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Direct Determination of Electron‐Transfer Properties of Dicopper‐Bound Reduced Dioxygen Species by a Cryo‐Spectroelectrochemical Approach.
Author(s) -
López Isidoro,
Cao Rui,
Quist David A.,
Karlin Kenneth D.,
Le Poul Nicolas
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201705066
Subject(s) - chemistry , redox , cyclic voltammetry , electron transfer , electrochemistry , dielectric spectroscopy , outer sphere electron transfer , kinetics , dichloromethane , electron , photochemistry , analytical chemistry (journal) , crystallography , inorganic chemistry , electrode , ion , organic chemistry , solvent , physics , quantum mechanics
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.