新型吡啶环液晶化合物的合成及性能

doi:10.11944/j.issn.1000-0518.2016.05.150314

摘要/Abstract

摘要：

以2-溴-5-吡啶甲醛和5-溴-2-吡啶甲醛为起始原料,合成出4种新型含吡啶环二联芳基和三联芳基化合物,总收率20%~30%。热性能研究结果表明,二联芳基化合物未呈现出液晶相,而三联芳基化合物在加热和冷却过程中均表现向列相液晶态,且当氮原子位于正丁基的间位时,其与不含氮原子的三联苯化合物(2c)相比,熔点降低了11.7 ℃,清亮点升高6.3 ℃,液晶相区拓宽了18 ℃,表现出了良好的热性能。光电性能测试结果表明,用吡啶环替代苯环后,化合物的光学各向异性值均较参比化合物(1c或2c)增大;当N原子位于正丁基的邻位的化合物,介电各向异性值较参比化合物增大,且液晶的阈值电压、饱和电压均降低。通过对三环同分异构体化合物的不同构象能量态的计算分析,解释了介电各向异性的变化规律。

关键词: 吡啶, 合成, 介电各向异性, 液晶

Abstract:

Four new bi-aryl and tri-aryl compounds containing pyridine ring were synthesized by using 2-bromopyridine-5-carbaldehyde and 5-bromopyridine-2-carbaldehyde as starting materials. The total yields are around 20%~30%. Thermal analysis results show that the bi-aryl compounds exhibit no mesophase, while the tri-aryl compounds exhibit nematic phase during both heating and cooling process. For the compound with nitrogen atoms located at the ortho position of n-butyl group, its melting point is decreased by 11.7 ℃ and its clearing point is increased by 6.3 ℃, and the mesophase range is broadened by 18 ℃, compared with the reference terphenyl compound(2c). Optic-electronic property analysis results show that the birefringence is improved when one of benzene ring in the reference compounds(1c or 2c) is replaced by with pyridine ring. Besides, the dielectric anisotropy values are increased when the nitrogen atoms locate at ortho position of n-butyl, and the threshold voltage and saturation voltage are decreased. The rule of the dielectric anisotropy variation is explained by conformation energy calculation of three-ring isomers.

Key words: pyridine ring, synthesis, dielectric anisotropy, liquid crystal

莫玲超, 李建, 郭兆琦, 李娟利, 胡明刚, 安忠维. 新型吡啶环液晶化合物的合成及性能[J]. 应用化学, 2016, 33(5): 542-548.

MO Lingchao, LI Jian, GUO Zhaoqi, LI Juanli, HU Minggang, AN Zhongwei. Synthesis and Properties of Novel Liquid Crystal Compounds Containing Pyridine Ring[J]. Chinese Journal of Applied Chemistry, 2016, 33(5): 542-548.

参考文献

[1]	Detlef P,Kazuaki T. Advanced Liquid Crystals for Television[J]. J Mater Chem,2004,14(8):1219-1227.
[2]	Gray G W,Hird M,Lacey D,et al.The Synthesis and Transition Temperatures of Some 4,4″-Dialkyl-1,1'-4',1″-Terphenyl and 4,4″-Alkoxyalkyl-1,1'-4',1″-Terphenyl with 2,3-Difluoro or 2',3'-Difluoro Substituents and of Their Biphenyl Analogs[J]. J Chem Soc,Perkin Trans 2,1989,1989(12):2041-2053.
[3]	Reiffenrath V,Finkenzeller U,Poetsch E,et al.Synthesis and Properties of Liquid Crystalline Materials with High Optical Anisotropy[J]. SPIE,1990,1257:84-94.
[4]	Kirsch P,Reiffenrath V,Bremer M. Nematic Liquid Crystals with Negative Dielectric Anisotropy: Molecular Design and Synthesis[J]. Synlett,1999,1999(4):389-396.
[5]	Kirsch P,Tarumi K. A Novel Type of Liquid Crystals Based on Axially Fluorinated Cyclohexane Units[J]. Angew Chem lnt Ed,1998,37(4):484-489.
[6]	Kirsch P,Heckmeier M,Tarumi K. Design and Synthesis of Nematic Liquid Crystals with Negative Dielectric Anisotropy[J]. Liq Cryst,1999,26(3):449-452.
[7]	Chen Y,Peng F L,Yamaguchi T,et al.High Performance Negative Dielectric Anisotropy Liquid Crystals for Display Applications[J]. Crystals,2013,3(3):483-452.
[8]	Gauza S,Jiao M,Wu S T,et al.High Birefringence and Low Viscosity Negative Dielectric Anisotropy Liquid Crystals[J]. Liq Cryst,2008,35(12):1401-1408.
[9]	LI Jian,DU Weisong,HU Minggang,et al.Molecular Design and Synthesis of New Ethynyl-bridged Bond Liquid Crystal Compounds[J]. Acta Chim Sin,2008,66(23):2631-2636.(in Chinese) 李建,杜渭松,胡明刚,等. 新型的含乙炔桥键液晶分子设计与合成[J]. 化学学报,2008,66(23):2631-2636.
[10]	Kirsch P,Maillard D. Liquid Crystals Based on Axially Fluorinated 1,3-Dioxanes:Synthesis, Properties and Computational Study[J]. Eur J Org Chem,2006,2006(15):3326-3331.
[11]	Araki K,Yamamoto T,Tanaka R,et al.Stereoselective Synthesis and Physicochemical Properties of Liquid-Crystal Compounds Possessing a trans-2,5-Disubstituted Tetrahydropyran Ring with Negative Dielectric Anisotropy[J]. Chem Eur J,2015,21(6):2458-2466.
[12]	Gotoh Y. Synthesis and Properties of Novel Negative Dielectric Liquid Crystal Compounds with a Tetrahydropyran Ring[J]. Mol Cryst Liq Cryst,2011,542(1):16-27.
[13]	Fujita A, Masukawa1 T, Kawasaki1 S, et al. New Liquid Crystalline Tetrahydropyran Derivatives[J]. Mol Cryst Liq Cryst,2009,509(1):245-262.
[14]	Burrow M P,Gray G W,Lacey D,et al.The Synthesis and Liquid Crystal Properties of Some 2,5-Disubstituted Pyridines[J]. Liq Cryst,1988,3(12):1643-1653.
[15]	Reiffenrath V,Bremer M. New Materials for Liquid Crystal Displays:Structure-Property Relationship of 2-Fluoropyridines[J]. Angew Chem Int Ed,1994,33(13):1386-1389.
[16]	Bremer M,Kirsch P,Klasen M,et al.The TV in Your Pocket:Development of Liquid-Crystal Materials for the New Millennium[J]. Angew Chem Int Ed,2013,52(34):8880-8896.
[17]	MO Lingchao,LIANG Xiaoqin,AN Zhongwei,et al.Synthesis and Properties of Lateral Multi-fluorine Sibstotited Internal Alkynes Liquid Crystals[J]. Chinese J Appl Chem,2013,30(8):861-866(in Chinese). 莫玲超,梁晓琴,安忠维,等. 侧向多氟取代二芳基乙炔类液晶的合成及性能[J]. 应用化学,2013,30(8):861-866.