Efficient divalent metal cation extractions with di-ionizable calix[4]arene-1,2-crown-4 compounds |
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Authors: | Chuqiao Tu |
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Institution: | Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, 79409-1061 TX, USA |
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Abstract: | Di-ionizable calix4]arene-1,2-crown-4 ethers in the cone conformation were synthesized and their conformation and regioselectivity verified by NMR spectroscopy. These new ligands exhibited high Ba2+ selectivity in competitive solvent extraction of alkaline earth metal cations from aqueous solutions into chloroform. The selectivity order was Ba2+>>Sr2+>Ca2+>Mg2+ with Ba2+/Sr2+ selectivity exceeding 100. The ligands also exhibited high extraction ability for Pb2+ and for Hg2+ in single species extraction. With variation of proton-ionizable groups, which are oxyacetic acid moieties and N-(X)sulfonyl oxyacetamide units with X=methyl, phenyl, 4-nitrophenyl, and trifluoromethyl, ‘tunable’ ligand acidity was obtained. |
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Keywords: | Calixarenes Crown compounds Molecular recognition |
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