Abstract

Ru-polypyridyl complexes are widely selected as the photosensitiser, while Pt or Pd based moieties bound via a bridging ligand are attractive catalytic centers due to their low overpotential for proton reduction, which is very challenging due to their short lifetimes We have recently observed for a series of Ru/Pd and Ru/Pt photocatalysts that photoexcitation not only leads to population of Franck-Condon states localised on the bridging ligand, but also on states localised on the peripheral ligands. UV/Vis, resonance-Raman, and transient- absorption spectroscopy have been employed to characterize the catalytically competent intermediate. [(tbbipy)2 Ru(tpphz) PdCl2] (PF6)2, (Ru/ Pd) 1, where tbbpy=4,4`-di-tert-butyl-2,2`-bipyridine, tpphz= tetrapyrido [ 3,2-a: 2`,3`c: 3``,2``, -h:2```, 3```-j] phenazine). [(tbbipy) 2Ru (tpphz) PtCl2] (PF6)2 2, (Ru/Pt), and [(tbbipy) 2Ru (tpphz) RuC l2] (PF6)2 3, photocatalyst for the hydrogenation of nicotinamide reduce the catalytic activity upon visible-light irradiation fowling by both chromatography and resonance-Raman spectroscopy.