EQUILIBRIUM STUDIES OF LANTHANIDE NITRATE COMPLEXATION IN AQUEOUS METHANOL

The complexation between Er(III) and Nd(III) with nitrate and Perchlorate was studied by UV-vis spectroscopy. In water, no complexes are detected between the lanthanide cations and Perchlorate. The addition of methanol causes complexation only between Er(III) and Perchlorate. Under the same conditions, the stoichiometries of the nitrate complexes in water are different for Nd(III) and Er(III) compared to Eu(III). These differences continue as a function of solvent composition even at low water mole fractions where Eu(III) and Er(III) form complexes up to the tris complex, whereas Nd(III) only forms complexes up to the bis complex. Equilibrium constants and complexation thermodynamics are presented and used in discussing differences within the lanthanide series. © 1990, American Chemical Society. All rights reserved.