Nanosecond transient absorption spectroscopy of a Ru polypyridine phenothiazine dyad

A bipyridine phenothiazine ligand [(PTZEtv2bpy) and metal complexes [Ru(Ph2phen)3]2+ (1), [(Ph2phen)2Ru(PTZEtv2bpy)]2+ (2), and [(PTZEtv2bpy)(Ph2phen)Ru(dpp)]2+ (3) were synthesized and characterized, where Ph2phen is 4,7-diphenyl-1,10-phenanthroline, dpp is 2,3-bis(2-pyridyl)pyrazine and PTZEtv2bpy is 4,4′ ethylene bridged phenothiazine 2,2′bipyridine. The reduction potentials of PTZEtv2bpy, 1, 2, and 3 were determined by cyclic and square wave voltammetric methods. The absorbance and emission spectra of complexes 2 and 3 yield intense, visible Metal-to-Ligand Charge Transfer (MLCT) transitions. The nanosecond transient absorption data indicate formation of both the 3MLCT state and a ligand localized 3PTZ state.91