Iridium(III) complexes with orthometalated quinoxaline ligands : Subtle tuning of emission to the saturated red color

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Author(s)

  • Fu-Ming Hwang
  • Hsing-Yi Chen
  • Po-Shen Chen
  • Chao-Shiuan Liu
  • Ching-Fong Shu
  • Fang-Iy Wu
  • Pi-Tai Chou
  • Shie-Ming Peng
  • Gene-Hsiang Lee

Detail(s)

Original languageEnglish
Pages (from-to)1344-1353
Journal / PublicationInorganic Chemistry
Volume44
Issue number5
Online published4 Feb 2005
Publication statusPublished - 1 Mar 2005
Externally publishedYes

Abstract

Rational design and syntheses of four iridium complexes (1-4) bearing two substituted quinoxalines and an additional 5-(2-pyridyl) pyrazolate or triazolate as the third coordinating ligand are reported. Single-crystal X-ray diffraction studies of 1 reveal a distorted octahedral geometry, in which two dpqx ligands adopt an eclipse configuration, for which the quinoxaline N atoms and the C atoms of orthometalated phenyl groups are located at the mutual trans-and cis-positions, respectively. The lowest absorption band for all complexes consists of a mixture of heavy-atom Ir(III)-enhanced 3MLCT and 3ππ* transitions, and the phosphorescent peak wavelength can be fine-tuned to cover the spectral range of 622-649 nm with high quantum efficiencies. The cyclic voltammetry was measured, showing a reversible, metal-centered oxidation with potentials at 0.76-1.03 V, as well as two reversible reduction waves with potentials ranging from -1.61 to -2.06 V, attributed to the sequential addition of two electrons to the more electron-accepting heterocyclic portion of two distinctive cyclometalated C∧N ligands. Complex 1 was used as the representative example to fabricate the red-emitting PLEDs by blending it into a PVK-PBD polymer mixture. The devices exhibited the characteristic emission profile of 1 with peak maxima located at 640 nm. The maximum external quantum efficiency was 3.15% ph/el with a brightness of 1751 cd/m2 at a current density of 67.4 mA/cm 2, and the maximum brightness of 7750 cd/m2 was achieved at the applied voltage of 21 V and with CIE coordinates of (0.64, 0.31).  

Citation Format(s)

Iridium(III) complexes with orthometalated quinoxaline ligands : Subtle tuning of emission to the saturated red color. / Hwang, Fu-Ming; Chen, Hsing-Yi; Chen, Po-Shen; Liu, Chao-Shiuan; Chi, Yun; Shu, Ching-Fong; Wu, Fang-Iy; Chou, Pi-Tai; Peng, Shie-Ming; Lee, Gene-Hsiang.

In: Inorganic Chemistry, Vol. 44, No. 5, 01.03.2005, p. 1344-1353.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review