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

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 tfmppy=4-trifluoromethylphenylpyridine; dfppy=4,6-difluorophenylpyridine; afCNppy=6-fluoro-4-octyloxy-5-cyano-phenylpyridine; CNpyN(3)=2-(4-cyano-phenyl)-[1,2,3]-triazole; 2fphpta=2-(2,6-difluoro-phenyl-[1,2,4]-triazol-3-yl)-pyridine; tpip=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 (phi) reported for 1 was found to be closely related to both its smaller S-1-T-1 splitting energy ( ES1-T1) and larger transition electric dipole moment ( s1) upon the S-0 S-1 transition. Complex 5 is expected to be a potential candidate for blue-emitting material with good organic light-emitting diodes performances. We propose that the optical properties of this class of materials can be tuned by the modifications of the cyclometalated ligands. (c) 2013 Wiley Periodicals, Inc.