Low-temperature phase transition in [Mn(OS(CH3)2)6](ClO4)2 studied by single crystal X-ray diffraction, infrared absorption and Raman scattering spectroscopies

Single crystal X-ray diffraction studies of [Mn(OS(CH3)(2))(6)](ClO4)(2) have shown that the low temperature phase transition, detected by differential scanning calorimetry (DSC) at about 223 K. is associated with the crystal symmetry's reduction from an orthorhombic crystallographic system (Fdd2, No. 43) to a monoclinic one (Cc, No. 9). The analysis of the full width at half maximum of the bands connected with: delta(d)(OCIO)F-2 and rho(CH3) vibrational modes in the FT-IR and FT-RS spectra, respectively, registered in the function of temperature, proved that the reorientational motions of ClO4- anions and CH3 groups from (CH3)(2)SO ligands, began to slow down at temperatures below the phase transition at about 223 K. Mean values of activation energy for ClO4- reorientation in the high temperature phase I and low temperature phase II are: E-a(I) approximate to 14 kJ mol(-1) and E-a(II) approximate to 10 kJ mol(-1), respectively. Analogous values for CH3 reorientation are: E-a(I) approximate to 23 kJ mol(-1) and E-a(II) approximate to 1 kJ mol(-1), respectively. (C) 2011 Elsevier B.V. All rights reserved.