Low-temperature phase transitions in [Cd(DMSO)6](BF4)2 studied by differential scanning calorimetry, X-ray single crystal diffraction and infrared absorption spectroscopy

Abstract

The differential scanning calorimetry (DSC) measurements made for [Cd(DMSO)6](BF4)2, in the temperature range of 113–298K revealed existence of two low-temperature solid–solid phase transitions: phase Cr 3↔phase Cr 2 at Tc2c=218K and phase Cr 2↔phase Cr 1 at Tc1c=246K. X-ray single crystal diffraction studies of [Cd(DMSO)6](BF4)2 have shown that these transitions are related to a crystal symmetry reduction from an orthorhombic crystallographic system (Fdd2, No. 43) to a monoclinic one (Cc, No. 9). The [Cd(DMSO)6](BF4)2 compound undergoes also series of reversible high temperature phase transitions but they are not a subject of this work and will be presented in our next paper. The characteristic changes of the FT-FIR, FT-MIR and FT-RS spectra of [Cd(DMSO)6](BF4)2 at the phase transitions’ temperatures confirmed that phase transitions phase Cr 3↔phase Cr 2↔phase Cr 1 are related to the crystal structure change. It was also found that the reorientation of the BF4− anions and DMSO ligands freezes below 218K.