Standard Enthalpies of Formation of [Ln(Gly)3(H2O)2]Cl3·2H2O (Ln = Pr, Nd; Gly = Glycine): A Calorimetric Study

Abstract

Crystals of two coordination compounds of rare earth chlorides with glycine, [Ln(Gly)3(H2O)2]Cl3·2H2O (Ln = Pr, Nd; Gly = glycine), were prepared and characterized. Using a solution-reaction isoperibol calorimeter, the standard molar enthalpies of reaction for the general thermochemical reaction, LnCl3·6H2O(s) + 3Gly(s) = [Ln(Gly)3(H2O)2]Cl3·2H2O(cr) + 2H2O(l) (Ln = Pr, Nd; Gly = glycine), were determined at T = 298.15 K, as (19.2 ± 0.4) kJ·mol-l and (63.4 ± 0.5) kJ·mol-l, respectively. From the above standard molar enthalpies of reaction and other auxiliary thermodynamic quantities, the standard molar enthalpies of formation of [Ln(Gly)3(H2O)2]Cl3·2H2O (Ln = Pr, Nd; Gly = glycine), at T = 298.15 K, have been derived to be −(3875.7 ± 1.1) kJ·mol-l and −(3825.2 ± 1.1) kJ·mol-l, respectively.