Dioxygen reactivity of synthetic analogues for the active site of heme-copper oxidases: Copper-ligand influences in iron(II)/copper(I)/oxygen chemistry

The dioxygen reactivity of small molecule heme-copper complexes have attracted many synthetic modeling chemists, because such a reaction occurs at the active site of heme-copper oxidases for energy production in the respiration of aerobic organisms. Although individual heme-O2 and Cu-O 2 chemistries are separately well studied, the dioxygen reactivity of a heme and copper environment is relatively new and not yet established. To better understand the fundamental chemistry of the heme/Cu/O2 reactivity, here we describe the dioxygen chemistry of well-defined small molecule iron and/or copper complexes, which include reaction dynamics, structure, spectroscopy and O2-reduction chemistry.; Chapter 1 reviews the relevant biochemistry of heme-copper oxidases, in which structural, reactivity and spectroscopic studies of the enzyme heme a3-CuB binuclear site are discussed. It also includes considerable coverage of synthetic modeling studies, particularly focusing on O2-chemistry of reduced synthetic heme-copper assemblies.; In Chapter 2, the O2-reaction chemistry of 1:1 mixtures of (F8)FeII and [(LMe2N)CuI] + is described. Spectroscopic investigations, along with stopped-flow kinetics reveal that low-temperature oxygenation of (F8)Fe II/[(LMe2N)CuI]+ leads to rapid formation of a heme-superoxo species (F8)FeIII -(O2-), regardless of a copper ion is present. Complex (F8)FeIII-(O2 -) subsequently reacts with [(LMe2N)Cu I]+ to form [(F8)FeIII-(O 22-)-CuII(LMe2N)]+ which thermally converts to [(F8)FeIII-(O)-Cu II(LMe2N)]+, which has an unusually bent Fe-O-Cu bond moiety. Tridentate Cu-chelation, compared to tetradentate, is shown to dramatically lower the nu(O-O) values observed in [(F8 )FeIII-(O22-)-Cu II(LMe2N)]+ and give rise to the novel structural features in [(F8)FeIII-(O)-Cu II(LMe2N)]+.; Chapter 3 investigates further on the copper ligand influences on heme-copper/O 2 chemistry, using a heterobinuclear heme-copper complex [(2 L)FeIICuI]+ with extensive spectroscopic studies. The results obtained from this system add new insights into the FeII/CuI/O2 reaction chemistry, which includes dramatic ligand influences on the formation, structure, physical properties, and small molecule (CO, PPh3) reactivity of the heme-peroxo-copper species obtained, [(2L)FeIII-(O2 2-)-CuII]+.; In Chapter 4, synthesis, characterization, and initial dioxygen reactivity of novel copper complexes possessing imidazole-phenol (or anisole) cross-links, [CuI(LN4OH)]+ and [Cu I(LN4OMe)]+, are described.; Chapter 5 contains additional studies and further kinetic/thermodynamic insights into the [CuI(LN4OH)]+/O 2 reaction using stopped-flow UV-vis spectroscopy. (Abstract shortened by UMI.)...