Water soluble diaza crown ether derivative: Synthesis and barium complexation studies

The combination of a mcrocyclic cavity with o-diaminobenzene derivative offers a new redox-active and water-soluble ligand for barium that incorporates 12 potential donors. The chelator was synthesized in four steps from diaza-18-crown-6-ether and fully characterized in solution by cyclic voltammetry, UV–Visible and NMR spectroscopies in the presence of barium. The corresponding complex exhibits a 1:1 stoichiometry in solution whereas it crystallizes as 3:2 (M:L) as evidenced by X-ray diffraction studies. The high affinity constant for barium estimated by NMR and electronic absorption techniques in aqueous medium, makes this ligand a promising candidate for redox-induced barium release.

Graphical abstractBarium complexation studies of this new redox-active diazacrownether chelator evidenced widely different stoichiometries in aqueous solution and in the solid state.Figure optionsDownload full-size imageDownload as PowerPoint slide