Synthesis, characterization and standard molar enthalpy of formation of La(C7H5O3)2•(C9H6NO)

The product from reaction of lanthanum chloride seven-hydrate with salicylic acid and 8-hydroxyquinoline, La(C7H5O3)(2)center dot(C9H6NO), was characterized by IR, elemental analysis, molar conductance, and thermogravimetric analysis. The standard molar enthalpies of solution of [LaCl3 center dot 7H(2)O(s)], [2C(7)H(6)O(3) (s)], [C9H7NO (s)] and [La(C7H5O3)(2)center dot(C9H6NO) (s)] in a mixed solvent of absolute ethyl alcohol, dimethyl formamide (DMF) and perchloric acid were determined by calorimetry to be Delta H-s(m)Theta [LaCl3 center dot 7H(2)O (s), 298.15 K] = -96.45 +/- 0.18 kJ mol(-1), Delta H-s(m)Theta [2C(7)H(6)O(3) (s), 298.15 K] = 14.99 +/- 0.17 kJ mol(-1), Delta H-s(m)Theta[C9H7NO (s), 298.15 K] = -3.86 +/- 0.06 kJ mol(-1) and Delta H-s(m)Theta[La(C7H5O3)(2)center dot(C9H6NO) (s), 298.15 K] = - 117.78 +/- 0.11 kJ mol(-1). The enthalpy change of the reaction LaCl3 center dot 7H(2)O (s) + 2C(7)H(6)O(3) (s) + C9H7NO (s) = La (C7H5O3)(2)center dot(C9H6NO) (s) + 3HCl (g) + 7H(2)O (1) was determined to be Delta H-r(m)Theta = 91.57 +/- 0.34 kJ mol(-1). From data in the literature, through Hess' law, the standard molar enthalpy of formation of La(C7H5O3)(2)center dot(C9H7NO) (s) was estimated to be Delta H-f(m)Theta[La(C7H5O3)(2)center dot(C9H6NO) (s), 298.15 K] 2076.5 +/- 3.9 kJ mol(-1). (C) 2005 Elsevier B.V. All rights reserved.