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Abstract
The heat capacity of a 3:1 thiourea-ferrocene channel inclusion compound has been measured with an adiabatic-type calorimeter between 13 and 280 K. Five phase transitions were found at 147.2 (TC1), 159.79(TC2, 171.4(TC3, 185.5(TC4 and 220K(TC5. The enthalpy and entropy asssociated with these transitions have been determined. The two lowest-temperature transitions are responsitble for an order-disorder-type of reorientation of the molecular axis of ferocene in the thiourea host lattice. This reorientational disrodering was proved to proceed in two steps; in the first stage the reorientational motion is excited within the channel plane in a group of, say, three ferrocene molecules as a unit keeping the short-range order while in the second stage this restriction is lifted and the jump process between the channel plane and the channel axis is allowed. The remaining thre phase transitions with small entropy change have been attributed to unkonwn but intrinsic characters of the present clathrate. The dielectric constant measurements revealed no ferroelectric nature. The infrared and Raman spectra have also been recorde. Comparison of the transition mechanisms between solid ferrocene and the present clathrate has been maede.