Substituent-effect investigation of facial and meridional tris(phenylbenzimidazolinato) Ir(III) carbene complexes: A theoretical perspective

Abstract A DFT/TDDFT investigation was carried out to understand the electronic structures and photophysical properties of a series of facial and meridional Ir(III) complexes fac -Ir( R -pmb) 3 and mer -Ir( R -pmb) 3 (R = H, CF 3 , CN, OCH 3 , t Bu, Ph, respectively) bearing phenylbenzimidazolinato ligand. Substitution effects and fac - mer isomer factors were both investigated. The results herein show that the variation of substituent on the phenyl ring does not cause obvious effects on the metal-related bond lengths and absorption spectra of these complexes. However, the HOMO and LUMO energy levels are affected significantly by the substitution effects. Meanwhile, the most intense absorptions of mer -Ir( R -pmb) 3 are found to be blue shifted (∼10 nm) compared with their fac isomers, and the absorption intensities of mer Ir(III) complexes are l enhanced. In addition, we also find that both the electron-donating and electron-withdrawing substituents lead to a red shift on the emissions of these fac and mer Ir(III) carbene complexes and the emissive natures are controlled by the chelate ligand with significant structural changes upon S 0 → T 1 excitation.