Abstract:

We designed and synthesized a new pyrazine derivative containing the carbazyl moiety, 2,3-di(4-(9-carbazylmethyl)phenyl)-5-methylpyrazine(CzMPMP) and investigated its reaction with iridium(III) ion to form the iridium complex Ir(CzMPMP)2(acac) (acac: acetyl acetone). The complex was characterized by nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS) and elemental analysis (EA) and its photophysical properties were investigated by UV-Vis spectroscopy as well as solution and solid state photoluminescence (PL) techniques. By comparing Ir(CzMPMP)2(acac) with Ir(DPMP)2(acac) (DPMP: 2,3-diphenyl-5-methylpyrazine), we find that the carbazyl group greatly influences the photophysical properties of the complexes. Firstly, Ir(DPMP)2(acac) has a strong and broad excimer peak in its solid state PL spectrum, while Ir(CzMPMP)2(acac) has no such peak under the same conditions. Furthermore, the PL intensity of Ir(CzMPMP)2(acac) in solution increased significantly compared with Ir(DPMP)2(acac). These results suggest that steric hindrance from the carbazyl groups may play an important role in preventing excimer formation and thus resulting in the increased PL intensity.

Key words: Carbazole, Pyrazine, Iridium(III) complex, Organic light-emitting device, Phosphorescence