Temperature Dependence of 2H Quadrupole Coupling Constants in 2H2O and Ionic Motions in Crystalline [M(2H2O)6] [SnCl6] (M: Mg, Ca), Studied by 2H NMR and Neutron Powder Diffraction

Abstract

Abstract The temperature dependence of 2H NMR spectra was measured at 130-430 K on [M(D2O)6] [SnCl6] (M : Mg, Ca) (rhombohedral, space group: R3̅), and neutron powder diffraction on the Mg salt was performed at room temperature. Based on the accurate orientation of D2O molecules in an octahedral cation, spectra with a large asymmetry parameter η, observed around 200 K, were explained by a model of 180° flip of water molecules. Another motional narrowing observed above room temperature was assigned to a cationic overall reorientation about the C3-axis.