Thermodynamics of complexation of lanthanides by methoxybenzoates

The thermodynamic parameters of complexation of lanthanide cations by ortho-, meta- and para- methoxybenzoates have been measured using potentiometric and calorimetric techniques at 25 °C and an ionic strength of 0.10 M (NaClO4). The values of logβ101 correlate well with the ligand acid values of pKa, reflecting the strongly ionic nature of the metal-ligand interaction. No evidence is found for extra charge polarization in these aromatic ligands due to the lanthanide complexation.