Growth, structure, phase transition, thermal properties, and structural dynamics of organic-inorganic hybrid [NH(CH)NH]ZnCl crystal.

In this study, the physicochemical properties of [NH(CH)NH]ZnCl crystals were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis, and nuclear magnetic resonance (NMR). The crystals at 300 K had a monoclinic structure with C2/c space group and lattice constants are a = 21.4175 Å, b = 7.3574 Å, c = 19.1079 Å, β = 120.5190°, and Z = 8. Three endothermic peaks at 256, 390, and 481 K were observed in the DSC curve. From the single-crystal XRD patterns, powder XRD patterns, and optical microscopy results based on the temperature change, the phase transition and melting temperatures were determined to be 390 and 481 K, respectively. NMR studies indicated no change in H chemical shifts, but a change in the chemical shifts for C2, located between C1 and C3 of the cation at 340 K. Increase in molecular motion caused an increase in the spin-lattice relaxation time, T, at low spinning rates, under magic-angle spinning rate conditions. This crystal showed a minor change in the N-H···Cl hydrogen bond, related to the coordination geometry of the ZnCl anion.