ABSTRACT Here, laterally monofluorinated heterocyclic mesogenic compounds, 2-[4-[2-[4-alkoxy-phenyl]-ethynyl]-3-fluorophenyl]-benzoxazole derivatives (nPEFPBx) with hydrogen, methyl and nitro terminal substituents (coded as nPEFPBH, nPEFPBM and nPEFPBN, respectively) at 5-position of benzoxazole unit, are synthesised and characterised. They display enantiotropic nematic mesophase with mesophase ranges of 22–30°C and 32–39°C on heating and cooling for nPEFPBH, 67–92°C and 87–115°C for nPEFPBM, 31–84°C and 42–51°C for nPEFPBN (n < 7), respectively, which is better than nonfluorinated and laterally difluorinated analogous . Improved mesophase property is ascribed to reduced dipole moment resulting from introduction of lateral fluorine atom in opposite direction of polar benzoxazole unit. This indicates that monofluorine substituent contributes to improve nematic mesophase for benzoxazole-terminated mesogenic compounds. In addition, the compounds nPEFPBx have high birefringence of 0.513–0.650 because of large π-conjugated mesogenic core composed of benzene, ethynyl and benzoxazole groups, which suggests a possible application in liquid crystal mixture to enhance birefringence. Meanwhile, except nPEFPBN, the compounds nPEFPBx show intense photoluminescence emission at 406–407 nm in methylene chloride solution with exciting them at absorption maxima. Graphic Abstract

中文翻译：

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通过苯并恶唑封端的介晶化合物上的侧氟取代基改善介晶性质

摘要这里，横向单氟化杂环介晶化合物，2-[4-[2-[4-烷氧基-苯基]-乙炔基]-3-氟苯基]-苯并恶唑衍生物 (nPEFPBx) 具有氢、甲基和硝基末端取代基（编码为 nPEFPBH ，分别为 nPEFPBM 和 nPEFPBN）在苯并恶唑单元的 5 位，被合成和表征。它们显示出对映向列中间相，nPEFPBH 加热和冷却时中间相范围为 22–30°C 和 32–39°C，nPEFPBM 为 67–92°C 和 87–115°C，31–84°C 和 42–51 nPEFPBN (n < 7) 分别为 °C，优于非氟化和侧向二氟化类似物。中间相性能的改善归因于在极性苯并恶唑单元的相反方向引入侧向氟原子导致偶极矩降低。这表明单氟取代基有助于改善苯并恶唑封端的介晶化合物的向列中间相。此外，由于由苯、乙炔基和苯并恶唑基团组成的大π共轭介晶核，化合物nPEFPBx具有0.513-0.650的高双折射，这表明可能在液晶混合物中应用以增强双折射。同时，除 nPEFPBN 外，化合物 nPEFPBx 在二氯甲烷溶液中在 406-407 nm 处显示出强烈的光致发光发射，并在吸收最大值处激发它们。图形摘要 这表明可能应用于液晶混合物以增强双折射。同时，除 nPEFPBN 外，化合物 nPEFPBx 在二氯甲烷溶液中在 406-407 nm 处显示出强烈的光致发光发射，并在吸收最大值处激发它们。图形摘要 这表明可能应用于液晶混合物以增强双折射。同时，除 nPEFPBN 外，化合物 nPEFPBx 在二氯甲烷溶液中在 406-407 nm 处显示出强烈的光致发光发射，并在吸收最大值处激发它们。图形摘要