Structure and properties of 2-cyanopyridinium perchlorate [2-CNPyH][ClO4]

• Published in: Journal of physics. Condensed matter Vol. 18; no. 12; pp. 3307 - 3324
• Main Authors: Czupiński, O, Wojtaś, M, Zaleski, J, Jakubas, R, Medycki, W
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 29.03.2006; Institute of Physics
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Dielectric, piezoelectric, ferroelectric and antiferroelectric materials; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Exact sciences and technology; Physics; Polymers; organic compounds; Structure of solids and liquids; crystallography; Differential scanning calorimetry; Order-disorder transformations; Dilatometry; Pyridinium compounds; Phase transformations; Displacive transformations; Pyroelectricity; Nuclear magnetic resonance; Perchlorates; Dielectric relaxation; Crystal structure
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/18/12/012

The crystal structure of 2-cyanopyridinium perchlorate, [2-CNPyH][ClO4], has been determined at 100 (phase II) and 293 K (phase I). It is monoclinic P 21 at 100 K and orthorhombic P 212121 at 293 K. The dynamic properties of the crystal were studied by differential scanning calorimetry, dilatometry, pyroelectric, dielectric, proton (1H NMR), chlorine (35Cl NMR) magnetic resonance spectroscopies and the infrared method. The crystal undergoes a structural phase transition () at 170 K characterized by a complex mechanism involving both 'order-disorder' and 'displacive' contributions. It reveals pyroelectric properties below 170 K. The dielectric relaxation existing over phase I is due to the motion of the cyano group, whereas the dynamics of the [ClO4] anions is reflected in the significant dielectric increment around the phase transition.