A Bioinspired Nonheme Fe-(O)-Cu Complex with an = 1 Ground State.

Cytochrome oxidase (CcO) is a heme copper oxidase (HCO) that catalyzes the natural reduction of oxygen to water. A profound understanding of some of the elementary steps leading to the intricate 4e/4H reduction of O is presently lacking. A total spin = 1 Fe-(O)-Cu () intermediate is proposed to reduce the overpotentials associated with the reductive O-O bond rupture by allowing electron transfer from a tyrosine moiety without the necessity of any spin-surface crossing. Direct evidence of the involvement of in the CcO catalytic cycle is, however, missing. A number of heme copper peroxido complexes have been prepared as synthetic models of , but all of them possess the catalytically nonrelevant = 0 ground state resulting from antiferromagnetic coupling between the = 1/2 Fe and Cu centers. In a complete nonheme approach, we now report the spectroscopic characterization and reactivity of the Fe-(O)-Cu intermediates and , which differ only by a single -CH versus -H substituent on the central amine of the tridentate ligands binding to copper. Complex with an end-on peroxido core and ferromagnetically ( = 1) coupled Fe and Cu centers performs H-bonding-mediated O-O bond cleavage in the presence of phenol to generate oxoiron(IV) and exchange-coupled copper(II) and PhO moieties. In contrast, the μ-η:η peroxido complex , with a = 0 ground state, is unreactive toward phenol. Thus, the implications for spin topology contributions to O-O bond cleavage, as proposed for the heme Fe-(O)-Cu intermediate in CcO, can be extended to nonheme chemistry.