The heat capacity of compound tris(1,1,1,5,5,5-hexafluoro 2,4-pentanodionate) iron(III) has been measured by the adiabatic method within the temperature range 4.8-321 K. The thermodynamic functions: entropy, enthalpy and reduced Gibbs' energy have been calculated. The components of heat capacity related to intermolecular and intramolecular vibrations have been analyzed. An anomaly has been discovered in the heat capacity with a maximum at 44.6 K. A critical change in spectral density of phonon states has been marked at the same temperature. (c) 2005 Elsevier B.V. All rights reserved.