Phosphorescent copper(I) complexes bearing 2-(2-benzimidazolyl)-6-methylpyridine and phosphine mixed ligands

Two 2-(2-benzimidazolyl)-6-methylpyridine (Hbmp) copper(I) complexes bearing PPh3 and 1,4-bis(diphenylphosphino)butane (dppb), namely, [Cu(Hbmp)(PPh3)2](ClO4) (1) and [Cu(Hbmp)(dppb)](ClO4) (2), have been synthesized. X-ray diffraction analysis reveals that the most significant influence of the phosphine ligands on the structures is on the P–Cu–P bond angle. Both two Cu(I) complexes exhibit a weak low-energy absorption at 360–450 nm, ascribed to the Cu(I) to Hbmp metal-to-ligand charge-transfer (MLCT) transition, perhaps mixed with some ILCT character inside Hbmp. The room-temperature luminescences are observed for 1 and 2, both in solution and in the solid state, which originate from the MLCT excited states and vary markedly with the phosphine ligands.