Highly efficient visible-light-driven CO2 reduction to CO using a Ru(II)-Re(I) supramolecular photocatalyst in an aqueous solution

In an aqueous solution, [Ru(dmb)(2)-(BL)-Re(CO)(3)Cl](2+) (BL = bridging ligand) most efficiently photocatalyzed the reduction of CO2 to CO under visible-light irradiation using 2-(1,3-dimethyl-2,3-dihydro-1H-benzimidazol-2-yl) benzoic acid (BI(CO2H)H) as a water-soluble sacrificial reductant (Phi(CO) = 13%, TON = 130). Since BI(CO2H)H could efficiently produce one-electron-reduced species of [Ru(diimine)(3)](2+)-type complexes under visible-light irradiation even in an aqueous solution, that is one of the main reasons why the photocatalytic system induced the highly efficient CO2 reduction. This result strongly indicates that BI(CO2H)H should be a useful reductant for evaluating the real abilities of various photocatalytic systems in water as well.