A theoretical study on the electronic and photophysical properties of two series of iridium(iii) complexes with different substituted N^N ligand

Abstract

A density functional theory/time-depended density functional theory has been applied to explore the geometrical, electronic and photophysical properties of the recently reported pyrazolyl-pyridine- or triazolyl-pyridine-containing iridium(III) complexes 1 and 2. The calculated absorption and emission wavelengths are in agreement with experimental data. Based on complexes 1 and 2, two series of Ir(III) complexes 1a–1c and 2a–2c with different N^N ligand have been designed. It is found that the photophysical properties of these complexes are greatly affected by the properties of the adopted ligands. From 2 to 2c, the ancillary ligands based on a bis(triazolyl-pyridine) moiety with a m-phenylene spacer group render an increase of the HOMO–LUMO energy gap, but relatively weak absorption intensities. It is believed that the larger ³MC/d–d → ³MLCT/π–π* energy gap, higher μ_S1 and MLCT % values, as well as the smaller ΔE_S1–T1 for 2b and 2c, are good indications for the higher quantum efficiency compared with that of experimental structure 2. Therefore, the newly designed complexes 2b and 2c are expected to be highly efficient deep-blue emitters for OLEDs application.