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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 32, Number 12
BKCSDE 32(12)
December 20, 2011 

 
Title
Red-Orange Emissive Cyclometalated Neutral Iridium(III) Complexes and Hydridoiridium(III) Complex Based on 2-Phenylquinoxaline : Structure, Photophysics and Reactivity of Acetylacetone Towards Cyclometalated Iridium Dimer
Author
Nallathambi Sengottuvelan, Seong-Jae Yun, Sung Kwon Kang, Young-Inn Kim*
Keywords
Iridium(III) complex, Luminescence, Orange-red phosphorescence, Hydridoiridium(III) complex
Abstract
A new series of heteroleptic cyclometalated iridium(III) complexes has been synthesized and characterized by absorption, emission and cyclic voltammetry studies: (pqx)2Ir(acac) (1), (dmpqx)2Ir(acac) (2) and (dfpqx)2Ir(acac) (3) where pqx=2-phenylquinoxalinate, dmpqx=2-(2,4-dimethoxyphenyl)quinoxalinate, dfpqx=2-(2,4-difluorophenyl) quinoxalinate and acac=acetylacetonate anion. The reaction of excess acetylacetone with μ- chloride-bridged dimeric iridium complex, [(C^N)2Ir(μ-Cl)]2, gives a complex 1 and an unusual hydridoiridium(III) complex, (pqx)IrH(acac)2 (4). The complex 1, 2 and 3 show their emissions in an orangered region (λPL,max = 583-616 nm), and the emission maxima can be tuned by the change of substituent at phenyl ring of 2-phenylquinoxaline ligand. The phosphorescent line shape indicates that the emissions originate predominantly from 3MLCT states with little admixture of ligand-based 3(π-π*) excited states. The structures of complex 3 and 4 are additionally characterized by a single crystal X-ray diffraction method. The complex 3 shows a distorted octahedral geometry around iridium(III) metal ion. A strong trans influence of the phenyl ring is examined. In complex 4, there are two discrete molecules which are mirror images each other at the ratio of 1:1 in an unit cell. We propose that the phosphorescent complex 1, 2 and 3 are possible candidates for the phosphors in OLEDs applications.
Page
4321 - 4326
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