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.