Bioinorganic Chemistry Special Feature: Superoxo μ-peroxo and μ-oxo complexes from heme/O2 and heme-Cu/O2 reactivity: Copper ligand influences in cytochrome c oxidase models

摘要

The O2-reaction chemistry of 1:1 mixtures of (F8)Fe^II (1; F8 = tetrakis(2,6-diflurorophenyl)porphyrinate) and [(L^Me2N)Cu^I]⁺ (2; L^Me2N = N,N-bis{2-[2-(N′,N′-4-dimethylamino)pyridyl]ethyl}methylamine) is described, to model aspects of the chemistry occurring in cytochrome c oxidase. Spectroscopic investigations, along with stopped-flow kinetics, reveal that low-temperature oxygenation of 1/2 leads to rapid formation of a heme-superoxo species (F8)Fe^III-(O) (3), whether or not 2 is present. Complex 3 subsequently reacts with 2 to form [(F8)Fe^III–(O)–Cu^II(L^Me2N)]⁺ (4), which thermally converts to [(F8)Fe^III–(O)–Cu^II(L^Me2N)]⁺ (5), which has an unusually bent (Fe–O–Cu) bond moiety. Tridentate chelation, compared with tetradentate, is shown to dramatically lower the ν(O–O) values observed in 4 and give rise to the novel structural features in 5.