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Asymmetric Heteroleptic Ir(III) Phosphorescent Complexes with Aromatic Selenide and Selenophene Groups: Synthesis and Photophysical, Electrochemical, and Electrophosphorescent Behaviors

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journal contribution
posted on 21.08.2018, 12:50 by Zhao Feng, Dezhi Wang, Xiaolong Yang, Deyuan Jin, Daokun Zhong, Boao Liu, Guijiang Zhou, Miaofeng Ma, Zhaoxin Wu
With the aim of evaluating the potential of selenium-containing groups in developing electroluminescent (EL) materials, a series of asymmetric heteroleptic Ir­(III) phosphorescent complexes (Ir-Se0F, Ir-Se1F, Ir-Se2F, and Ir-Se3F) have been synthesized by using 2-selenophenylpyridine and one ppy-type (ppy = 2-phenylpyridine) ligand with a fluorinated selenide group. To the best of our knowledge, these complexes represent unprecedented examples of asymmetric heteroleptic Ir­(III) phosphorescent emitters bearing selenium-containing groups. Natural transition orbital (NTO) analysis based on optimized geometries of the first triplet state (T1) have shown that the phosphorescent emissions of these Ir­(III) complexes dominantly show 3π–π* features of the 2-selenophenylpyridine ligand with slight metal to ligand charge transfer (MLCT) contribution. In comparison with their symmetric parent complex Ir-Se with two 2-selenophenylpyridine ligands, these asymmetric heteroleptic Ir­(III) phosphorescent complexes can show much higher phosphorescent quantum yields (ΦP) of ca. 0.90. Both the hole- and electron-trapping ability of these Ir­(III) phosphorescent complexes can be enhanced by selenophene and fluorinated selenide groups to improve their EL efficiencies. The EL abilities of these asymmetric heteroleptic Ir­(III) phosphorescent emitters fall in the order Ir-Se3F > Ir-Se2F > Ir-Se1F > Ir-Se0F. The highest EL efficiencies have been achieved by Ir-Se3F in the solution-processed OLEDs with external quantum efficiency (ηext), current efficiency (ηL), and power efficiency (ηP) of 19.9%, 65.6 cd A–1, and 57.3 lm W–1, respectively. These encouraging EL results clearly indicate the great potential of selenium-containing groups in developing high-performance Ir­(III) phosphorescent emitters.

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