Red-Light-Driven Photocatalytic Reduction of CO2 using Os(II)–Re(I) Supramolecular Complexes

The novel supramolecular complexes, which are composed of an Os (5dmb) 2 (BL) (2+) -type complex (5dmb = 5, 5'-dimethyl-2, 2'-bipyridine; BL = 1, 2-bis (4'-methyl-2, 2'-bipyridin-4-yl) ethane) as a photosensitizer and cis, trans-Re (BL) (CO) 2P (p-X-C6H4) 32 (+) -type complexes (X = F, Cl) as a catalyst, have been synthesized. They photocatalyzed selective reduction of CO2 to CO under red-light irradiation (λ > 620 nm). The photocatalytic abilities were affected by the phosphine ligands on the Re unit, and the supramolecule with P (p-Cl-C6H4) 3 ligands exhibited better photocatalysis (ΦCO = 0. 12, TONCO = 1138, TOFCO = 3. 3 min (-1) ). The detailed studies clarified the electron balance and material balance; i. e. , one molecule of the sacrificial electron donor (1, 3-dimethyl-2-phenyl-2, 3-dihydro-1H-benzodimidazole (BIH) ) donated two electrons, one molecule of CO2 accepted the two electrons, and another CO2 molecule served as an "O (2-) " acceptor to give each molecule of the two-electron oxidized compound of BIH, CO, and HCO3 (-).