Preparation and Photophysical Properties of Bis(tridentate) Iridium(III) Emitters: Pincer Coordination of 2,6-Di(2-pyridyl)phenyl.

The way to prepare molecular emitters [5t + 4t'] of iridium(III) with a 5t ligand derived from the abstraction of the hydrogen atom at position 2 of the aryl group of 1,3-di(2-pyridyl)benzene (dpybH) is shown. In addition, the photophysical properties of the new emitters are compared with those of their counterparts resulting from the deprotonation of 1,3-di(2-pyridyl)-4,6-dimethylbenzene (dpyMebH), at the same position, which are also synthesized. Treatment of 0.5 equiv of the dimer [Ir(μ-Cl)(η2-COE)2]2 (COE = cyclooctene) with 1.0 equiv of Hg(dpyb)Cl leads to the iridium(III) derivative IrCl2{κ3-N,C,N-(dpyb)}(η2-COE) (3), which reacts with 2-(1H-imidazol-2-yl)-6-phenylpyridine (HNImpyC6H5) and 2-(1H-benzimidazol-2-yl)-6-phenylpyridine (HNBzimpyC6H5) in the presence of Na2CO3 to give Ir{κ3-C,N,N-(NImpyC6H4)}{κ3-N,C,N-(dpyb)} (4) and Ir{κ3-C,N,N-(NBzimpyC6H4)}{κ3-N,C,N-(dpyb)} (5), respectively. Similar reactions of the Williams's dimer [IrCl(μ-Cl){κ3-N,C,N-(dpyMeb)}]2 with HNImpyC6H5 and HNBzimpyC6H5 in the presence of Na2CO3 afford the dimethylated counterparts Ir{κ3-C,N,N-(NImpyC6H4)}{κ3-N,C,N-(dpyMeb)} (6) and Ir{κ3-C,N,N-(NBzimpyC6H4)}{κ3-N,C,N-(dpyMeb)} (7), whereas 2-(6-phenylpyridine-2-yl)-1H-indole (HIndpyC6H5) initially gives IrH{κ2-N,N-(IndpyC6H5)}{κ3-N,C,N-(dpyMeb)} (8) and subsequently Ir{κ3-C,N,N-(IndpyC6H4)}{κ3-N,C,N-(dpyMeb)} (9). Complexes 4-7 are phosphorescent green emitters (λem 490-550 nm), whereas 9 is greenish yellow emissive (λem 547-624 nm). They display lifetimes in the range 0.5-9.7 μs and quantum yields in both doped poly(methyl)methacrylate films and in 2-methyltetrahydrofuran at room temperature depending upon the ligands: 0.5-0.7 for 6 and 7, about 0.4 for 4 and 5, and 0.3-0.2 for 9.