Photochemical Hydrogen Evolution from Neutral Water with a Cobalt Metallopeptide Catalyst.

CoGGH, a Gly-Gly-His tripeptide coordinated to a cobalt ion, is shown to catalyze the reduction of aqueous protons to hydrogen (H2) in a light-driven reaction in water near neutral pH. Using [Ru(bpy)3]2+ as a photosensitizer and ascorbate as an electron donor, a turnover number up to 2200 with respect to CoGGH has been observed with the system remaining active for more than 48 h. The reaction conditions that favor H2 production are consistent with a reductive quenching mechanism. Results also suggest that CoGGH is robust under these reaction conditions and loss of activity over time results from [Ru(bpy)3]2+ degradation.