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 (M=Pd or Pt, dceb=diethyl 2,2'-bipyridine-4,4'-dicarboxylate, bpy=2,2'-bipyridine and bisbpy=2,2':5',3'':6'',2'''-quaterpyridine) are reported. Photocatalytic hydrogen generation was dependent on the nature of the peripheral ligand, on the catalytic centre and on the amount of water present in the photocatalytic mixture. The best catalytic conditions were obtained with the dceb peripheral ligand (turnover numbers up to 513 after 18 h). The experimental data and DFT calculations on both the bpy- and dceb-based compounds indicated that the peripheral dceb ligands participated in the photocatalytic process.