含氟吡咯联苯类液晶的合成及其光学性能研究
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摘要
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.通过进一步甲酰化、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.将其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)和元素分析(EA)对新分子进行了结构表征,通过热差扫描量热分析(DSC)、偏光显微镜(POM)观察、热重分析(TGA)、紫外和荧光分析等研究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(多为近晶相)以及良好的热稳定性,分解温度在288.3～402.0℃.含氰基的液晶分子具有较高的荧光强度.基于理论计算,含氟液晶分子的偶极距(5.804 9～7.805 9 D)大于相应无氟液晶分子的偶极距(1.681 5～3.554 4 D),偶极距的增大有利于提高液晶分子的介电常数.这些以氟基和氰基取代的吡咯作为一类新的砌块,为将来合成大偶极距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)-1 H-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)-1 H-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(1 H NMR,19 F 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(most of them show smectic phase) and good thermal stability(decomposition temperature 288.3-402.0 ℃). Compounds with cyano group on the fluoropyrrole display stronger fluorescence intensity. Based on theoretical calculations,the fluorinated compounds have the larger dipole moments(5.804 9-7.805 9 D) than the compounds without fluorine(1.681 5-3.554 4 D),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.
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)-1 H-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)-1 H-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(1 H NMR,19 F 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(most of them show smectic phase) and good thermal stability(decomposition temperature 288.3-402.0 ℃). Compounds with cyano group on the fluoropyrrole display stronger fluorescence intensity. Based on theoretical calculations,the fluorinated compounds have the larger dipole moments(5.804 9-7.805 9 D) than the compounds without fluorine(1.681 5-3.554 4 D),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.
引文
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[18] FELLER D. An ab-initio study of the magnetic hyperfine properties of difluoride ion(F2-(2Σu+))[J]. Journal of Chemical Physics,1990,93(1):579-589.
[2] KIRSCH P,BREMER M. Nematic liquid crystals for active matrix displays:Molecular design and synthesis[J]. Angewandte Chemie International Edition,2000,39(23):4216-4235.
[3] HIRD M. Fluorinated liquid crystals-properties and applications[J]. Chemical Society Reviews,2007,36:2070-2095.
[4] GRAY G W,HIRD M,TOYNE K J. Some developments in the synthesis of liquid crystal materials[J]. Molecular Crystals&Liquid Crystals,1991,204(1):91-110.
[5] HU K,CHEN P,WENG Q,et al. Improved mesophase stability of benzoxazole derivatives via dipole moment modification[J]. Liquid Crystals,2015,42(11):1643-1653.
[6] GRAY G W,HIRD M,LACEY D,et al. The synthesis and transition temperatures of some fluoro-substituted 4-cyanophenyl and 4-cyanobiphenyl-4'-yl 4-pentyl-and 4-butoxy-benzoates[J]. Molecular Crystals&Liquid Crystals,1989,172(1):165-189.
[7] MCDONNELL D G,RAYNES E P,SMITH R R A. Dipole moments and dielectric properties of fluorine substituted nematic liquid crystals[J]. Liquid Crystals,1989,6(5):515-523.
[8] GOODBY J W,MANDLE R J,DAVIS E J,et al. What makes a liquid crystal? The effect of free volume on soft matter[J]. Liquid Crystals,2015,42(5/6):593-622.
[9] GRAY G W,HIRD M,TOYNE K J,et al. The synthesis and transition temperatures of some lateral monofluorosubstituted 4,4″-dialkyl-and 4,4″-alkoxyalkyl-1,1':4',1″-terphenyls[J]. Molecular Crystals&Liquid Crystals,1991,195(1):221-237.
[10] GRAY G W,HARRISON K J,NASH J A. Wide range nematic mixtures incorporating 4″-n-alkyl-4-cyano-pterphenyls[J]. Journal of the Chemical Society Chemical Communications,1974,11(11):431-432.
[11] GOTO Y,KITANO K. Trifluorobenzene derivatives and liquid crystal compositions containing the same:EP0387032 B1[P]. 1993-06-16.
[12] DEMUS D,GOTO Y,SAWADA S,et al. Trifluorinated liquid crystals for TFT displays[J]. Molecular Crystals&Liquid Crystals,2006,260(1):1-21.
[13] GLENDENNING M E,GOODBY J W,HIRD M,et al.The synthesis and mesomorphic properties of 4,4''-dialkyl-2,2',3-and 2,2',3'-Trifluoro-1,1':4',1''-terphenyls for high dielectric biaxiality ferroelectric liquid crystal mixtures[J]. Journal of the Chemical Society Perkin Transactinos,2000,2(1):27-34.
[14] PULITH D,TARUMI K. Advanced liquid crystals for television[J]. Journal of Materials Chemistry,2004,14(8):1219-1227.
[15] GRAY G W,HIRD M,TOYNE K J,et al. Thesynthesis and transition temperatures of some fluoro-substituted 4-cyanophenyl and 4-cyanobiphenyl-4'-yl 4-pentyl-and4-butoxy-benzoates[J]. Molecular Crystals&liquid Crystals,1989,172(1):165-189.
[16]李惠娟,刘培炼,陈虹任,等.含氟吡咯、吡咯烷液晶分子的合成与性能研究[J].华南师范大学学报(自然科学版),2014,46(3):75-81.LI H J,LIU P L,CHEN H R,et al. Synthesis and mesomorphic studies on liquid crystals with fluorinated pyrrole,and pyrrolidine[J]. Journal of South China Normal University(Natural Science Edition),2014,46(3):75-81.
[17]陈刚,孙士祥,刘浩,等. TN型液晶双折射率的简易测量方法[J].现代显示,2011,22(10):32-34.CHEN G,SUN S X,LIU H,et al. Simple approach for measurement of birefringence of TN liquid crystal[J].Advanced Display,2011,22(10):32-34.
[18] FELLER D. An ab-initio study of the magnetic hyperfine properties of difluoride ion(F2-(2Σu+))[J]. Journal of Chemical Physics,1990,93(1):579-589.