The synthesis and characterization for a series of symmetrical 1,3-dialkylimidazolium salts with different chain lengths and counter anions together with their 1-alkylimidazole precursors are described. Liquid crystal (LC) properties of these salts are studied. Images under polarizing optical microscopy show focal conic texture together with homeotropic domains. A smectic A mesophase, typical for rod-like imidazolium salts, is assigned. Studies from powder X-ray diffraction suggest a lamellar structure with noninterdigitated monolayer arrangement for the LC salts in the mesophase. In addition, a short note on the structure and property relationship for rod-like, disc-or fan-like, and dendritic shaped imidazolium ionic liquid crystals (ImILCs) forming smectic, columnar, and cubic phase is briefly summarized. A comparison of minimum alkyl chain length needed for 1-alkyl-3-methyl and symmetrical 1,3-dialkyl ImILCs to exhibit LC behavior is addressed.
A series of N,N 0 -dihexylbenzimidazolium salts with three anions, Br À , I À and PF 6 À , have been synthesized and characterized by single-crystal X-ray diffraction. These salts exhibit some anionindependent structural properties, which include the U-shaped conformation, the interdigitated bilayer packing and the thickness of the ionic layer. These salts also show anion-controlled inter-headgroup interactions; the benzimidazolium headgroups form a dimer motif via p-p interaction when the anions are Br À and I À , however, a 1D catemer motif is formed via C-H/p interactions when the anion is PF 6 À . The influence of the anion sizes on the arrangement of the benzimidazolium headgroups and the alkyl chains is discussed, with particular reference to the areas of the four adjacent headgroups and the degree of the alkyl chain tilting angles.
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