Raman scattering study of temperature induced phase transition in [C8H10NO]2 [ZnCl4]

The Raman spectra of bis (4-acetylanilinium) tetrachloridozincate single crystals were studied in the range of 100-3500 cm−1 as a function of temperature of 298 K to 398 K. The bands mainly associated with the internal modes of the ZnCl4 anions only undergo weak changes. However, the strong evolutions of wavenumbers, widths and intensities of many lines associated with the organic cations are observed with discontinuities in the vicinity of the phase transition at 351 K. A phase transition at Tc = 351K was observed and characterized by the differential scanning calorimetry (DSC). The most important changes are observed for two lines at 3197.13 cm−1 and 3167.10 cm−1 (at room temperature) issued from asymmetric and symmetric stretching vibrations of (C-H) band and (NH3) group, respectively. The spectral characteristics of these lines are analyzed and consistently described in the framework of an order–disorder model for the phase transition.