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- 2018
含氟吡咯联苯类液晶的合成及其光学性能研究
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Abstract:
本文设计了一系列基于含氟吡咯衍生物为末端结构的新型联苯类液晶分子，其关键中间体3,4-二氟-1-(4-碘苯基)吡咯通过环化、脱氟化氢芳构化两步反应获得. 进一步甲酰化、成肟、脱水氰化得到侧位衍生的2-氰基-3,4-二氟-1-(4-碘苯基)吡咯. 将它们与联苯类液晶砌块芳基硼酸偶联，得到目标产物. 采用核磁共振氢谱（1H NMR）、核磁共振氟谱（19F NMR）、质谱（MS）、高分辨质谱（HRMS）或元素分析（EA）对新分子进行了结构表征，通过热差扫描量热仪（DSC）、偏光显微镜（POM）、热重分析仪（TGA）、紫外和荧光检测其物理性质和液晶性能，结果表明，这些新分子具有典型的液晶相，以及良好的热稳定性. 含氰基的液晶分子具有较高的荧光强度. 计算结果表明，含氟液晶分子的偶极距大于相应无氟液晶分子的偶极距，偶极距的增大有利于提高液晶分子的的介电常数.这些氟和氰基取代的吡咯作为一类新的砌块，为将来合成偶极距大的液晶新分子提供了实验依据.
： A series of new Liquid crystals (LCs) based on fluorinated pyrrole derivatives as skeleton was designed. The key intermediate, 3, 4-difluoro-1-(4-iodophenyl)-1H-pyrrole was prepared by cyclization, dehydrofluorination arylation procedure. The intermediate was treated by formylation, dehydration and cyaniding reaction to yield 3,4-difluoro-1-(4-iodophenyl)-1H-pyrrole-2-carbonitrile. Further, these pyrrole derivatives coupled with substituted phenylboronic acid by Suzuki coupling reaction to give the target products. These new molecules were characterized by Nuclear magnetic resonance ( 1H NMR，19F NMR), Mass spectrum (MS), high resolution mass spectrometry (HRMS) or Elemental analysis (EA). Their liquid crystal phases were investigated by Polarizing optical microscope (POM) and Differential scanning calorimeter (DSC). Thermal stabilities were determined by Thermal gravimetric analysis (TGA). The absorption and photoluminescence spectra of these compounds were analyzed by UV/Vis. These new molecules exhibit typical mesomorphic behaviors and good thermal stability. Compounds with cyano group on the fluoropyrrole display stronger fluorescence intensity. Based on theoretical calculations, the fluorinated compounds have the larger dipole moments, which is in favour of improving the dielectric anisotropy. As a serious of new liquid crystal building blocks, these pyrrole derivatives substituted by fluorine atoms and cyano groups provided experimental basis for synthesis of large dipole moment molecules of liquid crystals in the future
