Photocatalytic hydrogen evolution by iridium(III)–rhodium(III) system: Effect of the free ligand addition

Abstract Rh(III) complexes of the general form {RhL 4 Cl 2 } with pyridine derivatives ligands (L) were used for the first time as water reduction catalysts in photocatalytic hydrogen generation process in pair with [Ir(ppy) 2 bpy] + complex as a photosynthesizer. The efficiency of given Ir(III)–Rh(III) systems in the photocatalytic hydrogen generation process was found to be on the level of 20–30% which is corresponding to the highest currently achieved quantum efficiency values for homogeneous photocatalysts. Fast deactivation of the systems due to destruction of {RhL 4 Cl 2 } units was observed but it was suppressed via addition of extra amount of free L ligand in the reaction mixture. Quantum efficiency of modified in this manner [Ir(ppy) 2 bpy] + /{RhL 4 Cl 2 } systems achieved up to 80% value.