Theoretical investigation of the electronic structure and photophysical properties of a series of Ir(iii) complexes bearing pentafluorosulfanyl groups

Abstract

The electronic structure, absorption and emission spectra, charge injection/transport ability and phosphorescence quantum efficiency of a series of cyclometalated iridium(III) complexes with different ancillary ligands are studied using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. Based on complex 1 Ir(SF₅-ppy)₃, complexes 2 and 5 incorporate thd and tpip (thd = anionic 2,2,6,6-tetramethylheptane-3,5-dionato-κO³,κO⁶; tpip = tetraphenylimidodiphosphinate) ligands as their ancillary ligands. Complexes 3 and 4 incorporate thiazole and nitrobenzene on thd ancillary ligands based on complex 2 as their ancillary ligands (ptd = 4-(1-hydroxy-2,2-dimethyl-propylidene)-4H-thiazol-5-one, ntd = 1-(2-hydroxy-5-nitro-phenyl)-2,2-dimethyl-propan-1-one). The calculated results demonstrate that ntd and ptd ancillary ligands increase the intensity of absorption, ΔE_S1–T1, μ_S1, and then enhance the electron injection ability. The thd and tpip ancillary ligands could not only decrease ΔE_S1–T1 but also increase μ_S1, thus enhancing the phosphorescence quantum efficiency. And the ntd ancillary ligand can not only decrease the LUMO energy level and the energy gap, but can also decrease the electron and hole transport ability, and balance ability. The ptd ancillary ligand could enhance the electron and hole balance ability. Complex 2 has the highest Φ_PL value. Complex 1 has the best hole and electron transport ability. The ntd ancillary ligand can decrease the electron transport ability, hole transport ability and balance ability. Complexes 1–5 are potential green-blue or green emitting materials.