Change of the lateral chain conformation in the solid and the nematic phase in laterally substituted nematogens
作者:
F. Perez,
P. Berdagué,
P. Judeinstein,
J.P. Bayle,
H. Allouchi,
D. Chasseau,
M. Cotrait,
E. Lafontaine,
期刊:
Liquid Crystals
(Taylor Available online 1995)
卷期:
Volume 19,
issue 3
页码: 345-352
ISSN:0267-8292
年代: 1995
DOI:10.1080/02678299508031991
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
A new homologous series of 4-(4′-ethoxybenzoyloxy)-2-alkoxy-4′-(4-butoxysalicylaldimine)-azobenzenes has been synthesized. These compounds contain four rings in the main core and a lateral alkoxy branch on one of the inner rings and present enantiotropic nematic properties. The X-ray crystal structure (MoKαradiation, λ = 0.7071 Å, graphite monochromator) of 4-(4′-ethoxybenzoyloxy)-2-butoxy-4′-(4-butoxysalicylaldimine)azobenzene was investigated (T= 293K,R= 0.059 for the 2855 observed reflections). This compound (C36H39N3O6) crystallizes in the monoclinic system with C2/c space group; (Z= 8);a= 28.052(7) A,b= 7.545(4) Å,c= 33.823(7) Å and β = 112.70(1)°. There is a strong chelated hydrogen bond between the OH group and the neighbouring nitrogen atom engaged in the imine bridge. In the solid state, the molecule is roughly linear with a 31 Å length. The lateral butoxy chain is quasi-perpendicular to the long axis of the main core. The crystal cohesion is due to numerous Van der Waals interactions. At the solid to nematic transition, a change in the conformation of the lateral chain occurs from an alltrans-conformation to one involving acis-conformation in the first part of the lateral chain. This change can be monitored by the evolution of the13C chemical shift of the OCH2belonging to the lateral alkoxy chain.
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