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Effect of counter ions on the mesogenic ionic N-phenylpyridiniums


Two series of ILCs derived from N-phenylpyridinium 1-2 were prepared and their mesomorphic properties were investigated. A versatile and effective method was developed to prepare these ionic compounds 2-X from their precursor chloride 2-Cl. X-ray crystal-structure analyses of three single crystals revealed that a sandwiched head-to-head or bilayer lamellar structure induced by H-bonds in the solid state was observed. The anion was proximity intercalated near the head group. Weak H-bonds were induced and attributed to the formation of mesophases. The type of counter anions has a significant influence on the stability of the mesophase; ΔTSmA = 221.3 (2-Cl) > 213.1 (2-SCN) > 173.9 (2-BF4) > 85.4 (2-RSO3) > 63.8 (2-PF6) > 41.4 C (2-OTf) for all derivatives with n = 12. The compound 2-BF4 (n = 16) has a widest temperature range of SmA phase (i.e. ΔTSmA = 234.3 C), significantly broader than those of other reported ILCs. Also compound 2-NTf2 (n = 14) was the first phenylpyridinium-based ILC and compound 2-SCN (n = 16) was indeed the room temperature ILC. The XRD experiments confirmed the structure of SmA phase and it showed a strong dependence of bilayer structure with various anions. A linear correlation plot (R2 = 0.9643) of the clearing temperatures of compounds 2-X with the calculated effective radius (Reff) of the anions was obtained.

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Publication details

The article was received on 23 Feb 2018, accepted on 06 Apr 2018 and first published on 09 Apr 2018

Article type: Paper
DOI: 10.1039/C8CE00286J
Citation: CrystEngComm, 2018, Accepted Manuscript
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    Effect of counter ions on the mesogenic ionic N-phenylpyridiniums

    C. K. Lai, R. Wang and G. Lee, CrystEngComm, 2018, Accepted Manuscript , DOI: 10.1039/C8CE00286J

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