Ionizable (Thia)calix[4]crowns as Highly Selective 226Ra2+ Ionophores


Leeuwen, Fijs W.B. van and Beijleveld, Hans and Miermans, Cornelis J.H. and Huskens, Jurriaan and Verboom, Willem and Reinhoudt, David N. (2005) Ionizable (Thia)calix[4]crowns as Highly Selective 226Ra2+ Ionophores. Analytical Chemistry, 77 (14). pp. 4611-4617. ISSN 0003-2700

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Abstract:The 226Ra2+ selectivity of the ionizable (thia)calix[4]crowns 1-4 was determined in the presence of a large excess of the most common alkali and alkaline earth cations. Selective 226Ra2+ (2.9 × 10-8 M) extraction occurs even at extremely high Mn+/226Ra2+ ratios of 3.5 × 107 [Mn+ = Na+, K+, Rb+, Cs+, Mg2+, Ca2+, and Sr2+ (1 M)] and an ionophore concentration of 10-4 M. The selectivity coefficients log(KRaex/KMex) are ~3.5 for Mg2+, Ca2+, and Sr2+. In the presence of Ba2+, which has very similar chemical properties, only the thiacalix[4]crown-6 derivative 4 showed a selectivity for 226Ra2+. In addition to the remarkable 226Ra2+ selectivities, the effective pH range (pH 8-13) of the thiacalix[4]crown dicarboxylic acids (3 and 4) allows for full regeneration of the ionophores at lower pH values (pH <6).
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Copyright:© 2005 American Chemical Society
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Metis ID: 225094