物理化学学报 >> 1993, Vol. 9 >> Issue (06): 795-801.doi: 10.3866/PKU.WHXB19930614

研究论文 上一篇    下一篇

二种新型有侧向取代基液晶化合物结构及性质

杨清传; 戴胜; 周洪兵; 周其凤; 唐有祺   

  1. 北京大学化学系，北京 100871
  • 收稿日期:1992-05-09 修回日期:1992-07-10 发布日期:1993-12-15
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The Molecular and Crystal Structures and Thermal Properties of the Mesogenic 2,5-BIS(4-Ethylbenzoyl) Oxystyrene and 2,5-BIS(4-Methoxybenzoyl) Oxybenzaldehyde

Yang Qing-Chuan; Dai Sheng; Zhou Hong-Bing; Zhou Qi-Feng; Tang You-Qi   

  1. Department of Chemistry, Peking University, Beijing 100871
  • Received:1992-05-09 Revised:1992-07-10 Published:1993-12-15
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摘要： 用X射线单晶衍射方法测定了液晶化合物2,5-双(4-乙基苯甲酰氯基)苯乙烯(Ⅰ)和2,5-双(4-甲氧基苯甲酰氧基)苯甲醛(Ⅱ)的单晶结构和分子结构. 化合物Ⅰ属三斜晶系, 空间群P(1), 晶胞参数: a=0.9356(6) nm, b=0.9842(6) nm, c=1.3357(8) nm, α=108.68(5)°, β=105.67(5)°, γ=96.36(5)°, Z=2; 化合物Ⅱ属单斜晶系, 空间群P_n, 晶胞参数: a=0.9109(2) nm, b=0.9187(3) nm, c=2.3166(8) nm, β=93.93(2)°, Z=4. 在化合物Ⅰ和Ⅱ晶体中, 分子均呈伸展构象, 分子中的三个苯环平面取向相互成一定的夹角. 分子在晶胞中治其伸展方向相互平行堆积, 相邻分子的侧链基团(乙烯基, 甲醛基)以较短的分子间距0.47-0.56 nm相向排列. 化合物Ⅰ晶胞中分子堆积密度比化合物Ⅱ松散. 晶体结构分析结果合理地解释了化合物Ⅰ的高聚合性.

关键词: 侧链型液晶化合物, 晶体结构, 分子结构

Abstract: The crystal and molecular structures of the mesogenic 2,5-bis-(4-ethylbenzoyl) oxystyrene(Ⅰ) and 2,5-bis(4-methoxybenzoyl) oxybenzaldehyde (Ⅱ) have been determined by single crystal X-ray diffraction methods. Both compound Ⅰ and compound Ⅱ are liquid crystalline.
Crystal data:
Compound Ⅰ, C_2H_5·C_6H_4·COO·C_6H_3(CH:CH_2)·OOC·C_6H_4·C_2H_5, triclinic, space group P(1) (No.2), a=0.9356(6), b=0.9842(6), c=1.3357(8) nm, α=108.68(5)°, β=105.67(5)°, γ=96.36(5)°, Z=2; Compound Ⅱ, H_3CO·C_6H_4·COO·C_6H_3(CHO)·OOC·C_6H_4·OCH_3, monoclinic, space group Pn (No.7), a=0.9109(2), b=0.9187(3), c=2.3166(8) nm, β=93.93(2)°, Z=2.
In both crystals, the molecules take fully extended form with the long molecular axes of 2.27 nm for compound I and of 2.22 nm for compound II. The molecules of these two compounds are not plate-like but rather rod-like. The middle phenyl rings of the molecules rotate from the other two phenyl rings by 86.3° and 135.8 for compound I; and by 84.9° and 84.7° for compound II. All molecules are arranged parallel along their long axes in the crystals.
Compound I is a polymerizalbe monomer, it easily forms high molecular weight polymer upon heating without any initiators at about 140 ℃. Its high polymerizability might be explained by the fact that the molecules are packed such that the lateral vinyl groups of neighbouring molecules are closely correlated with a distance of only 0.47 nm and the energy-favorable parallel molecular arrangement, which is similar to the arrangment of the mesogens in its polymer.

Key words: Liquid crystal compound with laterally substituted mesogen, Crystal and molecular structure