Theoretical Study On The Effect Of Different Substituents On The Photoelectric Properties Of Phosphorescent Ir(â…¢) Complexes

Transition metal Iridium complexes with phosphorescent properties have increasingly attracted a lot of attention, especially in the application of organic light-emitting diodes(OLEDs). DFT calculations have been successfully applied to investigate molecular structure and properties, spectroscopy, reaction mechanism, quantum efficiency calculation. DFT calculations not only provide a theoretical basis for the existing experimental data, but also provide theoretical guidance for the further design of high-efficiency light-emitting material.1、DFT/TDDFT calculations have been conducted to investigate the influence on the photophysical properties different substituents of PR2^SiO complexes. The following conclusions can be made.(1) The energy levels of the FMOs are influenced by molecular volume size of PR2^OSi.(2) Geometry structure is not strongly affected by the addition of fluorination. The existence of CH3 which size is smaller than phenyl group makes the steric hindrance decreased, strengthening the interaction of Ir atom with P(CH3)2^SiO group.(3) Compared with the parent complex 1, the lowest-lying absorption bands of 2 is nearly the same, while it is red-shifted for 3.(4) The complexes 2 and 3 have smaller ??S1–T1 and larger ?S1. Thus, they could have higher quantum yield. Complexes 2 and 3 are potentially excellent blue material.2 、 DFT/TDDFT calculations have been performed to investigate the influence on electronic structure, absorption spectra, emission color and quantum efficiency of the studied complexes induced by the introduction of different N^O ligands. In this study, the following conclusions can be drawn:(1) the composition of the LUMO is significantly affected, when the C–C bond is substituted with N–N bond.(2) Compared with 1 and 2, the emission wavelengths for 4 and 5 are red-shifted, while they are blue-shifted significantly for 3 and 6. Especially, the emission color of the complex 6 is in deep blue region, which is promising as a blue-emitting material.(3) The results show that the different ancillary ligands in 3, 5 and 6 lead to a relatively large MLCT% and a small ??S1–T1 and thus a high quantum yield.3 、 DFT/TDDFT investigations are carried out on the electronic and photophysical properties of recently synthesized blue mitting Ir(III) complexes SOFIrpic(1a) and POFIrpic(1b). The calculated results reveal that the different ancillary ligands in 1b-1d and 2b-2d stabilize the energy level of LUMOs more than that of HOMOs. Thus, the energy gap between HOMO and LUMO can be tuned. The lowest absorption bands for 1b-1d(2b-2d) are blue-shifted compared with the parent complexes 1a(2a), and they have excellent blue light emitting properties. The higher quantum yield of 1a compared with 2a in the experiment is found to be closely related to smaller energy separation between the singlet S1 and the triplet T3 of the former. The smaller S1-T3 energy difference for 1b, 2b and 2c compared with that of 1a and 2a could blue shift the emission spectra and enhance the quantum efficiency.It is expected that the designed 1b, 2b and 2c could bepotential candidates as blue-emitting materials.