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. 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

  13. 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

  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. 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)

  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. (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.

  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. 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.

  15. 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,…

  16. 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.

  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. 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

  4. 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.

  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

    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.

  20. 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.

  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. 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

  8. 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

  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. 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)

  2. 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

  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. 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

  8. 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.

  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. 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…

  13. 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…

  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. 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

  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. 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

  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. 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.

  1. 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

  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. 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

  13. 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.).

  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. 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.

  16. 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.

  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. 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.

  5. 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

  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. 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

  16. 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.

  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. 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

  2. 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

  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.