Synthesis, Crystal Structure, Photophysical and Redox Properties of a Novel Ru(II) Complex with Carbazole-grafted 2-(2-Pyridyl)benzimidazole

A novel Ru(II) complex [(bpy)(2)Ru(PBC)](PF6)(2) (PBC = N-[4-(9-carbazole)buty1]-2-(2-pyridypbenzimidazole) has been synthesized and verified by H-1 NMR, elemental analysis and X-ray crystallography. The crystal (C48H40F12N8P2Ru, M-r = 1119.89) belongs to the triclinic system, space group P (1) over bar, with a = 13.128(4), b = 13.814(4), c = 14.184(4) angstrom, alpha = 84.112(6), beta = 88.473(6), gamma = 78.196(6)degrees, Z = 2, V = 2504.6(13) angstrom(3), D-c = 1.485 g/cm(3), F(000) = 1132, R = 0.0750 and wR = 0.1896. The Ru atom adopts a distorted-octahedral coordination geometry with the bond distances and bond angles falling in normal ranges. The complex shows an intense metal-to-ligand charge transfer ((MLCT)-M-1) (d pi(Ru) -> pi*(L)) transition (epsilon similar to 1.2x10(4) dm(3)mol(-1)cm(-1)) at 457 nm in the UV-Vis absorption spectrum and a strong red phosphorescence at 632 nm in the CH3CN solution at ambient temperature. An efficient intramolecular energy transfer process from the carbazole unit to the [(bpy)(2)Ru(PB)](2+) emissive center exists by selective optical-simulation. Its electrochemical behavior shows multiplicate redox processes based on the metal center, the grafting carbazole moiety and the 2-(2-pyridyl)benzimidazole unit.