Structural characterization, thermal, dielectric, vibrational properties and molecular motions in |
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Authors: | A Piecha R Jakubas A Pietraszko J Baran W Medycki D Kruk |
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Institution: | aFaculty of Chemistry, University of Wrocław, Joliot-Curie 14, 50-383 Wrocław, Poland;bInstitute of Low Temperature and Structure Research, PAS, Okólna 2, 50-950 Wrocław, Poland;cInstitute of Molecular Physics, PAS, M. Smoluchowskiego 17, 60-179 Poznań, Poland;dInstitute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland |
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Abstract: | C3N2H5]6Bi4Br18] has been synthesized and characterized by the X-ray (at 293 and 110 K), calorimetric, dilatometric and dielectric measurements. At room temperature it crystallizes in the monoclinic space group, C2/m. A crystal structure consists of disordered imidazolium cations and ordered discrete tetramers of Bi4Br18]6-. This compound reveals a rich polymorphism in a solid state. It undergoes three solid–solid phase transitions: from phase I to II at 426/423 K (heating–cooling), II→III at 227 K and III→IV at 219.5/219 K. A clear dielectric relaxation process is found in the room temperature phase II. Infrared studies of the polycrystalline C3N2H5]6Bi4Br18] showed that the ν(N–H), δ(ring) and δ(C–H) modes of the imidazolium cations appeared to be very sensitive to the IV→III phase transition. 1H NMR measurements confirmed a key role of the imidazolium cations in the phase transitions mechanisms at low temperatures. |
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Keywords: | Imidazolium Bismuthate(III) Phase transition Dielectric relaxation Infrared 1H NMR |
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