Syntheses, structures and properties of multinuclear copper clusters and biologically relevant Molybdenum complexes
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.