Two bipolar blue-emitting fluorescent materials based on 1,3,5-triazine and peripheral pyrene for organic light-emitting diodes

Two bipolar blue-emitting materials, composed of the electron-withdrawing triphenyl-triazine core and the peripheral electron-donating 1-position substituted and 2-positon substituted pyrene moieties respectively, were designed, synthesized, and fully characterized by spectroscopies, cyclic voltammetry (CV) and Gaussian 03 molecular orbital calculations. The relationship between the structure and property was clearly demonstrated from the observed spectroscopic features (UV/Vis, photoluminescence and the solvatochromism) and molecular configuration. 1-Position substituted analogue exhibited a large twist angle of 52.0° and a strong electronic coupling between the core and the peripheral moieties, resulting in the strong dipolar property and the high fluorescent quantum efficiency of over 80% in the solution and the solid state. With the 1-position substituted analogue as the guest, the doped electroluminescence device showed a stable and efficient blue emission with the maximum luminance of 4306 cd/m2, the current efficiency of 1.15 cd/A, the external quantum efficiency of 0.97% and the CIE coordinate of (0.13, 0.06).