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Title: Influence of the counteranion on the ability of 1-dodecyl-3-methyltriazolium ionic liquids to form mesophases

The influence of the counteranion on the ability of the mesogenic cation 1-methyl-3-dodecyl-triazolium to form mesophases is explored. To that avail, salts of the cation with anions of different size, shape, and hydrogen bonding capability such as Cl, Br, I, I3, PF6, and Tf2N [bis(trifluorosulfonyl)amide] were synthesized and characterized. The crystal structures of the bromide, the iodide, and the triiodide reveal that the cations form bilayers with cations oriented in opposite directions featuring interdigitated alkyl tails. Within the layers, the cations are separated by anions. The rod-shaped triiodide anion forces the triazolium cation to align with it in this crystal structure but due to its space requirement reduces the alkyl chain interdigitation which prevents the formation of a mesophase. Rather the compound transforms directly from a crystalline solid to an (ionic) liquid like the analogous bis(trifluorosulfonyl)amide. In contrast, the simple halides and the hexafluorophosphate form liquid crystalline phases. As a result, their clearing points shift with increasing anion radius to lower temperatures.
Authors:
 [1] ;  [1] ;  [1] ;  [2]
  1. Ruhr-Univ. Bochum, Bochum (Germany)
  2. Ruhr-Univ. Bochum, Bochum (Germany); Ames Lab., Ames, IA (United States); Iowa State Univ., Ames, IA (United States)
Publication Date:
OSTI Identifier:
1239141
Report Number(s):
IS-J--8603
Journal ID: ISSN 1528-7483
Grant/Contract Number:
AC02-07CH11358
Type:
Accepted Manuscript
Journal Name:
Crystal Growth and Design
Additional Journal Information:
Journal Volume: 15; Journal Issue: 2; Journal ID: ISSN 1528-7483
Publisher:
American Chemical Society
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE Advanced Research Projects Agency - Energy (ARPA-E)
Country of Publication:
United States
Language:
English
Subject:
ionic liquids; liquid crystals; ionic liquid crystals; structure analysis