Thermochemical analysis on rare earth complex of gadolinium with salicylic acid and 8-hydroxyquinoline

The rare earth complex, Gd(C7H5O3)2·(C9H6NO), was synthesized by the reaction of Gadolinium nitrate hexahydrate with salicylic acid (C7H6O3) and 8-hydroxyquinoline (C9H7NO). And it was characterized by elemental analysis, UV spectra, IR spectra, molar conductance and thermogravimetric analysis. In a optimalizing calorimetric solvent, the dissolution enthalpies were determined by an advanced solution-reaction isoperibol microcalorimeter, respectively: image [2 C7H6O3(s) + C9H7NO(s), 298.15 K] = 41.95 ± 0.44 kJ mol−1, image [Gd(NO3)3·6H2O(s), 298.15 K] = −29.11 ± 0.39 kJ mol−1, image [Gd(C7H5O3)2·(C9H6NO)(s), 298.15 K] = −46.99 ± 0.39 kJ mol−1 and image [Solution D(aq), 298.15 K] = −90.33 ± 0.37 kJ mol−1. The enthalpy change of the synthesized reaction was estimated to be image. From data in the literature, through Hess’ law, the standard molar enthalpy of formation of Gd(C7H5O3)2·(C9H7NO)(s) was calculated to be image [Gd(C7H5O3)2·(C9H6NO)(s), 298.15 K] = −1890.7 ± 3.1 kJ mol−1.