Low-temperature phase transition in [Cd(OS(CH3)2)6](ClO4)2 studied by inelastic and elastic neutron scattering, Raman light scattering, and infrared absorption spectroscopy

The vibrational and reorientational dynamics of CH3 groups from (CH3)2SO ligands in the high- and low-temperature phases of [Cd(OS(CH3)2)6](ClO4)2 were investigated by Fourier transform infrared (FT-IR) and Raman (FT-Raman) spectroscopy, and quasielastic and inelastic incoherent neutron scattering (QENS and IINS) methods. The results show that in the high temperature phases the CH3 groups and ClO4− anions perform fast (τR ≈ 10−12 s) reorientational motions. These molecular motions do not change significantly at low-temperature phase transition (detected earlier by differential scanning calorimetry (DSC) at TC4c=235K on cooling and at TC4c=242K on heating). Neutron powder diffraction (NPD) measurements, performed simultaneously with QENS and IINS, indicated that this phase transition is associated with a change of the crystal structure. The comparison of FT-IR, FT-Raman and the proton-weighted phonon density of states function G(ν) calculated from IINS experimental spectra at low temperature phase of [Cd(OS(CH3)2)6](ClO4)2 was made.