New gadolinium(III) complexes with simple organic acids (Oxalic, Glycolic and Malic Acid)

The formation of colorless gadolinium complexes (x, y, z), between x gadolinium ions, y ligands and z protons, of some organic acids, has been studied in aqueous solution. In this work we present the results of investigations on the interaction of the gadolinium ion (Gd(III)) with simple carboxylic acids such as oxalic acid, glycolic acid and malic acid, in dilute aqueous solution with pH values between 5.50 and 7.50. The obtained gadolinium complexes with oxalate, glycolate and malate ion are colorless and havenʹt any absorption band in UV-visible, in this sense, the indirect photometry studies used to identify the major di-nuclear and tri-nuclear complexes. This technique allowed us to calculate the compositions and the stabilities constants of these major complexes in solution and the stability constant depends on acidity, the structures of the final complexes were determined by means of IR and Raman spectroscopies.