Grafting of phosphorus-containing tetrahydroxy(thia)calixarenes on silica enhances europium(III) adsorption

Abstract

One pot sequential reactions of silica gel with tetrachlorosilane/triethylamine mixture and after with the conical upper rim tetraphosphorylated tetrahydroxy(thia)calixarenes yielded porous organo-inorganic sorbents modified by spatially ordered phosphonate, phosphinate or phosphine oxide groups capable of co-operative binding of metal cations. The grafting improves efficacy of europium(III) sorption by the silica gels. DFT calculations of the calixarene-Eu³⁺ complexes predict a calixarene flattened cone conformation with the coordination of Eu³⁺ cation to three of four P = O oxygen atoms and one of the aromatic systems. Adding three water molecules excludes completely cation–π interactions.

GRAPHICAL ABSTRACT

Keywords:

• Calixarenes
• organophosphorus ligands
• silica gel
• sorbents
• europium

Acknowledgements

A. B. Rozhenko thanks TURBOMOLE GmbH for kind providing the license for the newest version (v. 7.6) of the TURBOMOLE set of programs.

Disclosure Statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This work was partially supported by the National Academy of Sciences of Ukraine through grant «Synthesis of selective ligands and surface modification of polymeric materials for radionuclide extraction».