Photocatalytic water reduction by three new Ru(II),Rh(III) supramolecular bimetallic complexes with substitution of 2,2′-bipyridine coordinated to Rh has been examined and a strong correlation between σ-donating ability of the substituted bipyridine and catalytic activity of the bimetallic complex has been observed. [(Ph2phen)2Ru(dpp)RhCl2(dmeb)](PF6)3, [(Ph2phen)2Ru(dpp)RhCl2(bpy)](PF6)3 and [(Ph2phen)2Ru(dpp)RhCl2(Me2bpy)](PF6)3 (Ph2phen = 4,7-diphenyl-1,10-phenanthroline; dpp = 2,3-bis(2-pyridyl)pyrazine; dmeb = 4,4′-dimethyl ester-2,2′-bipyridine; bpy = 2,2′-bipyridine; Me2bpy = 4,4′-dimethyl-2,2′-bipyridine) all reduce water in the presence of a sacrificial electron donor (N,N′-dimethylaniline) under 470 nm irradiation. [(Ph2phen)2Ru(dpp)RhCl2(dmeb)](PF6)3 is a significantly better photocatalyst than [(Ph2phen)2Ru(dpp)RhCl2(bpy)](PF6)3 and [(Ph2phen)2Ru(dpp)RhCl2(Me2bpy)](PF6)3, producing 63 ± 7 turnovers in the first 20 hours compared with 35 ± 3 and 30 ± 4 turnovers, respectively. Photocatalytic activity of a dirhenium complex will also be discussed.

Photocatalyst design with consideration for ligand sigma-donating ability and substrate accessibility to catalytically active site

251st National Meeting (2016)

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