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

• Published in: Journal of molecular structure Vol. 1092; pp. 81 - 88
• Main Authors: Szostak, Elżbieta, Migdał-Mikuli, Anna, Bernard, Paweł
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.07.2015
• Subjects: DSC; FT-IR; Hexadimethylsulfoxidecadmium tetrafluoroborate; Phase transitions; Reorientational motions; XRD; FT-IR; XRD; Reorientational motions; DSC; Phase transitions; Hexadimethylsulfoxidecadmium tetrafluoroborate
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2015.02.058

[Display omitted] •We examine phase polymorphism of [Cd(DMSO)6](BF4)2.•The crystal structures of Cr 3 and Cr 1 phase are different.•The fast reorientational motions of the BF4− and CH3 are slowed down below 218K. 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.