Synergistic lanthanide extraction triggered by self-assembly of heterodinuclear Zn(II)/Ln(III) Schiff base/carboxylic acid complexes

ABSTRACT

The studies reported here focus on the extraction of La(III), Eu(III), and Yb(III) by chelating hexadentate 3-alkoxy-2-hydroxyphenyl substituted diimine ligands using the extraction system Ln(NO₃)₃–Zn(NO₃)₂–NaNO₃–buffer–H₂O/diimine-n-caprylic acid–CHCl₃. Significant synergistic enhancement has been observed for the Ln(III) extraction from nitrate media in the presence of Zn(II) and n-caprylic acid. These effects can be interpreted by self-assembly of heterodinuclear Zn(II)/Ln(III) complexes with both deprotonated extractants in the organic phase taking into account solution and solid-state structural studies. The structures identified and the extraction behavior as well as the different factors influencing the process will be discussed in detail. The goals of these experiments are to find preferred structure-extractability relationships for the synergistic systems investigated.

KEYWORDS:

• Synergistic lanthanide extraction
• schiff base ligands
• supramolecular chemistry
• self-assembly of heterodinuclear Zn(II)/Ln(III) complexes
• x-ray crystal structures

Acknowledgments

The authors would like to thank Professor Katsutoshi Inoue for his excellent contributions in the field of solvent extraction and for his great support and friendship during our longstanding collaboration.

The authors thank the Federal Ministry of Education and Research in Germany (BMBF project 02NUK014A) for financial support. They also thank M. Kokoschka who provided the computational calculations and P. Lange for carrying out analytical measurements. Thanks are also due to J. J. Weigand for his support and M. Acker for providing radiotracer technique.

Supplementary material

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