Theoretical research on the photophysical properties of two series of iridium(III) complexes with β-ketoiminate and N , N ′-diisopropylbenzamidinate ancillary ligands

On the basis of complexes synthesized experimentally 1a and 1b, two series of iridium(III) complexes have been theoretically designed by introducing different ancillary ligands or different functional groups on main ligands. The electronic structure, absorption and emission spectra, charge injection/transport properties and phosphorescence quantum efficiency have been studied by density functional theory and time-dependent density functional theory. The N,N′-diisopropylbenzamidinate (dipba) ancillary ligand can result in the emission wavelength blueshift, decrease the singlet–triplet splitting energy value, increase the intersystem crossing rate and then increase the quantum efficiency. Introducing the electron-donating group –C(CH3)3 can increase the HOMO and LUMO energy levels and enhance the absorption strength and hole injection ability. Introducing the electron-withdrawing group –CN can decrease the HOMO and LUMO energy levels and the gaps between HOMO and LUMO, make the absorption peak redshift, decrease the singlet–triplet splitting energy and then increase the radiative rate constant (kr) and the quantum efficiency, also enhance the electron injection ability and hole or electron transport ability.