Abstract: The geometries of S₀ and T₁ states of a series of iridium(Ⅲ) complexes (C^N)₂Ir(pic-X)（C^N=ppy(1),  dfpmpy(2),  cyppy(3),  dfpmpy(4),  ocfppy(5),  ppy=Phenylpyridine,  dfpmpy=2-(2,4-difluorophenyl)-4-methylpyri-dine,  cyppy=2-(3-cyanophenyl)- pyridine,  ocfppy=2-(2-octyl-3-cyano-4-fluorophenyl)pyridine;  pic=2-carboxyl-pyridine;  X=H(1,2,3,5), EO₂(4),  EO₂=4-diethyloxy）were optimized by the B3LYP and  UB3LYP methods,  respectively. Time dependent density functional theory (TD-DFT) method together with the solvation model in Gauss program were used to obtain their spectral properties in CHCl₃  solvent. The results show that the structural parameters and spectral datas are close to their experimental values. The lowest energy absorptions and phosphorescence emissions are at 459,415,412,397,393 nm, and 567,532,544，491,490 nm,  respectively. The highest occupied molecular orbital (HOMOs) of complexes 1—5 are mainly localized on the Ir atom and C^N ligands,   the lowest unoccupied molecular orbital (LUMOs) are mainly contributed by the pic ligand for complexes  1,2,3,5,  and dominantly localized on the C^N and pic ligands for complex 4. Therefore,  they have different transition characteristics of metal to ligand and ligand to ligand charge transfer (MLCT/LLCT). The calculation results show that the phosphorescence color can be changed by altering the π electron-donating ability of substituent group.

Key words: iridium(Ⅲ) complex,  , color conversion,  , luminescent material,  , spectral property