Combined experimental and density functional theory studies on novel 9-(4/3/2-cyanophenyl)-9H-carbazole-3-carbonitrile compounds for organic electronics

We have synthesized a series of novel hybrid molecules 9-(2-cyanophenyl)-9H-carbazole-3-carbonitrile (o-CNCbzCN), 9-(3-cyanophenyl)-9H-carbazole-3-carbonitrile (m-CNCbzCN) and 9-(4-cyanophenyl)-9H-carbazole-3-carbonitrile (p-CNCbzCN), comprising electron-donating carbazole and electron-accepting nitrile groups. Three positional isomers were synthesized with a view to tune photophysical and electrochemical properties of the hybrids. The photophysical study displayed absorption maxima in the range of 281-340 nm and 277-298 nm whereas emission maxima in the range of 349-366 nm and 366-369 nm in toluene and dimethylformamide (DMF), respectively. These molecules demonstrated suitable frontier molecular orbital (FMO) energy levels and ensure good thermal and morphological stability. Among these synthesized molecules, m-CNCbzCN showed very high decomposition temperature (T-d = 341 degrees C) whereas p-CNCbzCN exhibited good glass transition (T-g = 182 degrees C) as well as melting temperature (T-m = 236 degrees C), indicating its significant stability and potential utility as a bipolar host material for efficient phosphorescent organic light-emitting diodes (PhOLEDs).