Highly Phosphorescent Bis-Cyclometalated Iridium Complexes Containing Benzoimidazole-Based Ligands

New benzoimidazoles (bi) have been synthesized. These compounds readily undergo cyclometalation with iridium trichloride, and bis-cyclometalated iridium complexes, (bi)2Ir(acac) (bi = cyclometalated benzoimidazole; acac = acetylacetonate), can be isolated. One of the complexes, (fbi)2Ir(acac) (fbi = 2-(9,9-diethyl-9H-fluoren-2-yl-1H-benzoimidazole), was also characterized by single-crystal X-ray structural determination. Some of the complexes, (bi)2Ir(acac), are highly phosphorescent at ambient condition. Light-emitting devices using these complexes as dopants were fabricated, and the emission colors range from green to red. Some green- and yellow-emitting devices exhibit very high efficiencies.