Photochemical Hydrogenation of π-Conjugated Bridging Ligands in Photofunctional Multinuclear Complexes.

Vinylene or ethynylene linkers in the bridging ligands of photofunctional multinuclear complexes synthesized by various coupling reactions, such as the Mizoroki-Heck reaction, olefin metathesis, and Sonogashira coupling, were successfully converted to their corresponding saturated carbon chains using photochemical hydrogenation, which proceeded in an MeCN-pyridine-CF3COOH (3:1:0.1 v/v/v) mixed solution containing the starting metal complexes and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH) as a sacrificial electron donor under visible light irradiation in high yields. Hydrogenation of linkers in a Ru2-Re trinuclear complex improved the photocatalytic ability for CO2 reduction.