Highly Phosphorescent Bis-Cyclometalated Iridium\nComplexes Containing Benzoimidazole-Based Ligands

Abstract

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