Wydział Chemii

Anna Piecha-Bisiorek

Alina Bieńko

Ryszard Jakubas

Roman Boča

Marek Weselski

Vasyl V. Kinzhybalo

Adam Pietraszko

Martyna Wojciechowska

Wojciech Medycki

Danuta Kruk

2016

Journal of Physical Chemistry A

120

2014-2021

10.1021/acs.jpca.5b11924

Naukowa

Angielski

Artykuł

(C₃N₂H₅)₂[CoCl₄] (ICC) was characterized in a wide temperature range by the single-crystal X-ray diffraction method. Differential scanning calorimetry revealed two structural phase transitions: continuous at 245.5 K (from phase I to II) and a discontinuous one at 234/237 K (cooling/heating) (II → III). ICC adopts monoclinic space groups C2/c and P21/c in phase (I) and (III), respectively. The intermediate phase (II) appears to be incommensurately modulated. Dynamic properties of polycrystalline ICC were studied by means of dielectric spectroscopy and proton magnetic resonance (1H NMR). The presence of a low frequency dielectric relaxation process in phase III reflects libration motion of the imidazolium cations. The temperature dependence of the 1H spin–lattice relaxation time indicated two motional processes with similar activation energies that are by about an order of magnitude smaller than the activation energy obtained from dielectric studies. There are no abrupt changes in the 1H relaxation time at the phase transitions indicating that the dynamics of the imidazolium rings gradually varies with temperature; that is, it does not change suddenly at the phase transition. Negative values of the Weiss constant and the intermolecular exchange parameter were obtained, confirming the presence of a weak antiferromagnetic interaction between the nearest cobalt centers. Moreover, the magnitude of zero field splitting was determined. The AC susceptibility measurements show that a slow magnetic relaxation is induced by small external magnetic field.

http://dx.doi.org/10.1021/acs.jpca.5b11924

https://www.acs.org/content/acs/en.html