2,4,6-Trimethylpyridinium perchlorate: Polar properties and correlations with molecular structure of organic–inorganic hybrid crystal |
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Authors: | M Wojta A Gagor O Czupiski A Pietraszko R Jakubas |
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Institution: | aFaculty of Chemistry, University of WrocŁaw, Joliot–Curie 14, 50–383 WrocŁaw, Poland;bW. Trzebiatowski Institute of Low Temperature and Structure Research PAS, P.O. box 1410, 50–950 WrocŁaw, Poland |
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Abstract: | (CH3)3C5H2NH]ClO4] has been synthesized and characterized by X-ray (at 344, 245, 180 and 115 K), calorimetric, dilatometric, dielectric and pyroelectric measurements. At room temperature the crystal structure is polar, space group Pmn21. It consists of discrete disordered ClO4]- anions and ordered trimethylpyridinium cations giving the 3D network of hydrogen bonds. The compound reveals a rich polymorphism in the solid state. It undergoes four solid–solid phase transitions: from phases I to II at 356/327 K (heating/cooling), II→III at 346/326, III→IV at 226 K and IV→V at 182/170 K. (CH3)3C5H2NH]ClO4] reveals a strong pyroelectric response over a wide temperature region (phases III, IV and V) with the spontaneous polarization changes (ΔPs) of the order of . The spontaneous polarization is irreversible over all the polar phases, however, the magnitude of the ΔPs in the vicinity of the phase transitions is characteristic of compounds with the ferroelectric order. The molecular mechanism of the successive phases transitions in the studied crystal is proposed. |
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Keywords: | Perchlorate Phase transition X-ray Dielectric Pyroelectric |
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