Synthesis, structural characterization, and thermochemistry of complexes of pyridine 2,6-dicarboxylate with metals (Mg and Sr)

Two novel complexes [Mg(DPC)(H2O)3]·2H2O(s) and Sr2(H2DPC)2(HDPC)2(DPC)(H2O)2(s) were synthesized by the method of liquid phase reflux. X-ray crystallography, chemical analysis, and elemental analysis were applied to characterize the structures and compositions of the two complexes. Low-temperature heat capacities of the complexes were measured over the temperature ranges from 78 to 350 and 78 to 352 K for [Mg(DPC)(H2O)3]·2H2O(s) and Sr2(H2DPC)2(HDPC)2(DPC)(H2O)2(s), respectively. The polynomial regressions as a function of temperature were carried out through least square fitting method according to the experiment points. The polynomial fitted values of the molar heat capacities and the thermodynamic functions relative to the standard reference temperature 298.15 K based on the polynomial equations were derived. In addition, thermal behavior of the two compounds was investigated by thermal analysis techniques, differential scanning calorimetry/thermogravimetric analysis.