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Issue 22, 2011
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Carboxylic acid functionalized imidazolium salts: sequential formation of ionic, zwitterionic, acid-zwitterionic and lithium salt-zwitterionic liquid crystals

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Abstract

Carboxylic acid functionalized imidazolium salts, their deprotonated carboxylate zwitterions and acid-zwitterion adducts have been studied, and are denoted as [N-Cn,N′-CO2H-Im][X] (Cn = CnH2n+1; X = Cl, Br, BF4 and PF6), [N-Cn,N′-CO2-Im] and [(N-Cn,N′-CO2-Im)2H][anion] (anion = NO3 and Br), respectively. Crystal structures of [N-C10,N′-CO2-Im]Br and [N-Cn,N′-CO2-Im]·2H2O studied by single-crystal X-ray diffraction indicate that carboxylic acid and carboxylate groups provide rich C–H⋯Br and/or C–H⋯O hydrogen bonding interactions in the construction of helical architecture. Except the PF6 salts, all the other types of compounds with long alkyl chains exhibit wide range SmA mesophase. Zwitterions and adducts represent two new classes of imidazolium based liquid crystals. The adducts [(N-Cn,N′-CO2-Im)2H]Br display wider mesophase range than the other series of compounds. Mixtures of lithium salts with zwitterion of [N-C10,N′-CO2-Im] form lithium containing liquid crystals at or near room temperature. A preliminary study of the mixtures of [N-C10,N′-CO2-Im]/[LiClO4] (3 : 1) and [N-C10,N′-CO2-Im]/[LiBF4] (3 : 1) placed between two ITO glasses shows that lithium ion conductivities increase upon increasing the temperature in the mesophase, yet decrease beyond the clearing temperature.

Graphical abstract: Carboxylic acid functionalized imidazolium salts: sequential formation of ionic, zwitterionic, acid-zwitterionic and lithium salt-zwitterionic liquid crystals

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Publication details

The article was received on 08 Feb 2011, accepted on 25 Mar 2011 and first published on 03 May 2011


Article type: Paper
DOI: 10.1039/C1JM10580A
Citation: J. Mater. Chem., 2011,21, 8110-8121
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    Carboxylic acid functionalized imidazolium salts: sequential formation of ionic, zwitterionic, acid-zwitterionic and lithium salt-zwitterionic liquid crystals

    J. C. Y. Lin, C. Huang, Y. Lee, K. Lee and I. J. B. Lin, J. Mater. Chem., 2011, 21, 8110
    DOI: 10.1039/C1JM10580A

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