New design of two series of Ir(Ⅲ) complexes by changing substitute group at main ligand or ancillary ligand from theoretical viewpoint

Abstract

Using DFT/TDDFT methods to investigate the electronic structure, absorption and emission spectra, charge injection/transport ability and phosphorescence quantum efficiency of two series of Ir(Ⅲ) complexes. Complexes 1a–1c introduce F atom, acetyl group (–COCH3), 1-fluoro-4-methanesulfonyl-benzene group (–SO2PhF) to substitute methyl on benzene ring of mpmi main ligand (1-(4- tolyl)-3-methyl-imidazole) in complex 1, and complexes 2–4 introduce different ligands to substitute the dmpypz ancillary ligand (3,5-dimethyl-2-(1H-pyrazol-5-yl)pyridine) of complex 1, such as heppy ligand (4-(1-hydroxy-ethyl)-5-methyl-2-phenyl-3,4-dihydro-2H-pyrazol-3-ol), typy ligand (2-thiophen-2-yl-pyridine), quol ligand (quinolin-8-ol). The introduction of F atom, –COCH3 and –SO2PhF has the important effect on the photophysical properties of all studied complexes. Thereinto, introducing –COCH3 and –SO2PhF have great influence on the transition dipole moment from S0 to S1 state (μS1) and can improve electron transport property. Introducing different ancillary ligands can adjust emission wavelength effectively, has great influence on μS1, typy ligand and quol ligand can adjust hole/electron injection ability. Typy ancillary ligand could improve electron balance ability. Complexes 1–1c and 2 have larger HOMO–LUMO energy level, and they are potential blue materials. Complex 1c has better electron injection ability. Complexes 3 and 4 have the larger μS1, so they may have higher quantum efficiency.