Spectroscopic, kinetic and mechanistic studies of the influence of ligand and substrate concentration on the activation by peroxides of CuI–thiolate and other CuI complexes

Both free-radical and non-radical routes for peroxide oxidation of CuI can be identified for copper complexes obtained by the reduction of CuII by thiols, including glutathione. Copper(I)–thiolate complexes are obtained, except in the presence of e.g. 1,10-phenanthroline, and these undergo ready reaction with H2O2 and tBuOOH. EPR spin-trapping studies establish a free-radical reaction mechanism (to give tBuO˙) with the latter, and the formation of HO˙ from the former occurs only at low concentrations of copper. Kinetic studies (using UV-vis and EPR spectroscopies), together with NMR analysis, lead to the proposal that CuI aggregates react via non-radical pathways in contrast to monomeric CuI.