beryllium contamination at LLNL Site 300; {sup 9}Be NMR studies previously unstudied at LLNL; secondary ionization mass spec (SIMS) imaging of beryllium in spleen and lung tissue; beryllium interactions with aerogel/GAC material for environmental cleanup. The results show that chelator development using modern chemical techniques such as chemical thermodynamic modeling, was successful in identifying and utilizing tried and tested beryllium chelators for use in medical and environmental scenarios. Additionally, a study of uranium speciation in simulated biological fluids identified uranium species present in urine, gastric juice, pancreatic fluid, airway surface fluid, simulated lung fluid, bile, saliva, plasma, interstitial fluid and intracellular fluid.

  4. Chemistry Notes.

    ERIC Educational Resources Information Center

    School Science Review, 1982

    1982-01-01

    Presents procedures, experiments, demonstrations, teaching suggestions, and information on a variety of chemistry topics including, for example, inert gases, light-induced reactions, calculators, identification of substituted acetophenones, the elements, analysis of copper minerals, extraction of metallic strontium, equilibrium, halogens, and…

  5. Surface chemistry and structural properties of mackinawite prepared by reaction of sulfide ions with metallic iron

    NASA Astrophysics Data System (ADS)

    Mullet, Martine; Boursiquot, Sophie; Abdelmoula, Mustapha; Génin, Jean-Marie; Ehrhardt, Jean-Jacques

    2002-03-01

    Tetragonal FeS 1- x mackinawite, has been synthesized by reacting metallic iron with a sodium sulfide solution and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), transmission Mössbauer spectroscopy (TMS) and X-ray photoelectron spectroscopy (XPS). Based on XRD and TEM analyses, synthetic mackinawite exhibits crystallization and is identical to the natural mineral. Unit cell parameters derived from XRD data are a = b = 0.3670 nm and c = 0.5049 nm. The bulk Fe:S ratio derived from the quantitative dispersive energy analysis is practically 1. XPS analyses, however, showed that mackinawite surface is composed of both Fe(II) and Fe(III) species bound to monosulfide. Accordingly, monosulfide is the dominant S species observed at the surface with lesser amount of polysulfides and elemental sulfur. TMS analysis revealed the presence of both Fe(II) and Fe(III) in the mackinawite structure, thus supporting the XPS analysis. We propose that the iron monosulfide phase synthesized by reacting metallic iron and dissolved sulfide is composed of Fe(II) and S(-II) atoms with the presence of a weathered thin layer covering the bulk material that consists of both Fe(II) and Fe(III) bound to S(-II) atoms and in a less extent of polysulfide and elemental sulfur.

  6. Antibodies labeled with metallic radionuclides: influence of nuclide chemistry on dose distribution.

    PubMed

    Vaughan, A T; Yankuba, S C; Anderson, P

    1987-01-01

    An antibody with human CEA specificity has been labeled with either yttrium-90, scandium-47, or indium-111, via a diethylenetriamine pentaacetic acid (DTPA) link covalently bound to the protein. The clearance of these proteins from the blood of mice can be described by a single exponential; the half-life decreases in the order indium-111 greater than yttrium-90 greater than scandium-47. Associated with the blood clearance is an uptake of radioactivity into the liver; scandium-47 has the highest concentration, indium-111 has the least, and yttrium-90 is intermediate. There is no correlation between these results and the equilibrium stability constants of the metals with DTPA-like ligands. The results obtained show that, in vivo, scandium-47 and yttrium-90 are more easily displaced from DTPA by other ions than is indium-111. They also show that free DTPA is able to extract yttrium-90 and scandium-47, but not indium-111, from the liver of treated animals, indicating that indium-111 is resistant to ligand exchange reactions in vivo. These data indicate that 1) the equilibrium stability constant is not a good indicator of the in vivo stability of metal-labeled proteins and 2) it is possible to manipulate the ion distribution and therefore the dose from scandium-47 and yttrium-90 after injection of the labeled proteins. PMID:3029601

  7. Growth and characterization of an organometallic tri-allylthiourea complex nonlinear optical crystals

    NASA Astrophysics Data System (ADS)

    Perumal, R.; Moorthy Babu, S.

    2008-04-01

    A novel family of allylthiourea metal complexes was identified for photonic applications with allylthiourea serving as a double ligand, and II (B) group metals were chosen as a co-ordination metal. This family belongs to an island-type organometallic category. A series of optically negative nonlinear optical (NLO) crystals (ATCC, ATCB, ATMC and ATMB) have been prepared. Their SHG efficiency was an order of magnitude higher than that of the well-known organic crystal, urea. The properties of allylthiourea complex with central atom Cd were compared with the crystals with another central atom Hg. The latter has longer transparency cut-off wavelength, higher thermal stability and SHG efficiencies. These organometallic tri-allylthiourea complex crystals were grown from the aqueous solution by temperature-lowering technique. Comprehensive studies of synthesis, solubility, crystal growth and the general properties including structural, spectral, optical and thermal properties were analyzed by conducting various characterization techniques. They were synthesized in the de-ionized water and the solubilities of each material were determined by employing thermogravimetric analysis. The growth conditions were analyzed in terms of the pH value of the mother solution because it plays a vital role during the growth. Their structural properties were examined by recording the powder X-ray diffraction pattern. The crystal formation and the metal co-ordination were confirmed by the spectral analysis. The transmission spectrum of these crystals shows a wide transparent UV-vis-NIR band. The thermal behavior of these complexes was studied from the thermal studies. Their NLO efficiencies were analyzed through the Kurt'z technique.

  8. Aqueous and surface chemistry of calcium-metal hydroxides in high pH environments

    SciTech Connect

    Cocke, D.L.; Mollah, M.Y.A.; Hess, T.R.; Lin, T.C.

    1997-08-01

    There is considerable interest in the chemistry associated with hazardous waste treatment by cement. The hydration of Portland cement is retarded in presence of zinc, cadmium and lead ions. Mixed hydroxides of calcium, zinc, cadmium and lead have been recently identified in the high pH environments of hydrating cement. FTIR, XRD, SEM, and SPM have been used to characterize these systems. A chemical equilibrium model of the early hydration of a zinc-doped cement/water system, Na-K-Ca-ZnH-SO{sub 4}-OH-Zn(OH){sub 2}-Zn(OH){sub 3}-Zn(OH){sub 4}-H{sub 2}O, has been developed to better understand the mechanism of the surface formation of calcium hydroxyzincate (CHZ). The model is based on Pitzer`s semi-empirical method for calculation of ion-activity coefficients at high ionic strength. The Pitzer parameters for Na{sup +}-Zn{sup 2+}, Na{sup +}-Zn{sup 2+}-SO{sub 4}{sup 2{minus}} and K{sup +}-Zn(OH){sub 4}{sup 2{minus}} have been evaluated, and the results successfully predict the equilibria (solubilities) of Na{sub 2}SO{sub 4}-ZnSO{sub 4}-H{sub 2}O, NaOH-Zn(OH){sub 2}-H{sub 2}O and KOH-ZnO-H{sub 2}O systems. The chemical model clearly demonstrates that the formation of CHZ on the calcium-silica-hydrate (C-S-H) surface is critically controlled by the Ca{sup 2+} ion concentration as well as pH of the pore water system. The results of this study suggest that the growth of CHZ is preceded by surface complex formation. Sequential charge control and sequential structure development have been used to discuss the surface selectivity of these compounds and their control of cement hydration.

  9. Organometallic Ru(II) Photosensitizers Derived from π-Expansive Cyclometalating Ligands: Surprising Theranostic PDT Effects.

    PubMed

    Sainuddin, Tariq; McCain, Julia; Pinto, Mitch; Yin, Huimin; Gibson, Jordan; Hetu, Marc; McFarland, Sherri A

    2016-01-01

    The purpose of the present study was to investigate the influence of π-expansive cyclometalating ligands on the photophysical and photobiological properties of organometallic Ru(II) compounds. Four compounds with increasing π conjugation on the cyclometalating ligand were prepared, and their structures were confirmed by HPLC, 1D and 2D (1)H NMR, and mass spectrometry. The properties of these compounds differed substantially from their Ru(II) polypyridyl counterparts. Namely, they were characterized by red-shifted absorption, very weak to no room temperature phosphorescence, extremely short phosphorescence state lifetimes (<10 ns), low singlet oxygen quantum yields (0.5-8%), and efficient ligand-centered fluorescence. Three of the metal complexes were very cytotoxic to cancer cells in the dark (EC50 values = 1-2 μM), in agreement with what has traditionally been observed for Ru(II) compounds derived from small C^N ligands. Surprisingly, the complex derived from the most π-expansive cyclometalating ligand exhibited no cytotoxicity in the dark (EC50 > 300 μM) but was phototoxic to cells in the nanomolar regime. Exceptionally large phototherapeutic margins, exceeding 3 orders of magnitude in some cases, were accompanied by bright ligand-centered intracellular fluorescence in cancer cells. Thus, Ru(II) organometallic systems derived from π-expansive cyclometalating ligands, such 4,9,16-triazadibenzo[a,c]napthacene (pbpn), represent the first class of potent light-responsive Ru(II) cyclometalating agents with theranostic potential. PMID:26672769

  10. Synthesis and Microstructural Investigations of Organometallic Pd(II) Thiol-Gold Nanoparticles Hybrids

    PubMed Central

    2008-01-01

    In this work the synthesis and characterization of gold nanoparticles functionalized by a novel thiol-organometallic complex containing Pd(II) centers is presented. Pd(II) thiol,trans, trans-[dithiolate-dibis(tributylphosphine)dipalladium(II)-4,4′-diethynylbiphenyl] was synthesized and linked to Au nanoparticles by the chemical reduction of a metal salt precursor. The new hybrid made of organometallic Pd(II) thiol-gold nanoparticles, shows through a single S bridge a direct link between Pd(II) and Au nanoparticles. The size-control of the Au nanoparticles (diameter range 2–10 nm) was achieved by choosing the suitable AuCl4−/thiol molar ratio. The size, strain, shape, and crystalline structure of these functionalized nanoparticles were determined by a full-pattern X-ray powder diffraction analysis, high-resolution TEM, and X-ray photoelectron spectroscopy. Photoluminescence spectroscopy measurements of the hybrid system show emission peaks at 418 and 440 nm. The hybrid was exposed to gaseous NOxwith the aim to evaluate the suitability for applications in sensor devices; XPS measurements permitted to ascertain and investigate the hybrid –gas interaction. PMID:21350592

  11. Towards 9 weight percent, reversible, room temperature hydrogen adsorbents: Hydrogen saturated organometallic bucky balls

    NASA Astrophysics Data System (ADS)

    Zhao, Yufeng

    2005-03-01

    A new concept for high-capacity hydrogen absorbents is introduced by first-principles calculations. Transition metal (TM) atoms bound to fullerenes are proposed as a medium for high density, room temperature, ambient pressure storage of hydrogen. TMs bind to C60 or C48B12 by charge transfer interactions to produce stable organometallic bucky balls (OBBs) and bind to multiple dihydrogen molecules through the so-called Kubas interaction [1]. A particular scandium OBB can bind as many as eleven hydrogen atoms per TM, ten of which are bound in the form of dihydrogen molecular ligands that can be adsorbed and desorbed reversibly. In this case, the calculated binding energy is around 0.3 eV/H2, which is ideal for use on-board vehicles. The theoretical maximum retrievable H2 storage density is about 9 weight percent. This work was supported by the U.S. DOE EERE, BES/MS, and BES/CS under contract No. DEAC36-99GO10337. [1] G.J. Kubas, J. Organometallic Chem. 635, 37 (2001).

  12. Studies of the surface reactivity of metal oxyhydroxides and sulfides with relevance to environmental chemistry

    NASA Astrophysics Data System (ADS)

    Pierre-Louis, Andro-Marc

    With the benefits of an ever increasing advance of industrialization around the globe come formidable environmental problems. Three environmental problems that have relevance to the research described in this thesis are the 1) buildup of atmospheric CO2 gas through the burning of fossil fuels, 2) eutrophication of aquatic systems, and 3) the acidification of environments from acid mine drainage (AMD) resulting from coal-mining activities. In particular research is presented in this thesis that investigated the surface chemistry of CO2 and phosphate (PO43-) on a suite of environmentally relevant iron oxyhydroxide materials and the chemistry of phospholipid molecules on environmentally relevant iron sulfide surfaces to suppress AMD. To develop a microscopic understanding of the surface chemistry of the different systems, an array of experimental and computational techniques were used in the research. Techniques included X-ray photoelectron spectroscopy, atomic adsorption, X-ray diffraction, scanning transmission microscopy with electron dispersive X-ray spectroscopy (STEM/EDS), ion chromatography (IC), and attenuated total reflectance Fourier transform Infrared (ATR-FTIR). Results from the latter technique were interpreted with the aid of density function theory (DFT) calculations. Iron oxyhydroxides, which consisted of ferrihydrite (FeOOH), goethite (α-FeOOH), ferrimagnetic ferrihydrite (FerriFh), and aluminum-doped iron oxyhydroxide (content from 0-100 mol%) were synthesized and studied before and after exposure to gaseous CO2, CO32-, and PO43- species. FeOOH and mixed Al/Fe oxyhydroxide surfaces showed high affinities for the formation of carbonate and bicarbonate species upon exposure to gaseous CO2. Within the Al/Fe oxyhydroxide circumstance, a low Al level of incorporation in the iron oxyhydroxide structure caused a slight increase in surface area and increase in the amount of oxyanion (e.g., CO32- or PO43-) adsorption up to an Al level of 30 mol%. Significant

  13. Studies of the surface reactivity of metal oxyhydroxides and sulfides with relevance to environmental chemistry

    NASA Astrophysics Data System (ADS)

    Pierre-Louis, Andro-Marc

    With the benefits of an ever increasing advance of industrialization around the globe come formidable environmental problems. Three environmental problems that have relevance to the research described in this thesis are the 1) buildup of atmospheric CO2 gas through the burning of fossil fuels, 2) eutrophication of aquatic systems, and 3) the acidification of environments from acid mine drainage (AMD) resulting from coal-mining activities. In particular research is presented in this thesis that investigated the surface chemistry of CO2 and phosphate (PO43-) on a suite of environmentally relevant iron oxyhydroxide materials and the chemistry of phospholipid molecules on environmentally relevant iron sulfide surfaces to suppress AMD. To develop a microscopic understanding of the surface chemistry of the different systems, an array of experimental and computational techniques were used in the research. Techniques included X-ray photoelectron spectroscopy, atomic adsorption, X-ray diffraction, scanning transmission microscopy with electron dispersive X-ray spectroscopy (STEM/EDS), ion chromatography (IC), and attenuated total reflectance Fourier transform Infrared (ATR-FTIR). Results from the latter technique were interpreted with the aid of density function theory (DFT) calculations. Iron oxyhydroxides, which consisted of ferrihydrite (FeOOH), goethite (α-FeOOH), ferrimagnetic ferrihydrite (FerriFh), and aluminum-doped iron oxyhydroxide (content from 0-100 mol%) were synthesized and studied before and after exposure to gaseous CO2, CO32-, and PO43- species. FeOOH and mixed Al/Fe oxyhydroxide surfaces showed high affinities for the formation of carbonate and bicarbonate species upon exposure to gaseous CO2. Within the Al/Fe oxyhydroxide circumstance, a low Al level of incorporation in the iron oxyhydroxide structure caused a slight increase in surface area and increase in the amount of oxyanion (e.g., CO32- or PO43-) adsorption up to an Al level of 30 mol%. Significant

  14. Metal-Templated Ligand Architectures for Trinuclear Chemistry: Tricopper Complexes and Their O2 Reactivity

    PubMed Central

    Lionetti, Davide; Day, Michael W.

    2013-01-01

    A trinucleating framework was assmbled by templation of a heptadentate ligand around yttrium and lanthanides. The generated complexes orient three sets of two or three N-donors each for binding additional metal centers. Addition of three equivalents of copper(I) leads to the formation of tricopper(I) species. Reactions with dioxygen at low temperatures generate species whose spectroscopic features are consistent with a μ3,μ3-dioxo-tricopper complex. Reactivity studies were performed with a variety of substrates. The dioxo-tricopper species deprotonates weak acids, undergoes oxygen atom transfer with one equivalent of triphenylphosphine to yield triphenylphosphine oxide, and abstracts two hydrogen atom equivalents from tetramethylpiperidine-N-hydroxide (TEMPO-H). Thiophenols reduce the oxygenated species to a CuI3 complex and liberate two equivalents of disulfide, consistent with a four-electron four-proton process. PMID:23539341

  15. Elucidation of noble metal/formic acid chemistry during DWPF feed preparation

    SciTech Connect

    Landon, L.F.

    1991-01-01

    Eleven reports are included: evaluation of noble metal compounds as catalysts for aerobic decomposition of formic acid; reaction of NaNO[sub 3] and NaNO[sub 2] with formic acid under argon; effects of Ru, Rh, Pd chlorides on formic acid decomposition in presence of IDMS (pH=11.0) sludge; effects of additives on catalysts on decomposition of formic acid to hydrogen; Rh-catalyzed decomposition of formic acid; the question of whether this decomposition can be heterogeneous catalysis; inhibition of this reaction by additives; nitrilotriacetic acid inhibitor; uses of gelatin and other water soluble polymers to control flocculation rate; comparison of catalytic activities of Rh, Ru, Pd in Purex and HM sludges; experiments on homogeneous vs heterogeneous nature of Rh catalyst. Figs, refs, tabs.

  16. Elucidation of noble metal/formic acid chemistry during DWPF feed preparation. Revision 1

    SciTech Connect

    Landon, L.F.

    1991-12-31

    Eleven reports are included: evaluation of noble metal compounds as catalysts for aerobic decomposition of formic acid; reaction of NaNO{sub 3} and NaNO{sub 2} with formic acid under argon; effects of Ru, Rh, Pd chlorides on formic acid decomposition in presence of IDMS (pH=11.0) sludge; effects of additives on catalysts on decomposition of formic acid to hydrogen; Rh-catalyzed decomposition of formic acid; the question of whether this decomposition can be heterogeneous catalysis; inhibition of this reaction by additives; nitrilotriacetic acid inhibitor; uses of gelatin and other water soluble polymers to control flocculation rate; comparison of catalytic activities of Rh, Ru, Pd in Purex and HM sludges; experiments on homogeneous vs heterogeneous nature of Rh catalyst. Figs, refs, tabs.

  17. Linking interfacial chemistry of CO2 to surface structures of hydrated metal oxide nanoparticles: hematite.

    PubMed

    Chernyshova, Irina V; Ponnurangam, Sathish; Somasundaran, Ponisseril

    2013-05-14

    A better understanding of interaction with dissolved CO2 is required to rationally design and model the (photo)catalytic and sorption processes on metal (hydr)oxide nanoparticles (NPs) in aqueous media. Using in situ FTIR spectroscopy, we address this problem for rhombohedral 38 nm hematite (α-Fe2O3) nanoparticles as a model. We not only resolve the structures of the adsorbed carbonate species, but also specify their adsorption sites and their location on the nanoparticle surface. The spectral relationships obtained present a basis for a new method of characterizing the microscopic structural and acid-base properties (related to individual adsorption sites) of hydrated metal (hydr)oxide NPs using atmospherically derived CO2 as a probe. Specifically, we distinguish two carbonate species suggesting two principally different adsorption mechanisms. One species, which is more weakly adsorbed, has an inner-sphere mononuclear monodentate structure which is formed by a conventional ligand-exchange mechanism. At natural levels of dissolved carbonate and pH from 3 to 11, this species is attached to the most acidic/reactive surface cations (surface states) associated with ferrihydrite-like surface defects. The second species, which is more strongly adsorbed, presents a mixed C and O coordination of bent CO2. This species uniquely recognizes the stoichiometric rhombohedral {104} facets in the NP texture. Like in gas phase, it is formed through the surface coordination of molecular CO2. We address how the adsorption sites hosting these two carbonate species are affected by the annealing and acid etching of the NPs. These results support the nanosize-induced phase transformation of hematite towards ferrihydrite under hydrous conditions, and additionally show that the process starts from the roughened areas of the facet intersections. PMID:23552484

  18. Shape and surface chemistry effects on the cytotoxicity and cellular uptake of metallic nanorods and nanospheres.

    PubMed

    Favi, Pelagie Marlene; Valencia, Mariana Morales; Elliott, Paul Robert; Restrepo, Alejandro; Gao, Ming; Huang, Hanchen; Pavon, Juan Jose; Webster, Thomas Jay

    2015-12-01

    Metallic nanoparticles (such as gold and silver) have been intensely studied for wound healing applications due to their ability to be easily functionalized, possess antibacterial properties, and their strong potential for targeted drug release. In this study, rod-shaped silver nanorods (AgNRs) and gold nanorods (AuNRs) were fabricated by electron beam physical vapor deposition (EBPVD), and their cytotoxicity toward human skin fibroblasts were assessed and compared to sphere-shaped silver nanospheres (AgNSs) and gold nanospheres (AuNSs). Results showed that the 39.94 nm AgNSs showed the greatest toxicity with fibroblast cells followed by the 61.06 nm AuNSs, ∼556 nm × 47 nm (11.8:1 aspect ratio) AgNRs, and the ∼534 nm × 65 nm (8.2:1 aspect ratio) AuNRs demonstrated the least amount of toxicity. The calculated IC50 (50% inhibitory concentration) value for the AgNRs exposed to fibroblasts was greater after 4 days of exposure (387.3 μg mL(-1)) compared to the AgNSs and AuNSs (4.3 and 23.4 μg mL(-1), respectively), indicating that these spherical metallic nanoparticles displayed a greater toxicity to fibroblast cells. The IC50 value could not be measured for the AuNRs due to an incomplete dose response curve. The reduced cell toxicity with the presently developed rod-shaped nanoparticles suggests that they may be promising materials for use in numerous biomedical applications. PMID:26053238

  19. Short-term inactivation rates of selected Gram-positive and Gram-negative bacteria attached to metal oxide mineral surfaces: role of solution and surface chemistry.

    PubMed

    Asadishad, Bahareh; Ghoshal, Subhasis; Tufenkji, Nathalie

    2013-06-01

    Metal oxides such as ferric or aluminum oxides can play an important role in the retention of bacteria in granular aquatic environments; however, their role in bacterial inactivation is not well understood. Herein, we examined the role of water chemistry and surface chemistry on the short-term inactivation rates of three bacteria when adhered to surfaces. To evaluate the role of water chemistry on the inactivation of attached bacteria, the loss in membrane integrity of bacteria attached to an iron oxide (Fe2O3) surface was measured over a range of water ionic strengths of either monovalent or divalent salts in the absence of a growth substrate. The influence of surface chemistry on the inactivation of attached bacteria was examined by measuring the loss in membrane integrity of cells attached to three surfaces (SiO2, Fe2O3, and Al2O3) at a specific water chemistry (10 mM KCl). Bacteria were allowed to attach onto the SiO2 or metal oxide coated slides mounted in a parallel-plate flow cell, and their inactivation rate (loss in membrane integrity) was measured directly without removing the cells from the surface and without disturbing the system. X-ray photoelectron spectroscopy analysis revealed a high correlation between the amounts of C-metal or O-metal bonds and the corresponding bacterial inactivation rates for each surface. Finally, for all three surfaces, a consistent increase in inactivation rate was observed with the type of bacterium in the order: Enterococcus faecalis, Escherichia coli O157:H7, and Escherichia coli D21f2. PMID:23679056

  20. Emergence of electrophilic alumination as the counterpart of established nucleophilic lithiation: an academic sojourn in organometallics with William Kaska as fellow traveler.

    PubMed

    Eisch, John J

    2015-04-21

    William Kaska pursued doctoral studies with John Eisch in mechanistic organometallic chemistry, first with organolithium reactions at St. Louis University and then at the University of Michigan with organoaluminum reactions. Thereby he revealed the change in mechanism from nucleophilic lithiation and carbolithiation to that of electrophilic alumination, carboalumination and hydroalumination of organic substrates, which reactions were previously observed by Karl Ziegler in his empirical studies of organoaluminum reactions. Our findings were the first mechanistic studies attempting to set such Ziegler chemistry on a modern theoretical basis. PMID:25820225

  1. The Development and Study of Surface Bound Ruthenium Organometallic Complexes

    NASA Astrophysics Data System (ADS)

    Abbott, Geoffrey Reuben

    The focus of this project has been on the use of mono-diimine ruthenium organometallic complexes, of the general structure [H(Ru)(CO)(L)2(L') 2][PF6] (L=PPh3, DPPENE and L'=Bpy, DcBpy, MBpyC, Phen, AminoPhen) bound to surfaces as luminescent probes. Both biological and inorganic/organic hybrid surfaces have been studied. The complexes were characterized both bound and unbound using standard analytical techniques such as NMR, IR and X-ray crystallography, as well as through several photophysical methods as well. Initially the study focused on how the photophyscial properties of the complexes were affected by incorporation into biological membranes. It was found that by conjugating the probes to a more rigid cholesterol moiety that luminescence was conserved, compared to conjugation with a far more flexible lipid moiety, where luminescence was either lost or reduced. Both the cholesterol and lipid conjugates were able to insert into a lipid membrane, and in the more rigid environment some of the lipid conjugates regained some of their luminescence, but often blue shifted and reduced, depending on the conjugation site. Silica Polyamine Composites (SPCs) were a hybrid material developed in the Rosenberg Lab as useful metal separation materials, that could be easily modified, and had several benefits over current commercially available polymers, or inorganic materials. These SPCs also provided an opportunity for the development of a heterogeneous platform for luminescent complexes as either catalysts or sensors. Upon binding of the luminescent Ru complexes to the surface no loss, or major change in luminescence was seen, however, when bound to the rigid surface a significant increase in excited state lifetime was measured. It is likely that through binding and interacting with the surface that the complexes lost non-radiative decay pathways, resulting in the increase in lifetime, however, these interactions do not seem to affect the energy level of the MLCT band in a

  2. Synthesis and Metalation of a Ligand: An Interdisciplinary Laboratory Experiment for Second-Year Organic and Introductory Inorganic Chemistry Students

    ERIC Educational Resources Information Center

    Kasting, Benjamin J.; Bowser, Andrew K.; Anderson-Wile, Amelia M.; Wile, Bradley M.

    2015-01-01

    An interdisciplinary laboratory experiment involving second-year undergraduate organic chemistry and introductory inorganic chemistry undergraduate students is described. Organic chemistry students prepare a series of amine-bis(phenols) via a Mannich reaction, and characterize their products using melting point; FTIR; and [superscript 1]H,…

  3. Probing the chemistry of nickel/metal hydride battery cells using electrochemical impedance spectroscopy

    NASA Technical Reports Server (NTRS)

    Isaac, Bryan J.

    1994-01-01

    Electrochemical Impedance Spectroscopy (EIS) is a valuable tool for investigating the chemical and physical processes occurring at electrode surfaces. It offers information about electron transfer at interfaces, kinetics of reactions, and diffusion characteristics of the bulk phase between the electrodes. For battery cells, this technique offers another advantage in that it can be done without taking the battery apart. This non-destructive analysis technique can thus be used to gain a better understanding of the processes occurring within a battery cell. This also raises the possibility of improvements in battery design and identification or prediction of battery characteristics useful in industry and aerospace applications. EIS as a technique is powerful and capable of yielding significant information about the cell, but it also requires that the many parameters under investigation can be resolved. This implies an understanding of the processes occurring in a battery cell. Many battery types were surveyed in this work, but the main emphasis was on nickel/metal hydride batteries.

  4. Transport of two metal oxide nanoparticles in saturated granular porous media: role of water chemistry and particle coating.

    PubMed

    Petosa, Adamo Riccardo; Brennan, Spencer John; Rajput, Faraz; Tufenkji, Nathalie

    2012-03-15

    The growing use of nanosized titanium dioxide (nTiO2) and zinc oxide (nZnO) in a large number of commercial products raises concerns regarding their release and subsequent mobility in natural aquatic environments. Laboratory-scale sand-packed column experiments were conducted with bare and polymer-coated nTiO2 and nZnO to improve our understanding of the mobility of these nanoparticles in natural or engineered water saturated granular systems. The nanoparticles are characterized over a range of environmentally relevant water chemistries using multiple complimentary techniques: dynamic light scattering, nanoparticle tracking analysis, transmission electron microscopy, and scanning electron microscopy. Overall, bare (uncoated) nanoparticles exhibit high retention within the water saturated granular matrix at solution ionic strengths (IS) as low as 0.1 mM NaNO3 for bare nTiO2 and 0.01 mM NaNO3 for bare nZnO. Bare nTiO2 and nZnO also display dynamic (time-dependent) deposition behaviors under selected conditions. In contrast, the polymer-coated nanoparticles are much less likely to aggregate and exhibit significant transport potential at IS as high as 100 mM NaNO3 or 3 mM CaCl2. These findings illustrate the importance of considering the extent and type of surface modification when evaluating metal oxide contamination potential in granular aquatic environments. PMID:22236555

  5. EFFECT OF CHEMISTRY VARIATIONS IN PLATE AND WELD FILLER METAL ON THE CORROSION PERFORMANCE OF NI-CR-MO ALLOYS

    SciTech Connect

    D.V. Fix

    2006-02-07

    The ASTM standard B 575 provides the requirements for the chemical composition of Nickel-Chromium-Molybdenum (Ni-Cr-Mo) alloys such as Alloy 22 (N06022) and Alloy 686 (N06686). The compositions of each element are given in a range. For example, the content of Mo is specified from 12.5 to 14.5 weight percent for Alloy 22 and from 15.0 to 17.0 weight percent for Alloy 686. It was important to determine how the corrosion rate of welded plates of Alloy 22 using Alloy 686 weld filler metal would change if heats of these alloys were prepared using several variations in the composition of the elements even though still in the range specified in B 575. All the material used in this report were especially prepared at Allegheny Ludlum Co. Seven heats of plate were welded with seven heats of wire. Immersion corrosion tests were conducted in a boiling solution of sulfuric acid plus ferric sulfate (ASTM G 28 A) using both as-welded (ASW) coupons and solution heat-treated (SHT) coupons. Results show that the corrosion rate was not affected by the chemistry of the materials in the range of the standards.

  6. Laser-assisted solar cell metallization processing

    NASA Technical Reports Server (NTRS)

    Dutta, S.

    1984-01-01

    Laser-assisted processing techniques utilized to produce the fine line, thin metal grid structures that are required to fabricate high efficiency solar cells are examined. Two basic techniques for metal deposition are investigated; (1) photochemical decomposition of liquid or gas phase organometallic compounds utilizing either a focused, CW ultraviolet laser (System 1) or a mask and ultraviolet flood illumination, such as that provided by a repetitively pulsed, defocused excimer laser (System 2), for pattern definition, and (2) thermal deposition of metals from organometallic solutions or vapors utilizing a focused, CW laser beam as a local heat source to draw the metallization pattern.

  7. ROMP Synthesis of Iron-Containing Organometallic Polymers.

    PubMed

    Dragutan, Ileana; Dragutan, Valerian; Filip, Petru; Simionescu, Bogdan C; Demonceau, Albert

    2016-01-01

    The paper overviews iron-containing polymers prepared by controlled "living" ring-opening metathesis polymerization (ROMP). Developments in the design and synthesis of this class of organometallic polymers are highlighted, pinpointing methodologies and newest trends in advanced applications of hybrid materials based on polymers functionalized with iron motifs. PMID:26861276

  8. Organometalic carbosilane polymers containing vanadium and their preparation

    NASA Technical Reports Server (NTRS)

    Yajima, S.; Okamura, K.; Shishido, T.; Fukuda, K.

    1983-01-01

    The present invention concerns a new organometallic polymer material containing in part a vanadium-siloxane linkage (V-0-Si), which has excellent resistance to heat and oxidation and a high residue ratio after high temperature treatment in a non-oxidizing atmosphere, for example, nitrogen, argon, helium, ammonia, or hydrogen.

  9. Ligand Rearrangements of Organometallic Complexes inSolution

    SciTech Connect

    Shanoski, Jennifer E.

    2006-05-08

    Many chemical reactions utilize organometallic complexes as catalysts. These complexes find use in reactions as varied as bond activation, polymerization, and isomerization. This thesis outlines the construction of a new ultrafast laser system with an emphasis on the generation of tunable mid-infrared pulses, data collection, and data analysis.

  10. Preparation of activated carbons with mesopores by use of organometallics

    SciTech Connect

    Yamada, Yoshio; Yoshizawa, Noriko; Furuta, Takeshi

    1996-12-31

    Activated carbons are commercially produced by steam or CO{sub 2} activation of coal, coconut shell and so on. In general the carbons obtained give pores with a broad range of distribution. The objective of this study was to prepare activated carbons from coal by use of various organometallic compounds. The carbons were evaluated for pore size by nitrogen adsorption experiments.

  11. 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

    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.

  12. Unimolecular chemistry of metal ion-coordinated [alpha]-dipeptide radicals

    NASA Astrophysics Data System (ADS)

    Pingitore, Francesco; Bleiholder, Christian; Paizs, Béla; Wesdemiotis, Chrys

    2007-09-01

    The Li+ complexes of the isomeric [alpha]-dipeptide radicals H2NCHC(O)NHCH2COOH (GlyGly) and H2NCH2C(O)NHCHCOOH (GlyGly) are formed in the gas phase from the isomeric complexes [PheGly + Li]+ and [GlyPhe + Li]+, respectively, via homolytic cleavage of the corresponding benzyl side chains. The isomers undergo distinctively different reactions upon collisionally activated dissociation (CAD) and, hence, represent unique, non-interconverting species. The investigation of deuterated isotopomers and of dipeptide radicals with Ala residues permits complete elucidation of the dissociation pathways of the radical complexes. The majority of reactions observed are promoted by the radical site, with the location of the unpaired electron playing an important role in the types of reactions taking place. Analogous differences are found for dilithiated complexes of GlyGly and GlyGly, in which the COOH termini are derivatized to COO-Li+ salt bridges. Density functional theory calculations confirm that the lithiated and dilithiated [alpha]-dipeptide radicals have distonic character; the radical is largely localized on the N- or C-terminal [alpha]-C atom and the charge is largely localized on the metal ions. In the most stable conformers, the Li+ ion(s) are bound between the amide carbonyl and C-terminal carbonyl (or carboxylate) groups. Theory predicts a higher thermodynamic stability for the complexes of the N-terminal radical GlyGly, as reflected by the significantly higher yield, with which these complexes are formed (from their PheGly precursors), compared to the GlyGly complexes.

  13. Surface chemistry of plasma-assisted atomic layer deposition of Al2O3 studied by infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Langereis, E.; Keijmel, J.; van de Sanden, M. C. M.; Kessels, W. M. M.

    2008-06-01

    The surface groups created during plasma-assisted atomic layer deposition (ALD) of Al2O3 were studied by infrared spectroscopy. For temperatures in the range of 25-150°C, -CH3 and -OH were unveiled as dominant surface groups after the Al(CH3)3 precursor and O2 plasma half-cycles, respectively. At lower temperatures more -OH and C-related impurities were found to be incorporated in the Al2O3 film, but the impurity level could be reduced by prolonging the plasma exposure. The results demonstrate that -OH surface groups rule the surface chemistry of the Al2O3 process and likely that of plasma-assisted ALD of metal oxides from organometallic precursors in general.

  14. Atomic Scale Imaging of the Electronic Structure and Chemistry of Graphene and Its Precursors on Metal Surfaces

    SciTech Connect

    Flynn, George W

    2015-02-16

    Executive Summary of Final Report for Award DE-FG02-88ER13937 Project Title: Atomic Scale Imaging of the Electronic Structure and Chemistry of Graphene and its Precursors on Metal Surfaces Applicant/Institution: Columbia University Principal Investigator: George W. Flynn Objectives: The objectives of this project were to reveal the mechanisms and reaction processes that solid carbon materials undergo when combining with gases such as oxygen, water vapor and hydrocarbons. This research was focused on fundamental chemical events taking place on single carbon sheets of graphene, a two-dimensional, polycyclic carbon material that possesses remarkable chemical and electronic properties. Ultimately, this work is related to the role of these materials in mediating the formation of polycyclic aromatic hydrocarbons (PAH’s), their reactions at interfaces, and the growth of soot particles. Our intent has been to contribute to a fundamental understanding of carbon chemistry and the mechanisms that control the formation of PAH’s, which eventually lead to the growth of undesirable particulates. We expect increased understanding of these basic chemical mechanisms to spur development of techniques for more efficient combustion of fossil fuels and to lead to a concomitant reduction in the production of undesirable solid carbon material. Project Description: Our work treated specifically the surface chemistry aspects of carbon reactions by using proximal probe (atomic scale imaging) techniques to study model systems of graphene that have many features in common with soot forming reactions of importance in combustion flames. Scanning tunneling microscopy (STM) is the main probe technique that we used to study the interfacial structure and chemistry of graphene, mainly because of its ability to elucidate surface structure and dynamics with molecular or even atomic resolution. Scanning tunneling spectroscopy (STS), which measures the local density of quantum states over a single

  15. MALDI-TOFMS analysis of coordination and organometallic complexes: a nic(h)e area to work in.

    PubMed

    Wyatt, Mark F

    2011-07-01

    A mini-review of the characterisation of metal-containing compounds by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) is presented. Organometallic and coordination compounds have many varied applications, most notably in industrial catalytic processes and also in the electronics and healthcare sectors. In general, the compounds discussed, be they small or large molecules, have a high percentage metal content, rather than simply containing 'a metal atom'. A brief history of the field is given, but the main scope over the last 5 years is covered in some detail. How MALDI-TOFMS compliments electrospray for metal-containing compounds is highlighted. Perspectives on recent advances, such as solvent-free and air/moisture-sensitive sample preparation, and potential future challenges and developments, such as nanomaterials and metallodrug/metallometabolite imaging, are given. PMID:21744419

  16. Lattice-Directed Formation of Covalent and Organometallic Molecular Wires by Terminal Alkynes on Ag Surfaces.

    PubMed

    Liu, Jing; Chen, Qiwei; Xiao, Lianghong; Shang, Jian; Zhou, Xiong; Zhang, Yajie; Wang, Yongfeng; Shao, Xiang; Li, Jianlong; Chen, Wei; Xu, Guo Qin; Tang, Hao; Zhao, Dahui; Wu, Kai

    2015-06-23

    Surface reactions of 2,5-diethynyl-1,4-bis(phenylethynyl)benzene on Ag(111), Ag(110), and Ag(100) were systematically explored and scrutinized by scanning tunneling microscopy, molecular mechanics simulations, and density functional theory calculations. On Ag(111), Glaser coupling reaction became dominant, yielding one-dimensional molecular wires formed by covalent bonds. On Ag(110) and Ag(100), however, the terminal alkynes reacted with surface metal atoms, leading to one-dimensional organometallic nanostructures. Detailed experimental and theoretical analyses revealed that such a lattice dependence of the terminal alkyne reaction at surfaces originated from the matching degree between the periodicities of the produced molecular wires and the substrate lattice structures. PMID:25990647

  17. Absorption of organic compounds and organometallics on ceramic substrates for wear reduction

    SciTech Connect

    Kennedy, P.J.; Agarwala, V.S.

    1996-12-31

    The concept of employing thermally stable compounds (that is, metal oxides) as high temperature vapor phase ceramic lubricants was investigated. A major part of this study was devoted to the development of various calorimetric and tribological techniques that could be used to determine interfacial reactions between thermally stable compounds and ceramic substrates such as zirconia and alumina. This interaction is pivotal in understanding the mechanism of high temperature lubricity. The approach consisted of selecting low sublimation temperature materials and measuring their thermodynamic interactions as vapors with the ceramic substrates. The materials studied included two easily sublimable organic compounds (that is, naphthalene and salicylic acid) and several organometallics (for example, copper phthalocyanine). Thermodynamic data such as heat of adsorption, packing density, and reversibility of the adsorption were obtained on some of these compounds and were related to wear characteristics. All of these compounds provided effective lubrication at room temperature. Copper phthalocyanine was an effective lubricant at temperatures up to 400 C.

  18. Electronic and magnetic properties of silicon supported organometallic molecular wires: a density functional theory (DFT) study.

    PubMed

    Liu, Xia; Tan, Yingzi; Li, Xiuling; Wu, Xiaojun; Pei, Yong

    2015-08-28

    The electronic and magnetic properties of transition metal (TM = Sc, Ti, V, Cr and Mn) atom incorporated single and double one-dimensional (1D) styrene molecular wires confined on the hydrogen-terminated Si(100) surface are explored for the first time by means of spin-polarized density functional theory, denoted as Si-[TM(styrene)]. It is unveiled that TM atoms bind asymmetrically to the adjacent phenyl rings, which leads to novel electronic and magnetic properties in stark contrast to the well-studied gas phase TM-benzene molecular wires. Si-[Mn(styrene)]∞ and Si-[Cr(styrene)]∞ single molecular wires (SMWs) are a ferromagnetic semiconductor and half metal, respectively. Creation of H-atom defects on the silicon surface can introduce an impurity metallic band, which leads to novel half-metallic magnetism of a Si-[Mn(styrene)]∞ system. Moreover, double molecular wires (DMWs) containing two identical or hetero SMWs are theoretically designed. The [Mn(styrene)]∞-[Cr(styrene)]∞ DMW exhibits half-metallic magnetism where the spin-up and spin-down channels are contributed by two single molecular wires. Finally, we demonstrate that introducing a TM-defect may significantly affect the electronic structure and magnetic properties of molecular wires. These studies provide new insights into the structure and properties of surface supported 1-D sandwiched molecular wires and may inspire the future experimental synthesis of substrate confined organometallic sandwiched molecular wires. PMID:26219748

  19. In silico characterization of a fourfold magnesium organometallic compound in PTCDA thin films.

    PubMed

    Zazza, Costantino; Sanna, Nico; Palma, Amedeo

    2009-12-31

    In this contribution, using first principles calculations within a density functional theory framework, we report, for the first time, evidence for the formation of a fourfold magnesium organometallic compound upon metal deposition on perylene-3,4,9,10-tetracarboxyl dianhydride (PTCDA) organic semiconductor. Current investigation clearly indicates that in the bulk of the organic crystallographic structure the magnesium atom mainly interacts with three PTCDA molecules. The reactive metal is bound both to carboxylic oxygen atoms of the anhydride-end moieties and to a perylene carbon atom which changes its hybridization state, from sp(2) to sp(3), in the presence of metal impurities. In turn, the analysis of the electronic structure of the reacted system prevalently reveals the formation of four covalent bonds, as a consequence of a weak charge transfer toward the organic material. Such a result confirms the capability of the PTCDA thin films to host metal atoms providing, inside their structural empty channels, a rather accessible and soft chemical environment. Interestingly, in the light of these findings and of previous works, a relationship between first ionization potential of the doping metal and the character of the newly formed chemical bonds is confirmed. PMID:19788293

  20. Incorporation of metal related materials into electrically neutral polymers

    NASA Technical Reports Server (NTRS)

    St. Clair, A. K.; Taylor, L. T.

    1981-01-01

    Developments in the field of metal-containing polymers are reviewed with emphasis on neutral polymers incorporating dissolved metal salts, metal complexes, organometallic compounds, and metals. Polymer systems discussed include: polyamides, polyimides, polyalcohols, polyesters, polyacetylene, polyethylene, and polysiloxane. Most of the studies focus on the modification of polymer properties such as adhesive properties, thermal behavior, electrical conductivity, polymer flammability, and mechanical properties.

  1. High-Valent Organometallic Copper and Palladium in Catalysis

    PubMed Central

    Hickman, Amanda J.; Sanford, Melanie S.

    2015-01-01

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

  2. Metal-containing polymers: building blocks for functional (nano)materials.

    PubMed

    Wang, Xiaosong; McHale, Ronan

    2010-02-16

    The incorporation of metallic units into polymer chains has emerged as a promising route towards functional metal-containing (nano)materials. The resulting polymers possess rich functions derived from their metallic elements, such as redox, optical, catalytic and magnetic properties. In addition, the directional and dynamic nature of metal coordination interactions provides further variables for the exploration of novel materials with designed nanostructures. These types of polymers can be synthesized through direct metal-ligand coordination or chain polymerization of metal containing monomers. Depending on the polymerization techniques and starting components, the resulting polymers, akin to their organic counterparts, can be produced in the form of insoluble networks, processible chain structures, gels or colloids. Research into this rising multidisciplinary subject has benefited from recent progress in several related areas such as supramolecular chemistry, colloidal chemistry etc., with the combination of the relative merits of each ensuring further developments in each individual discipline. For example, as a result of studies into organometallic block copolymers self-assembly behavior, living supramolecular polymerization has been unprecedentedly realized for the architectural design of micelles (see image on the right). Nevertheless, the field is still in a developmental stage and offers ample opportunities for fundamental research, as well as material exploration. In this Feature Article, we intend to overview the field with a brief survey of recent literature. PMID:21590911

  3. Carbon–heteroatom bond formation catalysed by organometallic complexes

    PubMed Central

    Hartwig, John F.

    2010-01-01

    At one time the synthetic chemist’s last resort, reactions catalysed by transition metals are now the preferred method for synthesizing many types of organic molecule. A recent success in this type of catalysis is the discovery of reactions that form bonds between carbon and heteroatoms (such as nitrogen, oxygen, sulphur, silicon and boron) via complexes of transition metals with amides, alkoxides, thiolates, silyl groups or boryl groups. The development of these catalytic processes has been supported by the discovery of new elementary reactions that occur at metal–heteroatom bonds and by the identification of factors that control these reactions. Together, these findings have led to new synthetic processes that are in daily use and have formed a foundation for the development of processes that are likely to be central to synthetic chemistry in the future. PMID:18800130

  4. A GREEN CHEMISTRY APPROACH TO PREPARATION OF CORE (FE OR CU)-SHELL (NOBLE METALS) NANOCOMPOSITES USING AQUEOUS ASCORBIC ACID

    EPA Science Inventory

    A greener method to fabricate novel core (Fe or Cu)-shell (noble metals) nanocomposites of transition metals such as Fe and Cu and noble metals such as Au, Pt, Pd, and Ag using aqueous ascorbic acid is described. Transition metal salts such as Cu and Fe were reduced using ascor...

  5. Effectiveness of various organometallics as antiwear additives in mineral oil

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1977-01-01

    Sliding friction experiments were conducted with 1045 steel contacting 302 stainless steel and lubricated with various organometallics in mineral oil. Auger emission spectroscopy was used to determine the element present in the wear contact zone. The results indicate that there are organometallics which are as effective an antiwear additives as the commonly used zinc dialkyl dithiophosphate. These include dimethyl cadmium, triphenyl lead thiomethoxide, and triphenyl tin chloride. The additives were examined in concentrations to 1 weight percent. With dimethyl cadmium at concentrations of 0.5 weight percent and above, cadmium was detected in the contact zone. Coincident with the detection of cadmium, a marked decrease in the friction coefficient was observed. All additives examined reduced friction, but only the aforementioned reduced wear to a level comparable to that observed with zinc dialkyl dithiophosphate.

  6. Controlled Variable Oxidative Doping of Individual Organometallic Nanoparticles.

    PubMed

    Feng, Ann; Cheng, Wei; Holter, Jennifer; Young, Neil; Compton, Richard G

    2016-05-10

    The charging and controlled oxidative doping of single organometallic ferrocene nanoparticles is reported in aqueous sodium tetrafluoroborate using the nano-impacts method. It is shown that ferrocene nanoparticles of approximately 105 nm diameter are essentially quantitatively oxidatively doped with the uptake of one tetrafluoroborate anion per ferrocene molecule at suitably high overpotentials. By using lower potentials, it is possible to achieve low doping levels of single nanoparticles in a controlled manner. PMID:27038252

  7. Synthesis of high molecular weight PEO using non-metal initiators

    DOEpatents

    Yang, Jin; Sivanandan, Kulandaivelu; Pistorino, Jonathan; Eitouni, Hany Basam

    2015-05-19

    A new synthetic method to prepare high molecular weight poly(ethylene oxide) with a very narrow molecular weight distribution (PDI<1.5) is described. The method involves a metal free initiator system, thus avoiding dangerous, flammable organometallic compounds.

  8. p-type Mesoscopic Nickel Oxide/Organometallic Perovskite Heterojunction Solar Cells

    PubMed Central

    Wang, Kuo-Chin; Jeng, Jun-Yuan; Shen, Po-Shen; Chang, Yu-Cheng; Diau, Eric Wei-Guang; Tsai, Cheng-Hung; Chao, Tzu-Yang; Hsu, Hsu-Cheng; Lin, Pei-Ying; Chen, Peter; Guo, Tzung-Fang; Wen, Ten-Chin

    2014-01-01

    In this article, we present a new paradigm for organometallic hybrid perovskite solar cell using NiO inorganic metal oxide nanocrystalline as p-type electrode material and realized the first mesoscopic NiO/perovskite/[6,6]-phenyl C61-butyric acid methyl ester (PC61BM) heterojunction photovoltaic device. The photo-induced transient absorption spectroscopy results verified that the architecture is an effective p-type sensitized junction, which is the first inorganic p-type, metal oxide contact material for perovskite-based solar cell. Power conversion efficiency of 9.51% was achieved under AM 1.5 G illumination, which significantly surpassed the reported conventional p-type dye-sensitized solar cells. The replacement of the organic hole transport materials by a p-type metal oxide has the advantages to provide robust device architecture for further development of all-inorganic perovskite-based thin-film solar cells and tandem photovoltaics. PMID:24755642

  9. From linking of metal-oxide building blocks in a dynamic library to giant clusters with unique properties and towards adaptive chemistry.

    PubMed

    Müller, Achim; Gouzerh, Pierre

    2012-11-21

    Following Nature's lessons, today chemists can cross the boundary of the small molecule world to construct multifunctional and highly complex molecular nano-objects up to protein size and even cell-like nanosystems showing responsive sensing. Impressive examples emerge from studies of the solutions of some oxoanions of the early transition metals especially under reducing conditions which enable the controlled linking of metal-oxide building blocks. The latter are available from constitutional dynamic libraries, thus providing the option to generate multifunctional unique nanoscale molecular systems with exquisite architectures, which even opens the way towards adaptive and evolutive (Darwinian) chemistry. The present review presents the first comprehensive report of current knowledge (including synthesis aspects not discussed before) regarding the related giant metal-oxide clusters mainly of the type {Mo(57)M'(6)} (M' = Fe(III), V(IV)) (torus structure), {M(72)M'(30)} (M = Mo, M' = V(IV), Cr(III), Fe(III), Mo(V)), {M(72)Mo(60)} (M = Mo, W) (Keplerates), {Mo(154)}, {Mo(176)}, {Mo(248)} ("big wheels"), and {Mo(368)} ("blue lemon") - all having the important transferable pentagonal {(M)M(5)} groups in common. These discoveries expanded the frontiers of inorganic chemistry to the mesoscopic world, while there is probably no collection of discrete inorganic compounds which offers such a versatile chemistry and the option to study new phenomena of interdisciplinary interest. The variety of different properties of the sphere- and wheel-type metal-oxide-based clusters can directly be related to their unique architectures: The spherical Keplerate-type capsules having 20 crown-ether-type pores and tunable internal functionalities allow the investigation of confined matter as well as that of sphere-surface-supramolecular and encapsulation chemistry - including related new aspects of the biologically important hydrophobic effects - but also of nanoscale ion transport and

  10. Sterically Hindered Square-Planar Nickel(II) Organometallic Complexes: Preparation, Characterization, and Substitution Behavior

    ERIC Educational Resources Information Center

    Martinez, Manuel; Muller, Guillermo; Rocamora, Merce; Rodriguez, Carlos

    2007-01-01

    The series of experiments proposed for advanced undergraduate students deal with both standard organometallic preparative methods in dry anaerobic conditions and with a kinetic study of the mechanisms operating in the substitution of square-planar complexes. The preparation of organometallic compounds is carried out by transmetallation or…

  11. Organometallic Palladium Reagents for Cysteine Bioconjugation

    PubMed Central

    Vinogradova, Ekaterina V.; Zhang, Chi; Spokoyny, Alexander M.; Pentelute, Bradley L.; Buchwald, Stephen L.

    2015-01-01

    Transition-metal based reactions have found wide use in organic synthesis and are used frequently to functionalize small molecules.1,2 However, there are very few reports of using transition-metal based reactions to modify complex biomolecules3,4, which is due to the need for stringent reaction conditions (for example, aqueous media, low temperature, and mild pH) and the existence of multiple, reactive functional groups found in biopolymers. Here we report that palladium(II) complexes can be used for efficient and highly selective cysteine conjugation reactions. The bioconjugation reaction is rapid and robust under a range of biocompatible reaction conditions. The straightforward synthesis of the palladium reagents from diverse and easily accessible aryl halide and trifluoromethanesulfonate precursors makes the method highly practical, providing access to a large structural space for protein modification. The resulting aryl bioconjugates are stable towards acids, bases, oxidants, and external thiol nucleophiles. The broad utility of the new bioconjugation platform was further corroborated by the synthesis of new classes of stapled peptides and antibody-drug conjugates. These palladium complexes show potential as a new set of benchtop reagents for diverse bioconjugation applications. PMID:26511579

  12. Organometallic palladium reagents for cysteine bioconjugation.

    PubMed

    Vinogradova, Ekaterina V; Zhang, Chi; Spokoyny, Alexander M; Pentelute, Bradley L; Buchwald, Stephen L

    2015-10-29

    Reactions based on transition metals have found wide use in organic synthesis, in particular for the functionalization of small molecules. However, there are very few reports of using transition-metal-based reactions to modify complex biomolecules, which is due to the need for stringent reaction conditions (for example, aqueous media, low temperature and mild pH) and the existence of multiple reactive functional groups found in biomolecules. Here we report that palladium(II) complexes can be used for efficient and highly selective cysteine conjugation (bioconjugation) reactions that are rapid and robust under a range of bio-compatible reaction conditions. The straightforward synthesis of the palladium reagents from diverse and easily accessible aryl halide and trifluoromethanesulfonate precursors makes the method highly practical, providing access to a large structural space for protein modification. The resulting aryl bioconjugates are stable towards acids, bases, oxidants and external thiol nucleophiles. The broad utility of the bioconjugation platform was further corroborated by the synthesis of new classes of stapled peptides and antibody-drug conjugates. These palladium complexes show potential as benchtop reagents for diverse bioconjugation applications. PMID:26511579

  13. Organometallic palladium reagents for cysteine bioconjugation

    NASA Astrophysics Data System (ADS)

    Vinogradova, Ekaterina V.; Zhang, Chi; Spokoyny, Alexander M.; Pentelute, Bradley L.; Buchwald, Stephen L.

    2015-10-01

    Reactions based on transition metals have found wide use in organic synthesis, in particular for the functionalization of small molecules. However, there are very few reports of using transition-metal-based reactions to modify complex biomolecules, which is due to the need for stringent reaction conditions (for example, aqueous media, low temperature and mild pH) and the existence of multiple reactive functional groups found in biomolecules. Here we report that palladium(II) complexes can be used for efficient and highly selective cysteine conjugation (bioconjugation) reactions that are rapid and robust under a range of bio-compatible reaction conditions. The straightforward synthesis of the palladium reagents from diverse and easily accessible aryl halide and trifluoromethanesulfonate precursors makes the method highly practical, providing access to a large structural space for protein modification. The resulting aryl bioconjugates are stable towards acids, bases, oxidants and external thiol nucleophiles. The broad utility of the bioconjugation platform was further corroborated by the synthesis of new classes of stapled peptides and antibody-drug conjugates. These palladium complexes show potential as benchtop reagents for diverse bioconjugation applications.

  14. Magnetism in Chemistry

    ERIC Educational Resources Information Center

    Brookes, R. W.; McFadyen, W. D.

    1975-01-01

    Discusses the technical aspects of paramagnetism and an electrostatic model called Crystal Field Theory (CFT), very often used in the case of transition metal compounds. Suggests that this discussion be included as an option for college chemistry courses. (MLH)

  15. Environmental Bioinorganic Chemistry

    ERIC Educational Resources Information Center

    Ochiai, Ei-Ichiro

    1974-01-01

    Discusses some important aspects of bioinorganic chemistry, including interactions of organisms with metallic and nonmetallic elements and compounds. Indicates that many environmental problems are created by human exploitation of nature and technologies if studied from a bioinorganic chemical viewpoint. (CC)

  16. Chemistry and morphology of coal liquefaction. Annual report, October 1, 1979-September 30, 1980

    SciTech Connect

    Heinemann, H.

    1980-09-01

    The present annual report summarizes quarterly reports and includes work performed during the last quarter of fiscal 1980. The first year of this project has just been completed and much of the time and effort has been concentrated on equipment building, assembling, testing, and on staffing. This, of course, has been more true in the areas of work with spectroscopic and high pressure equipment than in organic chemical reactions. More experimental results are therefore reported in the areas of hydrogen transfer mechanisms and catalysis and organo-metallic chemistry. A few of the significant results in these and other areas are the evidence for catalysis in hydrogen transfer from tetralin; a novel and possibly very important new synthesis of alkyl aromatics from benzene, carbon monoxide, and hydrogen; the study of coals in the transmission electron microscope identifying coal macerals, minerals and metals, and leading to the possibility of observing location of and catalytic influences on pyrolysis and hydrogenation at elevated temperatures; the finding that scales formed on deactivated cobalt-molybdena-alumina-hydrogenation catalysts contain not only metals from the liquid feedstocks, but also molybdenum sulfide which must derive from migration from the catalyst interior to and beyond the surface. Insights gained in mechanisms of pyrolysis, hydrogenation, hydrogen transfer, and indirect liquefaction of coal promise to lead to improving technology by defining problem areas and showing routes to by-pass problems.

  17. FORUM: Bioinspired Heme, Heme/non-heme Diiron, Heme/copper and Inorganic NOx Chemistry: ·NO(g) Oxidation, Peroxynitrite-Metal Chemistry and ·NO(g) Reductive Coupling

    PubMed Central

    Schopfer, Mark P.; Wang, Jun; Karlin, Kenneth D.

    2010-01-01

    The focus of this Forum review highlights work from our own laboratories and those of others in the area of biochemical and biologically inspired inorganic chemistry dealing with nitric oxide (nitrogen monoxide, ·NO(g)) and its biological roles and reactions. The latter focus is on (i) oxidation of ·NO(g) to nitrate by nitric oxide dioxygenases (NOD’s), and (ii) reductive coupling of two molecules of ·NO(g) to give N2O(g). In the former case, NOD’s are described and the highlighting of possible peroxynitrite-heme intermediates and consequences of this are given by discussion of recent works with myoglobin and a synthetic heme model system for NOD action. Summaries of recent copper complex chemistries with ·NO(g) and O2(g) leading to peroxynitrite species are given. The coverage of biological reductive coupling of ·NO(g) deals with bacterial nitric oxide reductases (NOR’s) with heme/non-heme diiron active sites, and on heme/Cu oxidases such as cytochrome c oxidase which can mediate the same chemistry. Recent designed protein and synthetic model compound (heme/non-heme diiron or heme/copper) as functional mimics are discussed in some detail. We also highlight examples from the chemical literature, not necessarily involving biologically relevant metal ions, which describe the oxidation of ·NO(g) to nitrate (or nitrite) and possible peroxynitrite intermediates, or reductive coupling of ·NO(g) to give nitrous oxide. PMID:20666386

  18. Metal complexes containing natural and and artificial radioactive elements and their applications.

    PubMed

    Kharissova, Oxana V; Méndez-Rojas, Miguel A; Kharisov, Boris I; Méndez, Ubaldo Ortiz; Martínez, Perla Elizondo

    2014-01-01

    Recent advances (during the 2007-2014 period) in the coordination and organometallic chemistry of compounds containing natural and artificially prepared radionuclides (actinides and technetium), are reviewed. Radioactive isotopes of naturally stable elements are not included for discussion in this work. Actinide and technetium complexes with O-, N-, N,O, N,S-, P-containing ligands, as well π-organometallics are discussed from the view point of their synthesis, properties, and main applications. On the basis of their properties, several mono-, bi-, tri-, tetra- or polydentate ligands have been designed for specific recognition of some particular radionuclides, and can be used in the processes of nuclear waste remediation, i.e., recycling of nuclear fuel and the separation of actinides and fission products from waste solutions or for analytical determination of actinides in solutions; actinide metal complexes are also usefulas catalysts forcoupling gaseous carbon monoxide,as well as antimicrobial and anti-fungi agents due to their biological activity. Radioactive labeling based on the short-lived metastable nuclide technetium-99m ((99m)Tc) for biomedical use as heart, lung, kidney, bone, brain, liver or cancer imaging agents is also discussed. Finally, the promising applications of technetium labeling of nanomaterials, with potential applications as drug transport and delivery vehicles, radiotherapeutic agents or radiotracers for monitoring metabolic pathways, are also described. PMID:25061724

  19. Surface chemistry, friction and wear of Ni-Zn and Mn-Zn ferrites in contact with metals

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1982-01-01

    X-ray photoelectron and Auger electron spectroscopy analysis were used in sliding friction experiments. These experiments were conducted with hot-pressed polycrystalline Ni-Zn and Mn-Zn ferrites, and single-crystal Mn-Zn ferrite in contact with various transition metals at room temperature in both vacuum and argon. The results indicate that Ni2O3 and Fe3O4 were present on the Ni-Zn ferrite surface in addition to the nominal bulk constituents, while MnO2 and Fe3O4 were present on the Mn-Zn ferrite surface in addition to the nominal bulk constituents. The coefficients of friction for the ferrites in contact with metals were related to the relative chemical activity of these metals. The more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites were correlated with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite does strengthen the metal-ferrite contact and increase the friction. The ferrites exhibit local cracking and fracture with sliding under adhesive conditions. All the metals transferred to he surfaces of the ferrites in sliding.

  20. Electronic and magnetic properties of silicon supported organometallic molecular wires: a density functional theory (DFT) study

    NASA Astrophysics Data System (ADS)

    Liu, Xia; Tan, Yingzi; Li, Xiuling; Wu, Xiaojun; Pei, Yong

    2015-08-01

    The electronic and magnetic properties of transition metal (TM = Sc, Ti, V, Cr and Mn) atom incorporated single and double one-dimensional (1D) styrene molecular wires confined on the hydrogen-terminated Si(100) surface are explored for the first time by means of spin-polarized density functional theory, denoted as Si-[TM(styrene)]. It is unveiled that TM atoms bind asymmetrically to the adjacent phenyl rings, which leads to novel electronic and magnetic properties in stark contrast to the well-studied gas phase TM-benzene molecular wires. Si-[Mn(styrene)]∞ and Si-[Cr(styrene)]∞ single molecular wires (SMWs) are a ferromagnetic semiconductor and half metal, respectively. Creation of H-atom defects on the silicon surface can introduce an impurity metallic band, which leads to novel half-metallic magnetism of a Si-[Mn(styrene)]∞ system. Moreover, double molecular wires (DMWs) containing two identical or hetero SMWs are theoretically designed. The [Mn(styrene)]∞-[Cr(styrene)]∞ DMW exhibits half-metallic magnetism where the spin-up and spin-down channels are contributed by two single molecular wires. Finally, we demonstrate that introducing a TM-defect may significantly affect the electronic structure and magnetic properties of molecular wires. These studies provide new insights into the structure and properties of surface supported 1-D sandwiched molecular wires and may inspire the future experimental synthesis of substrate confined organometallic sandwiched molecular wires.The electronic and magnetic properties of transition metal (TM = Sc, Ti, V, Cr and Mn) atom incorporated single and double one-dimensional (1D) styrene molecular wires confined on the hydrogen-terminated Si(100) surface are explored for the first time by means of spin-polarized density functional theory, denoted as Si-[TM(styrene)]. It is unveiled that TM atoms bind asymmetrically to the adjacent phenyl rings, which leads to novel electronic and magnetic properties in stark contrast to

  1. The Quantitative Resolution of a Mixture of Group II Metal Ions by Thermometric Titration with EDTA. An Analytical Chemistry Experiment.

    ERIC Educational Resources Information Center

    Smith, Robert L.; Popham, Ronald E.

    1983-01-01

    Presents an experiment in thermometric titration used in an analytic chemistry-chemical instrumentation course, consisting of two titrations, one a mixture of calcium and magnesium, the other of calcium, magnesium, and barium ions. Provides equipment and solutions list/specifications, graphs, and discussion of results. (JM)

  2. Electronic configurations and magnetic anisotropy in organometallic metallocenes

    NASA Astrophysics Data System (ADS)

    Nawa, Kenji; Kitaoka, Yukie; Nakamura, Kohji; Akiyama, Toru; Ito, Tomonori

    2015-05-01

    Electronic configurations and magnetic anisotropy of organometallic metallocenes (MCp2s) were investigated by means of first principles calculations based on the constraint density functional theory. The results predict that the ground states for M = Cr, Mn, Fe, Co, and Ni are the 3E2 g, 2E2 g, 1A1 g, 2E1 g, and 3A2 g states, respectively. The magnetizations of the CoCp2 and NiCp2 energetically favor highly orienting along the perpendicular and parallel directions to the cyclopentadienyl (Cp) plane, respectively, and the others show almost no preference for the magnetic easy axis.

  3. CVD Of Thin Films From Single Organometallic Precursors

    NASA Technical Reports Server (NTRS)

    Hepp, Aloysius F.; Barron, Andrew R.; Power, Michael B.; Macinnes, Andrew N.; Jenkins, Phillip P.

    1996-01-01

    Method of forming thin inorganic films involves chemical vapor deposition (CVD) from single organometallic precursors. No toxic constituents, minimizes impurities, and yields films having substantially uniform crystal structure and composition. Especially suitable for depositing high-quality passivating or buffer layers of GaS on GaAs semiconductor substrates. Also applicable to formation of high-quality films for purposes other than buffering or passivation, and to different materials in which another element from same group in periodic table of elements substituted for all or portion of each element in GaS/GaAs system.

  4. Mass Spectrometry Uncovers Molecular Reactivities of Coordination and Organometallic Gold(III) Drug Candidates in Competitive Experiments That Correlate with Their Biological Effects.

    PubMed

    Meier, Samuel M; Gerner, Christopher; Keppler, Bernhard K; Cinellu, Maria Agostina; Casini, Angela

    2016-05-01

    The reactivity of three cytotoxic organometallic gold(III) complexes with cyclometalated C,N,N and C,N ligands (either six- or five-membered metallacycles), as well as that of two representative gold(III) complexes with N-donor ligands, with biological nucleophiles has been studied by ESI-MS on ion trap and time-of-flight instruments. Specifically, the gold compounds were reacted with mixtures of nucleophiles containing l-histidine (imine), l-methionine (thioether), l-cysteine (thiol), l-glutamic acid (carboxylic acid), methylseleno-l-cysteine (selenoether), and in situ generated seleno-l-cysteine (selenol) to judge the preference of the gold compounds for binding to selenium-containing amino acid residues. Moreover, the gold compounds' reactivity was studied with proteins and nucleic acid building blocks. These experiments revealed profound differences between the coordination and organometallic families and even within the family of organometallics, which allowed insights to be gained into the compounds mechanisms of action. In particular, interactions with seleno-l-cysteine appear to reflect well the compounds' inhibition properties of the seleno-enzyme thioredoxin reductase and to a certain extent their antiproliferative effects in vitro. Therefore, mass spectrometry is successfully applied for linking the molecular reactivity and target preferences of metal-based drug candidates to their biological effects. Finally, this experimental setup is applicable to any other metallodrug that undergoes ligand substitution reactions and/or redox changes as part of its mechanism of action. PMID:26866307

  5. Mass spectrometry. [in organic ion and biorganic chemistry and medicine

    NASA Technical Reports Server (NTRS)

    Burlingame, A. L.; Cox, R. E.; Derrick, P. J.

    1974-01-01

    Review of the present status of mass spectrometry in the light of pertinent recent publications spanning the period from December 1971 to January 1974. Following an initial survey of techniques, instruments, and computer applications, a sharp distinction is made between the chemistry of organic (radical-)ions and analytical applications in biorganic chemistry and medicine. The emphasis is on the chemistry of organic (radical-)ions at the expense of inorganic, organometallic, and surface ion chemistry. Biochemistry and medicine are chosen because of their contemporary importance and because of the stupendous contributions of mass spectroscopy to these fields in the past two years. In the review of gas-phase organic ion chemistry, special attention is given to studies making significant contributions to the understanding of ion chemistry.

  6. Preparation, Characterization, and Postsynthetic Modification of Metal-Organic Frameworks: Synthetic Experiments for an Undergraduate Laboratory Course in Inorganic Chemistry

    ERIC Educational Resources Information Center

    Sumida, Kenji; Arnold, John

    2011-01-01

    Metal-organic frameworks (MOFs) are crystalline materials that are composed of an infinite array of metal nodes (single ions or clusters) linked to one another by polyfunctional organic compounds. Because of their extraordinary surface areas and high degree of control over the physical and chemical properties, these materials have received much…

  7. Structural biology of the sequestration and transport of heavy metal toxins: NMR structure determination of proteins containing the -Cys-X-Y-Cys-metal binding motifs. 1997 annual progress report

    SciTech Connect

    Opella, S.J.

    1997-01-01

    'There are enormous amounts of heavy metals in the environment, much of it in the form of organometallic compounds resulting from various types of industrial and military waste. Nearly all of these metals and compounds are highly toxic to biological organisms including humans. However, some bacteria thrive in the presence of high concentrations of heavy metal toxins because they possess efficient mechanisms for the detoxification of these metals and compounds. Heavy metals appear to be universally toxic because of their non-selective chemistry, for example Hg(II) reacts with essentially all exposed sulfhydryl groups on proteins, thus, it may seem surprising that any organism at all can survive these chemical insults much less those that grow in a toxic milieu. However, the prebiotic environment was undoubtedly heavily polluted with heavy metals from geological processes, and the most primitive organisms simply had to evolve mechanisms for dealing with them if they were going to be able to utilize Cys, His, and the other amino acids that contribute to metal binding sites in their proteins. Genes associated with bacterial resistance to Ag, AsO{sub 2}, AsO{sub 4}, Bi, Cd, Co, CrO{sub 4}, Cu, Hg, iNi, TeO{sub 3}, TI, Pb, Zn, and other metals of environmental concern have been described (Silver, 1992; Silver and Walderhaug, 1995).'

  8. Development of a method for detecting trace metals in aqueous solutions based on the coordination chemistry of hexahydrotriazines.

    PubMed

    Wojtecki, Rudy J; Yuen, Alexander Y; Zimmerman, Thomas G; Jones, Gavin O; Horn, Hans W; Boday, Dylan J; Hedrick, James L; García, Jeannette M

    2015-08-01

    The detection of trace amounts (<10 ppb) of heavy metals in aqueous solutions is described using 1,3,5-hexahydro-1,3,5-triazines (HTs) as chemical indicators and a low cost fluorimeter-based detection system. This method takes advantage of the inherent properties of HTs to coordinate strongly with metal ions in solution, a fundamental property that was studied using a combination of analytical tools (UV-Vis titrations, (1)H-NMR titrations and computational modeling). Based on these fundamental studies that show significant changes in the HT UV signature when a metal ion is present, HT compounds were used to prepare indicator strips that resulted in significant fluorescence changes when a metal was present. A portable and economical approach was adopted to test the concept of utilizing HTs to detect heavy metals using a fluorimeter system that consisted of a low-pressure mercury lamp, a photo-detector, a monolithic photodiode and an amplifier, which produces a voltage proportional to the magnitude of the visible fluorescence emission. Readings of the prepared HT test strips were evaluated by exposure to two different heavy metals at the safe threshold concentration described by the U.S. Environmental Protection Agency (EPA) for Cr(3+) and Ag(2+) (100 μg L(-1) and 6.25, respectively). This method of detection could be used to the presence of either metal at these threshold concentrations. PMID:26035633

  9. Two-Photon Absorption in Organometallic Bromide Perovskites.

    PubMed

    Walters, Grant; Sutherland, Brandon R; Hoogland, Sjoerd; Shi, Dong; Comin, Riccardo; Sellan, Daniel P; Bakr, Osman M; Sargent, Edward H

    2015-09-22

    Organometallic trihalide perovskites are solution-processed semiconductors that have made great strides in third-generation thin film light-harvesting and light-emitting optoelectronic devices. Recently, it has been demonstrated that large, high-purity single crystals of these perovskites can be synthesized from the solution phase. These crystals' large dimensions, clean bandgap, and solid-state order have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW(-1) at 800 nm, comparable to epitaxial single-crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics. PMID:26196162

  10. Chemistry and fate of heavy metals in soils. (Latest citations from the Selected Water Resources Abstracts data base). Published Search

    SciTech Connect

    Not Available

    1992-05-01

    The bibliography contains citations concerning the kinetics, mobilization, uptake, and disposition of heavy metals in soil, sediment, loam, clay, gravel, silt, and sand. Heavy metal species studied include cadmium, zinc, lead, mercury, and arsenic. Environmental studies from governmental agencies, universities, and private industry covering ground water transport, bioaccumulation, sources of contamination, analytical methods, and chemical reactions are presented. (Contains 250 citations and includes a subject term index and title list.)

  11. New Mechanistic Insights on the Selectivity of Transition-Metal-Catalyzed Organic Reactions: The Role of Computational Chemistry.

    PubMed

    Zhang, Xinhao; Chung, Lung Wa; Wu, Yun-Dong

    2016-06-21

    With new advances in theoretical methods and increased computational power, applications of computational chemistry are becoming practical and routine in many fields of chemistry. In organic chemistry, computational chemistry plays an indispensable role in elucidating reaction mechanisms and the origins of various selectivities, such as chemo-, regio-, and stereoselectivities. Consequently, mechanistic understanding improves synthesis and assists in the rational design of new catalysts. In this Account, we present some of our recent works to illustrate how computational chemistry provides new mechanistic insights for improvement of the selectivities of several organic reactions. These examples include not only explanations for the existing experimental observations, but also predictions which were subsequently verified experimentally. This Account consists of three sections discuss three different kinds of selectivities. The first section discusses the regio- and stereoselectivities of hydrosilylations of alkynes, mainly catalyzed by [Cp*Ru(MeCN)3](+) or [CpRu(MeCN)3](+). Calculations suggest a new mechanism that involves a key ruthenacyclopropene intermediate. This mechanism not only explains the unusual Markovnikov regio-selectivity and anti-addition stereoselectivity observed by Trost and co-workers, but also motivated further experimental investigations. New intriguing experimental observations and further theoretical studies led to an extension of the reaction mechanism. The second section includes three cases of meta-selective C-H activation of aryl compounds. In the case of Cu-catalyzed selective meta-C-H activation of aniline, a new mechanism that involves a Cu(III)-Ar-mediated Heck-like transition state, in which the Ar group acts as an electrophile, was proposed. This mechanism predicted a higher reactivity for more electron-deficient Ar groups, which was supported by experiments. For two template-mediated, meta-selective C-H bond activations catalyzed by

  12. Alumina-supported bimetallics of palladium alloyed with germanium, tin, lead, or antimony from organometallic precursors I. Preparation and characterization

    SciTech Connect

    Aduriz, H.R.; Bodnariuk, P. , Bahia Blanca ); Coq, B.; Figueras, F. )

    1989-09-01

    Bimetallic PdSn, PdSb, PdPb, and PdGe on alumina catalysts with a low metal content have been prepared using either chloride or organometallic precursors. For the catalysts obtained from chloride precursors no interaction was observed between the two metals, and the catalysts behaved like pure Pd/Al{sub 2}O{sub 3}. In contrast, the reactions of (C{sub 4}H{sub 9}){sub 4}Sn, (C{sub 4}H{sub 9}){sub 4}Pb, (C{sub 4}H{sub 9}){sub 4}Ge, or (C{sub 4}H{sub 9}){sub 3}Sb in n-heptane solution with reduced Pd/Al{sub 2}O{sub 3} catalyst yielded a supported alloy. The interaction between metallic palladium and the organic modifier is highly selective and leads to the formation of a well-tailored bimetallic catalyst. When these final solids are reduced at 573 or 773 K, the second metal locates preferentially at the outer layer of the bimetallic aggregates. After reduction at 773 K large metallic aggregates are obtained (particle size 15 nm), and the formation of {beta}-palladium hydride, which can be formed with pure palladium catalysts, is suppressed by the addition of a small amount of the second metal. The specific activity of the palladium surface atoms for isoprene hydrogenation is then lowered, and the selectivity increased.

  13. Formation of Metal-Semiconductor Interfaces on Mbe-Grown Gallium ARSENIDE(100): Surface Photovoltage, Chemistry and Band Bending

    NASA Astrophysics Data System (ADS)

    Mao, Duli

    1992-01-01

    The chemical, structural and electronic properties of the metal-GaAs interfaces formed on the polar (100) surface are studied using high resolution core level photoemission spectroscopy (PES) and low energy electron diffraction (LEED). The clean (4 x 2)-c(8 x 2) reconstructed GaAs(100) surface, prepared by molecular beam epitaxy and subsequent thermal decapping of an As protective layer, is characterized carefully. Ga 3d and As 3d core levels are analyzed using test square curve fitting. Two Ga surface components are resolved while only one surface component is necessary for As. The assignment of these surface components to different surface atomic arrangements is discussed. The surface Fermi level position with respect to the valence band maximum is also investigated as a function of decapping temperature. Metal (In, Ga, Au)/GaAs(100) interfaces, formed at both room (RT) and low temperature (LT), are studied. The morphology of these interfaces resembles that of metal/GaAs(110) interfaces formed at LT, in that the deposited metal atoms reside at the surface as isolated adatoms rather than as clusters at submonolayer coverage. Metal clustering is only important at coverages higher than a few monolayers and is more prominent at RT than at LT. The GaAs(100) band bending is studied as a function of metal coverage and deposition temperature. At submonolayer metal coverages, In and Ga both cause reduced band bending (~ 0.2eV) on n-type GaAs, a phenomenon similar to the Fermi level overshoot observed at LT-formed metal/p-GaAs(110) interfaces and indicative of formation of adatom-induced donor levels in the upper part of the band gap. With Au, In and Ga, the Fermi level is pinned at 0.4eV, 0.6eV and 0.68eV above the valence band maximum respectively, in good agreement with the results obtained at metal/GaAs(110) interfaces. This contradicts recent claims of near-Schottky limit for these interfaces. Evidence of correlation between pinning and overlayer metallization is

  14. Chemistry of glass-ceramic to metal bonding for header applications. I. Effect of treatments on Inconel 718 and Hastelloy C-276 metallic surfaces

    SciTech Connect

    Kramer, D P; Craven, S M; Schneider, R E; Moddeman, W E; Brohard, D W

    1984-02-02

    Auger electron spectroscopy and depth Auger profiling were used to study the surfaces of Inconel 718 and Hastelloy C-276. The metal surfaces were processed in the same manner as is presently being used in the manufacturing of glass-ceramic headers. At each step in the process, samples were studied with Auger spectroscopy to determine their resultant elemental surface composition and film thickness. In addition, the effect of a final plasma cleaning operation on the metal surface was examined. The results show that the type and concentration of surface species and the thickness of the surface oxides are dependent on the processing technique.

  15. Combining Organometallic Reagents, the Sulfur Dioxide Surrogate DABSO, and Amines: A One-Pot Preparation of Sulfonamides, Amenable to Array Synthesis**

    PubMed Central

    Deeming, Alex S; Russell, Claire J; Willis, Michael C

    2015-01-01

    We describe a method for the synthesis of sulfonamides through the combination of an organometallic reagent, a sulfur dioxide equivalent, and an aqueous solution of an amine under oxidative conditions (bleach). This simple reaction protocol avoids the need to employ sulfonyl chloride substrates, thus removing the limitation imposed by the commercial availability of these reagents. The resultant method allows access to new chemical space, and is also tolerant of the polar functional groups needed to impart favorable physiochemical properties required for medicinal chemistry and agrochemistry. The developed chemistry is employed in the synthesis of a targeted 70 compound array, prepared using automated methods. The array achieved a 93 % success rate for compounds prepared. Calculated molecular weights, lipophilicities, and polar surface areas are presented, demonstrating the utility of the method for delivering sulfonamides with drug-like properties. PMID:25431118

  16. Combining organometallic reagents, the sulfur dioxide surrogate DABSO, and amines: a one-pot preparation of sulfonamides, amenable to array synthesis.

    PubMed

    Deeming, Alex S; Russell, Claire J; Willis, Michael C

    2015-01-19

    We describe a method for the synthesis of sulfonamides through the combination of an organometallic reagent, a sulfur dioxide equivalent, and an aqueous solution of an amine under oxidative conditions (bleach). This simple reaction protocol avoids the need to employ sulfonyl chloride substrates, thus removing the limitation imposed by the commercial availability of these reagents. The resultant method allows access to new chemical space, and is also tolerant of the polar functional groups needed to impart favorable physiochemical properties required for medicinal chemistry and agrochemistry. The developed chemistry is employed in the synthesis of a targeted 70 compound array, prepared using automated methods. The array achieved a 93% success rate for compounds prepared. Calculated molecular weights, lipophilicities, and polar surface areas are presented, demonstrating the utility of the method for delivering sulfonamides with drug-like properties. PMID:25431118

  17. Structural chemistry of peroxo compounds of group VI transition metals: II. Peroxo complexes of molybdenum and tungsten: A review

    SciTech Connect

    Sergienko, V. S.

    2008-01-15

    The specific features revealed in the structure of the molybdenum and tungsten peroxo complexes with the ratios M: O{sub 2} = 1: 1, 1: 2, and 1: 4 are considered. It is demonstrated that the geometry of the coordination polyhedron of the metal atom is primarily determined by the 'metal: peroxo ligand' ratio. Formally, the pentagonal bipyramidal coordination polyhedra of the Mo(VI) and W(VI) oxo monoperoxo and oxo diperoxo complexes (the coordination numbers of the metal atoms are equal to seven) have different geometries, namely, the MO(O{sub 2})A{sub 4} pseudooctahedral and MO(O{sub 2}){sub 2}A{sub 2} pseudotrigonal bipyramidal configurations.

  18. Heavy metal contents in the sediments of astatic ponds: Influence of geomorphology, hydroperiod, water chemistry and vegetation.

    PubMed

    Gołdyn, Bartłomiej; Chudzińska, Maria; Barałkiewicz, Danuta; Celewicz-Gołdyn, Sofia

    2015-08-01

    The contents of heavy metals (Cd, Cr, Cu, Ni, Pb, Zn) were analysed in the bottom sediments of 30 small, astatic ponds located in the agricultural landscape of Western Poland. The samples were collected from 118 stations located in patches of four vegetation types. Relationships between the contents of particular elements and four groups of factors (geomorphology, hydroperiod, water quality and vegetation) were tested using Redundancy Analysis (RDA). The most important factors influencing the heavy metal contents were the maximum depth and area of the pond, its hydroperiod, water pH and conductivity values. In general, low quantities of heavy metals were recorded in the sediments of kettle-like ponds (small but located in deep depressions) and high in water bodies of the shore-bursting type (large but shallow). Moreover, quantities of particular elements were influenced by the structure of the vegetation covering the pond. Based on the results, we show which types of astatic ponds are most exposed to contamination and suggest some conservation practices that may reduce the influx of heavy metals. PMID:25919341

  19. Formamide-based synthesis of nucleobases by metal(II) octacyanomolybdate(IV): implication in prebiotic chemistry.

    PubMed

    Kumar, Anand; Sharma, Rachana; Kamaluddin

    2014-09-01

    We propose that double metal cyanides that formed in primeval seas might have played a vital role in chemical evolution and the origin of life. An array of metal octacyanomolybdates (MOCMos) has been synthesized, and their role as catalyst in the formation of nucleobases from formamide has been studied. Formamide, a hydrolysis product of HCN, was taken as starting material for the formation of nucleobases. Recent studies support the presence of formamide on some celestial bodies. Metal octacyanomolybdates, MOCMos (M = Mn, Fe, Co, Ni, Cu, Zn, Cd), are found to be highly efficient catalysts in the conversion of formamide into different nucleobases. Neat formamide is converted to purine, 4(3H)-pyrimidinone, cytosine, adenine, 9-(hydroxyacetyl)-purine, and thymine in good yield when using MOCMos. The products formed were characterized by high-performance liquid chromatography and electrospray ionization mass spectrometry techniques. The results of our study show that insoluble double metal cyanides might have acted as efficient catalysts in the synthesis of various biologically important compounds (e.g., purines, pyrimidines) under primeval seas on Earth or elsewhere in our solar system. PMID:25192494

  20. Organo- and Organometallic-Catalytic Intramolecular [1,5]-Hydride Transfer/Cyclization Process through C(sp(3) )-H Bond Activation.

    PubMed

    Kwon, Su Jin; Kim, Dae Young

    2016-06-01

    The direct functionalization of C(sp(3) )-H bonds is one of the most synthetically powerful research areas in current organic synthesis. Organocatalytic C(sp(3) )-H bond activation reactions have recently been developed in addition to the traditional metal-catalyzed C(sp(3) )-H activation reactions. In this review, we aim to give a brief overview of organo- and organometallic internal redox cascade reactions with respect to the mechanism, the reactivity of hydrogen donors and acceptors, and the migration modes of hydrogen. PMID:27062480

  1. Preparation of Y-Ba-Cu-O high T(c) superconducting thin films by plasma-assisted organometallic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Bai, G. R.; Tao, W.; Wang, R.; Xie, L. M.; Zhang, X. K.

    1989-07-01

    This paper reports the preparation of Y-Ba-Cu-O superconducting films with smooth, shiny surfaces, uniform composition, and high T(c) using plasma-assisted organometallic chemical vapor deposition (PAOMCVD). In addition to the advantages of pyrolysis OMCVD, PAOMCVD also affords some characteristics of physical vapor deposition. By adjusting the deposition conditions to get an appropriate combination of the features of physical vapor deposition with those of pyrolysis OMCVD, it is possible to prepare high T(c) metal oxide superconducting thin films having even better properties.

  2. Synthesis of a sugar-organometallic compound 1,1‧-difurfurylferrocene and its microwave preparation of carbon/iron oxide nanocomposite

    NASA Astrophysics Data System (ADS)

    Zhao, Shanyu; Cooper, Daniel C.; Xu, Haixun; Zhu, Pinghua; Suggs, J. William

    2013-01-01

    In order to synthesize a carbon-metal or metal oxide combination sphere, carbonaceous resource furfural 1 was introduced, which was nucleophilic treated with 1,1‧-dilithioferrocene 2 to form a sugar-organometallic compound: ferrocenyl monosaccharide derivative 1,1‧-difurfurylferrocene 3. 1,1‧-Difurfurylferrocene 3 can be hydrothermally treated in a microwave reactor to give 300-500 nm microspheres with the α-Fe2O3 or Fe3O4 nanocrystals formed on the surface, which may be favorable for new magnetic materials preparation or instead of iron with other metal ions, versatile carbon/metal composites will be possibly synthesized for catalysis, drug delivery and magnetic uses.

  3. Vibrational spectral characterization, NLO studies and charge transfer analysis of the organometallic material L-Alanine cadmium chloride

    NASA Astrophysics Data System (ADS)

    Arun Sasi, B. S.; Bright, K. C.; James, C.

    2016-01-01

    An organometallic nonlinear crystal, L-Alanine Cadmium Chloride (LACC) was synthesized by slow evaporation technique. The effects of hydrogen bonding on the structure, binding of ligand to metal ion, natural orbital occupancies, and vibrational frequencies were investigated using density functional theory (DFT) with the combined B3LYP and LANL2DZ basis set. Vibrational assignments were made on the basis of calculated potential energy distribution values from MOLVIB program. The topological analysis of electron localization function (ELF) provides basin population N (integrated density over the attractor basin), standard deviation (σ), and their relative fluctuation, defined as λ = σ2/N, which are sensitive criteria of delocalization. The molecular stability, electronic exchange interaction, and bond strength of the molecule were studied by natural bond orbital (NBO) analysis. The second harmonic generation (SHG) efficiency was determined using Kurtz and Perry method. Natural bond orbital analysis was carried out to study various intramolecular interactions that are responsible for the stabilization of the molecule.

  4. Studies of Gilbert magnetization damping in NiFe/organometallic trihalide perovskite bilayers investigated by broadband ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Groesbeck, Matthew; Sun, Dali; McLaughlin, Ryan; Zhang, Chuang; Liu, Haoliang; Vardeny, Zeev Valy

    Organo-metallic trihalide perovskites (OTP) have recently been suggested as promising candidates for spintronics applications, motivated by the presence of strong spin-orbit coupling, and recent studies of spin dynamics in CH3NH3PbI3. To help elucidate the spin transport properties in these materials, we have studied the Gilbert magnetization damping parameter in NiFe ferromagnetic films related to spin-pumping into adjacent OTP layers under ferromagnetic resonance (FMR) excitation conditions, using a broadband FMR detection system. We found an increase of the damping parameter associated with spin-pumping into the OTP. The obtained thickness-dependent results are compared to those of NiFe/Cu and NiFe/Pt bilayer structures, where spin transport characteristics are well-known. Research sponsored by the DOE, Office of Science, Grant DE-SC0014579.

  5. Laser Direct Writing of Conductive Silver Film on Polyimide Surface from Decomposition of Organometallic Ink

    NASA Astrophysics Data System (ADS)

    Cai, Zhixiang; Zeng, Xiaoyan; Liu, Jianguo

    2011-03-01

    Laser direct writing of organometallic ink to manufacture silver films was investigated by using a continuous-wave, Yb-doped fiber laser beam at a wavelength of 1071 nm. The organometallic ink consisted of an organometallic silver complex and a carrier vehicle, which was prepared by reaction of silver oxide with ammonium carbamates in methanol. The organometallic silver decomposed at a laser power of 0.1 W. The electrical resistivity values of silver conductors that were fabricated at a laser power of 0.5 W were about four times that of bulk silver. The morphology and electrical properties of the silver film were observed to be controllable as a function of laser processing parameters. The fabricated silver film exhibited excellent adherence to the polyimide substrate surface according to evaluation using the peel-off testing method.

  6. A Review of the Tissue Residue Approach for Organic and Organometallic Compounds in Aquatic Organisms

    EPA Science Inventory

    This paper reviews the tissue residue approach (TRA) for toxicity assessment as it applies to organic chemicals and some organometallic compounds (tin, mercury, and lead). Specific emphasis was placed on evaluating key factors that influence interpretation of critical body resid...

  7. Plasma deposition of amorphous metal alloys

    DOEpatents

    Hays, A.K.

    1979-07-18

    Amorphous metal alloy coatings are plasma-deposited by dissociation of vapors of organometallic compounds and metalloid hydrides in the presence of a reducing gas, using a glow discharge. Tetracarbonylnickel, phosphine, and hydrogen constitute a typical reaction mixture of the invention, yielding a NiPC alloy.

  8. Plasma deposition of amorphous metal alloys

    DOEpatents

    Hays, Auda K.

    1986-01-01

    Amorphous metal alloy coatings are plasma-deposited by dissociation of vapors of organometallic compounds and metalloid hydrides in the presence of a reducing gas, using a glow discharge. Tetracarbonylnickel, phosphine, and hydrogen constitute a typical reaction mixture of the invention, yielding a NiPC alloy.

  9. Planetary nebulae: the universal mass-metallicity relation for Local Group dwarf galaxies and the chemistry of NGC 205

    NASA Astrophysics Data System (ADS)

    Gonçalves, Denise R.; Magrini, Laura; Teodorescu, Ana M.; Carneiro, Carolina M.

    2014-10-01

    Here we study 16 planetary nebulae (PNe) in the dwarf irregular galaxy NGC 205 by using Gemini Multi-Object Spectrographs (GMOS@Gemini) spectra to derive their physical and chemical parameters. The chemical patterns and evolutionary tracks for 14 of our PNe suggest that there are no type I PNe among them. These PNe have an average oxygen abundance of 12+log(O/H) = 8.08 ± 0.28 and progenitor masses of 2-2.5 M⊙ and thus were born ˜1.0-1.7 Gyr ago. Our results are in good agreement with previous PN studies of NGC 205. The present 12+log(O/H) is combined with our previous work and results in the literature to study the PN metallicity trends of Local Group (LG) dwarf galaxies, in an effort to establish the PN luminosity-metallicity and mass-metallicity relations (LZR and MZR) for LG dwarf irregulars (dIrrs) and dwarf spheroidals (dSphs). Previous attempts to obtain such relations failed to provide correct conclusions because they were based on limited samples. As far as we are able to compare stellar with nebular metallicities, our MZR is in very good agreement with the slope of the MZR recently obtained for LG dwarf galaxies using spectroscopic stellar metallicities by Kirby and coauthors. In fact, we found that both dIrr and dSph galaxies follow the same MZR, at variance with the differences claimed in the past. Moreover, our MZR is also consistent with the global MZR of star-forming galaxies, which span a wider stellar mass range (˜106-1011 M⊙).

  10. Single and multijunction space solar cells grown by organometallic vapor phase epitaxy (OM-VPE)

    SciTech Connect

    Borden, P.G.; Gregory, P.E.; Larue, R.A.; Ludowise, M.J.

    1982-08-01

    Organometallic Vapor Phase Epitaxy (OM-VPE) is a versatile technique for growing III-V compound semiconductor solar cells. It has good uniformity and morphology, control that allows growth of extremely thin layers, and is a technique readily automated. The vehicle for the present discussion is a metal interconnected cascade (MIC/sup 2/) solar cell that has achieved 16.6% AM0 and 22% AM3 efficiency (uncorrected for 14% grid coverage). These are the best results reported to date for a cascade solar cell. Features include a 9-layer epitaxial structure, the thinnest of which is less than 1000 thick, a high-efficiency 30% AlGaAs top cell only 1.5 microns thick, a GaAs bottom cell that has survived the 780/sup 0/C, 20-minute top cell growth, and process yields greater than 4 cm/sup 2/ per wafer. The paper describes the cell design requirements, how it was grown by OM-VPE, and performance results.

  11. Effect of organometallic fuel additives on nanoparticle emissions from a gasoline passenger car.

    PubMed

    Gidney, Jeremy T; Twigg, Martyn V; Kittelson, David B

    2010-04-01

    Particle size measurements were performed on the exhaust of a car operating on a chassis dynamometer fueled with standard gasoline and gasoline containing low levels of Pb, Fe, and Mn organometallic additives. When additives were present there was a distinct nucleation mode consisting primarily of sub-10 nm nanoparticles. At equal molar dosing Mn and Fe gave similar nanoparticle concentrations at the tailpipe, whereas Pb gave a considerably lower concentration. A catalytic stripper was used to remove the organic component of these particles and revealed that they were mainly solid and, because of their association with inorganic additives, presumably inorganic. Solid nucleation mode nanoparticles of similar size and concentration to those observed here from a gasoline engine with Mn and Fe additives have also been observed from modern heavy-duty diesel engines without aftertreatment at idle, but these solid particles are a small fraction of the primarily volatile nucleation mode particles emitted. The solid nucleation mode particles emitted by the diesel engines are likely derived from metal compounds in the lubrication oil, although carbonaceous particles cannot be ruled out. Significantly, most of these solid nanoparticles emitted by both engine types fall below the 23 nm cutoff of the PMP number regulation. PMID:20192164

  12. Field-induced conductance switching by charge-state alternation in organometallic single-molecule junctions.

    PubMed

    Schwarz, Florian; Kastlunger, Georg; Lissel, Franziska; Egler-Lucas, Carolina; Semenov, Sergey N; Venkatesan, Koushik; Berke, Heinz; Stadler, Robert; Lörtscher, Emanuel

    2016-02-01

    Charge transport through single molecules can be influenced by the charge and spin states of redox-active metal centres placed in the transport pathway. These intrinsic properties are usually manipulated by varying the molecule's electrochemical and magnetic environment, a procedure that requires complex setups with multiple terminals. Here we show that oxidation and reduction of organometallic compounds containing either Fe, Ru or Mo centres can solely be triggered by the electric field applied to a two-terminal molecular junction. Whereas all compounds exhibit bias-dependent hysteresis, the Mo-containing compound additionally shows an abrupt voltage-induced conductance switching, yielding high-to-low current ratios exceeding 1,000 at bias voltages of less than 1.0 V. Density functional theory calculations identify a localized, redox-active molecular orbital that is weakly coupled to the electrodes and closely aligned with the Fermi energy of the leads because of the spin-polarized ground state unique to the Mo centre. This situation provides an additional slow and incoherent hopping channel for transport, triggering a transient charging effect in the entire molecule with a strong hysteresis and large high-to-low current ratios. PMID:26571004

  13. Computational Raman spectroscopy of organometallic reaction products in lithium and sodium-based battery systems.

    PubMed

    Sánchez-Carrera, Roel S; Kozinsky, Boris

    2014-11-28

    A common approach to understanding surface reaction mechanisms in rechargeable lithium-based battery systems involves spectroscopic characterization of the product mixtures and matching of spectroscopic features to spectra of pure candidate reference compounds. This strategy, however, requires separate chemical synthesis and accurate characterization of potential reference compounds. It also assumes that atomic structures are the same in the actual product mixture as in the reference samples. We propose an alternative approach that uses first-principles computations of spectra of the possible reaction products and by-products present in advanced battery systems. We construct a library of computed Raman spectra for possible products, achieving excellent agreement with reference experimental data, targeting solid-electrolyte interphase in Li-ion cells and discharge products of Li-air cells. However, the solid-state crystalline structure of Li(Na) metal-organic compounds is often not known, making the spectra computations difficult. We develop and apply a novel technique of simplifying spectra calculations by using dimer-like representations of the solid state structures. On the basis of a systematic investigation, we demonstrate that molecular dimers of Li(Na)-based organometallic material provide relevant information about the vibrational properties of many possible solid reaction products. Such an approach should serve as a basis to extend existing spectral libraries of molecular structures relevant for understanding the link between atomic structures and measured spectroscopic data of materials in novel battery systems. PMID:25310385

  14. Field-induced conductance switching by charge-state alternation in organometallic single-molecule junctions

    NASA Astrophysics Data System (ADS)

    Schwarz, Florian; Kastlunger, Georg; Lissel, Franziska; Egler-Lucas, Carolina; Semenov, Sergey N.; Venkatesan, Koushik; Berke, Heinz; Stadler, Robert; Lörtscher, Emanuel

    2016-02-01

    Charge transport through single molecules can be influenced by the charge and spin states of redox-active metal centres placed in the transport pathway. These intrinsic properties are usually manipulated by varying the molecule's electrochemical and magnetic environment, a procedure that requires complex setups with multiple terminals. Here we show that oxidation and reduction of organometallic compounds containing either Fe, Ru or Mo centres can solely be triggered by the electric field applied to a two-terminal molecular junction. Whereas all compounds exhibit bias-dependent hysteresis, the Mo-containing compound additionally shows an abrupt voltage-induced conductance switching, yielding high-to-low current ratios exceeding 1,000 at bias voltages of less than 1.0 V. Density functional theory calculations identify a localized, redox-active molecular orbital that is weakly coupled to the electrodes and closely aligned with the Fermi energy of the leads because of the spin-polarized ground state unique to the Mo centre. This situation provides an additional slow and incoherent hopping channel for transport, triggering a transient charging effect in the entire molecule with a strong hysteresis and large high-to-low current ratios.

  15. Electronic configurations and magnetic anisotropy in organometallic metallocenes

    SciTech Connect

    Nawa, Kenji Kitaoka, Yukie; Nakamura, Kohji; Akiyama, Toru; Ito, Tomonori

    2015-05-07

    Electronic configurations and magnetic anisotropy of organometallic metallocenes (MCp{sub 2}s) were investigated by means of first principles calculations based on the constraint density functional theory. The results predict that the ground states for M = Cr, Mn, Fe, Co, and Ni are the {sup 3}E{sub 2g}, {sup 2}E{sub 2g}, {sup 1}A{sub 1g}, {sup 2}E{sub 1g}, and {sup 3}A{sub 2g} states, respectively. The magnetizations of the CoCp{sub 2} and NiCp{sub 2} energetically favor highly orienting along the perpendicular and parallel directions to the cyclopentadienyl (Cp) plane, respectively, and the others show almost no preference for the magnetic easy axis.

  16. Organometallic Rhenium Complexes Divert Doxorubicin to the Mitochondria.

    PubMed

    Imstepf, Sebastian; Pierroz, Vanessa; Rubbiani, Riccardo; Felber, Michael; Fox, Thomas; Gasser, Gilles; Alberto, Roger

    2016-02-18

    Doxorubicin, a well-established chemotherapeutic agent, is known to accumulate in the cell nucleus. By using ICP-MS, we show that the conjugation of two small organometallic rhenium complexes to this structural motif results in a significant redirection of the conjugates from the nucleus to the mitochondria. Despite this relocation, the two bioconjugates display excellent toxicity toward HeLa cells. In addition, we carried out a preliminarily investigation of aspects of cytotoxicity and present evidence that the conjugates disrupt the mitochondrial membrane potential, are strong inhibitors of human Topoisomerase II, and induce apoptosis. Such derivatives may enhance the therapeutic index of the aggressive parent drug and overcome drug resistance by influencing nuclear and mitochondrial homeostasis. PMID:26799241

  17. Anticancer Organometallic Osmium(II)-p-cymene Complexes.

    PubMed

    Păunescu, Emilia; Nowak-Sliwinska, Patrycja; Clavel, Catherine M; Scopelliti, Rosario; Griffioen, Arjan W; Dyson, Paul J

    2015-09-01

    Osmium compounds are attracting increasing attention as potential anticancer drugs. In this context, a series of bifunctional organometallic osmium(II)-p-cymene complexes functionalized with alkyl or perfluoroalkyl groups were prepared and screened for their antiproliferative activity. Three compounds from the series display selectivity toward cancer cells, with moderate cytotoxicity observed against human ovarian carcinoma (A2780) cells, whereas no cytotoxicity was observed on non-cancerous human embryonic kidney (HEK-293) cells and human endothelial (ECRF24) cells. Two of these three cancer-cell-selective compounds induce cell death largely via apoptosis and were also found to disrupt vascularization in the chicken embryo chorioallantoic membrane (CAM) model. Based on these promising properties, these compounds have potential clinical applications. PMID:26190176

  18. Scalable Synthesis of Piperazines Enabled by Visible-Light Irradiation and Aluminum Organometallics

    PubMed Central

    Suárez-Pantiga, Samuel; Colas, Kilian; Johansson, Magnus J; Mendoza, Abraham

    2015-01-01

    The development of more active C–H oxidation catalysts has inspired a rapid, scalable, and stereoselective assembly of multifunctional piperazines through a [3+3] coupling of azomethine ylides. A combination of visible-light irradiation and aluminum organometallics is essential to promote this transformation, which introduces visible-light photochemistry of main-group organometallics and sets the basis for new and promising catalysts. PMID:26337253

  19. Development of ultrafast photochromic organometallics and photoinduced linkage isomerization of arene chromium carbonyl derivatives.

    PubMed

    To, Tung T; Heilweil, Edwin J; Duke, Charles B; Ruddick, Kristie R; Webster, Charles Edwin; Burkey, Theodore J

    2009-03-26

    We review recent studies of processes relevant to photoinduced linkage isomerization of organometallic systems with the goal of preparing organometallics with an efficient and ultrafast photochromic response. The organometallic system thus corresponds to two linkage isomers with different electronic environments that are responsible for different optical properties. Much of this work has focused on examining processes following irradiation of cyclopentadienyl manganese tricarbonyl derivatives (compounds 3-21) including solvent coordination, thermal relaxation, solvent displacement by tethered functional groups (chelation), dissociation of tethered functional groups, and linkage isomerization. A new platform is investigated for obtaining a photochromic response in new experiments with arene chromium dicarbonyl complexes. A photochromic response is observed for arene chromium dicarbonyl complexes with tethered pyridine and olefin functional groups based on light-driven linkage isomerization on the nanosecond time scale. Irradiation at 532 nm of 23 ([Cr{eta(6)-C(6)H(5)CH(2-Py-kappaN)CH(2)CH=CH(2)}(CO)(2)]) (Py = pyridine) results in the isomerization to 22 ([Cr{eta(6)-C(6)H(5)CH(2-Py)CH(2)-eta(2)-CH=CH(2)}(CO)(2)]), and 355 nm irradiation isomerizes 22 to 23. The ultrafast linkage isomerization has been investigated at room temperature in n-heptane solution on the picosecond to microsecond time scale with UV- or visible-pump and IR-probe transient absorption spectroscopy by comparing the dynamics with model compounds containing only a tethered pyridine. Irradiation of 24 ([Cr{eta(6)-C(6)H(5)(CH(2))(3)(2-Py)}(CO)(3)]) and 25 ([Cr{eta(6)-C(6)H(5)(CH(2))(2)(2-Py)}(CO)(3)]) at 289 nm induces CO loss to immediately yield a Cr-heptane solvent coordinated intermediate of the unsaturated Cr fragment, which then converts to the kappaN(1)-pyridine chelate within 200 and 100 ns, respectively. Irradiation of 26 ([Cr{eta(6)-C(6)H(5)CH(2)(2-Py)}(CO)(3)]) also induces CO loss to

  20. DFT and time-resolved IR investigation of electron transfer between photogenerated 17- and 19-electron organometallic radicals

    SciTech Connect

    Cahoon, James B.; Kling, Matthias F.; Sawyer, Karma R.; Andersen, Lars K.; Harris, Charles B.

    2008-04-30

    The photochemical disproportionation mechanism of [CpW(CO){sub 3}]{sub 2} in the presence of Lewis bases PR{sub 3} was investigated on the nano- and microsecond time-scales with Step-Scan FTIR time-resolved infrared spectroscopy. 532 nm laser excitation was used to homolytically cleave the W-W bond, forming the 17-electron radicals CpW(CO){sub 3} and initiating the reaction. With the Lewis base PPh{sub 3}, disproportionation to form the ionic products CpW(CO){sub 3}PPh{sub 3}{sup +} and CpW(CO){sub 3}{sup -} was directly monitored on the microsecond time-scale. Detailed examination of the kinetics and concentration dependence of this reaction indicates that disproportionation proceeds by electron transfer from the 19-electron species CpW(CO){sub 3}PPh{sub 3} to the 17-electron species CpW(CO){sub 3}. This result is contrary to the currently accepted disproportionation mechanism which predicts electron transfer from the 19-electron species to the dimer [CpW(CO){sub 3}]{sub 2}. With the Lewis base P(OMe){sub 3} on the other hand, ligand substitution to form the product [CpW(CO){sub 2}P(OMe){sub 3}]{sub 2} is the primary reaction on the microsecond time-scale. Density Functional Theory (DFT) calculations support the experimental results and suggest that the differences in the reactivity between P(OMe){sub 3} and PPh{sub 3} are due to steric effects. The results indicate that radical-to-radical electron transfer is a previously unknown but important process for the formation of ionic products with the organometallic dimer [CpW(CO){sub 3}]{sub 2} and may also be applicable to the entire class of organometallic dimers containing a single metal-metal bond.

  1. Apollo 14 - Oxide, metal, and olivine mineral chemistries in 14072 with a bearing on the temporal relationships of subsolidus reduction

    NASA Technical Reports Server (NTRS)

    Haggerty, S. E.

    1977-01-01

    One of three primary objectives of the reported study is related to the definition of the distribution of troilite and Fe and the evaluation of the role of FeS in subsolidus reduction assemblages. Another objective was concerned with the definition of the lower limit of stabilizing elements such as Mg, Al, and Cr in ulvospinel to determine the terminal compositions at which reduction is inhibited. The third objective involves a comparison of the mineral chemistries of decomposed olivine with unaltered olivine in an attempt to determine the temperature limits. The sample was selected because it is one of the most intensely reduced samples returned from the moon. The model invoked for reduction is a magmatic-deuteric process which requires an environment approximating that of a closed system in which the volatile constituents are contained and in which reduction proceeds continuously with crystallization.

  2. Microwave-assisted cross-coupling and hydrogenation chemistry by using heterogeneous transition-metal catalysts: an evaluation of the role of selective catalyst heating.

    PubMed

    Irfan, Muhammed; Fuchs, Michael; Glasnov, Toma N; Kappe, C Oliver

    2009-11-01

    The concept of specific microwave effects in solid/liquid catalytic processes resulting from the selective heating of a microwave-absorbing heterogeneous transition-metal catalyst by using 2.45 GHz microwave irradiation was evaluated. As model transformations Ni/C-, Cu/C-, Pd/C-, and Pd/Al2O3-catalyzed carbon-carbon/carbon-heteroatom cross-couplings and hydrogenation reactions were investigated. To probe the existence of specific microwave effects by means of selective catalyst heating in these transformations, control experiments comparing microwave dielectric heating and conventional thermal heating at the same reaction temperature were performed. Although the supported metal catalysts were experimentally found to be strongly microwave absorbing, for all chemistry examples investigated herein no differences in reaction rate or selectivity between microwave and conventional heating experiments under carefully controlled conditions were observed. This was true also for reactions that use low-absorbing or microwave transparent solvents, and was independent of the microwave absorbtivity of the catalyst support material. In the case of hydrogenation reactions, the stirring speed was found to be a critical factor on the mass transfer between gas and liquid phase, influencing the rate of the hydrogenation in both microwave and conventionally heated experiments. PMID:19774573

  3. Post-synthetic modification of metal-organic framework thin films using click chemistry: the importance of strained C-C triple bonds.

    PubMed

    Wang, Zhengbang; Liu, Jinxuan; Arslan, Hasan K; Grosjean, Sylvain; Hagendorn, Tobias; Gliemann, Hartmut; Bräse, Stefan; Wöll, Christof

    2013-12-23

    In this work, we demonstrate that strain-promoted azide-alkyne cycloaddition (SPAAC) yields virtually complete conversion in the context of the post-synthetic modification (PSM) of metal-organic frameworks (MOFs). We use surface-anchored MOF (SURMOF) thin films, [Zn2(N3-bdc)2(dabco)], grown on modified Au substrates using liquid-phase epitaxy (LPE) as a model system to first show that, with standard click chemistry, presently, the most popular method for rendering additional functionality to MOFs via PSM, quantitative conversion yields, cannot be reached. In addition, it is virtually impossible to avoid contaminations of the product by the cytotoxic Cu(I) ions used as a catalyst, a substantial problem for applications in life sciences. Both problems could be overcome by SPAAC, where a metal catalyst is not needed. After optimization of reaction conditions, conversion yields of nearly 100% could be achieved. The consequences of these results for various applications of PSM-modified SURMOFs in the fields of membranes, optical coatings, catalysis, selective gas separation, and chemical sensing are briefly discussed. PMID:24283622

  4. Tribromobenzene on Cu(111): Temperature-dependent formation of halogen-bonded, organometallic, and covalent nanostructures

    SciTech Connect

    Fan, Qitang; Wang, Tao; Zhu, Junfa; Liu, Liming; Zhao, Jin; Gottfried, J. Michael

    2015-03-14

    The temperature-controlled surface-assisted synthesis of halogen bonded, organometallic, and covalent nanostructures based on 1,3,5-tribromo-benzene (TriBB) was studied with scanning tunneling microscopy and X-ray photoemission spectroscopy in ultrahigh vacuum. Vapor deposition of TriBB onto a Cu(111) surface held at 90 K leads to the formation of large domains of a honeycomb-like organic monolayer structure stabilized by triangular nodes with Br⋯Br intermolecular bonds. Upon annealing the organic monolayer to ∼140 K, a new hexagonal close-packed structure with intact TriBB molecules connected by Cu adatoms is formed. Further warming up the sample to 300 K gives rise to the scission of C–Br bonds and formation of C–Cu–C bonds between phenyl fragments such that stable dendritic organometallic networks are formed. Larger islands of organometallic networks are obtained by maintaining the temperature of Cu(111) at 420 K during deposition of TriBB. Simultaneously, large islands of Br atoms are formed around the organometallic networks. Annealing the more extended organometallic network (prepared at 420 K) to 520 K leads to the formation of a branched covalent organic framework (COF) which comprises structural elements of porous graphene and is surrounded by Br islands. These organometallic networks and COFs appear as small dendritic and branched domains, most likely due to the steric influence exerted by the Br islands.

  5. Tribromobenzene on Cu(111): Temperature-dependent formation of halogen-bonded, organometallic, and covalent nanostructures

    NASA Astrophysics Data System (ADS)

    Fan, Qitang; Wang, Tao; Liu, Liming; Zhao, Jin; Zhu, Junfa; Gottfried, J. Michael

    2015-03-01

    The temperature-controlled surface-assisted synthesis of halogen bonded, organometallic, and covalent nanostructures based on 1,3,5-tribromo-benzene (TriBB) was studied with scanning tunneling microscopy and X-ray photoemission spectroscopy in ultrahigh vacuum. Vapor deposition of TriBB onto a Cu(111) surface held at 90 K leads to the formation of large domains of a honeycomb-like organic monolayer structure stabilized by triangular nodes with Br⋯Br intermolecular bonds. Upon annealing the organic monolayer to ˜140 K, a new hexagonal close-packed structure with intact TriBB molecules connected by Cu adatoms is formed. Further warming up the sample to 300 K gives rise to the scission of C-Br bonds and formation of C-Cu-C bonds between phenyl fragments such that stable dendritic organometallic networks are formed. Larger islands of organometallic networks are obtained by maintaining the temperature of Cu(111) at 420 K during deposition of TriBB. Simultaneously, large islands of Br atoms are formed around the organometallic networks. Annealing the more extended organometallic network (prepared at 420 K) to 520 K leads to the formation of a branched covalent organic framework (COF) which comprises structural elements of porous graphene and is surrounded by Br islands. These organometallic networks and COFs appear as small dendritic and branched domains, most likely due to the steric influence exerted by the Br islands.

  6. Model for the Vaporization of Mixed Organometallic Compounds in the Metalorganic Chemical Vapor Deposition of High Temperature Superconducting Films

    NASA Technical Reports Server (NTRS)

    Meng, Guangyao; Zhou, Gang; Schneider, Roger L.; Sarma, Bimal K.; Levy, Moises

    1993-01-01

    A model of the vaporization and mass transport of mixed organometallics from a single source for thin film metalorganic chemical vapor deposition is presented. A stoichiometric gas phase can be obtained from a mixture of the organometallics in the desired mole ratios, in spite of differences in the volatilities of the individual compounds. Proper film composition and growth rates are obtained by controlling the velocity of a carriage containing the organometallics through the heating zone of a vaporizer.

  7. Understanding the electron-stimulated surface reactions of organometallic complexes to enable design of precursors for electron beam-induced deposition

    NASA Astrophysics Data System (ADS)

    Spencer, Julie A.; Rosenberg, Samantha G.; Barclay, Michael; Wu, Yung-Chien; McElwee-White, Lisa; Howard Fairbrother, D.

    2014-12-01

    Standard practice in electron beam-induced deposition (EBID) is to use precursors designed for thermal processes, such as chemical vapor deposition (CVD). However, organometallic precursors that yield pure metal deposits in CVD often create EBID deposits with high levels of organic contamination. This contamination negatively impacts the deposit's properties (e.g., by increasing resistivity or decreasing catalytic activity) and severely limits the range of potential applications for metal-containing EBID nanostructures. To provide the information needed for the rational design of precursors specifically for EBID, we have employed an ultra-high vacuum (UHV) surface science approach to identify the elementary reactions of organometallic precursors during EBID. These UHV studies have demonstrated that the initial electron-induced deposition of the surface-bound organometallic precursors proceeds through desorption of one or more of the ligands present in the parent compound. In specific cases, this deposition step has been shown to proceed via dissociative electron attachment, involving low-energy secondary electrons generated by the interaction of the primary beam with the substrate. Electron beam processing of the surface-bound species produced in the initial deposition event usually causes decomposition of the residual ligands, creating nonvolatile fragments. This process is believed to be responsible for a significant fraction of the organic contaminants typically observed in EBID nanostructures. A few ligands (e.g., halogens) can, however, desorb during electron beam processing while other ligands (e.g., PF3, CO) can thermally desorb if elevated substrate temperatures are used during deposition. Using these general guidelines for reactivity, we propose some design strategies for EBID precursors. The ultimate goal is to minimize organic contamination and thus overcome the key bottleneck for fabrication of relatively pure EBID nanostructures.

  8. Chemistry for Artists and Art Buffs.

    ERIC Educational Resources Information Center

    Denio, Allen A.

    1979-01-01

    This course provides an attractive introduction to chemistry for a group of students who would normally avoid traditional chemistry courses. Topics include color, pigments, metals, ceramics, glass, paints, plastics, fibers, and dyes. (BB)

  9. 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

  10. pH-regulated metal-ligand switching in the HM loop of ATP7A: a new paradigm for metal transfer chemistry.

    PubMed

    Kline, Chelsey D; Gambill, Benjamin F; Mayfield, Mary; Lutsenko, Svetlana; Blackburn, Ninian J

    2016-08-01

    Cuproproteins such as PHM and DBM mature in late endosomal vesicles of the mammalian secretory pathway where changes in vesicle pH are employed for sorting and post-translational processing. Colocation with the P1B-type ATPase ATP7A suggests that the latter is the source of copper and supports a mechanism where selectivity in metal transfer is achieved by spatial colocation of partner proteins in their specific organelles or vesicles. In previous work we have suggested that a lumenal loop sequence located between trans-membrane helices TM1 and TM2 of the ATPase, and containing five histidines and four methionines, acts as an organelle-specific chaperone for metallation of the cuproproteins. The hypothesis posits that the pH of the vesicle regulates copper ligation and loop conformation via a mechanism which involves His to Met ligand switching induced by histidine protonation. Here we report the effect of pH on the HM loop copper coordination using X-ray absorption spectroscopy (XAS), and show via selenium substitution of the Met residues that the HM loop undergoes similar conformational switching to that found earlier for its partner PHM. We hypothesize that in the absence of specific chaperones, HM motifs provide a template for building a flexible, pH-sensitive transfer site whose structure and function can be regulated to accommodate the different active site structural elements and pH environments of its partner proteins. PMID:27242196

  11. Abnormal N-heterocyclic carbene main group organometallic chemistry: a debut to the homogeneous catalysis.

    PubMed

    Sen, Tamal K; Sau, Samaresh Chandra; Mukherjee, Arup; Hota, Pradip Kumar; Mandal, Swadhin K; Maity, Bholanath; Koley, Debasis

    2013-10-21

    Abnormal N-heterocyclic carbene (aNHC) adducts of zinc(II) (1) and aluminum(III) (2) were synthesized. The compounds were characterized by NMR spectroscopy and elemental analysis. The solid state structures of these complexes (1 and 2) were determined by single crystal X-ray study. Furthermore, these organozinc and organoaluminum adducts (1 and 2) were tested for the ring opening polymerization of cyclic esters. These adducts were found to be quite efficient catalysts for the polymerization of cyclicesters such as rac-lactide (rac-LA), ε-caprolactone (ε-CL), and δ-valerolactone (δ-VL). Furthermore, aNHC zinc adduct has been used as catalyst for the synthesis of a tri-block copolymer. PMID:23945705

  12. Spatial, Hysteretic, and Adaptive Host-Guest Chemistry in a Metal-Organic Framework with Open Watson-Crick Sites.

    PubMed

    Cai, Hong; Li, Mian; Lin, Xiao-Rong; Chen, Wei; Chen, Guang-Hui; Huang, Xiao-Chun; Li, Dan

    2015-09-01

    Biological and artificial molecules and assemblies capable of supramolecular recognition, especially those with nucleobase pairing, usually rely on autonomous or collective binding to function. Advanced site-specific recognition takes advantage of cooperative spatial effects, as in local folding in protein-DNA binding. Herein, we report a new nucleobase-tagged metal-organic framework (MOF), namely ZnBTCA (BTC=benzene-1,3,5-tricarboxyl, A=adenine), in which the exposed Watson-Crick faces of adenine residues are immobilized periodically on the interior crystalline surface. Systematic control experiments demonstrated the cooperation of the open Watson-Crick sites and spatial effects within the nanopores, and thermodynamic and kinetic studies revealed a hysteretic host-guest interaction attributed to mild chemisorption. We further exploited this behavior for adenine-thymine binding within the constrained pores, and a globally adaptive response of the MOF host was observed. PMID:26178173

  13. Surface Chemistry and Interface Evolution during the Atomic Layer Deposition of High-k Metal Oxides on InAs(100) and GaAs(100) Surfaces

    NASA Astrophysics Data System (ADS)

    Henegar, Alex J.

    Device scaling has been key for creating faster and more powerful electronic devices. Integral circuit components like the metal-oxide semiconductor field-effect transistor (MOSFET) now rely on material deposition techniques, like atomic layer deposition (ALD), that possess atomic-scale thickness precision. At the heart of the archetypal MOSFET is a SiO2/Si interface which can be formed to near perfection. However when the thickness of the SiO 2 layer is shrunk down to a few nanometers several complications arise like unacceptably high leakage current and power consumption. Replacing Si with III-V semiconductors and SiO2 with high-k dielectric materials is appealing but comes with its own set of challenges. While SiO2 is practically defect-free, the native oxides of III-Vs are poor dielectrics. In this dissertation, the surface chemistry and interface evolution during the ALD of high-k metal oxides on Si(100), GaAs(100) and InAs(100) was studied. In particular, the surface chemistry and crystallization of TiO2 films grown on Si(100) was investigated using transmission Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Large, stable, and highly reactive anatase TiO2 grains were found to form during a post-deposition heat treatment after the ALD at 100 °C. The remainder of this work was focused on the evolution of the interfacial oxides during the deposition of TiO2 and Al2O3 on InAs(100) and GaAs(100) and during the deposition of Ta2O 5 on InAs(100). In summary the ALD precursor type, deposited film, and substrate had an influence in the evolution of the native oxides. Alkyl amine precursors fared better at removing the native oxides but the deposited films (TiO2 and Ta2O5) were susceptible to significant native oxide diffusion. The alkyl precursor used for the growth of Al 2O3 was relatively ineffective at removing the oxides but was

  14. Binding of Copper and Silver to Single-Site Variants of Peptidylglycine Monooxygenase Reveals the Structure and Chemistry of the Individual Metal Centers

    PubMed Central

    2015-01-01

    Peptidylglycine monooxygenase (PHM) catalyzes the final step in the biosynthesis of amidated peptides that serve as important signaling molecules in numerous endocrine pathways. The catalytic mechanism has attracted much attention because of a number of unique attributes, including the presence of a pair of uncoupled copper centers separated by 11 Å (termed CuH and CuM), an unusual Cu(I)SMet interaction at the oxygen binding M-site, and the postulated Cu(II)–superoxo intermediate. Understanding the mechanism requires determining the catalytic roles of the individual copper centers and how they change during catalysis, a task made more difficult by the overlapping spectral signals from each copper center in the wild-type (WT) protein. To aid in this effort, we constructed and characterized two PHM variants that bound metal at only one site. The H242A variant bound copper at the H-center, while the H107AH108A double mutant bound copper at the M-center; both mutants were devoid of catalytic activity. Oxidized Cu(II) forms showed electron paramagnetic resonance and extended X-ray absorption fine structure (EXAFS) spectra consistent with their previously determined Cu(II)His3O and Cu(II)His2O2 ligand sets for the H- and M-centers, respectively. Cu(I) forms, on the other hand, showed unique chemistry. The M-center bound two histidines and a methionine at all pHs, while the H-center was two-coordinate at neutral pH but coordinated a new methionine S ligand at low pH. Fourier transform infrared studies confirmed and extended previous assignments of CO binding and showed unambiguously that the 2092 cm–1 absorbing species observed in the WT and many variant forms is an M-site Cu(I)–CO adduct. Silver binding was also investigated. When H107AH108A and M109I (a WT analogue with both sites intact) were incubated with excess AgNO3, each variant bound a single Ag(I) ion, from which it was inferred that Ag(I) binds selectively at the M-center with little or no affinity for

  15. Sample treatment in chromatography-based speciation of organometallic pollutants.

    PubMed

    Gómez-Riza, J L; Morales, E; Giráldez, I; Sánchez-Rodas, D; Velasco, A

    2001-12-14

    Speciation analysis is nowadays performed routinely in many laboratories to control the quality of the environment, food and health. Chemical speciation analyses generally include the study of different oxidation state of elements or individual organometallic compounds. The determination of the different chemical forms of elements is still an analytical challenge, since they are often unstable and concentrations in different matrices of interest are in the microg l(-1) or even in the ng l(-1) range (e.g., estuarine waters) or ng g(-1) in sediments and biological tissues. For this reason, sensitive and selective analytical atomic techniques are being used as available detectors for speciation, generally coupled with chromatography for the time-resolved introduction of analytes into the atomic spectrometer. The complexity of these instrumental couplings has a straightforward consequence on the duration of the analysis, but sample preparation to separate and transfer the chemical species present in the sample into a solution to be accepted readily by a chromatographic column is the more critical step of total analysis, and demands considerable operator skills and time cost. Traditionally, liquid-liquid extraction has been employed for sample treatment with serious disadvantages, such as consumption, disposal and long-term exposure to organic solvent. In addition, they are usually cumbersome and time-consuming. Therefore, the introduction of new reagents such as sodium tetraethylborate for the simultaneous derivatization of several elements has been proposed. Other possibilities are based in the implementation of techniques for efficient and accelerated isolation of species from the sample matrix. This is the case for microwave-assisted extraction, solid-phase extraction and microextraction, supercritical fluid extraction or pressurized liquid extraction, which offer new possibilities in species treatment, and the advantages of a drastic reduction of the extraction

  16. Synthesis and evaluation of new polynuclear organometallic Ru(II), Rh(III) and Ir(III) pyridyl ester complexes as in vitro antiparasitic and antitumor agents.

    PubMed

    Chellan, Prinessa; Land, Kirkwood M; Shokar, Ajit; Au, Aaron; An, Seung Hwan; Taylor, Dale; Smith, Peter J; Riedel, Tina; Dyson, Paul J; Chibale, Kelly; Smith, Gregory S

    2014-01-14

    New polynuclear organometallic Platinum Group Metal (PGM) complexes containing di- and tripyridyl ester ligands have been synthesised and characterised using analytical and spectroscopic techniques including (1)H, (13)C NMR and infrared spectroscopy. Reaction of these polypyridyl ester ligands with either [Ru(p-cymene)Cl2]2, [Rh(C5Me5)Cl2]2 or [Ir(C5Me5)Cl2]2 dimers yielded the corresponding di- or trinuclear organometallic complexes. The polyaromatic ester ligands act as monodentate donors to each metal centre and this coordination mode was confirmed upon elucidation of the molecular structures for two of the dinuclear complexes. The di- and trinuclear PGM complexes synthesized were evaluated for inhibitory effects on the human protozoal parasites Plasmodium falciparum strain NF54 (chloroquine sensitive), Trichomonas vaginalis strain G3 and the human ovarian cancer cell lines, A2780 (cisplatin-sensitive) and A2780cisR (cisplatin-resistant) cell lines. All of the complexes were observed to have moderate to high antiplasmodial activities and the compounds with the best activities were evaluated for their ability to inhibit formation of synthetic hemozoin in a cell free medium. The in vitro antitumor evaluation of these complexes revealed that the trinuclear pyridyl ester complexes demonstrated moderate activities against the two tumor cell lines and were also less toxic to model non-tumorous cells. PMID:24121555

  17. Organometallic Iridium(III) Anticancer Complexes with New Mechanisms of Action: NCI-60 Screening, Mitochondrial Targeting, and Apoptosis

    PubMed Central

    2013-01-01

    Platinum complexes related to cisplatin, cis-[PtCl2(NH3)2], are successful anticancer drugs; however, other transition metal complexes offer potential for combating cisplatin resistance, decreasing side effects, and widening the spectrum of activity. Organometallic half-sandwich iridium (IrIII) complexes [Ir(Cpx)(XY)Cl]+/0 (Cpx = biphenyltetramethylcyclopentadienyl and XY = phenanthroline (1), bipyridine (2), or phenylpyridine (3)) all hydrolyze rapidly, forming monofunctional G adducts on DNA with additional intercalation of the phenyl substituents on the Cpx ring. In comparison, highly potent complex 4 (Cpx = phenyltetramethylcyclopentadienyl and XY = N,N-dimethylphenylazopyridine) does not hydrolyze. All show higher potency toward A2780 human ovarian cancer cells compared to cisplatin, with 1, 3, and 4 also demonstrating higher potency in the National Cancer Institute (NCI) NCI-60 cell-line screen. Use of the NCI COMPARE algorithm (which predicts mechanisms of action (MoAs) for emerging anticancer compounds by correlating NCI-60 patterns of sensitivity) shows that the MoA of these IrIII complexes has no correlation to cisplatin (or oxaliplatin), with 3 and 4 emerging as particularly novel compounds. Those findings by COMPARE were experimentally probed by transmission electron microscopy (TEM) of A2780 cells exposed to 1, showing mitochondrial swelling and activation of apoptosis after 24 h. Significant changes in mitochondrial membrane polarization were detected by flow cytometry, and the potency of the complexes was enhanced ca. 5× by co-administration with a low concentration (5 μM) of the γ-glutamyl cysteine synthetase inhibitor L-buthionine sulfoximine (L-BSO). These studies reveal potential polypharmacology of organometallic IrIII complexes, with MoA and cell selectivity governed by structural changes in the chelating ligands. PMID:23618382

  18. Organometallic Iridium(III) anticancer complexes with new mechanisms of action: NCI-60 screening, mitochondrial targeting, and apoptosis.

    PubMed

    Hearn, Jessica M; Romero-Canelón, Isolda; Qamar, Bushra; Liu, Zhe; Hands-Portman, Ian; Sadler, Peter J

    2013-01-01

    Platinum complexes related to cisplatin, cis-[PtCl2(NH3)2], are successful anticancer drugs; however, other transition metal complexes offer potential for combating cisplatin resistance, decreasing side effects, and widening the spectrum of activity. Organometallic half-sandwich iridium (Ir(III)) complexes [Ir(Cp(x))(XY)Cl](+/0) (Cp(x) = biphenyltetramethylcyclopentadienyl and XY = phenanthroline (1), bipyridine (2), or phenylpyridine (3)) all hydrolyze rapidly, forming monofunctional G adducts on DNA with additional intercalation of the phenyl substituents on the Cp(x) ring. In comparison, highly potent complex 4 (Cp(x) = phenyltetramethylcyclopentadienyl and XY = N,N-dimethylphenylazopyridine) does not hydrolyze. All show higher potency toward A2780 human ovarian cancer cells compared to cisplatin, with 1, 3, and 4 also demonstrating higher potency in the National Cancer Institute (NCI) NCI-60 cell-line screen. Use of the NCI COMPARE algorithm (which predicts mechanisms of action (MoAs) for emerging anticancer compounds by correlating NCI-60 patterns of sensitivity) shows that the MoA of these Ir(III) complexes has no correlation to cisplatin (or oxaliplatin), with 3 and 4 emerging as particularly novel compounds. Those findings by COMPARE were experimentally probed by transmission electron microscopy (TEM) of A2780 cells exposed to 1, showing mitochondrial swelling and activation of apoptosis after 24 h. Significant changes in mitochondrial membrane polarization were detected by flow cytometry, and the potency of the complexes was enhanced ca. 5× by co-administration with a low concentration (5 μM) of the γ-glutamyl cysteine synthetase inhibitor L-buthionine sulfoximine (L-BSO). These studies reveal potential polypharmacology of organometallic Ir(III) complexes, with MoA and cell selectivity governed by structural changes in the chelating ligands. PMID:23618382

  19. Sulfur and Trace Metal Chemistry of a Methane Charged Brine Pool and Adjacent Porewaters in the Northern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Gilhooly, W. P.; Cable, J. E.; Carney, R. S.; Macko, S. A.; Lyons, T. W.

    2007-12-01

    A systematic study of a methane brine pool on the Louisiana continental slope reveals the extent to which steep chemical gradients associated with an anoxic hypersaline basin control the establishment and distribution of chemosynthetic organisms. The seep site, located in the Green Canyon lease block (GC233), provides habitat for a bivalve-dominated community of chemosynthetic mussels ( Bathymodiolus childressi). The pool is a brine-filled pockmark centered over a salt diapir buried within 500 m of the seafloor along which methane and vent fluids migrate to the surface. The depression slopes along its southern margin where brine overflows onto the seafloor. This study sought to establish the chemistry of the brine in an effort to better understand fluid transport to the seafloor and the extent to which brine influences chemosynthetic activity at a methane seep site. Ten sediment push cores were collected during submersible operations within the brine spillway and in upslope background sediments distal to the pool. Initial chemical analyses indicate the brine (128 ppt) is anoxic, chloride-rich (1994.8 mM) and sulfur-poor ([SO42-] = 0.4 mM, [HS-] = 8.2 uM). Steep porewater Cl- and Sr2+ concentration gradients observed in sediments downslope of the brine pool clearly indicate mixing between brine and seawater end members. Porewater sulfur profiles from sediments within the brine outflow indicate complete sulfate consumption within 30 cm below seafloor and sulfide production as great as 5 mM. The paired isotopic composition of dissolved sulfate and sulfide (Δ34SSO4-HS = 40‰) is consistent with bacterial sulfate reduction, potentially driven by the anaerobic oxidation of methane or non-methane hydrocarbons. The brine was nearly devoid of dissolved Mo (22 nM) and enriched in Mn (6.3 uM), relative to measured seawater casts ([Mo] = 112 nM; [Mn] below detection). Dissolved Mo enrichments, up to 392.8 nM, in surficial sediments decrease with depth may indicate brine

  20. Metal centers in the anaerobic microbial metabolism of CO and CO2.

    PubMed

    Bender, Güneş; Pierce, Elizabeth; Hill, Jeffrey A; Darty, Joseph E; Ragsdale, Stephen W

    2011-08-01

    Carbon dioxide and carbon monoxide are important components of the carbon cycle. Major research efforts are underway to develop better technologies to utilize the abundant greenhouse gas, CO(2), for harnessing 'green' energy and producing biofuels. One strategy is to convert CO(2) into CO, which has been valued for many years as a synthetic feedstock for major industrial processes. Living organisms are masters of CO(2) and CO chemistry and, here, we review the elegant ways that metalloenzymes catalyze reactions involving these simple compounds. After describing the chemical and physical properties of CO and CO(2), we shift focus to the enzymes and the metal clusters in their active sites that catalyze transformations of these two molecules. We cover how the metal centers on CO dehydrogenase catalyze the interconversion of CO and CO(2) and how pyruvate oxidoreductase, which contains thiamin pyrophosphate and multiple Fe(4)S(4) clusters, catalyzes the addition and elimination of CO(2) during intermediary metabolism. We also describe how the nickel center at the active site of acetyl-CoA synthase utilizes CO to generate the central metabolite, acetyl-CoA, as part of the Wood-Ljungdahl pathway, and how CO is channelled from the CO dehydrogenase to the acetyl-CoA synthase active site. We cover how the corrinoid iron-sulfur protein interacts with acetyl-CoA synthase. This protein uses vitamin B(12) and a Fe(4)S(4) cluster to catalyze a key methyltransferase reaction involving an organometallic methyl-Co(3+) intermediate. Studies of CO and CO(2) enzymology are of practical significance, and offer fundamental insights into important biochemical reactions involving metallocenters that act as nucleophiles to form organometallic intermediates and catalyze C-C and C-S bond formations. PMID:21647480

  1. Metal centers in the anaerobic microbial metabolism of CO and CO2

    PubMed Central

    Bender, Güneş; Pierce, Elizabeth; Hill, Jeffrey A.; Darty, Joseph E.

    2014-01-01

    Carbon dioxide and carbon monoxide are important components of the carbon cycle. Major research efforts are underway to develop better technologies to utilize the abundant greenhouse gas, CO2, for harnessing ‘green’ energy and producing biofuels. One strategy is to convert CO2 into CO, which has been valued for many years as a synthetic feedstock for major industrial processes. Living organisms are masters of CO2 and CO chemistry and, here, we review the elegant ways that metalloenzymes catalyze reactions involving these simple compounds. After describing the chemical and physical properties of CO and CO2, we shift focus to the enzymes and the metal clusters in their active sites that catalyze transformations of these two molecules. We cover how the metal centers on CO dehydrogenase catalyze the interconversion of CO and CO2 and how pyruvate oxidoreductase, which contains thiamin pyrophosphate and multiple Fe4S4 clusters, catalyzes the addition and elimination of CO2 during intermediary metabolism. We also describe how the nickel center at the active site of acetyl-CoA synthase utilizes CO to generate the central metabolite, acetyl-CoA, as part of the Wood-Ljungdahl pathway, and how CO is channelled from the CO dehydrogenase to the acetyl-CoA synthase active site. We cover how the corrinoid iron–sulfur protein interacts with acetyl-CoA synthase. This protein uses vitamin B12 and a Fe4S4 cluster to catalyze a key methyltransferase reaction involving an organometallic methyl-Co3+ intermediate. Studies of CO and CO2 enzymology are of practical significance, and offer fundamental insights into important biochemical reactions involving metallocenters that act as nucleophiles to form organometallic intermediates and catalyze C–C and C–S bond formations. PMID:21647480

  2. Four divalent transition metal carboxyarylphosphonate compounds: Hydrothermal synthesis, structural chemistry and generalized 2D FTIR correlation spectroscopy studies

    SciTech Connect

    Lei Ran; Chai Xiaochuan; Mei Hongxin; Zhang Hanhui; Chen Yiping; Sun Yanqiong

    2010-07-15

    Four divalent transition metal carboxyarylphosphonates, [Ni(4,4'-bipy)H{sub 2}L{sup 1}(HL{sup 1}){sub 2}(H{sub 2}O){sub 2}].2H{sub 2}O 1, [Ni{sub 2}(4,4'-bipy)(L{sup 2})(OH)(H{sub 2}O){sub 2}].3H{sub 2}O 2, Mn(phen){sub 2}(H{sub 2}L{sup 1}){sub 2}3 and Mn(phen)(HL{sup 2}) 4 (H{sub 3}L{sup 1}=p-H{sub 2}O{sub 3}PCH{sub 2}-C{sub 6}H{sub 4}-COOH, H{sub 3}L{sup 2}=m-H{sub 2}O{sub 3}PCH{sub 2}-C{sub 6}H{sub 4}-COOH, 4,4'-bipy=4,4'-bipyridine, phen=1,10-phenanthroline) were synthesized under hydrothermal conditions. 1 features 1D linear chains built from Ni(II) ions bridging 4,4'-bipy. In 2, neighboring Ni{sub 4} cluster units are connected by pairs of H{sub 3}L{sup 2} ligands to form 1D double-crankshaft chains, which are interconnected by pairs of 4,4'-bipy into 2D sheets. 3 exhibits 2D supramolecular layers via the R{sub 2}{sup 2}(8) ringed hydrogen bonding units. 4 has 1D ladderlike chains, in which the 4-membered rings are cross-linked by the organic moieties of the H{sub 3}L{sup 2} ligands. Additionally, 2D FTIR correlation analysis is applied with thermal and magnetic perturbation to clarify the structural changes of functional groups from H{sub 3}L{sup 1} and H{sub 3}L{sup 2} ligands in the compounds more efficiently. - Graphical abstract: A series of divalent transition metal carboxyarylphosphonate compounds were synthesized under hydrothermal conditions. The figure displays 2D sheet structure with large windows in compound 2.

  3. MN15-L and MN-15: New Kohn-Sham Density Functionals with Board Accuracy for Main-Group and Transition Metal Chemistry and Noncovalent Interactions

    NASA Astrophysics Data System (ADS)

    Yu, Haoyu; He, Xiao; Truhlar, Donald G.; Donald G. Truhlar Team

    The accuracy of Kohn-Sham density functional theory depends on the exchange-correlation functional. Local functionals depending on only the density (ρ) , density gradient (grad), and possibly kinetic energy density (τ) have been popular because of their low cost and simplicity, but the most successful functionals for chemistry have involved nonlocal Hartree-Fock exchange (hybrid functionals). We have designed a new meta gradient approximation called MN15-L and a new hybrid meta gradient approximation called MN15 and tested them systematically for 17 absolute atomic energies, 51 noncovalent interaction energies, 56 data on transition metal atoms and molecules, and for 298 other atomic and molecular energetic data, including main-group and transition metal bond energies, ionization potentials, proton affinities, reaction barrier heights, hydrocarbon thermochemistry, excitation energies, and isomerization energies. When compared with 84 previous density MN15 and MN15-L give respectively the smallest and second smallest mean unsigned errors (MUEs, in kcal/mol) on all 422 data with errors for the 4 subsets above being: MN15: 6, 0.26, 4.4, 1.6; MN15-L: 7, 0.45, 4.3, 2.0. Third best: M06: 4, 0.35, 7.7, 2.2. Best previous local functional: M06-L: 7, 0.42, 6.0, 3.5. Other popular functionals: B3LYP: 18, 0.82, 8.2, 4.3; HSE06: 33, 0.58, 8.8, 3.6; TPSS: 18, 0.89, 7.25, 5.0; PBE, 47, 0.88, 9.1, 6.0. MN15-L also performs well for solid-state cohesive energies. This research is supported by the U.S. Department of Energy and inorganic catalyst design center from university of Minnesota.

  4. Design and synthesis of magnetic binary metal oxides nanocomposites through dopamine chemistry for highly selective enrichment of phosphopeptides.

    PubMed

    Wang, Mengyi; Sun, Xueni; Li, Yan; Deng, Chunhui

    2016-03-01

    In this work, for the first time, magnetic binary metal oxides nanocomposites which integrated Zr and Ti into one entity on an atomic scale on polydopamine coated magnetic graphene (magG/PD/(Zr-Ti)O4 ) was designed and synthesized, and applied to the enrichment of phosphopeptides. The newly prepared magG/PD/(Zr-Ti)O4 composites gathered the advantages of large surface area, superparamagnetism, biocompatibility and the enhanced affinity properties to phosphopeptides. MagG/PD/ZrO2 , magG/PD/TiO2 , as well as the simple physical mixture of them were introduced to compare with magG/PD/(Zr-Ti)O4 composites. High sensitivity (1 pg/μL or 4.0 × 10(-11) M) and selectivity (weight ratio of β-casein and BSA reached up to 1:8000) toward phosphopeptides were also presented for magG/PD/(Zr-Ti)O4 composites. Additionally, mouse brain tissue was chose as the real samples to further investigate the phosphopeptides enrichment ability of this new material. PMID:26702589

  5. Four divalent transition metal carboxyarylphosphonate compounds: Hydrothermal synthesis, structural chemistry and generalized 2D FTIR correlation spectroscopy studies

    NASA Astrophysics Data System (ADS)

    Lei, Ran; Chai, Xiaochuan; Mei, Hongxin; Zhang, Hanhui; Chen, Yiping; Sun, Yanqiong

    2010-07-01

    Four divalent transition metal carboxyarylphosphonates, [Ni(4,4'-bipy)H 2L 1(HL 1) 2(H 2O) 2]·2H 2O 1, [Ni 2(4,4'-bipy)(L 2)(OH)(H 2O) 2]·3H 2O 2, Mn(phen) 2(H 2L 1) 23 and Mn(phen)(HL 2) 4 (H 3L 1= p-H 2O 3PCH 2-C 6H 4-COOH, H 3L 2= m-H 2O 3PCH 2-C 6H 4-COOH, 4,4'-bipy=4,4'-bipyridine, phen=1,10-phenanthroline) were synthesized under hydrothermal conditions. 1 features 1D linear chains built from Ni(II) ions bridging 4,4'-bipy. In 2, neighboring Ni 4 cluster units are connected by pairs of H 3L 2 ligands to form 1D double-crankshaft chains, which are interconnected by pairs of 4,4'-bipy into 2D sheets. 3 exhibits 2D supramolecular layers via the R 22(8) ringed hydrogen bonding units. 4 has 1D ladderlike chains, in which the 4-membered rings are cross-linked by the organic moieties of the H 3L 2 ligands. Additionally, 2D FTIR correlation analysis is applied with thermal and magnetic perturbation to clarify the structural changes of functional groups from H 3L 1 and H 3L 2 ligands in the compounds more efficiently.

  6. Influence of biocompatible metal ions (Ag, Fe, Y) on the surface chemistry, corrosion behavior and cytocompatibility of Mg-1Ca alloy treated with MEVVA.

    PubMed

    Liu, Yang; Bian, Dong; Wu, Yuanhao; Li, Nan; Qiu, Kejin; Zheng, Yufeng; Han, Yong

    2015-09-01

    Mg-1Ca samples were implanted with biocompatible alloy ions Ag, Fe and Y respectively with a dose of 2×10(17)ionscm(-2) by metal vapor vacuum arc technique (MEVVA). The surface morphologies and surface chemistry were investigated by SEM, AES and XPS. Surface changes were observed after all three kinds of elemental ion implantation. The results revealed that the modified layer was composed of two sublayers, including an outer oxidized layer with mixture of oxides and an inner implanted layer, after Ag and Fe ion implantation. Y ion implantation induced an Mg/Ca-deficient outer oxidized layer and the distribution of Y along with depth was more homogeneous. Both electrochemical test and immersion test revealed accelerated corrosion rate of Ag-implanted Mg-1Ca and Fe-implanted Mg-1Ca, whereas Y ion implantation showed a short period of protection since enhanced corrosion resistance was obtained by electrochemical test, but accelerated corrosion rate was found by long period immersion test. Indirect cytotoxicity assay indicated good cytocompatibility of Y-implanted Mg-1Ca. Moreover, the corresponding corrosion mechanisms involving implanting ions into magnesium alloys were proposed, which might provide guidance for further application of plasma ion implantation to biodegradable Mg alloys. PMID:26094143

  7. Deciphering Halogen Competition in Organometallic Halide Perovskite Growth

    DOE PAGESBeta

    Keum, Jong Kahk; Ovchinnikova, Olga S.; Chen, Shiyou; Du, Mao-Hua; Ivanov, Ilia N; Rouleau, Christopher; Geohegan, David B.; Xiao, Kai

    2016-03-01

    Organometallic halide perovskites (OHPs) hold great promise for next-generation, low-cost optoelectronic devices. During the chemical synthesis and crystallization of OHP thin films a major unresolved question is the competition between multiple halide species (e.g. I-, Cl-, Br-) in the formation of the mixed halide perovskite crystals. Whether Cl- ions are successfully incorporated into the perovskite crystal structure or alternatively, where they are located, is not yet fully understood. Here, in situ X-ray diffraction measurements of crystallization dynamics are combined with ex situ TOF-SIMS chemical analysis to reveal that Br- or Cl- ions can promote crystal growth, yet reactive I- ionsmore » prevent them from incorporating into the lattice of the final perovskite crystal structure. The Cl- ions are located in the grain boundaries of the perovskite films. These findings significantly advance our understanding of the role of halogens during synthesis of hybrid perovskites, and provide an insightful guidance to the engineering of high-quality perovskite films, essential for exploring superior-performance and cost-effective optoelectronic devices.« less

  8. Development of Organometallic S6K1 Inhibitors

    PubMed Central

    2015-01-01

    Aberrant activation of S6 kinase 1 (S6K1) is found in many diseases, including diabetes, aging, and cancer. We developed ATP competitive organometallic kinase inhibitors, EM5 and FL772, which are inspired by the structure of the pan-kinase inhibitor staurosporine, to specifically inhibit S6K1 using a strategy previously used to target other kinases. Biochemical data demonstrate that EM5 and FL772 inhibit the kinase with IC50 value in the low nanomolar range at 100 μM ATP and that the more potent FL772 compound has a greater than 100-fold specificity over S6K2. The crystal structures of S6K1 bound to staurosporine, EM5, and FL772 reveal that the EM5 and FL772 inhibitors bind in the ATP binding pocket and make S6K1-specific contacts, resulting in changes to the p-loop, αC helix, and αD helix when compared to the staurosporine-bound structure. Cellular data reveal that FL772 is able to inhibit S6K phosphorylation in yeast cells. Together, these studies demonstrate that potent, selective, and cell permeable S6K1 inhibitors can be prepared and provide a scaffold for future development of S6K inhibitors with possible therapeutic applications. PMID:25356520

  9. Facile Separation of Regioisomeric Compounds by a Heteronuclear Organometallic Capsule.

    PubMed

    Zhang, Wen-Ying; Lin, Yue-Jian; Han, Ying-Feng; Jin, Guo-Xin

    2016-08-24

    Owing to the often-similar physical and chemical properties of structural isomers of organic molecules, large efforts have been made to develop efficient strategies to isolate specific isomers. However, facile separation of regioisomeric compounds remains difficult. Here we demonstrate a universal organometallic capsule in which two silver centers are rigidly separated from each other by two tetranuclear [Rh4] pyramidal frustums, which selectively encapsulate a specific isomer from mixtures. Not only is the present heterometallic capsule suitable as a host for the encapsulation of a series of aromatic compounds, but also the receptor shows widely differing specificity for the various isomers. Direct experimental evidence is provided for the selective encapsulation of a series of para (p)-disubstituted benzene derivatives, such as p-xylene, p-dichlorobenzene, p-dibromobenzene, and p-diiodobenzene. The size and shape matching, as well as the Ag-π interactions, are the main forces governing the extent of molecular recognition. The encapsulated guest p-xylene can be released by using the solid-liquid solvent washing strategy, and the other guest molecules are easily liberated by using light stimulus. PMID:27463561

  10. Deciphering Halogen Competition in Organometallic Halide Perovskite Growth.

    PubMed

    Yang, Bin; Keum, Jong; Ovchinnikova, Olga S; Belianinov, Alex; Chen, Shiyou; Du, Mao-Hua; Ivanov, Ilia N; Rouleau, Christopher M; Geohegan, David B; Xiao, Kai

    2016-04-20

    Organometallic halide perovskites (OHPs) hold great promise for next-generation, low-cost optoelectronic devices. During the chemical synthesis and crystallization of OHP thin films, a major unresolved question is the competition between multiple halide species (e.g., I(-), Cl(-), Br(-)) in the formation of the mixed-halide perovskite crystals. Whether Cl(-) ions are successfully incorporated into the perovskite crystal structure or, alternatively, where they are located is not yet fully understood. Here, in situ X-ray diffraction measurements of crystallization dynamics are combined with ex situ TOF-SIMS chemical analysis to reveal that Br(-) or Cl(-) ions can promote crystal growth, yet reactive I(-) ions prevent them from incorporating into the lattice of the final perovskite crystal structure. The Cl(-) ions are located in the grain boundaries of the perovskite films. These findings significantly advance our understanding of the role of halogens during synthesis of hybrid perovskites and provide an insightful guidance to the engineering of high-quality perovskite films, essential for exploring superior-performing and cost-effective optoelectronic devices. PMID:26931634

  11. Degradation of organometallic perovskite solar cells induced by trap states

    NASA Astrophysics Data System (ADS)

    Song, Dandan; Ji, Jun; Li, Yaoyao; Li, Guanying; Li, Meicheng; Wang, Tianyue; Wei, Dong; Cui, Peng; He, Yue; Mbengue, Joseph Michel

    2016-02-01

    The degradation of organometallic perovskite solar cells (PSCs) is the key bottleneck hampering their development, which is typically ascribed to the decomposition of perovskite (CH3NH3PbI3). In this work, the degradation of PSCs is observed to be significant, with the decrease in efficiency from 18.2% to 11.5% in ambient air for 7 days. However, no obvious decomposition or structural evolution of the perovskite was observed, except the notable degradation phenomenon of the device. The degradation of PSCs derives from deteriorated photocurrent and fill factor, which are proven to be induced by increased trap states for enlarged carrier recombination in degraded PSCs. The increased trap states in PSCs over storage time are probably induced by the increased defects at the surface of perovskite. The trap states induced degradation provides a physical insight into the degradation mechanisms of PSCs. Moreover, as the investigations were performed on real PSCs instead of individual perovskite films, the findings here present one of their actual degradation mechanisms.

  12. Coordination Chemistry Inside Polymeric Nanoreactors: Interparticle Metal Exchange and Ionic Compound Vectorization in Phosphine-Functionalized Amphiphilic Polymer Latexes.

    PubMed

    Chen, Si; Gayet, Florence; Manoury, Eric; Joumaa, Ahmad; Lansalot, Muriel; D'Agosto, Franck; Poli, Rinaldo

    2016-04-25

    Stable latexes of hierarchically organized core-cross-linked polymer micelles that are functionalized at the core with triphenylphosphine (TPP@CCM) have been investigated by NMR spectroscopic analysis at both natural (ca. pH 5) and strongly basic (pH 13.6) pH values after core swelling with toluene. The core-shell interface structuring forces part of the hydrophilic poly(ethylene oxide) (PEO) chains to reside inside the hydrophobic core at both pH values. Loading the particle cores with [Rh(acac)(CO)2 ] (acac=acetylacetonate) at various Rh/P ratios yielded polymer-supported [Rh(acac)(CO)(TPP)] (TPP=triphenylphosphine). The particle-to-particle rhodium migration is very fast at natural pH, but slows down dramatically at high pH, whereas the size distribution of the nanoreactors remains unchanged. The slow migration at pH 13.6 leads to the generation of polymer-anchored [Rh(OH)(CO)(TPP)2 ], which is also generated immediately upon the addition of NaOH to the particles with a [Rh(acac)(CO)] loading of 50 %. Similarly, treatment of the same particles with NaCl yielded polymer-anchored [RhCl(CO)(TPP)2 ]. Interparticle coupling occurs during these rapid processes. These experiments prove that the major contribution to metal migration is direct core-core contact. The slow migration at the high pH value, however, must result from a pathway that does not involve core-core contact. The facile penetration of the polymer cores by NaOH and NaCl results from the presence of shell-linked poly(ethylene oxide) methyl ether functions both outside and inside the polymer core-shell interface. PMID:27001452

  13. The Evolving Chemistry Along Preferential Flow Paths in Alkaline Porous Media and its Significance for Heavy Metal Mobility

    NASA Astrophysics Data System (ADS)

    Bendz, D.; Flyhammar, P.; Ginn, T. R.

    2001-12-01

    It is common knowledge that physical and chemical heterogeneity are prominent features of geological formations and that they may have a large impact on the fate of contaminants. However, the particular influence of any underlying chemical heterogeneity is difficult to distinguish from experimental data because its manifestation depends on the hydraulic and physical properties of the system as well as the chemical components involved. Physical and chemical heterogeneity are also important features of man-made formations such as landfills. The chemical composition of the leachate that is discharged at the lower boundary of a landfill reflects the processes that take place in the landfill interior. However, anomalous behavior have been observed for both municipal solid waste landfills and municipal solid waste incineration bottom ash landfills: the chemical composition of the leachate indicates that the (bio-) geochemical conditions in the landfill interior alternate between different states depending on the leachate flux. The main hypothesis here is that this is an effect of chemical heterogeneity and a preferential flow field exhibiting a distribution of travel times ranging from hours to years. The importance of a non uniform flow field should not be underestimated when making predictions of expected leaching behavior on short and intermediate time scales, mainly because doing so may render predictions that are not conservative risk-wise. Model simulations demonstrate the influence of partial pressure of CO2, organic content, buffering capacity and matrix diffusion for the formation and movement of reaction (pH- and redox-) fronts and transport of heavy metals in an ensemble of preferential flow paths in a municipal solid waste incineration bottom ash landfill receiving acid rain.

  14. Metal plasma immersion ion implantation and deposition (MePIIID) on screw-shaped titanium implant: The effects of ion source, ion dose and acceleration voltage on surface chemistry and morphology.

    PubMed

    Kang, Byung-Soo; Sul, Young-Taeg; Jeong, Yongsoo; Byon, Eungsun; Kim, Jong-Kuk; Cho, Suyeon; Oh, Se-Jung; Albrektsson, Tomas

    2011-07-01

    The present study investigated the effect of metal plasma immersion ion implantation and deposition (MePIIID) process parameters, i.e., plasma sources of magnesium and calcium, ion dose, and acceleration voltage on the surface chemistry and morphology of screw-type titanium implants that have been most widely used for osseointegrated implants. It is found that irrespective of plasma ion source, surface topography and roughness showed no differences at the nanometer level; that atom concentrations increased with ion dose but decreased with acceleration voltage. Data obtained from X-ray photoelectron spectroscopy and auger electron spectroscopy suggested that MePIIID process produces 'intermixed' layer of cathodic arc deposition and plasma immersion ion implantation. The MePIIID process may create desired bioactive surface chemistry of dental and orthopaedic implants by tailoring ion and plasma sources and thus enable investigations of the effect of the surface chemistry on bone response. PMID:21334957

  15. TOXICOLOGY OF METALS. VOLUME III

    EPA Science Inventory

    ;Contents: General chemistry of metals; Sampling and analytical methods; Sources, transport, and transformation of metals in the environment; Effects - general principles underlying the toxic action of metals; Factors influencing effects and dose-response relationships of metals;...

  16. Chemistry Notes

    ERIC Educational Resources Information Center

    School Science Review, 1976

    1976-01-01

    Described are eight chemistry experiments and demonstrations applicable to introductory chemistry courses. Activities include: measure of lattice enthalpy, Le Chatelier's principle, decarboxylation of soap, use of pocket calculators in pH measurement, and making nylon. (SL)

  17. Chemistry Notes.

    ERIC Educational Resources Information Center

    School Science Review, 1983

    1983-01-01

    Presents background information, laboratory procedures, classroom materials/activities, and chemistry experiments. Topics include sublimation, electronegativity, electrolysis, experimental aspects of strontianite, halide test, evaluation of present and future computer programs in chemistry, formula building, care of glass/saturated calomel…

  18. ENVIRONMENTAL CHEMISTRY

    EPA Science Inventory

    Environmental chemistry is applied to estimating the exposure of ecosystems and humans to various chemical environmental stressors. Among the stressors of concern are mercury, pesticides, and arsenic. Advanced analytical chemistry techniques are used to measure these stressors ...

  19. Metal ion-containing epoxies

    NASA Technical Reports Server (NTRS)

    Stoakley, D. M.; St.clair, A. K.

    1982-01-01

    A variety of metallic and organometallic complexes to be used as potential additives for an epoxy used by the aerospace industry as a composite matrix resin were investigated. A total of 9 complexes were screened for compatibility and for their ability to accelerate or inhibit the cure of a highly crosslinkable epoxy resin. Methods for combining the metallic complexes with the resin were investigated, gel times recorded, and cure exotherms studied by differential scanning calorimetry. Glass transition temperatures of cured metal ion containing epoxy castings were determined by thermomechanical analysis. Thermal stabilities of the castings were determined by thermogravimetric analysis. Mechanical strength and stiffness of these doped epoxies were also measured.

  20. Generality of the 18-n Rule: Intermetallic Structural Chemistry Explained through Isolobal Analogies to Transition Metal Complexes.

    PubMed

    Yannello, Vincent J; Fredrickson, Daniel C

    2015-12-01

    Intermetallic phases exhibit a vast structural diversity in which electron count is known to be one controlling factor. However, chemical bonding theory has yet to establish how electron counts and structure are interrelated for the majority of these compounds. Recently, a simple bonding picture for transition metal (T)-main group (E) intermetallics has begun to take shape based on isolobal analogies to molecular T complexes. This bonding picture is summarized in the 18-n rule: each T atom in a T-E intermetallic phase will need 18-n electrons to achieve a closed-shell 18-electron configuration, where n is the number of electron pairs it shares with other T atoms in multicenter interactions isolobal to T-T bonds. In this Article, we illustrate the generality of this rule with a survey over a wide range of T-E phases. First, we illustrate how three structural progressions with changing electron counts can be accounted for, both geometrically and electronically, with the 18-n rule: (1) the transition between the fluorite and complex β-FeSi2 types for TSi2 phases; (2) the sequence from the marcasite type to the arsenopyrite type and back to the marcasite type for TSb2 compounds; and (3) the evolution from the AuCu3 type to the ZrAl3 and TiAl3 types for TAl3 phases. We then turn to a broader survey of the applicability of the 18-n rule through a study of the following 34 binary structure types: PtHg4, CaF2 (fluorite), Fe3C, CoGa3, Co2Al5, Ru2B3, β-FeSi2, NiAs, Ni2Al3, Rh4Si5, CrSi2, Ir3Ga5, Mo3Al8, MnP, TiSi2, Ru2Sn3, TiAl3, MoSi2, CoSn, ZrAl3, CsCl, FeSi, AuCu3, ZrSi2, Mn2Hg5, FeS2 (oP6, marcasite), CoAs3 (skutterudite), PdSn2, CoSb2, Ir3Ge7, CuAl2, Re3Ge7, CrP2, and Mg2Ni. Through these analyses, the 18-n rule is established as a framework for interpreting the stability of 341 intermetallic phases and anticipating their properties. PMID:26581113

  1. Experimental determination of contaminant metal mobility as a function of temperature, time and solution chemistry. 1997 annual progress report

    SciTech Connect

    Carroll, S.; Bruton, C.; O'Day, P.; Sahai, N.

    1997-01-01

    'Strontium is significantly more mobile than other hazardous radioactive metals. Its partitioning between aqueous and solid phases is controlled by reactions that occur at the interface between natural waters and minerals. At a groundwater site in Hanford (200-BP-5), the aerial extent of the {sup 90}Sr plume is 100 times larger than the aerial extent of the {sup 137}Cs and the {sup 239}Pu plumes. Similarly, contaminated, perched watertables at INEL have much higher aqueous concentrations of {sup 90}Sr than {sup 137}Cs, presumably because Cs is preferentially sorbed to solids (Duncan 1995). Under high physical flow conditions, such as those in the highly fractured rock at Hanford and INEL, {sup 90}Sr present in plumes may spread off-site and cause contamination of aquifers or other water sources. Geochemical factors that may contribute to the overall mobility of Sr in natural waters are the solubilities of phases such as strontianite (SrCO{sub 3}) and formation of strong complexes with sulfate and nitrate. Although {sup 90}Sr is mobilized in natural waters in these examples, significant concentrations may also be present in solid phases. Sorption experiments using a wide variety of substrates at room temperature have shown that Sr is removed from solution under certain conditions. Additionally, strontianite (SrCO{sub 3}) may precipitate at low Sr concentrations in the pH range of waters in contact with basaltic rocks, which varies between pH 8 and 10. Waters contain variable amounts of carbonate owing to atmospheric interactions; the partial pressure of CO{sub 2} is about 10 x 3.5 atm in air and commonly as high as 10 x 2.5 atm in soils. The objective of this work is to determine the fundamental data needed to predict the behavior of strontium at temperature and time scales appropriate to thermal remediation. The authors approach combines macroscopic sorption/precipitation and desorption/dissolution kinetic experiments, which track changes in solution composition

  2. The Pimlico Chemistry Trail.

    ERIC Educational Resources Information Center

    Borrows, Peter

    1984-01-01

    Describes a chemistry "trail" (similar to a nature trail) which focuses on chemical phenomena in the environment. The trail includes 20 stops in and around a local school. Types of phenomena examined include building materials, air pollution, corrosion of metals, swimming pools, and others. Additional activities are also suggested. (DH)

  3. STRUCTURAL BIOLOGY OF THE SEQUESTRATION & TRANSPORT OF HEAVY METAL TOXINS: NMR STRUCTURE DETERMINATION OF PROTEINS CONTAINING THE CYS-X-Y-CYS-METAL BINDING MOTIFS

    EPA Science Inventory

    There are enormous amounts of heavy metals in the environment, much of it in the form of organometallic compounds resulting from various types of industrial and military waste. Nearly all of these metals and compounds are highly toxic to biological organisms including humans. How...

  4. Organometallic photovoltaics: a new and versatile approach for harvesting solar energy using conjugated polymetallaynes.

    PubMed

    Wong, Wai-Yeung; Ho, Cheuk-Lam

    2010-09-21

    Energy remains one of the world's great challenges. Growing concerns about limited fossil fuel resources and the accumulation of CO(2) in the atmosphere from burning those fuels have stimulated tremendous academic and industrial interest. Researchers are focusing both on developing inexpensive renewable energy resources and on improving the technologies for energy conversion. Solar energy has the capacity to meet increasing global energy needs. Harvesting energy directly from sunlight using photovoltaic technology significantly reduces atmospheric emissions, avoiding the detrimental effects of these gases on the environment. Currently inorganic semiconductors dominate the solar cell production market, but these materials require high technology production and expensive materials, making electricity produced in this manner too costly to compete with conventional sources of electricity. Researchers have successfully fabricated efficient organic-based polymer solar cells (PSCs) as a lower cost alternative. Recently, metalated conjugated polymers have shown exceptional promise as donor materials in bulk-heterojunction solar cells and are emerging as viable alternatives to the all-organic congeners currently in use. Among these metalated conjugated polymers, soluble platinum(II)-containing poly(arylene ethynylene)s of variable bandgaps (∼1.4-3.0 eV) represent attractive candidates for a cost-effective, lightweight solar-energy conversion platform. This Account highlights and discusses the recent advances of this research frontier in organometallic photovoltaics. The emerging use of low-bandgap soluble platinum-acetylide polymers in PSCs offers a new and versatile strategy to capture sunlight for efficient solar power generation. Properties of these polyplatinynes--including their chemical structures, absorption coefficients, bandgaps, charge mobilities, accessibility of triplet excitons, molecular weights, and blend film morphologies--critically influence the device

  5. Forensic Chemistry

    NASA Astrophysics Data System (ADS)

    Bell, Suzanne

    2009-07-01

    Forensic chemistry is unique among chemical sciences in that its research, practice, and presentation must meet the needs of both the scientific and the legal communities. As such, forensic chemistry research is applied and derivative by nature and design, and it emphasizes metrology (the science of measurement) and validation. Forensic chemistry has moved away from its analytical roots and is incorporating a broader spectrum of chemical sciences. Existing forensic practices are being revisited as the purview of forensic chemistry extends outward from drug analysis and toxicology into such diverse areas as combustion chemistry, materials science, and pattern evidence.

  6. The direct synthesis of organic and organometallic-containing MICA-type aluminosilicates

    SciTech Connect

    Carrado, K.A.; Awaluddin, A.

    1993-08-01

    Layer-silicate clay structures can provide supramolecular organization for catalysis, chiral reactions, colloid science, and electron transfer. The authors have successfully modified the experimental preparations of several different layer silicates in order to incorporate a wide variety of organic and organometallic molecules in the clay galleries. Synthesis and physical characterization of these materials are described and compared to ion-exchanged natural clay analogs. In addition, the photophysical properties of organometallic Ru(II) complexes incorporated by direct hydrothermal crystallization into synthetic clays were measured. 3 tabs, 21 refs.

  7. Bimodal X-ray and Infrared Imaging of an Organometallic Derivative of Praziquantel in Schistosoma mansoni.

    PubMed

    Clède, Sylvain; Cowan, Noemi; Lambert, François; Bertrand, Hélène C; Rubbiani, Riccardo; Patra, Malay; Hess, Jeannine; Sandt, Christophe; Trcera, Nicolas; Gasser, Gilles; Keiser, Jennifer; Policar, Clotilde

    2016-06-01

    An organometallic derivative of praziquantel was studied directly in worms by using inductively coupled plasma-mass spectrometry (ICP-MS) for quantification and synchrotron-based imaging. X-ray fluorescence (XRF) and IR absorption spectromicroscopy were used for the first time in combination to directly locate this organometallic drug candidate in schistosomes. The detection of both CO (IR) and Cr (XRF) signatures proved that the Cr(CO)3 core remained intact in the worms. Images showed a preferential accumulation at the worm's tegument, consistent with a possible targeting of the calcium channel but not excluding other biological targets inside the worm. PMID:26991635

  8. Theoretical evidence of photo-induced charge transfer from DNA to intercalated ruthenium (II) organometallic complexes

    NASA Astrophysics Data System (ADS)

    Chantzis, Agisilaos; Very, Thibaut; Daniel, Chantal; Monari, Antonio; Assfeld, Xavier

    2013-07-01

    The absorption spectrum of two ruthenium (II) organometallic complexes intercalated into DNA is studied at the quantum mechanic/molecular mechanic level. The macromolecular environment is taken into account as to include geometric, electrostatic and polarization effects that can alter the excitation energy and oscillator strength. The inclusion of DNA base pairs into the quantum mechanic partition allows us for the first time to clearly evidence the presence of charge transfer excited states involving an electron withdraw from DNA base pairs to the organometallic complex.

  9. Chemical vapor deposition of group IIIB metals

    DOEpatents

    Erbil, A.

    1989-11-21

    Coatings of Group IIIB metals and compounds thereof are formed by chemical vapor deposition, in which a heat decomposable organometallic compound of the formula given in the patent where M is a Group IIIB metal, such as lanthanum or yttrium and R is a lower alkyl or alkenyl radical containing from 2 to about 6 carbon atoms, with a heated substrate which is above the decomposition temperature of the organometallic compound. The pure metal is obtained when the compound of the formula 1 is the sole heat decomposable compound present and deposition is carried out under nonoxidizing conditions. Intermetallic compounds such as lanthanum telluride can be deposited from a lanthanum compound of formula 1 and a heat decomposable tellurium compound under nonoxidizing conditions.

  10. Chemical vapor deposition of group IIIB metals

    DOEpatents

    Erbil, Ahmet

    1989-01-01

    Coatings of Group IIIB metals and compounds thereof are formed by chemical vapor deposition, in which a heat decomposable organometallic compound of the formula (I) ##STR1## where M is a Group IIIB metal, such as lanthanum or yttrium and R is a lower alkyl or alkenyl radical containing from 2 to about 6 carbon atoms, with a heated substrate which is above the decomposition temperature of the organometallic compound. The pure metal is obtained when the compound of the formula I is the sole heat decomposable compound present and deposition is carried out under nonoxidizing conditions. Intermetallic compounds such as lanthanum telluride can be deposited from a lanthanum compound of formula I and a heat decomposable tellurium compound under nonoxidizing conditions.

  11. Dispersed metal cluster catalysts by design. Synthesis, characterization, structure, and performance

    SciTech Connect

    Arslan, Ilke; Dixon, David A.; Gates, Bruce C.; Katz, Alexander

    2015-09-30

    To understand the class of metal cluster catalysts better and to lay a foundation for the prediction of properties leading to improved catalysts, we have synthesized metal catalysts with well-defined structures and varied the cluster structures and compositions systematically—including the ligands bonded to the metals. These ligands include supports and bulky organics that are being tuned to control both the electron transfer to or from the metal and the accessibility of reactants to influence catalytic properties. We have developed novel syntheses to prepare these well-defined catalysts with atomic-scale control the environment by choice and placement of ligands and applied state-of-the art spectroscopic, microscopic, and computational methods to determine their structures, reactivities, and catalytic properties. The ligands range from nearly flat MgO surfaces to enveloping zeolites to bulky calixarenes to provide controlled coverages of the metal clusters, while also enforcing unprecedented degrees of coordinative unsaturation at the metal site—thereby facilitating bonding and catalysis events at exposed metal atoms. With this wide range of ligand properties and our arsenal of characterization tools, we worked to achieve a deep, fundamental understanding of how to synthesize robust supported and ligand-modified metal clusters with controlled catalytic properties, thereby bridging the gap between active site structure and function in unsupported and supported metal catalysts. We used methods of organometallic and inorganic chemistry combined with surface chemistry for the precise synthesis of metal clusters and nanoparticles, characterizing them at various stages of preparation and under various conditions (including catalytic reaction conditions) and determining their structures and reactivities and how their catalytic properties depend on their compositions and structures. Key characterization methods included IR, NMR, and EXAFS spectroscopies to identify

  12. Mechanistic Insight into Ketone α-Alkylation with Unactivated Olefins via C-H Activation Promoted by Metal-Organic Cooperative Catalysis (MOCC): Enriching the MOCC Chemistry.

    PubMed

    Dang, Yanfeng; Qu, Shuanglin; Tao, Yuan; Deng, Xi; Wang, Zhi-Xiang

    2015-05-20

    Metal-organic cooperative catalysis (MOCC) has been successfully applied for hydroacylation of olefins with aldehydes via directed C(sp(2))-H functionalization. Most recently, it was reported that an elaborated MOCC system, containing Rh(I) catalyst and 7-azaindoline (L1) cocatalyst, could even catalyze ketone α-alkylation with unactivated olefins via C(sp(3))-H activation. Herein we present a density functional theory study to understand the mechanism of the challenging ketone α-alkylation. The transformation uses IMesRh(I)Cl(L1)(CH2═CH2) as an active catalyst and proceeds via sequential seven steps, including ketone condensation with L1, giving enamine 1b; 1b coordination to Rh(I) active catalyst, generating Rh(I)-1b intermediate; C(sp(2))-H oxidative addition, leading to a Rh(III)-H hydride; olefin migratory insertion into Rh(III)-H bond; reductive elimination, generating Rh(I)-1c(alkylated 1b) intermediate; decoordination of 1c, liberating 1c and regenerating Rh(I) active catalyst; and hydrolysis of 1c, furnishing the final α-alkylation product 1d and regenerating L1. Among the seven steps, reductive elimination is the rate-determining step. The C-H bond preactivation via agostic interaction is crucial for the bond activation. The mechanism rationalizes the experimental puzzles: why only L1 among several candidates performed perfectly, whereas others failed, and why Wilkinson's catalyst commonly used in MOCC systems performed poorly. Based on the established mechanism and stimulated by other relevant experimental reactions, we attempted to enrich MOCC chemistry computationally, exemplifying how to develop new organic catalysts and proposing L7 to be an alternative for L1 and demonstrating the great potential of expanding the hitherto exclusive use of Rh(I)/Rh(III) manifold to Co(0)/Co(II) redox cycling in developing MOCC systems. PMID:25915086

  13. Diamidophosphines with six-membered chelates and their coordination chemistry with group 4 metals: development of a trimethylene-methane-tethered [PN2]-type "molecular claw".

    PubMed

    Batke, S; Kothe, T; Haas, M; Wadepohl, H; Ballmann, J

    2016-02-28

    The coordination chemistry of the phosphine-tethered diamidophosphine ligands PhP(CH2CH2CH2NHPh)2 (pr[NPN]H2) and PhP(1,2-CH2-C6H4-NHSiMe3)2 (bn[NPN]H2) featuring six-membered N–C3–P chelates was explored with group 4 metals, which allowed for the consecutive development of a new trimethylene-methane-tethered [PN2] scaffold. In the case of the propylene-linked system pr[NPN]H2, access to the sparingly soluble dibenzyl derivative pr[NPN]ZrBn2 (3-Zr) was gained, while thermally sensitive zirconium and hafnium diiodo complexes bn[NPN]MI2 (5-M, M = Zr, Hf) were isolated in the case of the benzylene-linked derivative bn[NPN]H2. Despite the related phosphine-tethered backbone architectures of both of these ligands, their group 4 complexes were found to exhibit either C1-symmetric (bn[NPN]MX2) or averaged CS-symmetric (pr[NPN]MX2) structures in solution. To restrain the overall flexibility of these systems and thereby control the properties of the resulting complexes without disrupting the six-membered chelates, the new trimethylene-methane-tethered N,N′-di-(tert-butyl)-substituted [PN2]H2 protioligand was designed. This tripodal ligand system was prepared on a gram scale and its CS-symmetric dichloro complexes [PN2]MCl2 (6-M, M = Ti, Zr, Hf) were isolated subsequently. The benzene-soluble dibenzyl derivative [PN2]ZrBn2 (7-Zr) was synthesised as well and characterised by X-ray diffraction. These results are discussed not only in conjunction with the known [NPN]-coordinated group 4 complexes incorporating five-membered chelates, but also in the context of “molecular claws” that are related to the new [PN2] tripod. PMID:26804587

  14. Intermolecular bonding of metals or alloys by thermochemical decomposition

    NASA Technical Reports Server (NTRS)

    Wilson, R.

    1970-01-01

    Various metals and alloys are bonded at temperatures below their recrystallization temperature with a Ni-Fe-C alloy grown by thermochemical vapor deposition from organometallic plating compounds. Process time is short, the joints are strong, and microthrowing power is good.

  15. A new metalation complex for organic synthesis and polymerization reactions

    NASA Technical Reports Server (NTRS)

    Hirshfield, S. M.

    1971-01-01

    Organometallic complex of N,N,N',N' tetramethyl ethylene diamine /TMEDA/ and lithium acts as metalation intermediate for controlled systhesis of aromatic organic compounds and polymer formation. Complex of TMEDA and lithium aids in preparation of various organic lithium compounds.

  16. Synthetic Metal-Containing Polymers

    NASA Astrophysics Data System (ADS)

    Manners, Ian

    2004-04-01

    The development of the field of synthetic metal-containing polymers - where metal atoms form an integral part of the main chain or side group structure of a polymer - aims to create new materials which combine the processability of organic polymers with the physical or chemical characteristics associated with the metallic element or complex. This book covers the major developments in the synthesis, properties, and applications of synthetic metal-containing macromolecules, and includes chapters on the preparation and characterization of metal-containing polymers, metallocene-based polymers, rigid-rod organometallic polymers, coordination polymers, polymers containing main group metals, and also covers dendritic and supramolecular systems. The book describes both polymeric materials with metals in the main chain or side group structure and covers the literature up to the end of 2002.

  17. Introduction of Differential Scanning Calorimetry in a General Chemistry Laboratory Course: Determination of Heat Capacity of Metals and Demonstration of Law of Dulong and Petit

    ERIC Educational Resources Information Center

    D'Amelia, Ronald P.; Stracuzzi, Vincent; Nirode, William F.

    2008-01-01

    Today's general chemistry students are introduced to many of the principles and concepts of thermodynamics. In first-year general chemistry undergraduate courses, thermodynamic properties such as heat capacity are frequently discussed. Classical calorimetric methods of analysis and thermal equilibrium experiments are used to determine heat…

  18. Chemistry Notes

    ERIC Educational Resources Information Center

    School Science Review, 1972

    1972-01-01

    Twelve new chemistry expermiments are described. Broad areas covered include atomic structure, solubility, gaseous diffusion, endothermic reactions, alcohols, equilibrium, atomic volumes, and some improvised apparatus. (PS)

  19. New organic and organometallic salts for second-order nonlinear optics

    NASA Technical Reports Server (NTRS)

    Marder, Seth R.; Perry, Joseph W.; Tiemann, Bruce G.; Schaefer, William P.; Groves, Paul C.

    1989-01-01

    A series of organometallic and organic salts, in which the cation has been designed to have a large molecular hyperpolarizability, has been prepared. Variation of the counterion (anion) in many cases leads to materials with large powder second harmonic generation (SHG) efficiencies, the highest of which is roughly 2000 times that of a urea reference.

  20. Reaction of Glyconitriles with Organometallic Reagents: Access to Acyl β-C-Glycosides.

    PubMed

    Guisot, Nicolas E S; Ella Obame, Idriss; Ireddy, Prathap; Nourry, Arnaud; Saluzzo, Christine; Dujardin, Gilles; Dubreuil, Didier; Pipelier, Muriel; Guillarme, Stéphane

    2016-03-18

    A new strategy for the synthesis of acyl β-C-glycosides is described. The reactivity of glyconitriles toward organometallic reagents such as organomagnesium or organolithium derivatives was studied, affording acyl β-C-glycosides in moderate to good yields. In this study, glycal formation was efficiently prevented by deprotonating the hydroxyl group in position 2 of the glyconitriles during the process. PMID:26926714

  1. 40 CFR 721.10414 - Polycyclic polyamine diester organometallic compound (generic) (P-10-358).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Polycyclic polyamine diester organometallic compound (generic) (P-10-358). 721.10414 Section 721.10414 Protection of Environment ENVIRONMENTAL... compound (generic) (P-10-358). (a) Chemical substance and significant new uses subject to reporting....

  2. 40 CFR 721.10414 - Polycyclic polyamine diester organometallic compound (generic) (P-10-358).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Polycyclic polyamine diester organometallic compound (generic) (P-10-358). 721.10414 Section 721.10414 Protection of Environment ENVIRONMENTAL... compound (generic) (P-10-358). (a) Chemical substance and significant new uses subject to reporting....

  3. 40 CFR 721.10414 - Polycyclic polyamine diester organometallic compound (generic) (P-10-358).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Polycyclic polyamine diester organometallic compound (generic) (P-10-358). 721.10414 Section 721.10414 Protection of Environment ENVIRONMENTAL... compound (generic) (P-10-358). (a) Chemical substance and significant new uses subject to reporting....

  4. Organometallic macromolecules with piano stool coordination repeating units: chain configuration and stimulated solution behaviour.

    PubMed

    Cao, Kai; Ward, Jonathan; Amos, Ryan C; Jeong, Moon Gon; Kim, Kyoung Taek; Gauthier, Mario; Foucher, Daniel; Wang, Xiaosong

    2014-09-11

    Theoretical calculations illustrate that organometallic macromolecules with piano stool coordination repeating units (Fe-acyl complex) adopt linear chain configuration with a P-Fe-C backbone surrounded by aromatic groups. The macromolecules show molecular weight-dependent and temperature stimulated solution behaviour in DMSO. PMID:25036387

  5. Application of Organometallic Catalysis to the Commercial Production of L-DOPA.

    ERIC Educational Resources Information Center

    Knowles, W. S.

    1986-01-01

    Shows how asymmetric organometallic catalysts can be used to make complex organic molecules with extremely high enantioselectivity. The molecule considered is l-3, 4-dihydroxyphenylalanine (L-DOPA), an amino acid which was found to be effective in the treatment of Parkinson's disease. (JN)

  6. Using Molecular Modeling in Teaching Group Theory Analysis of the Infrared Spectra of Organometallic Compounds

    ERIC Educational Resources Information Center

    Wang, Lihua

    2012-01-01

    A new method is introduced for teaching group theory analysis of the infrared spectra of organometallic compounds using molecular modeling. The main focus of this method is to enhance student understanding of the symmetry properties of vibrational modes and of the group theory analysis of infrared (IR) spectra by using visual aids provided by…

  7. Highly selective electrocatalytic dehydrogenation at low applied potential catalyzed by an Ir organometallic complex.

    PubMed

    Bonitatibus, Peter J; Rainka, Matthew P; Peters, Andrea J; Simone, Davide L; Doherty, Mark D

    2013-11-21

    A homogeneous organometallic Ir complex was shown to catalyze the electro-oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde at a very low applied potential with remarkably high selectivity and Faradaic efficiency. In the chemical catalysis, when stoichiometric oxidant and anionic base were used to separately accept electrons and protons, aldehyde selectivity was in agreement with electrolysis results. PMID:24091876

  8. Confined Synthesis of Organometallic Chains and Macrocycles by Cu-O Surface Templating.

    PubMed

    Fan, Qitang; Dai, Jingya; Wang, Tao; Kuttner, Julian; Hilt, Gerhard; Gottfried, J Michael; Zhu, Junfa

    2016-03-22

    The bottom-up construction of low-dimensional macromolecular nanostructures directly on a surface is a promising approach for future application in molecular electronics and integrated circuit production. However, challenges still remain in controlling the formation of these nanostructures with predetermined patterns (such as linear or cyclic) or dimensions (such as the length of one-dimensional (1D) chains). Here, we demonstrate that a high degree of structural control can be achieved by employing a Cu(110)-(2×1)O nanotemplate for the confined synthesis of organometallic chains and macrocycles. This template contains ordered arrays of alternating stripes of Cu-O chains and bare Cu, the widths of which are controllable. Using scanning tunneling microscopy and low-energy electron diffraction, we show that well-defined, ordered 1D zigzag organometallic oligomeric chains with uniform lengths can be fabricated on the Cu stripes (width >5.6 nm) of the Cu(110)-(2×1)O surface. In addition, the lengths of the meta-terphenyl (MTP)-based chains can be adjusted by controlling the widths of the Cu stripes within a certain range. When reducing the widths of Cu stripes to a range of 2.6 to 5.6 nm, organometallic macrocycles including tetramer (MTP-Cu)4, hexamer (MTP-Cu)6, and octamer (MTP-Cu)8 species are formed due to the spatial confinement effect and attraction to the Cu-O chains. An overview of all formed organometallic macrocycles on the Cu stripes with different widths reveals that the origin of the formation of these macrocycles is the cis-configured organometallic dimer (MTP)2Cu3, which was observed on the extremely narrow Cu stripe with a width of 1.5 nm. PMID:26928582

  9. Chemistry Notes.

    ERIC Educational Resources Information Center

    School Science Review, 1981

    1981-01-01

    Outlines laboratory procedures, demonstrations, teaching suggestions, and content information related to chemistry. Topics include polarizing power; calorimetry and momentum; microcomputers in school chemistry; a constant-volume dispenser for liquids, floating magnets, and crystal lattices; preparation of chromium; and solvent polarity and…

  10. Uranium triamidoamine chemistry.

    PubMed

    Gardner, Benedict M; Liddle, Stephen T

    2015-07-01

    Triamidoamine (Tren) complexes of the p- and d-block elements have been well-studied, and they display a diverse array of chemistry of academic, industrial and biological significance. Such in-depth investigations are not as widespread for Tren complexes of uranium, despite the general drive to better understand the chemical behaviour of uranium by virtue of its fundamental position within the nuclear sector. However, the chemistry of Tren-uranium complexes is characterised by the ability to stabilise otherwise reactive, multiply bonded main group donor atom ligands, construct uranium-metal bonds, promote small molecule activation, and support single molecule magnetism, all of which exploit the steric, electronic, thermodynamic and kinetic features of the Tren ligand system. This Feature Article presents a current account of the chemistry of Tren-uranium complexes. PMID:26035690

  11. Shape-selective catalysts for Fischer-Tropsch chemistry : atomic layer deposition of active catalytic metals. Activity report : January 1, 2005 - September 30, 2005.

    SciTech Connect

    Cronauer, D. C.

    2011-04-15

    Argonne National Laboratory is carrying out a research program to create, prepare, and evaluate catalysts to promote Fischer-Tropsch (FT) chemistry - specifically, the reaction of hydrogen with carbon monoxide to form long-chain hydrocarbons. In addition to needing high activity, it is desirable that the catalysts have high selectivity and stability with respect to both mechanical strength and aging properties. The broad goal is to produce diesel fraction components and avoiding excess yields of both light hydrocarbons and heavy waxes. Originally the goal was to prepare shape-selective catalysts that would limit the formation of long-chain products and yet retain the active metal sites in a protected 'cage.' Such catalysts were prepared with silica-containing fractal cages. The activity was essentially the same as that of catalysts without the cages. We are currently awaiting follow-up experiments to determine the attrition strength of these catalysts. A second experimental stage was undertaken to prepare and evaluate active FT catalysts formed by atomic-layer deposition [ALD] of active components on supported membranes and particulate supports. The concept was that of depositing active metals (i.e. ruthenium, iron or cobalt) upon membranes with well defined flow channels of small diameter and length such that the catalytic activity and product molecular weight distribution could be controlled. In order to rapidly evaluate the catalytic membranes, the ALD coating processes were performed in an 'exploratory mode' in which ALD procedures from the literature appropriate for coating flat surfaces were applied to the high surface area membranes. Consequently, the Fe and Ru loadings in the membranes were likely to be smaller than those expected for complete monolayer coverage. In addition, there was likely to be significant variation in the Fe and Ru loading among the membranes due to difficulties in nucleating these materials on the aluminum oxide surfaces. The first

  12. Fenton chemistry: an introduction.

    PubMed

    Wardman, P; Candeias, L P

    1996-05-01

    In 1876, Fenton described a colored product obtained on mixing tartaric acid with hydrogen peroxide and a low concentration of a ferrous salt. Full papers in 1894 and 1896 showed the product was dihydroxymaleic acid. Haber, Weiss and Willstätter proposed in 1932-1934 the involvement of free hydroxyl radicals in the iron(II)/hydrogen peroxide system, and Baxendale and colleagues around 1950 suggested that superoxide reduces the iron(III) formed on reaction, explaining the catalytic nature of the metal. Since Fridovich and colleagues discovered the importance of superoxide dismutase in 1968, numerous studies have sought to explain the deleterious effects of cellular oxidative stress in terms of superoxide-driven Fenton chemistry. There remain questions concerning the involvement of free hydroxyl radicals or reactions of metal/oxo intermediates. However, these outstanding questions may obscure a wider appreciation of the importance of Fenton chemistry involving hypohalous acids rather than hydrogen peroxide as the oxidant. PMID:8619017

  13. Do Organometallic CH4-Me(+p) Adducts and X4H(+) (X = P, As) Clusters Undergo Two-Electron Three-Center Interactions? Some Aspects of Discussion.

    PubMed

    Lobayan, Rosana M; Bochicchio, Roberto C

    2015-07-01

    Most of the systems possessing true two-electron three-center interactions are electron deficient compounds like boron hydrids, closo-boranes, and some organic ions such as butonium cations. In this work, we perform a detailed study of the electron distribution for two different types of systems to which likewise interactions has been adjudicated: organometallic CH4-Me(+p) (p = 1, 2) adducts with Me, alkaline and earth alkaline metallic ions of Li, Na, K, Be, Mg, Ca in their stable gaseous phase and X4H(+) (X = P, As) simple clusters. For this purpose, topological analysis of the electron density decomposed into its effectively paired and unpaired contributions has been carried out looking for complex interactions. PMID:26061421

  14. NEW APPLICATIONS OF LC-MS AND LC-MS2 TOWARD UNDERSTANDING THE ENVIRONMENTAL FATE OF ORGANOMETALLICS

    EPA Science Inventory

    Over the last 40 years, many organometallic compounds have been synthesized and used in a variety of consumer, agricultural, and industrial products. Including wastewater effluents, leaching, and direct land and water applications, there are many pathways that can disperse organo...

  15. Rationalization of the inhibition activity of structurally related organometallic compounds against the drug target cathepsin B by DFT.

    PubMed

    Casini, Angela; Edafe, Fabio; Erlandsson, Mikael; Gonsalvi, Luca; Ciancetta, Antonella; Re, Nazzareno; Ienco, Andrea; Messori, Luigi; Peruzzini, Maurizio; Dyson, Paul J

    2010-06-21

    A series of organometallic compounds of general formula [(arene)M(PTA)(n)X(m)]Y (arene = eta(6)-C(10)H(14), eta-C(5)Me(5)); M = Ru(ii), Os(ii), Rh(iii) and Ir(iii); X = Cl, mPTA; Y = OTf, PF(6)) have been screened for their cytotoxicity and ability to inhibit cathepsin B in vitro, in comparison to the antimetastatic compound NAMI-A. The Ru and Os analogues and NAMI-A showed similar enzyme inhibition properties (with IC(50) values in the low muM range), whereas the Rh(iii) and Ir(iii) compounds were inactive. In order to build up a rational for the observed differences, DFT calculations of the metal complexes adducts with N-acetyl-l-cysteine-N'-methylamide, a mimic for the Cys residue in the cathepsin B active site, were performed to provide insights into binding thermodynamics in solution. Initial structure-activity relationships have been defined with the calculated binding energies of the M-S bonds correlating well with the observed inhibition properties of the compounds. PMID:20467693

  16. Design and synthesis of novel organometallic dyes for NiO sensitization and photo-electrochemical applications.

    PubMed

    Massin, Julien; Lyu, Siliu; Pavone, Michele; Muñoz-García, Ana B; Kauffmann, Brice; Toupance, Thierry; Chavarot-Kerlidou, Murielle; Artero, Vincent; Olivier, Céline

    2016-08-01

    Two metallo-organic dyes were synthesized and used for NiO sensitization in view of their photoelectrochemical applications. The new dyes present an original π-conjugated structure containing the [Ru(dppe)2] metal fragment with a highly delocalized allenylidene ligand on one side and a σ-alkynyl ligand bearing an electron-rich group, i.e. a thiophene or triphenylamine unit, and one or two anchoring functions on the other side. The optoelectronic, electrochemical and photoelectrochemical properties of the dyes were systematically investigated. A broad photoresponse was observed with the absorption maximum at 600 nm. The X-ray crystal structure of one precursor was obtained to elucidate the structural conformation of the organometallic complexes and theoretical calculations were performed in order to address the photophysical properties of the new dyes. These photosensitizers were further implemented in NiO-based photocathodes and tested as photocurrent generators under pertinent aqueous conditions in association with [Co(NH3)5Cl]Cl2 as an irreversible electron acceptor. The dye-sensitized photocathodes provided good photocurrent densities (40 to 60 μA cm(-2)) at neutral pH in phosphate buffer and a high stability was observed for the two dyes. PMID:27436175

  17. Circumstellar chemistry

    NASA Technical Reports Server (NTRS)

    Glassgold, Alfred E.; Huggins, Patrick J.

    1987-01-01

    The study of the outer envelopes of cool evolved stars has become an active area of research. The physical properties of CS envelopes are presented. Observations of many wavelengths bands are relevant. A summary of observations and a discussion of theoretical considerations concerning the chemistry are summarized. Recent theoretical considerations show that the thermal equilibrium model is of limited use for understanding the chemistry of the outer CS envelopes. The theoretical modeling of the chemistry of CS envelopes provides a quantitive test of chemical concepts which have a broader interest than the envelopes themselves.

  18. The chemistry of river-lake systems in the context of permafrost occurrence (Mongolia, Valley of the Lakes). Part I. Analysis of ion and trace metal concentrations

    NASA Astrophysics Data System (ADS)

    Szopińska, Małgorzata; Szumińska, Danuta; Polkowska, Żaneta; Machowiak, Katarzyna; Lehmann, Sara; Chmiel, Stanisław

    2016-07-01

    This study provides a description of water chemistry in river-lake systems located in central Mongolia, at the borderline of permafrost occurrence. The analysis involved water samples collected from two river-lake systems: Baydrag River-Böön Tsagaan Lake system, and Shargalyuut/Tuyn Rivers-Orog Lake system. In the water samples, ions and trace elements were detected and quantified. Additionally, the parameters of pH, electrical conductivity (SEC), total dissolved solids (TDS) and total organic carbon (TOC) were determined. Principal Component Analysis (PCA) was performed on the sample results. Water chemistry is mostly influenced by geochemical and hydrometeorological processes. Permafrost thawing could increase the concentration of nitrogen (NH4+, NO3-) as well as Na+ and Ca2+, Cl- and SO42 -. However, it may also be an effect of other factors such as livestock farming. Seasonal drying out of lakes (e.g., Lake Orog) may also influence water chemistry by deflation of evaporites from exposed lake beds and, at the same time, with lower concentration of chemical compounds in water. The PCA shows that water samples can be divided into two groups. The first group contains lake samples, where water chemistry is shaped by prevailing evaporation processes, whereas the second includes samples from rivers and springs. Water chemistry of the latter is predominantly influenced by geochemical and hydro-meteorological processes.

  19. Chemistry Notes.

    ERIC Educational Resources Information Center

    School Science Review, 1980

    1980-01-01

    Describes equipment, activities, and experiments useful in chemistry instruction, including among others, a rapid method to determine available chlorine in bleach, simple flame testing apparatus, and a simple apparatus demonstrating the technique of flash photolysis. (SK)

  20. Chemistry Notes

    ERIC Educational Resources Information Center

    School Science Review, 1973

    1973-01-01

    Several ideas are proposed for chemistry teachers to try in their classrooms. Subjects included are polymerization of acrylate, polymerization of styrene, conductivity, pollution, preparation of chlorine, redox equations, chemiluminescence, and molecular sieves. (PS)