Reversible O<sub>2</sub>-Binding and H<sub>2</sub>O<sub>2</sub>-Activation by Dicopper and Diiron Complexes

In aerobic organisms, a variety of metalloproteins regulate reactions involving molecular oxygen (O2). These include O2-transport proteins such as hemoglobin (Hb) and hemocyanin (Hc), electron transfer proteins and cytochrome c oxidase involved in mitochondrial oxidative phosphorylation, and various metalloproteins such as oxygenases and oxidases that catalyze selective oxidation of alkanes, alkenes, aromatics, and various natural products. These reactions involve the coordination of oxygen species such as O2, O2-•, and H2O2 to the metal and their activation. Since these processes involve redox reactions, redox-active metals such as iron and copper are present in the active center. Various highly functional metal complexes have been synthesized to understand these reactions and reaction mechanisms from the viewpoint of bioinorganic chemistry, and to develop practical catalysts and other practically useful compounds. In this Accounts, the authorʼs research in relation to them is summarized as follows: (1) development of dicopper complexes that reproduce the reversible O2-binding function at the dicopper site of hemocyanin, (2) development of diiron complexes that reproduce O2-activation at the diiron site of soluble methane monooxygenase and related selective oxidation of alkanes, alkenes, and various organic compounds.