Thermodynamic properties of complex compounds of iron(II) nitrate with tris(3,5-dimethylpyrazol-1-yl)methane

The temperature dependence of the heat capacity of a complex compound of iron(II) nitrate with tris(3,5-dimethylpyrazol-1-yl)methane is studied by adiabatic calorimetry in the range of 100–300 K. A specific heat anomaly is found and localized in the temperature range corresponding to the sharp spin transition 1 A 1 ↔ 5 T 2 with hysteresis on the temperature dependence of the magnetic susceptibility. The effects of cooperative interaction are revealed on the basis of thermodynamic and magnetochemical data, using two widely used models of spin transition.