Synthesis, electrochemistry and photophysics of ruthenium(II) diimine complexes of 1,1'-bis(diphenylphosphino)ferrocene (dppf). Crystal structure of [Ru(bipy)2(dppf)]2+ (bipy = 2,2'-bipyridine)

A series of ruthenium(II) diimine complexes of 1,1′-bis(diphenylphosphino)ferrocene (dppf ), [Ru(L–L) 2 (dppf )] 2+ [L–L = 2,2′-bipyridine (bipy), 4,4′-dimethyl-2,2′-bipyridine, 4,4′-di-tert-butyl-2,2′-bipyridine, or 1,10-phenanthroline] have been synthesized and their photophysical properties studied. The crystal structure of [Ru(bipy) 2 (dppf )] 2+ has been determined. These complexes have been shown to exhibit low-energy emission at ca. 550 nm at 77 K, attributed to a d π (Ru) → π*(L–L) metal-to-ligand charge transfer triplet excited state. The spectroscopic changes upon oxidation suggest it to occur on the ferrocene moiety