Divalent metal complexes of novel tripodal ligands: Synthesis, reactivity, and relevance to biological systems

The work outlined in this dissertation focuses on two main themes: (1) an examination of a metal-mediated amide alcoholysis reaction as a function of the structure of the supporting chelate ligand and the metal ion present, and (2) the development of new ligand systems for studying the effects of hydrogen-bonding and hydrophobic secondary environments on the reactivity of mononuclear metal centers. Both areas have relevance to biological systems, in particular the chemical factors that govern reactivity at mononuclear metal sites involved in catalysis.; The discovery of a zinc-mediated amide alcoholysis reaction of the bmppa ligand was important in that this reaction is of relevance to amide cleavage processes in biological systems. Detailed studies of this metal-mediated amide alcoholysis reaction, as a function of the chelate ligand structure and metal ion present, have revealed important insight into the effect of metal coordination environment on amide cleavage reactivity.; By using mixed nitrogen/sulfur ligands that differ in the availability of a single internal hydrogen bond donor, two families of zinc complexes having a single bound alcohol, formamide or sulfoxide ligand have been prepared and structurally and spectroscopically characterized. These complexes are relevant to substrate- and inhibitor-bound forms of liver alcohol dehydrogenase (LADH). The effect of the presence of a single hydrogen bond donor, similar to Ser ₄₈ in LADH, has been examined in regard to structural and spectroscopic features, and neutral oxygen donor binding properties of the complexes.; A pair of aryl-appended tris((pyridyl)methyl)amine ligands (6-Ph ₂TPA and (6-Me₂Ph)₂TPA) have been utilized to construct a series of divalent manganese, cobalt, nickel, and zinc complexes having either solvent or hydroxamate anion ligation. In both types of complexes, CH/π interactions involving the aryl substituents of the chelate ligands were identified. Isolation of novel mononuclear cobalt, nickel, and zinc hydroxamate complexes suggests that aryl-appended TPA ligands may be useful toward modeling intermediates in recently reported metalloenzymes.