1H and 19F NMR studies on molecular motions and phase transitions in solid triethylammonium tetrafluoroborate

Hiroshi Ono, Riki Seki, Ryuichi Ikeda, Hiroyuki Ishida

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15 Citations (Scopus)

Abstract

Measurements by differential thermal analysis and differential scanning calorimetry and of the spin-lattice relaxation time (T1), the spin-spin relaxation time (T2), and the second moment (M2) of 1H and 19F NMR were carried out in the three solid phases of (CH3CH2)3NHBF4. X-ray powder patterns were taken in the highest-temperature phase (Phase I) existing above 367 K and the room-temperature phase (Phase II) stable between 220 and 367 K. Phase I formed a NaCl-type cubic structure with a = 11.65(3) Å, Z = 4, V = 1581(13) Å3, and Dx = 0.794 g cm−3, and was expected to be an ionic plastic phase. In this phase, the self-diffusion of anions and the isotropic reorientation of cations were observed. Phase II formed a tetragonal structure with a = 12.47(1) and c = 9.47(3) Å, Z = 4, V = 1473(6) Å3, and Dx = 0.852 g cm−3. From the present DSC and NMR results in this phase, the cations and/or anions were considered to be dynamically disordered states. The C3 reorientation of the cation about the NH bond axis was detected and, in addition, the onset of nutation of the cations and local diffusion of the anions was suggested. In the low-temperature phase (Phase III) stable below 219 K, the C3 reorientations of the three methyl groups of cations and the isotropic reorientation of anions were observed. The motional parameters for these modes were evaluated.

Original languageEnglish
Pages (from-to)235-243
Number of pages9
JournalJournal of Molecular Structure
Volume345
DOIs
Publication statusPublished - Jan 1 1995

ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy
  • Organic Chemistry
  • Inorganic Chemistry

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