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

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 3shows 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. KCI Citation Count: 6