Synthesis and study on complexes of some lanthanides to L-isoleucine

The formation of lanthanide (La, Pr and Nd) complexes with L-isoleucine have been studied as a function of pH values. The titrations were performed at 25 oC, and the ionic strength of the medium was maintained at 0.10 M by using potassium nitrate. The formation curves of their complexes (n-p[L]) were obtained by means of the titration data. Then the stability constants were determined in relation to these curves. The complexes were synthesized in the mixture of water-ethanol. The coordination of the complexes were determined by elements analysis, 13C-NMR, 1H-NMR and IR methods. These complexes are formulated as Ln(HIle)3.(NO3)3.3H2O; (Ln: La, Pr and Nd,; L-Ile: L-isoleucine). Comparison of the IR, 13C-NMR and 1H-NMR spectra of the ligand with those of their complexes shows that isoleucine acts as a bidentate ligand bonding the lanthanide ions through the amino and carboxylate groups. (author)