Effect of Electron Availability on Selectivity of O₂ Reduction by Synthetic Monometallic Fe Porphyrins

Abstract

Herein we report that biomimetic analogues of cytochrome c oxidase (CcO) couple reduction of O(2) to oxidation of a single-electron carrier, Ru(NH(3))(6)(2+), under steady-state catalytic turnover. Higher Ru(II) concentrations favor the 4-electron vs 2-electron O(2) reduction pathway. Our data indicate that the capacity of electrode-adsorbed Fe-only porphyrins to catalyze reduction of O(2) to H(2)O is due to high availability of electrons and is eliminated under the biologically relevant slow electron delivery.