Light‐Driven Hydrogen Evolution by Nickel‐Substituted Rubredoxin

An enzymatic system for light‐driven hydrogen generation has been developed through covalent attachment of a ruthenium chromophore to nickel‐substituted rubredoxin (NiRd). The photoinduced activity of the hybrid enzyme is significantly greater than that of a two‐component system and is strongly dependent on the position of the ruthenium phototrigger relative to the active site, indicating a role for intramolecular electron transfer in catalysis. Steady‐state and time‐resolved emission spectra reveal a pathway for rapid, direct quenching of the ruthenium excited state by nickel, but low overall turnover numbers suggest initial electron transfer is not the rate‐limiting step. This approach is ideally suited for detailed mechanistic investigations of catalysis by NiRd and other molecular systems, with implications for generation of solar fuels.