Studies on the Complexes of Lanthanide ion with Multidentate Ligand (). Determination of Thermodynamic Parameters with Solution Calorimetric Method in Nonaqueous Solvents

摘要

Log K, ?aH and ?aS for the complexation of La3+, Ce3+ and Eu3+ with various multidentate ligand containing crown ether, diaza crown ether and diamine ether have been determined in methanol and acetonitril solutions at 25?é by solution calorimetric titration method. The greater stability constant of La3+-15C5 than those of 18C6 diaza [2.2] in methanol are discussed in terms of the size of metal ion and the ligand cavity and of metal ion solvation. The stabilities of Ce3+ and La3+ ion complexes with a various multidentate ligand in acetonitril are in the order of (diamine ether) < 18C6 < 15C5 < diaza [2. 1] < diaza [2.2]. This result are discussed in terms of the covalent bonding of -NH group in diaza ligand in addition to the ion-dipole interaction and of the optimum size concept and of the macrocyclic effect. The stability constants of Ce3+, La3+ and Eu3+-diaza [2.2] complexes in acetonitril are increased with the following order: Eu3+ < La3+ < Ce3+, that is increasing order of the optimum size and of the charge density of metal ion.