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

Rh(III) complexes of the general form {RhL₄Cl₂} 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)₂bpy]⁺ 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 {RhL₄Cl₂} 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)₂bpy]⁺/{RhL₄Cl₂} systems achieved up to 80% value.