Electrocatalytic Water Oxidation with a Copper(II) Polypeptide Complex

Abstract

A self-assembly-formed tri­glycyl­glycine macro­cyclic ligand (TGG^4–) complex of Cu­(II), [(TGG^4–)­Cu^II–OH₂]^2–, efficiently catalyzes water oxidation in a phosphate buffer at pH 11 at room temperature by a well-defined mechanism. In the mechanism, initial oxidation to Cu­(III) is followed by further oxidation to a formal “Cu­(IV)” with formation of a peroxide intermediate, which undergoes further oxidation to release oxygen and close the catalytic cycle. The catalyst exhibits high stability and activity toward water oxidation under these conditions with a high turnover frequency of 33 s^–1