Role of the Diphosphine Chelate in Emissive, Charge-Neutral Iridium(III) Complexes

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

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Author(s)

  • Jia-Ling Liao
  • Leon R. Devereux
  • Mark A. Fox
  • Yu-Cheng Chiang
  • Gene-Hsiang Lee

Detail(s)

Original languageEnglish
Pages (from-to)624-635
Journal / PublicationChemistry - A European Journal
Volume24
Issue number3
Online published12 Oct 2017
Publication statusPublished - 12 Jan 2018
Externally publishedYes

Abstract

A class of neutral tris-bidentate IrIII metal complexes incorporating a diphosphine as a chelate is prepared and characterized here for the first time. Treatment of [Ir(dppBz)(tht)Cl3] (1, dppBz=1,2-bis(diphenylphosphino)benzene, tht=tetrahydrothiophene) with fppzH (3-trifluoromethyl-5-(2′-pyridyl)-1H-pyrazole) afforded the dichloride complexes, trans-(Cl,Cl)[Ir(dppBz)(fppz)Cl2] (2) and cis-(Cl,Cl)[Ir(dppBz)(fppz)Cl2] (3). The reaction of 3 with the dianionic chelate precursor, 5,5′-di(trifluoromethyl)-3,3′-bipyrazole (bipzH2) or 5,5′-(1-methylethylidene)-bis(3-trifluoromethyl-1H-pyrazole) (mepzH2), in DMF gave the tris-bidentate complex [Ir(dppBz)(fppz)(bipz)] (4) or [Ir(dppBz)(fppz)(mepz)] (5), respectively. In contrast, a hydride complex [Ir(dppBz)(fppz)(bipzH)H] (6) was isolated instead of 4 in protic solvent, namely: diethylene glycol monomethyl ether (DGME). All complexes 2–6 are luminescent in powder form and thin films where the dichlorides (2, 3) emit with maxima at 590–627 nm (orange) and quantum yields (QYs) up to 90 % whereas the tris-bidentate (4, 5) and hydride (6) complexes emit at 455–458 nm (blue) with QYs up to 70 %. Hybrid (time-dependent) DFT calculations showed considerable metal-to-ligand charge transfer contribution to the orange-emitting 2 and 3 but substantial ligand-centered 3π–π* transition character in the blue-emitting 4–6. The dppBz does not participate in the radiative transitions in 4–6, but it provides the rigidity and steric bulk needed to promote the luminescence by suppressing the self-quenching in the solid state. Fabrication of an organic light-emitting diode (OLED) with dopant 5 gave a deep-blue CIE chromaticity of (0.16, 0.15). Superior blue emitters, which are vital in OLED applications, may be found in other neutral Ir III complexes containing phosphine chelates.

Research Area(s)

  • dianionic chelates, diphosphines, iridium, luminescent complexes

Citation Format(s)

Role of the Diphosphine Chelate in Emissive, Charge-Neutral Iridium(III) Complexes. / Liao, Jia-Ling; Devereux, Leon R.; Fox, Mark A.; Yang, Chun-Chieh; Chiang, Yu-Cheng; Chang, Chih-Hao; Lee, Gene-Hsiang; Chi, Yun.

In: Chemistry - A European Journal, Vol. 24, No. 3, 12.01.2018, p. 624-635.

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