Acta Chim. Sinica ›› 2016, Vol. 74 ›› Issue (2): 179-184.DOI: 10.6023/A15090603 Previous Articles     Next Articles

Article

基于苯并噻唑的新型双硼桥联梯形共轭骨架的合成、结构及其性质

张振宇a, 李婉君b, 叶开其a, 张红雨a   

  1. a 吉林大学化学学院超分子结构与材料国家重点实验室 长春 130012;
    b 太原工业学院化学与化工系 太原 030008
  • 收稿日期:2015-09-14 出版日期:2016-02-15 发布日期:2015-10-12
  • 通讯作者: 叶开其 E-mail:hongyuzhang@jlu.edu.cn
  • 基金资助:

    项目受国家自然科学基金(No.51173067)资助.

Synthesis, Structure and Properties of a Novel Benzothiazole-based Diboron-Bridged π-Conjugated Ladder

Zhang Zhenyuaa, Li Wanjunb, Ye Kaiqia, Zhang Hongyua   

  1. a State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012;
    b Department of Chemistry and Chemical Engineering, Taiyuan Institute of Technology, Taiyuan 030008
  • Received:2015-09-14 Online:2016-02-15 Published:2015-10-12
  • Supported by:

    Project supported by the National Natural Science Foundation of China (No. 51173067).

A novel diboron-bridged ladder-type molecule with extended π-conjugated skeleton has been designed and synthesized. Single crystal of the compound has been grown by the method of vacuum sublimation and the molecular structure determined by X-ray diffraction analysis demonstrate that this ladder-type molecule has a seven-ring fused skeleton, which is almost coplanar. And the two mesityl groups coordinated to each boron atom can effectively keep the luminescent units apart. No π-π interaction can be observed between the two extended π-conjugated planes. In the packing structures, we cannot find the intramolecular hydrogen bond, C-H…π interaction and other weak interaction. Based on UV-vis absorption and fluorescence emission spectra, the longest absorption band is peaked at 372 nm in dichloromethane solution and the emission band is at 544 nm which has a large stokes shift of 8499 cm-1. In the solid state, the compound shows yellow fluorescence with emission peak at 582 nm. The compound in condensed phase displays only slightly red shifted emission spectra and almost the same fluorescence quantum yield compared to that in dispersed phase, which is attributed to the bulky side groups on the boron atoms. The compound possesses a very high melting point (Tm=352℃) and decomposition temperature (Td5=360℃) due to the rigid π-conjugated plane that indicates its good thermal stability. The compound has two pairs of reversible reduction peaks and an irreversible oxidation peak which are similar to the reported four-coordinate compounds. The cyclic voltammogram curves indicate boron chelation can greatly lower the lowest unoccupied molecular orbital (LUMO). Thus, it makes cathodic reductions easier and thereby endows the π-conjugated ladder with enhanced electron-accepting nature. The electrochemical property suggests that the compound is suitable as an electron-transporting layer in organic light-emitting diode (OLED) devices. To obtain a deeper insight into the electronic structure and energy levels of the π-conjugated skeleton, density functional theory (DFT) calculations were performed. The LUMOs are delocalized on the entire seven-ring π-conjugated ladder while the central benzene ring and the mesityl chelated with the boron atom make a main contribution to the HOMOs. The general trend of the calculated HOMO/LUMO levels and energy gaps are basically consistent with the electrochemical and the photophysical data. Therefore, we fabricated OLEDs devices using the molecule as emitter and/or electron-transporting layers, which showed good EL performance.

Key words: four-coordinate boron, ladder-type skeleton, π-conjugated molecule, OLEDs, fluorescence emitter