1H, 7Li, and 23Na NMR study of the relaxation processes and molecular motions of Li 2NaH(SO 4) 2·H 2O single crystals

Abstract

Li 2NaH(SO 4) 2·H 2O single crystals were grown by using the slow evaporation method, and their phase transition temperatures were determined with differential scanning calorimetry (DSC). In addition, the temperature dependences of the NMR resonance lines and spin–lattice relaxation times, T 1, of the 1H, 7Li, and 23Na nuclei were obtained. Only one 7Li resonance line is present in the spectrum above 390 K, which means that at these temperatures the atoms surrounding Li + are probably disrupted by the loss of H 2O. The water protons were distinguished from the hydrogen-bond protons. From the variations with inverse temperature of the relaxation times of the hydrogen-bond protons, water protons, and 7Li nuclei, we conclude that the relaxation processes in this crystal are affected by reorientation motions. We determined the activation energies of the molecular motions involving the 7Li and 23Na nuclei, the hydrogen-bond protons, and water protons from these results.