The search for earth-abundant materials that efficiently catalyze water splitting poses a key scientific challenge in the development of renewable energy sources. Recently, our group demonstrated that cobalt complexes featuring the ligand 2,6-bis(1,1-di(pyridin-2-yl)ethyl)pyridine (PY5Me2) can electrocatalytically and photocatalytically generate hydrogen from neutral water with high turnover frequencies. Furthermore, the overpotential of hydrogen evolution can be tuned through judicious substitutions in the ligand scaffold. Herein we present the synthesis of a new generation of hydrogen-evolution catalysts featuring proton-responsive ligands. In contrast to redox-active ligands such as glyoximes and dithiolenes, proton-responsive ligands adjust their electron donating properties to accommodate different metal oxidation states throughout catalysis without delocalizing spin density from the reduced metal center onto the ligand. It is anticipated that this strategy will afford improved rates of catalysis whilst maintaining long-term stability. Preliminary electrochemical measurements suggest the complex [(HOPY5Me2)Co(CH3CN)]2+ catalyzes proton reduction in acidic aqueous media (pH 3 to 6).

Designing electrocatalysts for proton reduction: Lowering overpotentials through redox leveling

245th National Meeting (2013)

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