Architecture of supramolecular metal complexes for photocatalytic CO 2 reduction : III: Effects of length of alkyl chain connecting photosensitizer to catalyst

Abstract

New Ru(II)–Re(I) binuclear complexes [{Ru(dmb) 2}-LL-{Re(CO) 3Cl}] 2+(dmb = 4,4′-dimethyl-2,2′-bipyridine) with 1,2-bis(4′-methyl-[2,2′]bipyridinyl-4-yl)-ethane ( MebpyC 2 H 4 Mebpy), 1,4-bis(4′-methyl-[2,2′]bipyridinyl-4-yl)-butane ( MebpyC 4 H 8 Mebpy), and 1,6-bis(4′-methyl-[2,2′]bipyridinyl-4-yl)-hexane ( MebpyC 6 H 12 Mebpy) as bridge ligands (LL) have been synthesized, and their photocatalytic activity for CO 2 reduction has been investigated. The most efficient photocatalyst had MebpyC 2 H 4 Mebpy as the bridge ligand, but no difference in photocatalysis was observed between the diads with MebpyC 4 H 8 Mebpy and MebpyC 6 H 12 Mebpy. Weak interaction between the Ru and Re sites was observed only through the MebpyC 2 H 4 Mebpy ligand but not through the other bridge ligands. This interaction induces a higher reductive quenching efficiency of the 3MLCT excited state of the diad with MebpyC 2 H 4 Mebpy by the reductant, BNAH, and consequently the quantum yield of CO 2 reduction is higher.