Synthesis, crystal structure and thermochemistry of nickel hydrogen pyridine-2,6-dicarboxylate

Nickel hydrogen pyridine-2,6-dicarboxylate trihydrate (Ni(HDPC)2·3H2O) was synthesized by the method of liquid phase synthesis. The composition and crystal structure of the complex were determined by chemical analysis, elemental analysis, and X-ray crystallography. Low-temperature heat capacities of the complex were measured over the temperature range from 78 to 353 K. Smoothed molar heat capacities and thermodynamic functions of the complex relative to the standard reference temperature 298.15 K were calculated based on the fitted polynomial equation. A reasonable thermochemical cycle was designed, and the standard molar enthalpies of dissolution for the reactants and products of the synthesis reaction in a selected solvent were measured. Eventually, the standard molar enthalpy of formation of the title complex was derived to be −(2467.9 ± 3.2) kJ mol−1 in accordance with Hessʹs law.