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

Abstract

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.

Solid-state NMR of quadrupolar halogen nuclei

“…The chlorine site symmetry is approximately T d in all the perchlorates studied, but the small deviation from tetrahedral symmetry results in a nonzero QI at the chlorine nuclei in these salts. The chlorine C Q values are relatively small however, and they have been popular materials to study by chlorine SSNMR [70,[95][96][97][98][99][100][101][102][103].…”

Exploring Systematic Discrepancies in DFT Calculations of Chlorine Nuclear Quadrupole Couplings

“…[29][30] Chlorine SS-NMR has also been used for the characterization of a chloride ion receptor, 21 alkaline earth chlorides (including hydrates) 24,31 and has been used to comment on halogen bonding [32][33][34] and ion dynamics in solids. [35][36] Chlorine SS-NMR has also found applications in the study of materials such as sodalities 37 However, the optimal choice of the cluster for C Q calculations may not be obvious. For example, it is very difficult to build a suitable cluster model for alkaline earth chloride hydrates, which form extended three dimensional networks in the solid state.…”

3-(Ammoniomethyl)pyridinium bis(perchlorate)

“…For general background to perchlorate salts with organic cations, see: Czarnecki et al (1994); Czupinski et al (2002Czupinski et al ( , 2006. For related structures, see: Kapplinger & Keutel (1999); Ye et al (2002) Experimental Crystal data…”