Blue-Emitting Iridium Complexes with Substituted 1,2,4-Triazole Ligands: Synthesis, Photophysics, and Devices

Neutral heteroleptic mononuclear iridium(III) complexes with (2,4-difluoro)phenylpyridine and different pyridine-1,2,4-triazole ligands were synthesized and fully characterized. We investigated the effects of substituents in the
5-position of the triazole ring on the photophysical and electrochemical behavior. Increasing the electron-withdrawing
capabilities generally leads to a lowering of the HOMO level with a consequent slight widening of the HOMO−LUMO gap and a blue shift in emission. The complexes reported exhibit high emission quantum yields and long
luminescent lifetimes, typical of iridium(III) complexes, and most of them show reversible redox processes in solution.
Also, many of the complexes reported here have been obtained as single crystals suitable for X-ray crystallography.
Two of the complexes were further tested as phosphorescent dyes in OLED devices and showed high external
quantum efficiencies (∼7%) and color points better than the “standard” for blue iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C2‘]picolinate (FIrpic). We also report the full electrochemical investigation of FIrpic in different solvents.

本研究合成了含有(2,4-二氟)苯并吡啶和不同吡啶-1,2,4-三唑配体的中性异配位单核铱(III)配合物，并对其进行了全面表征。我们探讨了三唑环5位取代基对光物理和电化学性质的影响。提高电子抽取能力通常会导致最高占据分子轨道（HOMO）能级降低，进而使HOMO-LUMO能隙略微拓宽，并导致发射光的红移。所报道的配合物表现出铱(III)配合物典型的较高发射量子产率和长的发光寿命，并且大部分在溶液中表现出可逆的氧化还原过程。此外，许多报道的配合物已作为单晶获得，适用于X射线晶体学分析。其中两种配合物进一步作为OLED器件中的磷光染料进行了测试，表现出高外量子效率（约7%）和优于“标准”的蓝色铱(III)双[(4,6-二氟苯基)吡啶-N,C2']柠檬酸盐（FIrpic）的色点。我们还报道了FIrpic在不同溶剂中的全面电化学研究。