Greenish yellow organic light emitting devices based on novel iridium complexes containing 2-cyclohexenyl-1-phenyl-1H-benzo[d]imidazole

2-Cyclohexenyl-1-phenyl-1H-benzo[d]imidazole (Hcyclopbi) and its heterocyclometalated iridium complexes bis[2-cyclohexenyl-1-phenyl-1H-benzo[d]imidazole](acetylacetonate)iridium(III) [(cyclopbi)(2)Iracac] and bis[2-cyclohexenyl-1-phenyl-1H-benzo[d]imidazole][2-(3-(trifluoromethyl)-1H-pyrazol-5-yl)pyridinate]iridium(III) [(cyclopbi)(2)IrCF3] were firstly designed and synthesized. Owing to the strong electron withdrawing ability of 2-(3-(trifluoromethyl)-1H-pyrazol) compared to that of acetylacetonate, blue shifted phosphorescence 542 nm was obtained for (cyclopbi)(2)IrCF3 compared to that of (cyclopbi)(2)Iracac 545 nm with photoluminescence quantum yields (phi) 0.22 and 0.25, respectively, as well the highest occupied molecular orbit (HOMO) energy level was estimated to be -5.10 eV for (cyclopbi)(2)IrCF3, 0.19 eV lower than that of -4.91 eV for (cyclopbi)(2)Iracac. When (cyclopbi)(2)Iracac was doped into 4,4'-bis(9H-carbazol-9-yl)biphenyl (CBP) as the emitting layer, high efficiency organic light emitting devices (OLEDs) were obtained with maximum current efficiency (eta(c)) 22.3 cd/A at 3.1 mA/cm(2) and maximum brightness 16,300 cd/m(2) at 171.6 mA/cm(2), which were comparable to those of bis(2-phenylpyridine)(acetylacetonate)iridium(III) [(ppy)(2)Iracac] with the same device structure. This results indicate that (cyclopbi)(2)Iracac and (cyclopbi)(2)IrCF3 are potential phosphorescent dyes used for OLEDs. (C) 2013 Elsevier Ltd. All rights reserved