THERMODYNAMICS OF LANTHANIDE(III) COMPLEX-FORMATION WITH NITROGEN-DONOR LIGANDS IN DIMETHYL-SULFOXIDE

Potentiometric and calorimetric data for the complexation of lanthanid e(III) cations by the neutral nitrogen-donor ligands diethylenetriamin e or triethylenetetramine in anhydrous dimethyl sulfoxide at 25-degree s-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 c harge density of the metal ions, the solvation changes along the lanth anide(III) series and the structural and conformational characteristic s of the ligands.