Bis-Tridentate Iridium(III) Phosphors Bearing Functional 2-Phenyl-6-(imidazol-2-ylidene)pyridine and 2-(Pyrazol-3-yl)-6-phenylpyridine Chelates for Efficient OLEDs

Jun Lin, Nga Yuen Chau, Jia Ling Liao, Wai Yeung Wong, Cheng Yu Lu, Zong Ting Sie, Chih Hao Chang, Mark A. Fox, Paul J. Low, Gene Hsiang Lee, Yun Chi

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Abstract

Proligands to the monoanionic tridentate chelate 4-(tert-butyl)-2-(2,4-difluorophenyl)-6-(3-isopropyl-imidazol-2-ylidene)pyridine ((phpyim-H2)PF6) and dianionic tridentate chelates derived from functional 2-pyrazol-3-yl-6-phenylpyridine chelates, i.e. L1-H2-L5-H2, have been synthesized and characterized. Treatment of (phpyim-H2)PF6with [Ir(COD)(μ-Cl)]2in the presence of sodium acetate, followed by heating at 200 °C with 1 equiv of the dianionic chelate, afforded the respective charge-neutral, bis-tridentate Ir(III) complexes [Ir(phpyim)(Ln)] (1-5; n = 1-5). The hydride complex [Ir(phpyim)(L5-H)(H)] (6) was made when the "one-pot" reaction of (phpyim-H2)PF6, [Ir(COD)(μ-Cl)]2, and L5-H2was carried out at 140 °C. Complex 6 is likely an intermediate in the formation of 5, as it is converted to 5 on heating to 200 °C. Compounds 1-6 have been characterized by NMR spectroscopy and, in the cases of 1, 5, and 6, by X-ray structural analysis. TD-DFT computations confirmed that the emission bands are derived from3MLCT transitions involving the chelates L1-L5, resulting in a wide range of emission wavelengths from 473 (cyan) to 608 nm (orange-red) observed for 1 - 5. A series of green- and red-emitting organic light-emitting diodes (OLEDs) with a simplified trilayer architecture were fabricated using the as-prepared Ir(III) complexes 2 and 5, respectively. A maximum external quantum efficiency of 18.8%, a luminance efficiency of 58.5 cd/A, and a power efficiency of 57.4 lm/W were obtained for the green-emitting OLEDs (2), which compares with 15.4%, 10.4 cd/A, and 9.0 lm/W obtained for the red-emitting OLEDs (5). The high efficiencies of these OLED devices suggest great potential for these bis-tridentate Ir(III) metal phosphors in the fabrication of multicolored OLED devices.
Original languageEnglish
Pages (from-to)1813-1824
Number of pages12
JournalOrganometallics
Volume35
Issue number11
DOIs
Publication statusPublished - 13 Jun 2016
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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