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Direct Determination of Electron-Transfer Properties of Dicopper-Bound Reduced Dioxygen Species by a Cryo-Spectroelectrochemical Approach.

Isidoro LópezRui CaoDavid A QuistKenneth D KarlinNicolas le Poul
Published in: Chemistry (Weinheim an der Bergstrasse, Germany) (2017)
Direct experimental determination of redox properties of superoxo (O2.- ) and peroxo (O22- ) 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 CuI CuII mixed-valent species (12+ ) 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 22+ at E0 =0.11 V (vs. SCE) with a small inner sphere electron-transfer reorganization energy, λi =0.54 eV, determined from variable temperature electrochemical impedance spectroscopy. The data suggest that the O2.- /O22- redox process occurs directly on the O2 -derived core.
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