Thermodynamics of lanthanide(III) complex formation with nitrogen-donor ligands in dimethyl sulfoxide

Abstract

Potentiometric and calorimetric data for the complexation of lanthanide(III) cations by the neutral nitrogen-donor ligands diethylenetriamine or triethylenetetramine in anhydrous dimethyl sulfoxide at 25 °C and in an ionic medium of 0.1 mol dm^–3 NEt₄ClO₄ have been obtained. All the complexes are strongly enthalpy stabilized while the entropy changes are unfavourable. The results are discussed in terms of the charge density of the metal ions, the solvation changes along the lanthanide(III) series and the structural and conformational characteristics of the ligands.