Non-coordinating counteranion as a powerful tool to tune the activity of copper water oxidation catalysts

Abstract

Ten copper-bipyridine-type catalysts, [(bpyR)Cu(OH)₂]²⁺, featuring diverse counteranions (OAc⁻, Cl⁻, SO₄²⁻, NO₃⁻, OTf⁻) were synthesized. The observed substantial variations in turnover frequency (TOF) among these catalysts, coupled with insights gained from electrochemical investigations, underscore the pivotal influence of counteranions in fine-tuning the catalytic activity of metal complexes during water oxidation. The TOF value follows the trend of OAc⁻ > Cl⁻ > SO₄²⁻ > NO₃⁻ > OTf⁻, which is the same as the change of coordinating ability index, a™. Density Functional Theory (DFT) calculations reveal that counteranion coordination plays an important role in influencing the catalytic performance of these complexes.