Visible light-driven electron transfer and hydrogen generation catalyzed by bioinspired [2Fe2S] complexes.

Complexes [{(mu-SCH2)2NCH2C6H5}{Fe(CO)2L(1)}{Fe(CO)2L(2)}] (L(1) = CO, L(2) = P(Pyr) 3, 2; L(1) = L(2) = P(Pyr)3, 3) were prepared, which have the lowest reduction potentials for the mono- and double-CO-displaced diiron complexes reported so far. Hydrogen evolution, driven by visible light, was successfully observed for a three-component system, consisting of a ruthenium polypyridine complex, the biomimetic model complex 2 or 3, and ascorbic acid as both electron and proton donor in CH3CN/H2O. The electron transfer from photogenerated Ru(bpy)3(+) to 2 or 3 was detected by laser flash photolysis. Under optimal conditions, the total turnover number for hydrogen evolution was 4.3 based on 2 and 86 based on Ru(bpy)3(2+) in a three-hour photolysis.