摘要/Abstract
盘状液晶分子由稠环芳核和围绕的多条柔性链构成, 具有独特的自组装有序超分子结构、半导体性质和光学性质. 其可通过溶液或喷墨打印技术加工成为光电子薄膜器件, 具有低成本优势. 通过Suzuki-Miyaura交叉偶联和Scholl氧化环化策略, 合成了一系列新的具有苯并?结构的非对称酸酐、羧酸酯、酰亚胺和苯并咪唑稠环衍生物, 并对其液晶性和光物理性质进行了详细研究. 通过偏振光学显微镜(POM), 差示扫描量热法(DSC)和小角度X射线散射(SAXS)测试表明, 这些极性盘状化合物自组装堆积呈六方柱状(Colhex)液晶相, 其中, 最宽的液晶温度范围达206 ℃. 官能团和共轭体系大小决定了相变温度和液晶范围. 荧光测试结果表明, 化合物溶液中绝对量子产率高达34%, 根据官能团不同, 这些化合物发蓝、绿和红光. 借助密度泛函理论(DFT)计算, 解释了该系列极性盘状液晶分子发光性质的差异. 基于本工作的合成方法, 从萘酸酐原料出发为构建结构多变、性质丰富的π-共轭(杂环)芳烃盘状液晶化合物提供了新途径.
关键词: 苯并?, 苯并菲, 酰亚胺, 盘状液晶, 荧光, Suzuki-Miyaura偶联反应, Scholl反应
Discotic liquid crystal consisting of polycyclic aromatic hydrocarbon (PAH) core and peripheral alkyl chains is a kind of soft organic materials showing semiconductivity and fluorescence, and it can be fabricated into opto-electronic devices by solution process or printing technique, with low-cost advantage. We report benzo[g]chrysene unsymmetrical functional discotic liquid crystals, which were synthesized by Suzuki-Miyaura cross-coupling reaction and Scholl oxidative annulation. Five new π-extended compounds containing ester, anhydride, imide and benzoimidazole unit were synthesized and characterized. Their liquid crystalline property was fully characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and small-angle X-ray scattering (SAXS), these compounds showed ordered columnar hexagonal (Colhex) mesophase with broad mesophase range as wide as 206 ℃. The functional groups have essential impact on the phase transition temperatures. The ultraviolet-visible (UV-Vis) absorption and photoluminescent property were studied, they displayed fluorescent quantum yield as high as 34% in solution, and the emission spectra can be tuned from blue, green to red by functional group and π-conjugation extension. Density functional theory (DFT) computation results explained these physical properties. We anticipate that more π-extended functional molecules can be developed from naphthalic anhydride by our method.
Key words: benzo[g]chrysene, triphenylene, imide, discotic liquid crystal, fluorescence, Suzuki-Miyaura cross-coupling, Scholl reaction
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