Wydział Chemii

Magdalena T. Owczarek

Ryszard Jakubas

Grażyna Bator

Andrzej Pawlukojć

Jan Baran

Janusz Przesławski

Wojciech Medycki

2011

Chemical Physics

381

11-20

10.1016/j.chemphys.2011.01.002

Naukowa

Angielski

Artykuł

Dynamics of molecules in morpholinium tetrafluoroborate, [NH₂(C₂H₄)₂O][BF₄], has been studied in a wide temperature range by means of AC calorimetry, ¹H NMR and infrared spectroscopy. Simultaneously, DFT (density functional theory) calculations of the molecular structure and normal vibration frequencies have been performed by using various functionals for initial structural data of the low temperature phase. Infrared spectra of polycrystalline [NH₂(C₂H₄)₂O][BF₄] have been analyzed in a frequency range 4000–400 cm⁻¹. Substantial changes in a temperature evolution of internal modes of both morpholinium cations and [BF₄]⁻ anions are due to the freezing of these moieties motions below 117 K. A dynamic nonequivalence of protons involved in N–H⋯F and N–H⋯O hydrogen bonds has been detected. Heat capacity anomalies around structural phase transitions detected by AC calorimetry (117 and 153 K) have been evaluated and described. A molecular mechanism of the phase transitions is discussed on the basis of presented results.

AC calorimetry, 1H NMR, Infrared, DFT calculation, Morpholinium tetrafluoroborate

https://doi.org/10.1016/j.chemphys.2011.01.002

http://www.elsevier.com