Abstract
A series of bis(crown ether)sbased-upon a xanthene-4,5-dicarboxylic acid skeletonwas prepared and their ionophoric properties towardalkali metal cations were investigated. Bis(crownether)s bearing 15-crown-5 and 18-crown-6 moietiesexhibited pronounced extraction efficiencies towardK+ and Cs+ ions, respectively, and theextraction constant estimated by solvent extractionstudies was as high as 109 for the 2-K+ and 3-Cs+ systems. Using UVtitration of potassium picrate with 2 in THF, thecomplex was found to have a structure of a completelyencapsulated guest in the host. In transportexperiments, the bis(crown ether)s showed nosignificant selectivity pattern compared withextraction results, again implying the strongcomplexation of bis(crown ether)s. Ion-selectiveelectrode studies also demonstrated that the selectiveionophoric properties of 2 toward K+ werereminiscent of the natural antibiotic valinomycinexcept for a somewhat slow response.
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More From: Journal of Inclusion Phenomena and Molecular Recognition in Chemistry
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