Synthesis of Ionizable Calix[4]arenes for Chelation of Selected Divalent Cations

Markus Blumberg; Karrar Al-Ameed; Erik Eiselt; Sandra Luber; Constantin Mamat

doi:10.3390/molecules27051478

Synthesis of Ionizable Calix[4]arenes for Chelation of Selected Divalent Cations

Molecules. 2022 Feb 22;27(5):1478. doi: 10.3390/molecules27051478.

Authors

Markus Blumberg^{1

2}, Karrar Al-Ameed³, Erik Eiselt¹, Sandra Luber³, Constantin Mamat^{1

2}

Affiliations

¹ Helmholtz-Zentrum Dresden-Rossendorf, Institut für Radiopharmazeutische Krebsforschung, Bautzner Landstraße 400, D-01328 Dresden, Germany.
² Fakultät Chemie und Lebensmittelchemie, Technische Universität Dresden, D-01062 Dresden, Germany.
³ Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.

Abstract

Two sets of functionalised calix[4]arenes, either with a 1,3-crown ether bridge or with an open-chain oligo ether moiety in 1,3-position were prepared and further equipped with additional deprotonisable sulfonamide groups to establish chelating systems for selected cations Sr²⁺, Ba²⁺, and Pb²⁺ ions. To improve the complexation behaviour towards these cations, calix[4]arenes with oligo ether groups and modified crowns of different sizes were synthesized. Association constants were determined by UV/Vis titration in acetonitrile using the respective perchlorate salts and logK values between 3.2 and 8.0 were obtained. These findings were supported by the calculation of the binding energies exemplarily for selected complexes with Ba²⁺.

Keywords: barium; calixarenes; chelation.