Alkynyl Ligands as Building Blocks for the Preparation of Phosphorescent Iridium(III) Emitters: Alternative Synthetic Precursors and Procedures

Alkynyl ligands stabilize dimers [Ir­(μ-X)­(3b)2]2 with a cis disposition of the heterocycles of the 3b ligands, in contrast to chloride. Thus, the complexes of this classcis-[Ir­(μ2-η2-CCPh)­{κ2-C,N-(C6H4-Isoqui)}2]2 (Isoqui = isoquinoline) and cis-[Ir­(μ2-η2-CCR)­{κ2-C,N-(MeC6H3-py)}2]2 (R = Ph, tBu)have been prepared in high yields, starting from the dihydroxo-bridged dimers trans-[Ir­(μ-OH)­{κ2-C,N-(C6H4-Isoqui)}2]2 and trans-[Ir­(μ-OH)­{κ2-C,N-(MeC6H3-py)}2]2 and terminal alkynes. Subsequently, the acetylide ligands have been employed as building blocks to prepare the orange and green iridium­(III) phosphorescent emitters, Ir­{κ2-C,N-[C­(CH2Ph)­Npy]}­{κ2-C,N-(C6H4-Isoqui)}2 and Ir­{κ2-C,N-[C­(CH2R)­Npy]}­{κ2-C,N-(MeC6H3-py)}2 (R = Ph, tBu), respectively, with an octahedral structure of fac carbon and nitrogen atoms. The green emitter Ir­{κ2-C,N-[C­(CH2tBu)­Npy]}­{κ2-C,N-(MeC6H3-py)}2 reaches 100% of quantum yield in both the poly­(methyl methacrylate) (PMMA) film and 2-MeTHF at room temperature. In organic light-emitting diode (OLED) devices, it demonstrates very saturated green emission at a peak wavelength of 500 nm, with an external quantum efficiency (EQE) of over 12% or luminous efficacy of 30.7 cd/A.