Thermodynamic studies are necessary to understand the mechanism of such an interesting phenomenon as spin crossover in complex compounds. A number of reviews have already covered spin crossover in mononuclear complexes, so the suggested review considers in more detail the problems of obtaining thermodynamic data for polynuclear complex compounds of iron (II) with 4-substituted 1,2,4-triazole derivatives. The composition of trinuclear and polynuclear complexes of iron (II) with 1,2,4-triazoles was studied in terms of its effect on Cp(T) dependence; magnetochemical and thermodynamic data are also confronted with each other.
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