Two bipolar fluorophores, namely CEDF and CPDF containing carbazole moiety as electron donor and 4,5-diazafluorene unit as electron acceptor were synthesized and characterized. Carbazole units attached to C-2, C-7 and C-9 positions of 4,5-dizafluorene posing an ideal model of donor-acceptor systems to investigate their photo-physical properties for application in organic light emitting diode (OLED) devices. Both compounds possess high thermal stabilities (T_d > 450 °C) and high glass transition temperature (T_g), 182 °C and 180 °C for CEDF and CPDF respectively. These compounds revealed solvent polarity dependent emission spectra which confirm the excited state undergoes intramolecular charge-transfer (ICT) process in the molecule. Solid state emission is observed in the blue region at 447 nm for both the compounds. CPDF exhibit higher photoluminescence quantum yield (0.76) than CEDF (0.55) featuring its highly emissive ICT excited state. Using the oxidation and reduction potentials determined from cyclic voltammetry analysis, estimates of both the ionization potentials and electron affinity of the compounds are obtained under the same experimental conditions. HOMO and LUMO energy levels, singlet (E_S) and triplet (E_T) energy levels of the compounds were obtained through density functional theory (DFT) and time-dependent DFT calculations. A transient photoluminescence curve with a prompt fluorescent component gives an average lifetime of about 5.7 ns for both the compounds. These studies and the convenient synthetic methodologies starting from the 4,5-diazafluorene, make these molecules attractive opto-electronic materials for their application in OLED devices.

合成并表征了两种双极性荧光团，即CEDF和CPDF，其含有咔唑部分作为电子供体，并以4,5-二氮杂芴单元作为电子受体。咔唑单元连接到4,5-二氟芴的C-2，C-7和C-9位置，构成了供体-受体系统的理想模型，可研究它们在有机发光二极管（OLED）器件中的光物理性质。两种化合物均具有较高的热稳定性（T _d  > 450°C）和较高的玻璃化转变温度（T _g），对于CEDF和CPDF而言分别为182°C和180°C分别。这些化合物揭示了溶剂极性相关的发射光谱，该光谱确认了激发态在分子中经历了分子内电荷转移（ICT）过程。对于这两种化合物，在蓝色区域的447 nm处均观察到固态发射。与具有高发射ICT激发态的CEDF（0.55）相比，CPDF表现出更高的光致发光量子产率（0.76）。使用由循环伏安法分析确定的氧化和还原电位，可以在相同的实验条件下估算化合物的电离电位和电子亲和力。HOMO和LUMO能级，单重态（E _S）和三重态（E _T化合物的能级是通过密度泛函理论（DFT）和随时间变化的DFT计算获得的。两种化合物的瞬态光致发光曲线具有迅速的荧光成分，平均寿命约为5.7 ns。这些研究以及从4,5-二氮杂芴开始的便捷合成方法，使这些分子对于在OLED器件中的应用具有吸引力，成为光电材料。