Monodentate Benzo[d]imidazole‐Based Iridium(III) Complexes and Their Dual Fluorescent and Phosphorescent Emissions

Abstract

We herein reported the preparation of three heteroleptic iridium complexes possessing the monodentate benzo[d]imidazole ligand, namely IrBzH (bis[2‐(4,6‐difluorophenyl)pyridinato‐C^N](1‐pyridin‐2‐yl)‐1H‐benzo[d]imidazolate)iridium(III)), IrBzCN (bis[2‐(4,6‐difluorophenyl)pyridinato‐C^N](2‐(1H‐benzo[d]imidazolate‐1‐yl)isonicotinonitrile)iridium(III)), and IrBzBr (bis[2‐(4,6‐difluorophenyl)pyridinato‐C′N](1‐(4‐bromopyridin‐2‐yl)‐1H‐benzo[d]imidazolate)iridium(III)). The successful preparation of these complexes was confirmed by multinuclear NMR spectroscopy and elemental analysis, while the molecular structures were determined by X‐ray diffraction. The photoluminescence spectra of all three complexes in toluene at ambient temperature exhibited a dual‐emissive pattern in the high‐ and low‐energy regions. For IrBzCN and IrBzBr, the emissions were simultaneous in accordance with the excitation energies (λem = 342 and 370 nm), indicating that exhibiting both fluorescent (in the high‐energy region) and phosphorescent (in the low‐energy region) emissions is an inherent property of these complexes. Time‐dependent density functional theory calculations verified that each fluorescent emission of the Ir complexes is associated with a ligand‐to‐ligand charge transfer transition, and the phosphorescent emission can be attributed to typical triplet metal‐to‐ligand charge transfer transitions between Ir3+ and the difluorophenylpyridine ligand.