Motivated by the application of the First Order Reversal Curve (FORC) technique to obtain a distribution of like spin domains in the spin crossover complexes [FexM1-x(btr)2(NCS)2]·H2O with MII = Zn and Ni, we have performed Differential Scanning Calorimetry (DSC) experiments. We have measured the heat capacity in the heating and cooling modes and then calculated the enthalpy and the entropy variations at the phase transition. In the framework of an Ising-like model, we have converted the experimental thermal hysteresis into terms of physical parameters related to these compounds. We have also performed a statistical analysis of these parameters and concluded that the correlation between them increases with the dilution degree of these spin crossover complexes. © 2009 Elsevier Ltd. All rights reserved.