Theoretical study on the effect of N-substitution on the electronic structures and photophysical properties of phosphorescent Ir(III) complexes.
DFT/TDDFT calculations were carried out to investigate the electronic structures, absorption and emission spectra, and phosphorescence efficiency of recent synthesized Ir(III) complexes [Ir(tfmppy)2(tpip)] (1), [Ir(dfppy)2(tpip)] (2) (tfmppy = 4-trifluoromethylphenylpyridine; dfppy = 4,6-difluorophenylpyridine; tpip = tetraphenylimidodiphosphinate). The calculated absorption and emission wavelengths are in agreement with experimental data. The electron transition properties have been analyzed. Compared with 2, the higher quantum yield of experimental observation for 1 was explained by its larger separation between 3MLCT/π→π* and 3MC d–d states. Based on these experimental structures, a series of cyclometalated Ir(III) complexes have been designed by substituting “CH” groups with the N atom at 1-, 2-, 3-, and 4-positions on the pyridine moiety in C^N ligands of 1 and 2, respectively. The calculated results reveal that the N substitution not only tunes the emitting color of 1 and 2 but also enhances photoluminescence quantum efficiency. It is hoped that the designed 1a, 2a and 2c could be potential candidates as blue-emitting materials with high quantum efficiency. Moreover, the effects of different functionals on emission properties were also investigated.
State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China. ywang_2012@ciac.jl.cn zjwu@ciac.jl.cn.
Yanling
Y
Si
Yuqi
Y
Liu
Xiaochun
X
Qu
Ying
Y
Wang
Zhijian
Z
Wu