Thermochemical Study on Coordination Complex of Samarium with Salicylic Acid and 8-Hydroxyquinoline

Abstract The coordination complex Sm(C 7 H 5 O 3 ) 2 ·(C 9 H 6 NO), synthesized from the reaction of samarium chloride six-hydrate with salicylic acid and 8-hydroxyquinoline, was characterized with IR, elemental analysis, molar conductance, and thermogravimatric analysis. The standard molar enthalpies of solution of [SmCl 3 ·6H 2 O (s)], [2C 7 H 6 O 3 (s), [C 9 H 7 NO(s)] and [Sm(C 7 H 5 O 3 ) 2 ·(C 9 H 6 NO)(s)] in the calorimetric solvent were determined with the solution-reaction isoperibol calorimeter at 298.15 K to be Δ s H Θ m [SmCl 3 ·6H 2 O (s), 298.15 K] = −103.98 ± 0.04 kJ·mol −1 , Δ s H Θ m [2 C 7 H 6 O 3 (s), 298.15 K] = 16.35 ± 0.14 kJ·mol −1 , Δ s H Θ m [C 9 H 7 NO (s), 298.15 K] = −6.11 ± 0.08 kJ·mol −1 and Δ s H Θ m [SmC 7 H 5 O 3 ) 2 ·(C 9 H 6 NO) (s), 298.15 K] = −130.08 ± 0.04 kJ·mol −1 , respectively. The enthalpy was determined to be Δ r H Θ m = 89.59 ± 0.18 kJ·mol −1 for the reaction SmCl 3 ·6H 2 O(s) + 2C 7 H 6 O 3 (s) + C 9 H 7 NO(s) = Sm (C 7 H 5 O 3 ) 2 ·(C 9 H 6 NO) (s) + 3HCl(g) + 6H 2 O(1). According to the above results and the data given in literature and through Hess′ law, the standard molar enthalpy of formation of Sm(C 7 H 5 O 3 ) 2 ·(C 9 H 7 NO)(s) was estimated to be Δ r H Θ m [Sm(C 7 H 5 O 3 ) 2 ·(C 9 H 6 NO)(s), 298.15 K] = −2055.9 ± 3.03 kJ·mol −1 .