Thermal properties of polycrystalline [Mn(NH3)6](ClO4)2[Mn(NH_{3})_{6}](ClO_{4})_{2} : crystal structure and phase transitions

The X-ray powder diffraction (XRPD) pattern of [Mn(NH 3 ) 6 ](ClO 4 ) 2 at room temperature can be indexed in the regular (cubic) system (Fm 3m space group) with lattice cell parameter a = 11.5729 A ̊ and with four mole- cules per unit cell. The XRPD pattern at 100 K is evidently different, and it indicates lowering of the crystal structure. One phase transition at T h C1 = 143.5 K (on heating) and at T c C1 = 137.6 K (on cooling) was detected by DSC for [Mn(NH 3 ) 6 ](ClO 4 ) 2 in the range of 120–300 K. The fol- lowing thermodynamic parameters for phase I $ phase II transition were obtained: D H = 3.1 ± 0.2 kJ mol - 1 and D S = 21.6 ± 0.3 J mol - 1 K - 1 . The large value of entropy changes ( D S ) indicates considerable configurational disor- der in the high temperature phase. The presence of 5.9 K hysteresis of the phase transition temperature at T C and sharpness of the heat flow anomaly attest that the detected phase transition is of the first-order type. Appearing of the two new bands (splitting of d s (HNH) F 1u mode) in FT-MIR spectra at the vicinity of 1200 cm - 1 suggests that the phase transition undergoes a change of the crystal structure

Thermal properties of [Cr(NH3)6](BF4)3[Cr(NH_3)_6](BF_4)_3 studied by adiabatic and relaxation calorimetry

Four (solid–solid) phase transitions were detected in the temperature range of (9 to 300) K in polycrystalline [Cr(NH3)6](BF4)3 at TC1 = 240.7 K, TC2 = 108.0 K, TC3 = 91.9 K, and TC4 = 61.3 K by adiabatic calorimetry. The measurements by relaxation calorimetry were followed on lowering temperature from 20 K down to 0.35 K under six different external magnetic field values (9, 7, 5, 3, 1 and 0) T. For non-zero values of applied magnetic field well-defined Schottky anomaly appears. Magnetic heat capacity was calculated assuming the zero-field splitting for the decoupled Cr(III) ions. There is no discrepancy between the observed and calculated values. Isothermal magnetization curve recorded up to 5 T was measured at temperature of 1.8 K

IINS, FT-IR and DFT study of the internal dynamics of [4-apyH][SbCl4SbCl_4]

A combination of infrared and inelastic incoherent neutron scattering spectroscopies with the density functional theory and semi-empirical calculations was applied to propose an assignment of the vibrational spectra of 4-aminopyridine chloroantimonate(IV)