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Columnar and Smectic Liquid Crystals Based on Crown Ethers
Author(s) -
Steinke Nelli,
Frey Wolfgang,
Baro Angelika,
Laschat Sabine,
Drees Christina,
Nimtz Manfred,
Hägele Constanze,
Giesselmann Frank
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200500903
Subject(s) - crystallography , crown ether , mesogen , liquid crystal , small angle x ray scattering , mesophase , ether , side chain , chemistry , phase (matter) , alkoxy group , materials science , organic chemistry , liquid crystalline , alkyl , ion , scattering , physics , optoelectronics , optics , polymer
Unsymmetrical benzo[15]crown‐5 ethers 5 with one lateral ortho ‐terphenyl unit bearing alkoxy side chains of varying chain lengths (C5–C14) were prepared from 3,4‐dialkoxyphenylbromides 2 . Complexation with metal salts MX (M = Na, Cs) afforded the corresponding derivatives MX ⋅5 . The uncomplexed crown ethers 5 h and 5 i , with dodecyloxy and tetradecyloxy side chains, respectively, exhibit liquid crystalline properties. In the series of complexed crown ethers, liquid crystal properties appeared as early as NaI ⋅5 f with C 9 H 19 side chains. Whereas the uncomplexed 5 h , i form smectic mesophases, the complexed NaI ⋅5 g and NaI ⋅5 h exhibit textures typical of columnar mesophases. These results were supported by X‐ray diffraction measurements (WAXS, SAXS), which revealed smectic ( 5 h , i ), rectangular columnar (NaI ⋅5 g ), and hexagonal columnar (NaI ⋅5 h ) mesophases. As the liquid crystalline phase might retain packing features of the solid‐state structure, single‐crystal X‐ray analyses were also performed for some of the uncomplexed and complexed crown ether derivatives. The complex NaI 3 ⋅5 a displays a sandwich‐type structure, with the crown ether cores mutually antiperiplanar and maintaining an almost perfect crown conformation. In contrast, non‐mesogenic uncomplexed crown ether 5 b displays a layer‐type ordering in the solid phase.