Ion dynamics in closo-hydroborates Ag2[B10H10] and Tl2[B10H10]: 1H, 11B and 205Tl NMR studies

Abstract

Ag2[B10H10] and Tl2[B10H10] belong to the family of closo-hydroborates which are considered as promising solid electrolytes for battery applications. To study the dynamical properties of these compounds at the microscopic level, we have measured the 1H, 11B, and 205Tl nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation rates over the temperature range of 80 – 545 K. For both compounds, our measurements have revealed fast reorientational motion of the [B10H10]2− anions. The reorientational jump rates are found to reach ~10^8 s^-1 near 380 K for Ag2[B10H10] and near 480 K for Tl2[B10H10]. This reorientational motion is characterized by the activation energies of 352(18) meV and 685(40) meV, respectively. For Tl2[B10H10], our experiments have not revealed any effects of long-range translational cation mobility at the NMR frequency scale up to 500 K.