Preparation, photophysical, and electrochemical properties of three novel trinuclear Ru(II) polypyridyl complexes based on diazafluorenes

Three tripodal ligands 2,2′,2″-tris[(4,5-diazafluoren-9-ylimino)phenoxyethyl]amine (L1), 1,3,5-tris[(4,5-diazafluoren-9-ylimino)phenoxymethyl]-2,4,6-trimethylbenzene (L2), 1,1′,1″-tris[(4,5-diazafluoren-9-ylimino)phenoxymethyl]-1″′-(p-tosyloxymethyl)-methane (L3), and corresponding Ru(II) complexes [(bpy)6L1–3(RuII)3](PF6)6 (Ru-L1–3) have been prepared. Cyclic voltammetry of the three complexes are consistent with one Ru(II)-centered quasi-reversible oxidation and three ligand-centered reductions. Photophysical behaviors are investigated by UV–Vis absorption and fluorescence spectrometry. The three complexes display metal-to-ligand charge transfer absorption at 445 nm and emission at 578 nm.