Direct experimental determination of redox properties of superoxo (O ) and peroxo (O ) 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 Cu mixed-valent species (1 ) 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 at E =0.11 V (vs. SCE) with a small inner sphere electron-transfer reorganization energy, λ =0.54 eV, determined from variable temperature electrochemical impedance spectroscopy. The data suggest that the O /O redox process occurs directly on the O -derived core.