A large perturbation on electronic and photophysical properties of Ir(III) carbene complexes caused by the variation of N-substitution in N,N′-heteroaromatic ligands

DFT/TDDFT investigation was performed on the electronic and photophysical properties of blue-emitting Ir(III) carbene complexes (fpmi)3−xIr(N^N′)x (x = 1, 2) [fpmi = 1-(4-fluorophenyl)-3-methylimidazolin-2-ylidene-C,C2′, N^N′ = 2-(1H-pyrazol-5-yl)pyridinato (1a(x = 1)/1a′(x = 2)); 2-(1H-imidazol-5-yl)pyridinato (1b/1b′); 2-(1H-imidazol-2-yl)pyridinato (1c/1c′); 2-(1H-1,2,4-triazol-5-yl)pyridinato (2a/2a′); 2-(1H-1,2,3-triazol-5-yl)pyridinato (2b/2b′); 2-(4H-1,2,4-triazol-3-yl)pyridinato (2c/2c′)]. The absorption intensities and band positions are obviously affected by the variation of N substitution in N^N′ ligand. The emission properties show an apparent dependence on the solvent effects, and the N^N′ ligand plays an important role in governing the emissive state. The pyrazolyl-pyridyl-based N^N′ ligand is considered to be more beneficial for blue OLEDs emitters.