化学学报 ›› 2023, Vol. 81 ›› Issue (5): 469-479.DOI: 10.6023/A23010006 上一篇    下一篇

研究论文

星型苯并菲-三嗪多刺激响应盘状液晶: 合成、性质与应用

曾崇洋a, 胡平a, 汪必琴a, 方文彦b, 赵可清*,a(), Bertrand Donnioc   

  1. a 四川师范大学 化学与材料科学学院 成都 610066
    b 淮南师范学院 化学与材料工程学院 淮南 232038
  • 投稿日期:2023-01-10 发布日期:2023-04-14
  • 基金资助:
    国家自然科学基金(51773140); 国家自然科学基金(51973143)

Star-shaped Triphenylene-triazine Multi-stimuli Responsive Discotic Liquid Crystals: Synthesis, Properties and Applications

Chongyang Zenga, Ping Hua, Biqin Wanga, Wenyan Fangb, Keqing Zhaoa(), Bertrand Donnioc   

  1. a College of Chemistry and Materials Science, Sichuan Normal University, Chengdu 610066, China
    b School of Chemistry and Materials Engineering, Huainan Normal University, Huainan 232038, China
    c Institut de Physique et Chimie des Materiaux de Strasbourg (IPCMS), CNRS-Universite de Strasbourg (UMR 7504), Strasbourg, 67034, France
  • Received:2023-01-10 Published:2023-04-14
  • Contact: *E-mail: kqzhao@sicnu.edu.cn
  • Supported by:
    National Natural Science Foundation of China(51773140); National Natural Science Foundation of China(51973143)

盘状液晶作为有机光电功能材料具有学术研究价值和应用开发潜力. 通过Suzuki偶联反应合成了星型1,3,5-三嗪-苯并菲盘状液晶TPPTn (n=6, 8, 12). 化合物在溶液、薄膜与固体态都有良好的荧光发射, 具有聚集诱导效应, 有效克服了盘状分子聚集诱导荧光猝灭的弊端, 烷氧链长度的改变对化合物溶液、薄膜或固体的荧光性质影响相对较小. 重点研究的TPPT6呈现出由蓝到橙显著的溶致变色, 绝对量子产率最高可达43%; TPPT6在有机溶剂中呈现出较传统分子的升温猝灭不同的随温度升高荧光增强的温度刺激响应; TPPT6还具有明显的酸碱刺激响应, 核磁滴定证明质子化过程是导致酸致变色的关键; TPPTn系列化合物自组装呈矩形柱状中间相(Colrec), 柱状相温度最宽达278 ℃, 三氟乙酸通过对三嗪离子化可调控TPPT的介晶行为. 此外, TPPT6可用于制备安全墨水以及绿光有机发光二极管. 该系列化合物在液晶半导体、荧光传感、信息加密和有机发光二极管等领域具有潜在的应用价值.

关键词: 苯并菲, 1,3,5-均三嗪, 多刺激响应, 盘状液晶, 聚集诱导效应, Suzuki-Miyaura交叉偶联

The electronic and optical properties of π-conjugated materials are determined by their molecular structures and supramolecular architectures. Discotic liquid crystals consist of π-conjugated aromatic core and peripheral alkyl chains, they self-organize into two-dimensional discotic columnar mesophase, which can be applied as charge carrier transport channel in optical and electronic thin-film devices. Order and dynamics are two unique features of discotic liquid crystalline semiconductors. Three star-shaped 1,3,5-triazine-triphenylene discotic liquid crystals TPPTn (n=6, 8, 12) were synthesized by Suzuki-Miyaura cross-coupling reaction and characterized. Thermogravimetric analysis (TGA) shows that TPPTn have good thermal stability, and their thermal decomposition temperatures were higher than 350 ℃. The ultraviolet-visible (UV-Vis) absorption spectra and fluorescence spectra showed that they have outstanding fluorescence emissions in solution, thin film and even in solid state, and the length of alkoxy chain affects a little the fluorescence properties of the film or solid state by affecting the molecular aggregation. TPPTn have the aggregation-induced emission (AIE) effect: longer the alkoxy chain, more obvious the AIE phenomenon, this AIE effectively overcomes the disadvantage of aggregation caused quenching (ACQ) of π-extended discotic liquid crystalline molecules. Further, TPPT6 exhibits significant solvatochromism from blue to orange with the increasing of solvent polarity, due to the intramolecular charge transfer (ICT), which provides possibility for visual recognition of solvent polarity. The fluorescent emission absolute quantum yield is up to 43%. What is more, TPPT6 exhibits a temperature-responsive fluorescence enhancement with increasing temperature in solution, which is different from the temperature quenching of traditional molecules, and the fluorescence exhibits a reversible switching from green to blue with increasing/decreasing of temperature. TPPT6 also has obvious acid-base stimuli- responsive fluorescent response by CF3COOH and Et3N. 1H NMR titration proves that the protonation of triazine core is the mechanism to acid discoloration. Based on the acid-base stimuli response phenomena, two kinds of fluorescent safety inks have been designed and demonstrated. Differential scanning calorimetry (DSC), polarizing microscope (POM) and X-ray diffraction (XRD) indicate that these star-shaped molecules TPPTn have liquid crystal properties, self-organizing into columnar rectangular (Colrec) mesophase with mesophase temperature range as wide as 278 ℃. Trifluoroacetic acid (CF3COOH) modulates successfully the mesomorphic behavior of TPPTn by ionizing the triazine core. In addition, TPPT6 also displays electroluminescent properties, which has been applied to a green organic light-emitting diode (OLED), and the luminous efficiency of OLED reaches 7.41 lm/W. The star-shaped triphenylene-triazine TPPTn have potential applications as liquid crystalline semiconductors, fluorescence sensing, information encryption and organic light-emitting diodes.

Key words: triphenylene, triazine, multi-stimuli response, discotic liquid crystals, aggregation-induced emission, Suzuki- Miyaura cross-coupling reaction