Determination of the standard molar enthalpy of formation of the ternary complex of neodymium with vitamin B3 and 8-hydroxylquinoline by microcalorimetry

Abstract

A novel solid ternary complex, [Nd(C6H4NO2)2·C9H6NO·2H2O], was synthesized in a water bath (333.15 K) by three kinds of reagents: neodymium chloride, vitamin B3 (C6H5NO2), and 8-hydroxylquinoline (C9H7NO). Its composition and structure were characterized by elemental analysis, IR spectra, UV spectra, molar conductance, and thermogravimetric analysis. During the process of coordination, C6H5NO2 was bidentate-coordinated with Nd3+ in the form of an acidic group by removing the proton; hydroxyl oxygen atom and heterocyclic nitrogen atom of C9H7NO formed a chelate ring. Particularly, in this article, a thermochemical cycle in the calorimetric solvent (VHCl:VDMF:VEtOH = 3:1:1) was designed on the basis of Hess’s law. At 298.15 K, the dissolution enthalpies of the reactants and products were determined by a advanced solution–reaction isoperibol microcalorimeter, respectively. According to the above results and relevant literature data, the standard molar enthalpy of formation of [Nd(C6H4NO2)2·C9H6NO·2H2O], was estimated to be \( \Updelta_{f} H_{m}^{\Uptheta} \) [[Nd(C6H4NO2)2·C9H6NO·2H2O(s)], 298.15 K] = −(2,129.1 ± 2.5) kJ mol−1.