Reversible cleavage and formation of the dioxygen O-O bond within a dicopper complex

A key step in dioxygen evolution during photosynthesis is the oxidative generation of the O-O bond from water by a manganese cluster consisting of M₂(μ-O)₂ units (where M is manganese). The reverse reaction, reductive cleavage of the dioxygen O-O bond, is performed at a variety of dicopper and di-iron active sites in enzymes that catalyze important organic oxidations. Both processes can be envisioned to involve the interconversion of dimetal-dioxygen adducts, M₂(O₂), and isomers having M₂(μ-O)₂ cores. The viability of this notion has been demonstrated by the identification of an equilibrium between synthetic complexes having [Cu₂(μ-η²:η²-O₂)]²⁺ and [Cu₂(μ-O)₂]²⁺ cores through kinetic, spectroscopic, and crystallographic studies.