archives@tulane.edu / Metalloenzymes containing copper or molybdenum have attracted considerable attention during the past several decades, as they play significant roles in a variety of biological and chemical areas. In those enzymes, their active sites exhibit unique structural features for fundamental studies in coordination chemistry and for applications in various catalytic reactions. The work described in this dissertation focuses on systematic syntheses of organometallic complexes for use in enzymatic systems as nitrous-oxide reductases (N2OR), acetyl-CoA (acetyl coenzyme A) synthases, or carbon monoxide dehydrogenases (ACS/CODH). Synthesis of diaminobisthiolate (N2S2) ligands with phenyl-connected sulfur and nitrogen atoms are introduced in Chapter 1. The importance of the N2S2 donor atoms in functionalizing the overall enzyme active sites are discussed in Chapter 1. Compared to the previously reported procedures, the new routes in this work allow for improved synthetic control, resulting in enhanced synthetic yields under mild reaction conditions. In Chapter 2, we focus on the synthesis, characterizations and applications of Ni(N2S2) complexes. We start with a new Ni complex with a tetradentate diaminobisthiolate ligand which is a continuation of one of the focuses in the previous chapter. The differences between the new Ni(N2S2) complex and other previously reported complexes with similar structures are discussed. We use both theoretical method (density functional theory calculation) and electrochemical measurements to explore the structural-property characteristics of those complexes. Chapter 3 details the synthesis of several multi-copper clusters for assembling in CuZ active-site analogues for nitrous oxide reduction. In those complexes, tetradentate diaminobisthiolate (N2S2) is used as a backbone ligand. Those complexes exhibit unique redox features due to the mixed valence of the CuI/CuII couple. Their structures are characterized by detailed X-ray crystallography measurements. In chapter 4, we extend the studies in synthesizing analogues in molybdenum- dependent carbon monoxide dehydrogenases (Mo-CODH) active site. Two different synthetic routes are explored to yield a number of Mo- and Cu-based complexes. Electrochemical characterizations are used to investigate the redox features of those complexes. / 1 / bo Wang

Molybdenum may function as a catalyst in promoting and controlling some of the complex chemical reactions that go on in living systems. The lack of understanding which exists about these reactions is due to their obvious complexity and to the extremely minute quantities of molybdenum involved. Traces of molybdenum have been shown to have spectacular results on the growth of plants when added to certain soils. This metal is also required for the growth of azobacter, the nitrogen-fixing bacteria.

Includes bibliography.

Graduation date: 1999

Thesis (M.S.)--Ohio State University, 1984. / Includes bibliographical references (leaves 227-231). Available online via OhioLINK's ETD Center

Molybdenum disulfide (MoS2) catalysts are used for hydrodesulfurization processes, needed for the removal of sulfur from oil feedstocks. The commonly accepted active site of MoS2 is believed to have a S4 pyramidal geometry with molybdenum (IV) at the apex. This work is interested in small molecules as models. Recent work has shown that one ligand can be removed from a molybdenum trisdithiolene by reacting the metal complex with an olefin creates a labile chelate cap. The resulting structure resembles the active site of interest. The present contribution will show approaches to molybdenum bisdithiolenes with one or two labile solvent molecules. The use of acetonitrile, adiponitrile, isobutyronitrile, and oxalate has been investigated. A complex containing two different labile moieties (tetrahydrothiophene, acetonitrile) was crystallographically characterized. Other nitrile molybdenum complexes were monitored using NMR spectroscopy. Two complexes have been characterized with an oxalato ligand; a single unit, and a dimer.

Molybdenum disulfide (MoS2) catalysts are used for hydrodesulfurization processes, needed for the removal of sulfur from oil feedstocks. The commonly accepted active site of MoS2 is believed to have a S4 pyramidal geometry with molybdenum (IV) at the apex. This work is interested in small molecules as models. Recent work has shown that one ligand can be removed from a molybdenum trisdithiolene by reacting the metal complex with an olefin creates a labile chelate cap. The resulting structure resembles the active site of interest. The present contribution will show approaches to molybdenum bisdithiolenes with one or two labile solvent molecules. The use of acetonitrile, adiponitrile, isobutyronitrile, and oxalate has been investigated. A complex containing two different labile moieties (tetrahydrothiophene, acetonitrile) was crystallographically characterized. Other nitrile molybdenum complexes were monitored using NMR spectroscopy. Two complexes have been characterized with an oxalato ligand; a single unit, and a dimer.

In this study, the mechanical properties of nanocrystalline Mo and Zr thin films are examined. The specimens of nanocrystalline Mo and Zr thin films were all fabricated by DC magnetron sputtering at various temperatures. These specimens were annealed in RTA system and then investigated by X-ray diffractormeter as well as TEM. After that, nanocrystalline Mo and Zr thin films were tested by nanoindentation. The average grain sizes in Zr thin films annealed are larger than deposited at high temperature, but the films after annealing are stripped away from the substrates due to the thermal shock. The average grain sizes estimated by XRD patterns are in common with those estimated by TEM images. We suggest that the difference is deviation. Nanocrystalline Mo thin films were first tested by both nanoindentation and tensile tests. Mo thin films were stripped away during tensile tests. We consider that the phenomenon is due to the honeycombed structure of the films. The X-ray diffraction patterns and TEM observations indicated that there is no evident grain growth in the nanocrystalline Zr thin films, deposited at 100 ¢XC, 200 ¢XC, and 300 ¢XC, except at 400 ¢XC. The deposition temperature for apparent grain growth in the Zr thin films is at least above 300 ¢XC. After nanoindentation tests, the hardness (H) and Young¡¦s modulus (E) of specimens deposited at 400 ¢XC are higher than that of other specimens. Compared to coarse-grained Zr metals, we suggest that the slope k in the Hall-Petch relationship is quite small and in the range of nanocrystalline Zr thin films.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains viii, 53 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 51-53).

Thesis (M. Sc.)--University of Hong Kong, 1972. / Includes a reprint of a paper entitled Crystal and molecular structure of tricarbonyl ... by K.K. Cheung and others, from Journal of the Chemical Society, 1970. Offset from typescript.