Homogeneous Electrocatalytic Water Oxidation by a Rigid Macrocyclic Copper(II) Complex

A copper(II) complex with a rigid macrocyclic ligand has been synthesized and utilized as a homogeneous electrocatalyst for water oxidation in sodium phosphate buffer at pH 12.0. By using a glassy carbon electrode in a 3 h electrolysis, a high current density of 1.3-1.4 mA/cm(2) and a turn-over number of 4 can be obtained with 1.0 mmol center dot L-1 of the copper catalyst at an overpotential of 750 mV. Kinetic studies revealed that the electrocatalysis with this complex is a single-site catalysis with proton-coupled electron transfers. Finally, its possible catalytic mechanism was tentatively proposed.