This article reports the synthesis and thermodynamic properties of a novel rare earth coordination complex, samarium chloride hexahydrate (SmCl3 center dot 6H(2)O) with nicotinic acid (C6H5NO2) and 8-hydroxylquinoline (C9H7NO), whose composition and structure were characterized by elemental analysis, molar conductance, thermogravimetric analysis (TG-DTG), UV spectroscopy, IR spectroscopy, and X-ray powder diffraction. During the process of coordination, C6H5NO2 was bidentate-coordinated with the rare earth ion (Sm3+) through an acidic group that was formed by removing the proton; the hydroxyl oxygen atom and heterocyclic nitrogen atom of C9H6NO- formed a chelate ring with Sm3+ for coordination. The X-ray powder diffraction pattern demonstrated that the crystal type of [Sm(C6H4NO2)(2)center dot C9H6NO] is similar to that of C5H11NO2, with the cell parameters a = 5.426 nm, b = 22.105 nm, and c = 5.277 nm. At a constant temperature of 298.15 K, the dissolution enthalpies of the reactants and products of the coordination reaction in the optimized calorimetric solvent were determined with an advanced solution-reaction isoperibol microcalorimeter. The standard molar enthalpy change of the coordination reaction was determined to be Delta H-r(m)Theta = (167.49 +/- 0.39) kJ.mol(-1). The standard molar enthalpy of formation of the title complex, [Sm(C6H4NO2)(2)center dot C9H6NO], was estimated to be Delta H-f(m)Theta[Sm(C6H4NO2)(2)center dot C9H6NO(s), 298.15 K] = -(1483.4 +/- 2.4) kJ.mol(-1), from a combination of the experimental values of enthalpies of dissolution and some other auxiliary thermodynamic data through a designed thermochemical cycle based on a supposed chemical reaction.