Synthesis and Photophysical Studies of Iridium Complexes of New 2,3-Diphenylquinoxaline Derivatives for Organic Light-Emitting Diodes

For the application to organic light-emitting diodes (OLEDs), the new iridium complex containing 2,3-diphenylquinoxaline (dpqx) derivatives as a ligand were prepared. Variation of the substituents in the dpqx ligand backbone of the complex led to tuning of the emission color. The complexes, Ir(2,3-dpqx-F-2)(2)(acac), Ir(6-F-2,3-dpqx-F-2)(2)(acac) and Ir(6-F-2,3-dpqx-(OMe)(2))(2)(acac) were formed from the two-step reactions of the corresponding ligand with IrCl3 center dot H2O. In the photoluminescence (PL) spectra, Ir(2,3-dpqx-F-2)(2)(acac), Ir(6-F-2,3-dpqx-F-2)(2)(acac) and Ir(6-F-2,3-dpqx-(OMe)(2))(2)(acac) exhibited the luminescence peak at 631 nm, 638 nm and 645 nm, respectively. The OLEDs employing these compounds as a dopant were prepared and their electroluminescence was investigated. In the electroluminescence (EL) spectra, Ir(2,3-dpqx-F-2)(2)(acac), Ir(6-F-2,3-dpqx-F-2)(2)(acac) and Ir(6-F-2,3-dpqx-(OMe)(2))(2)(acac) exhibited the luminescence peak at 630 nm, 644 nm and 667 nm, respectively. The Commission Internationale de L'Eclairage (CIE) coordinates of Ir(2,3-dpqx-F-2)(2)(acac), Ir(6-F-2,3-dpqx-F-2)(2)(acac) and Ir(6-F-2,3-dpqx-(OMe)(2))(2)(acac) were (0.684, 0.311), (0.675, 0.313) and (0.697, 0.289), respectively.