The synthesis and transition temperatures of some 4′-alkyl- and 4′-alkoxy-4-cyano-3-fluorobiphenyls
作者:
GeorgeW. Gray,
Michael Hird,
AndersonD. Ifill,
WendyE. Smith,
KennethJ. Toyne,
期刊:
Liquid Crystals
(Taylor Available online 1995)
卷期:
Volume 19,
issue 1
页码: 77-83
ISSN:0267-8292
年代: 1995
DOI:10.1080/02678299508036722
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
The preparation of 4′-alkyl- and 4′-alkoxy-4-cyano-3-fluorobiphenyls by four different procedures is described and discussed; the best method involves palladium(0)-catalysed coupling of arylboronic acids and 4-bromo-(or 4-iodo-)-2-fluorobenzonitrile. The effects on transition temperatures of fluoro substitutionorthoto the terminal cyano group in biphenyls are compared with the effects in other terminal cyano compounds and in mesogens without a terminal cyano group. The effect of theorthofluoro substituent in 4-cyanobiphenyls is particularly large and is probably due to the severe disruption of antiparallel correlations; the depressions of the smectic A and nematic phase stabilities are similar which suggests that, as for compounds with alkyl or alkoxy terminal groups, the fluoro substituent at the 3-position has a tendency to enhance smectic character, but this is offset by the molecular broadening it causes.
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