Thermochemistry on K2[M(DPA)2]·7H2O(s) (M = Cu and Ni, H2DPA = pyridine-2,6-dicarboxylic acid)

Two hybrid transition-alkali metal complexes, K2[M(DPA)2]·7H2O(s) (M = Cu and Ni, H2DPA = pyridine-2,6-dicarboxylic acid), were structurally determined by X-ray crystallography. In accordance with Hessʹs law, two reasonable thermochemical cycles were designed and 100 cm3 of 5% (v/v) dilute aquaammonia was chosen as the calorimetric solvent. The standard molar enthalpies of dissolution for the reactants and products of the supposed reactions in the selected solvent were measured at 298.15 K by means of isoperibol solution-reaction calorimeter, respectively. The standard molar enthalpies of formation of K2[M(DPA)2]·7H2O(s) (M = Cu and Ni) were derived to be −(3947.7 ± 4.7) kJ mol−1 and −(4007.8 ± 4.7) kJ mol−1, respectively.