Bio-inspired copper complexes with Cu2S cores: (solvent)effects on oxygen reduction reactions.

Abstract

The need for effective alternative energy sources and “green” industrial processes is more than ever a societal topic. In this context, mastering the Oxygen Reduction Reactions (ORR) is a key step to develop fuel cells or to propose alternatives to energy-intensive setups such as the anthraquinone process for hydrogen peroxide production. Achieving this goal using bio-inspired metal complexes based on abundant and non-toxic elements could provide an environmentally friendly option. Given the prevalence of Cu-containing active sites capable of reductive activation of dioxygen in Nature, the development of Cu-based catalysts for ORR thus appears to be a relevant approach. We herein report the preparation, full characterization and (TD)DFT investigation of a new dinuclear mixed-valent copper complex 6 exhibiting a Cu₂S core and a bridging triflate anion. Its ORR activity is compared with that of its parent catalyst 1. Two types of solvents are used, acetonitrile or acetone, and various catalyst/Me₈Fc (electron source) ratios are tested. Our results highlight a counterintuitive solvent effect for 1 and a drastic drop of activity for 6 in coordinating acetonitrile along with modification of its chemical structure.