Enhancing photocatalytic hydrogen generation: The impact of the peripheral ligands in Ru/Pd and Ru/Pt complexes

The synthesis, photophysical properties and photocatalytic efficiency of a range of novel supramolecular assemblies of the type [Ru(dceb)2(µ-bisbpy)MCl2](PF6)2 and [Ru(bpy)2(µ-bisbpy)MCl2](PF6)2 (where M = Pd or Pt, dceb = diethyl 2,2'-bipyridine-4,4'-dicarboxylate, bpy = 2,2'-bipyridine and bisbpy = 2,2':5',5":2",2'''-quaterpyridine) are reported. Photocatalytic studies for hydrogen generation were found to be dependent on the nature of the peripheral ligand, on the catalytic centre and on the quantity of water present in the photocatalytic mixtures. The best catalytic conditions were obtained with dceb as the peripheral ligand, with turnover numbers up to 513 after 18 hours. The experimental data together with DFT calculations on both the bpy and dceb based compounds indicate that the peripheral dceb ligands participate in the photocatalytic process.