Photochemical hydrogen evolution catalyzed by trimetallic [Re–Fe] complexes

In order to conduct photoactive catalysts for hydrogen production, a novel trimetallic [Re-Fe] complex 1, consisting of the phenanthroline rhenium photosensitizer and the [2Fe2S] complex (connected by the axial coordination of a pyridyl group), was prepared and spectroscopically characterized. The apparent fluorescence quenching of the complex 1 was observed in comparison with the reference complex 1b, suggesting the possibility for an electron transfer from the excited state of the rhenium moiety to the [2Fe2S] moiety. Visible light-driven H2 generation was achieved by using triethylamine (sacrificial electron donor) in the presence of the complex 1 (catalyst) in CH3CN/H2O, with a turnover number reaching to 1.5. This is by far as we know the highest for the [Re-Fe] photocatalysts. In contrast to the molecular device, the multicomponent catalyst of complexes 1b and 1c, no H2 was detected by GC analysis in the same experimental condition. The plausible mechanism for the photochemical H2-evolution with this molecular device is discussed.