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.
Financial support from the MICIN/AEI/10.13039/501100011033 (PID2020-115286GB-I00 and RED2018-102387-T), Gobierno de Aragón (E06_20R and LMP23_21), FEDER, and the European Social Fund is acknowledged.