Theoretical Study on the Electronic Structures and Optical Properties of Blue-Green and Blue Phosphorescent Iridium(III) Complexes with Tetraphenylimidodiphosphinate Ligand

摘要

The electronic structures and photophysical properties of five iridium(III) complexes Ir(tfmppy)_2(tpip) (1), Ir(dfppy)_2(tpip) (2), Ir(afCNppy)_2(tpip) (3), Ir(CNpyN_3)_2(tpip) (4), and Ir(2fphpta)_2(tpip) (5) [where tfmppy54-trifluoromethylphenylpyridine; dfppy54,6-difluorophenylpyridine; afCNppy56-fluoro-4-octyloxy-5-cyanophenylpyridine; CNpyN_3=2-(4-cyano-phenyl)-[1,2,3]-triazole; 2fphpta 52-(2,6-difluoro-phenyl-[1,2,4]-triazol-3-yl)-pyridine; tpip5 tetraphenylimido-diphosphinate] have been investigated by using density functional theory (DFT) methods and time-dependent DFT ones, aiming at elucidating the influences of different substituents and cyclometalated ligands on the emission properties and quantum yield. The calculated results revealed that the different substituents in 1-3 have a great influence on the energy levels, in particular highest occupied molecular orbital. Meanwhile, we have also get a further insight into the reason for different phosphorescence quantum yields of the studied complexes. The higher quantum yield (Ф) reported for 1 was found to be closely related to both its smaller S_1-T_1 splitting energy (? E_(S1-T1)) and larger transition electric dipole moment (μ_(s1)) upon the S_0 → S_1 transition. Complex 5 is expected to be a potential candidate for blue-emitting material with good organic lightemitting diodes performances. We propose that the optical properties of this class of materials can be tuned by the modifications of the cyclometalated ligands.