Ligand Radical Mediated Water Oxidation by a Family of Copper <i>o</i>-Phenylene Bis-oxamidate Complexes

Understanding the reactivity landscape for activation of water until formation O-O bond and O2 release in molecular chemistry is a decisive step guiding elaboration cost-effective catalysts oxygen-evolving reaction (OER). Copper(II) complexes have recently caught attention chemists as 4e-/4H+ oxidation process. While copper(IV) intermediate has been proposed reactive species, no spectroscopic signature reported so far. Copper(III) ligand radical species also formulated supported by theoretical studies. We found, herein, that sequence with family o-phenylene bis-oxamidate function substitution pattern on periphery aromatic ring. In-situ EPR, FTIR, rR spectroelectrochemical studies helped to elementary electrochemical chemical events leading toward selectively at copper center. EPR FTIR spectroelectrochemistry suggests ligand-centered oxidations are preferred over metal-centered oxidations. study revealed accumulation bis-imine bound copper(II) superoxide intermediate, under catalytic turnover, which provides evidence during OER.