Copper Complexes of CF₃-Substituted Corroles for Affecting Redox Potentials and Electrocatalysis

Electrocatalysis by first-row transition metals chelated by porphyrins, corroles, and related macrocycles gains increased attention due to the need of developing approaches for clean and renewable energy. While some of the above complexes display good catalytic activity, their performance often suffers from much larger overpotentials than the extremely efficient, but not sustainable metal, platinum. Intrigued by the report of copper corroles as catalysts for the electrochemical conversion of protons to hydrogen gas, we hypothesized that trifluoromethylation of corroles would be most effective for inducing a positive shift of the potentials required for reduction of the copper chelated thereby. A combination of methodologies allowed for full characterization of the tris- and tetra-CF₃-substituted complexes and elucidation of their unique structural, physical, and chemical properties. The desired outcome was also achieved, as the potential required for reduction to the copper(I) oxidation state, postulated to be the catalytically active species, was the least negative. The tris-substituted complex was found to be a particularly good electrocatalyst for production of hydrogen from protons, with a remarkably early catalytic onset potential.