Effect of the bipyridine ligand substituents on the emission properties of phosphorescent Ir(III) compounds

초록

To investigate the effect of bipyridine ligand substituents on the emission properties of Ir(III) compounds, four homoleptic iridium(III) compounds, specifically, mer-Ir(Mepypy)(3) (1), mer-Ir(Me(2)pypy)(3) (2), fac-Ir(Me2PYP)(3) (3) and Ir(OMe(2)Bupypy)(3) (4), where Mepypy = 2'-methyl-2,3'-bipyridine, Me(2)pypy = 2',6'-dimethyl-2,3'-bipyridine, OMe(2)pypy = 2',6'-dimethoxy-2,3'-bipyridine and OMe2 Bupypy = 2',6'-dimethoxy-4-tert-butyl-2,3`-bipyridine, were prepared via a one-pot reaction of the corresponding methyl- or methoxy-substituted ligand with Ir[(COD)BF4 as the starting material. Under the same reaction conditions, the major isolated products differed depending on the substituent used. The methyl substituents resulted in Ir(III) compounds with a meridional geometry, while methoxysubstituted Ir(III) compounds with a facial geometry were isolated in high yields when the methoxy substituent was used. Compounds 1 and 2 emit a green phosphorescence (Phi(PL), = 0.3) with a lambda(max) = 459 463 nm, while 3 and 4 show a bright, sky-blue emission (Phi(PL) = 0.5). The dimethoxy-substituted bipyridine ligand was advantageous in terms of yield, thermal stability and quantum efficiency, and its iridium compound is a good candidate for triplet emitters in phosphorescence organic light-emitting diodes (PHOLEDs). (C) 2017 Elsevier Ltd. All rights reserved.

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