Physicochemical properties and structural dynamics of organic-inorganic hybrid [NH(CH)NH]ZnX (X = Cl and Br) crystals.

The physical properties of the organic-inorganic hybrid crystals having the formula [NH(CH)NH]ZnX (X = Cl, Br) were investigated. The phase transition temperatures (T; 268K for Cl and 272K for Br) of the two crystals bearing different halogen atoms in their skeletons were determined through differential scanning calorimetry. The thermodynamic properties of the two crystals were investigated through thermogravimetric analysis. The structural dynamics, particularly the role of the [NH(CH)NH] cation, were probed through H and C magic-angle spinning nuclear magnetic resonance spectroscopy as a function of temperature. The H and C NMR chemical shifts did not show any changes near T. In addition, the H spin-lattice relaxation time (T) varied with temperature, whereas the C T values remained nearly constant at different temperatures. The T values of the atoms in [NH(CH)NH]ZnCl were higher than those in [NH(CH)NH]ZnBr. The observed differences in the structural dynamics obtained from the chemical shifts and T values of the two compounds can be attributed to the differences in the bond lengths and halogen atoms. These findings can provide important insights or potential applications of these crystals.