Enhancing the electronic properties and quantum efficiency of sulfonyl/phosphoryl-substituted blue iridium complexes via different ancillary ligands

Abstract

A DFT/TDDFT investigation was performed on the electronic structures, absorption and emission properties, as well as the phosphorescence efficiency of the recently synthesized Ir(III) complexes SOFIrpic (1a) and POFIrpic (2a) with sulfonyl/phosphoryl substituted 2-(2,4-difluorophenyl)pyridine (dfppy) as the cyclometalated ligand. The calculated absorption and emission wavelengths are in agreement with experimental data. The higher quantum yield of experimental observation for 1a compared with 2a was explained by its smaller energy separation between the singlet S₁ and the triplet T₃ states. Based on these experimental structures, a series of cyclometalated Ir(III) complexes (1b, 1c, 1d and 2b, 2c, 2d) have been designed by introduction of different ancillary ligands. The calculated results reveal that the different ancillary ligands not only tune the energy gap but also enhance the photoluminescence quantum efficiency. It is expected that the designed complexes 1b, 2b and 2c could be potential candidates as blue-emitting materials with high quantum efficiency.