Iron–iron hydrogenase active subunit covalently linking to organic chromophore for light-driven hydrogen evolution

The first photocatalytic [FeFe]-hydrogenase ([FeFe]-H2ase) mimic 3 with noble-metal-free benzothiazole as donating photosensitizer had been successfully constructed via an easily accessible approach, and fully characterized by various spectroscopic and X-ray crystallographic techniques. Steady-state spectroscopy and electrochemistry revealed the evidences indicating that the photo-induced electron transfer occurred in 3. The reduced [FeIFe0] species was further confirmed by laser flash photolysis and considered to be responsible for the light-driven H2 evolution. As a result, the photocatalytic system consisting of the photocatalyst 3 and the sacrificial electron donor in the presence of proton source indeed produced H2 with a turnover number (TON) of 24.2 under light irradiation. The TON indicated a remarkably photocatalytic efficiency for an [FeFe]-H2ase mimic assembled by the covalent combination of a photosensitizer to the catalytic center. The results demonstrated the tremendous potential of present synthetic strategy for the construction of compact, inexpensive, easily accessible [FeFe]-H2ase model complexes as photocatalysts.