Ru(ii)-Re(i) binuclear photocatalysts connected by -CHXCH- (X = O, S, CH) for CO reduction.

We developed Ru(ii)-Re(i) supramolecular photocatalysts in which each metal complex unit is connected by a -CHXCH- (X = O, S, CH) chain. The photocatalyst with X = O exhibited the best photocatalytic efficiency for CO reduction in the reported systems using a NAD(P)H model compound as an electron donor because the introduced oxygen atom strengthened the oxidation power of the photosensitizer unit in the excited state and accelerated electron transfer from the one-electron-reduced photosensitizer unit to the catalyst unit. In contrast, the catalytic ability of the photocatalyst with X = S rapidly decreased during irradiation because the supramolecular structure split into mononuclear complexes. A detailed mechanism for the efficient photocatalytic reaction involving these supramolecular photocatalysts was investigated for the first time.