INNER AND OUTER-SPHERE COMPLEXATION BETWEEN EUROPIUM(III) AND GLYCINEIN AQUEOUS-METHANOL

The complexation between Eu(III) and glycine in water and aqueous meth anol was studied by UV-visible spectroscopy. Substantial increases in the extent of complexation occur with increasing methanol mole fractio n. Changes in the signs of the complexation enthalpy and entropy with increasing organic solvent character were interpreted in terms of incr easing inner sphere complexation, coupled to the formation of outer sp here complexes, which were not present to a measurable extent in aqueo us solutions. Only 1:1 complexes were found above 10% water compositio n, whereas a bis(glycinato) complex forms at lower water percentages.