Thiacalix(4)arene derivatives as radium ionophores: a study on the requirements for Ra2+ extraction

F.W.B. van Leeuwen, H. Beijleveld, Aldrik Velders, Jurriaan Huskens, Willem Verboom, David Reinhoudt

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13 Citations (Scopus)
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The synthesis and NOE-based structural characterization is described of thiacalix[4]arene tricarboxylic acid ( 7), thiacalix[4]crown-5 and -6 monocarboxylic acids ( 2 and 5), and the bis(N-methylsulfonyl)thiacalix[4]crowns-5 and -6 ( 4a,b). The 226Ra2+ selectivity coefficients, log(KRaex/KMex), of the new thiacalix[4]arene derivatives are compared directly with those of thiacalix[4]crown-5 and -6 ( 1a,b), thiacalix[4]crown-5 and -6 dicarboxylic acids ( 3a,b), and thiacalix[4]arene di- and tetracarboxylic acids ( 6 and 8). Thiacalix[4]arene dicarboxylic acid ( 6) already exhibits a high 226Ra2+ selectivity, but this is significantly improved in the case of 3b, having an additional crown-(6-)ether bridge. The covalent combination of a crown ether and carboxylic acid substituents as in the thiacalix[4]arenes 2, 3a,b, 4a,b, and 5 gives a better 226Ra2+ selectivity in the presence of Sr2+ or Ba2+ than mixtures of dibenzo-21-crown-7 and thiacalix[4]arene dicarboxylic acid ( 6) or of pentadecanoic acid and thiacalix[4]crown-6 ( 1b).
Original languageEnglish
Pages (from-to)1993-2001
JournalOrganic & biomolecular chemistry
Issue number10
Publication statusPublished - 2005


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