Raman scattering investigation of the high temperature phase transition in [N(C3H7)4]2SnCl6.

The phase transition at high temperature of bis-tetrapropylammoniumhexachlorostannate compound has been investigated by Raman spectroscopy as a function of temperature from 303 K to 393 K. While the bands mainly associated with the internal modes of the SnCl6 anions only undergo weak changes, 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 362 K. The most important changes are observed for two lines at 1137.5 cm(-1) and 1159.4 cm(-1) (at room temperature) issued from twisting of CH2 groups and skeletal deformation of the cations. The spectral characteristics of these lines are analyzed and consistently described in the framework of an order-disorder model for the phase transition. The temperature dependency of the reduced peak intensity allowed to determine the critical exponents and evolution of the correlation length on approaching the transition.