Abstract
Direct experimental determination of redox properties of superoxo (O(2)(.-) ) and peroxo (O(2)(2-) ) embedded in dicopper complexes bearing an unsymmetrical binucleating ligand was achieved using cryo-electrochemistry and cryo-spectroelectrochemistry in dichloromethane. Cyclic voltammetry for dicopper(I) (1(+) ) oxidation to a Cu(I) Cu(II) mixed-valent species (1(2+) ) under inert atmosphere at 193 K reveals slow heterogeneous electron-transfer kinetics, indicative of a large reorganization energy. Oxygenation of the dicuprous complex 1(+) gives the bridged peroxo dicopper(II) species 3(+) , which is reversibly oxidized to the superoxo complex 2(2+) at E(0) =0.11 V (vs. SCE) with a small inner sphere electron-transfer reorganization energy, λ(i) =0.54 eV, determined from variable temperature electrochemical impedance spectroscopy. The data suggest that the O(2)(.-) /O(2)(2-) redox process occurs directly on the O(2) -derived core.