Coordination chemistry efforts in copper(I)-dioxygen (O2) reactivity begin with the recognition that highly interesting, important as well as potentially practical chemistries occur at copper protein active-sites, including functioning in O2-transport, oxygenase activity (i.e., O-atom insertion into organic substrates) and O2-reduction to hydrogen peroxide or water as accompanied by substrate oxidation. A primary research approach in our program in copper-dioxygen chemistry focuses on ligand design and the use of cyrogenic solution syntheses for the generation of new complexes. The input of systematic ligand variations in order to show how such effects lead to changes in copper-O2 complex physical properties and reactivity contributes to a fundamental understanding of those factors which lead to the properties and functions observed in the natural systems. The first coordination sphere is the most important, the number and type of ligands, and their arrangement, i.e., coordination geometry.
In this presentation, an overview of known copper-dioxygen structural and spectroscopic types will be provided and in this context recent efforts on the chemistry of primary O2-adducts, copper(II)-superoxo complex species, will be highlighted. Aspects of their electronic nature and structures will be discussed, and details of reactivity toward exogenous substrates will presented. These investigations will include reactions of substrates possessing weak C–H bonds and phenol oxygenation chemistry. Cu-superoxide reduction (to peroxide) and reduction-protonation to give Cu(II)n-hydroperoxo (n = 1, 2) products will also be presented. We have recently observed that mono- or dicopper complex precursors to various Cu2O2 species can act in the solution phase catalytic four-electron four-proton reduction of O2 to water. For one particular binucleating ligand framework, a dicopper complex effects the catalytic and selective two-electron two-proton reduction of O2 to hydrogen peroxide.