Molecular motional and structural study of ammoniated titanium disulfide by proton NMR

G. W. O'Bannon, W. S. Glaunsinger, R. F. Marzke

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Abstract

Proton spin-lattice relaxation times and linewidths have been measured as a function of temperature at 25 MHz for (NH4+)0.21Ti20.21- and at 25 and 50 MHZ for (NH4+)0.22(NH3)0.37TiS20.22-. In the former compound, the NH4+ cations reorient randomly and rapidly on trigonal prismatic sites in the van der Waals gap of TiS2, and there is no evidence of other thermally activated motion between 3 K and the deintercalation temperature. In the latter compound, two distinct types of motions can be discerned from their characteristic NMR signals. At lower temperatures the NH3 molecules rotate about their three-fold axes and above 270 K translational diffusion occurs. An average proton-proton distance of 1.79±0.03 A ̊ in NH3 has been evaluated from the temperature dependence of the relaxation time associated with the C3 axis rotation. This large distance relative to that in normal pyramidal NH3 (1.65 Å) is consistent with a planar NH3 geometry and perhaps some lengthening of the normal NH bond length (1.008 Å). The activation energy for NH3 rotation (2.41 ± 0.02 kcal/mol NH3) is nearly equal to that measured in solid NH3 (2.3 kcal/mol NH3). A high-temperature minimum in the relaxation time has been attributed to NH3 diffusion, with an activation energy (13.3±3kcal/mol NH3) that is in good agreement with the NH3 deintercalation enthalpy.

Original languageEnglish (US)
Pages (from-to)15-23
Number of pages9
JournalSolid State Ionics
Volume26
Issue number1
DOIs
StatePublished - Jan 1988

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ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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