Mesogenic pyrazaboles:: Synthesis, properties, and structural characterization

被引:61
作者
Barberá, J [1 ]
Giménez, R [1 ]
Serrano, JL [1 ]
机构
[1] Univ Zaragoza, Fac Ciencias, Consejo Super Invest Cient, Inst Ciencia Mat,Dept Quim Organ, E-50009 Zaragoza, Spain
关键词
D O I
10.1021/cm991120c
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
A series of disklike compounds containing the pyrazabole ring have been prepared by reaction of 3,5-diarylpyrazoles and borane. The aryl groups are benzene rings substituted with one, two, or three hexyloxy, decyloxy, or tetradecyloxy groups. The study of the liquid crystalline properties shows that the optimal chain length to generate mesomorphism in this family of compounds is 10 carbon atoms. Thus, three compounds with decyloxy substituents show hexagonal columnar mesophases at relatively low temperatures. For two of them bearing 10 and 12 decyloxy chains the mesophase remains stable at room temperature for long periods of time, as confirmed by X-ray diffraction. The crystal structure of the nonmesogenic homologue 1,3,5,7-tetrakis(4'-methoxyphenyl)pyrazabole has been determined by X-ray diffraction. The structure analysis reveals that the pyrazabole cycle adopts a slightly twisted boat conformation. In the crystal packing its molecules stack in columns, which is consistent with the fact that the homologous compounds with long chains generate columnar mesophases.
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页码:481 / 489
页数:9
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