Abstract
The synthesis and mesomorphic properties of a new platinum(II) complexes with a formula [Pt(N^N)2] in which containing pyridylpyrazolate (complexes 1a-1d and 2), isoquinolylpyrazolate (complexes 3a-3b and 4) and pyridyltriazolate (complexes 5a-5b). The disc-like Pt(II) complexes (1a, 3a and 4) exhibited columnar hexagonal mesophases, which were characterized by DSC analysis and optical polarized microscopy. The structure of the mesophases was confirmed by X-ray powder diffraction (XRD). Single-crystal X-ray diffraction studies of 1a and 3b reveal the difference in the arrangement of the molecules. Complex 1a showed a columnar stacking with the molecules oriented in an alternating order, while complex 3b formed a columnar stacking of superimposed monomeric units. Complexes 1a-1c and 5a-5b display negative solvatochromic luminescence, which attributed to a common charge-transfer-to-pyridyl excited state. A Red-Polarized phosphorescent OLED device with multilayer configuration of ITO/rubbed PEDOT/F(MB)5:16%1a/TPBI/LiF/Al were fabricated using F(MB)5 layer doped with 16% of complex 1a. The device showed a red emission with λmax at 621nm. The device has a luminance of 150 cd m2 at 15 V and a maximum efficiency of 0.3 cd/A. The threshold voltage is 7 V. The polarization direction of phosphorescence is perpendicular to the rubbing direction. Both PL and EL dichroic ratios are about 2x (vertical/parallel).