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

Conducting polymers that contain metals are remarkable materials, because they have the properties of both organic backbones and metals. Depending on the position of the metal relative to the conjugated backbone, i.e. attached to or directly in the backbone, these two can couple resulting in advancement of the functionality and therefore potential applications of these types of materials. Complexes of tridentate ligands with donor atoms such as phosphorus, nitrogen, and sulfur also have a wide variety of applications. In addition, complexes of tridentate ligands have advantages of stability and control of electron density by variation of donor atoms. Therefore, conjugated polymers with tridentate ligand units will have promise for various applications and advantages in their designs. Complexes of PNP ligand with molybdenum and carbonyl ancillary ligands were synthesized and characterized. Isomerization and conversion reactions between them were investigated as well as the coordination modes. Many types of PNP ligands have been studied in the literature because the hemilabile property of the nitrogen atom promotes some catalytic reactions and gives different coordination geometries. Conducting polymers can be used as redox-active ligands and they can be used to control electron density on the metal attached to them. Synthesis and characterization of a novel polymerizable ligand 3,5-bis-EDOT-N,N-bis[2-diphenylphosphinoethyl]aniline was achieved. Related molybdenum complexes with ancillary ligands as carbonyls were also synthesized and characterized. Monomer complexes and the free ligand were electropolymerized and studied. Tris(bipyridine)ruthenium(II) chloride and analogous complexes have been studied extensively in the literature due to their luminescent and photochemical properties, and excited state lifetimes. Conducting polymers with similar ruthenium groups have been investigated for various applications. Synthesis of four ruthenium complexes with the polymerizable ligand 2,6-Bis[4-[2-(3,4-diethylenedioxy)thiophene]pyrazol-1-yl]pyridine and four different bidentate ligands were reproduced; electropolymerizations of the complexes were achieved; electrochemical, UV-Vis and luminescence studies were performed and discussed. Various complexes of copper, silver, platinum, and palladium with nitrogen and phosphorus donors have been reported for their luminescence behavior as well as their interesting structures. Model complexes of these metals with N,N-bis[2-(diphenylphosphino)ethyl]phenyl-amine (a PNP ligand) have been synthesized and characterized. Absorption and luminescence behaviors as well as the coordination modes were investigated. / text

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