Structural changes, thermodynamic properties, (1)H magic angle spinning NMR, and (14)N NMR of (NH(4))(2)CuCl(4)·2H(2)O

The structural changes and thermodynamic properties of (NH(4))(2)CuCl(4)·2H(2)O were studied by differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis. In addition, the chemical shift, line width, and spin-lattice relaxation time of the crystals were also investigated by (1)H magic angle spinning nuclear magnetic resonance (MAS NMR), focusing on the role of NH(4) and H(2)O near the phase transition temperature. The change at T(C2) (=406 K) and T(C3) (=437 K) seems to be a chemical change caused by thermal decomposition rather than a physical change such as a structural phase transition. The changes in the temperature dependence of these data near T(C2) are related to variations in the environments surrounding NH(4) and H(2)O. The (14)N NMR spectrum is also measured in order to investigate local phenomena related to the phase transition.