Photoexcited state chemistry of metal-oxygen complexes

Recent advances on the excited state chemistry of metal-oxygen synthetic complexes based on earth-abundant metals such as copper, cobalt, and manganese are reviewed to show a much enhanced reactivity of the photoexcited states as compared with their relative ground states. Mononuclear copper(ii)-superoxide and dinuclear copper(ii)-peroxo complexes underwent copper-oxygen bond cleavage, dioxygen release, and copper(i)/dioxygen rebinding upon photoexcitation at low temperature. Photoirradiation of the cobalt-oxygen compound [(TAML)Co^IV(O)]²⁻ (6) (TAML = tetraamidomacrocyclic ligand) at 5 °C yielded a cobalt-oxygen excited state with 0.6(1) ns lifetime, showing a high reactivity in the bimolecular electron-transfer oxidations of m-xylene and anisole. An extremely long-lived excited state was generated upon photoexcitation of a manganese(iv)-oxo complex binding two Sc(OTf)₃ molecules, which enabled the hydroxylation of benzene.