Influential effect of C^N ligands containing O, S, and Se heteroatoms in the color tuning of four phosphorescent Ir(III) complexes

Abstract A group of new iridium(III) complexes were rationally designed and synthesized with 2‐phenylbenzo[d]oxazole (bo), 2‐phenylbenzo[d]thiazole (bt), 2‐(thiophen‐2‐yl)benzo[d]thiazole (thbt), and 2‐(selenophen‐2‐yl)benzo[d]thiazole (sebt) as C^N ligands and bis(diphenylthiophosphoryl)amide (S‐tpip) as ancillary ligand. They are phosphorescent in a wide region of green to red with short lifetimes around 0.31–0.98 μs and quantum yields up to 64.7%. The detailed photophysical properties were investigated by experiment and further supported by density functional theory (DFT) calculation. These research results show that the spectroscopic properties are tuned by the replacement between oxygen, sulfur, and selenium or the change in aromatic ring. It has been demonstrated that the lowest energy‐level absorption and emission are dominated apparently by C^N ligands, and are ascribed to metal‐to‐ligand charge transfer (MLCT) and intra‐ligand charge transfer (ILCT) characters.