Oligoether‐Strapped Calix[4]pyrrole: An Ion‐Pair Receptor Displaying Cation‐Dependent Chloride Anion Transport |
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| Authors: | In‐Won Park Jaeduk Yoo Bohyang Kim Dr Suman Adhikari Dr Sung Kuk Kim Yerim Yeon Dr Cally J E Haynes Jennifer L Sutton Dr Christine C Tong Dr Vincent M Lynch Prof Jonathan L Sessler Prof Philip A Gale Prof Chang‐Hee Lee |
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| Institution: | 1. Department of Chemistry, Kangwon National University, Chun Cheon, 200‐701 (Korea), Fax: (+82)?33‐253‐7582;2. Department of Chemistry and Biochemistry, 1 University Station‐A5300, The University of Texas at Austin, Austin, Texas 78712‐0165 (USA), Fax: (+1)?512‐471‐5009;3. School of Chemistry, University of Southampton, Southampton, SO17 1BJ (UK), Fax: (+44)?23‐80596805 |
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| Abstract: | A ditopic ion‐pair receptor ( 1 ), which has tunable cation‐ and anion‐binding sites, has been synthesized and characterized. Spectroscopic analyses provide support for the conclusion that receptor 1 binds fluoride and chloride anions strongly and forms stable 1:1 complexes ( 1? F]? and 1? Cl]?) with appropriately chosen salts of these anions in acetonitrile. When the anion complexes of 1 were treated with alkali metal ions (Li+, Na+, K+, Cs+, as their perchlorate salts), ion‐dependent interactions were observed that were found to depend on both the choice of added cation and the initially complexed anion. In the case of 1? F]?, no appreciable interaction with the K+ ion was seen. On the other hand, when this complex was treated with Li+ or Na+ ions, decomplexation of the bound fluoride anion was observed. In contrast to what was seen with Li+, Na+, K+, treating 1?F ]? with Cs+ ions gave rise to a stable, host‐separated ion‐pair complex, F ?1? Cs], which contains the Cs+ ion bound in the cup‐like portion of the calix4]pyrrole. Different complexation behavior was seen in the case of the chloride complex, 1? Cl]?. Here, no appreciable interaction was observed with Na+ or K+. In contrast, treating with Li+ produces a tight ion‐pair complex, 1? Li ? Cl], in which the cation is bound to the crown moiety. In analogy to what was seen for 1? F]?, treatment of 1? Cl]? with Cs+ ions gives rise to a host‐separated ion‐pair complex, Cl ?1? Cs], in which the cation is bound to the cup of the calix4]pyrrole. As inferred from liposomal model membrane transport studies, system 1 can act as an effective carrier for several chloride anion salts of Group 1 cations, operating through both symport (chloride+cation co‐transport) and antiport (nitrate‐for‐chloride exchange) mechanisms. This transport behavior stands in contrast to what is seen for simple octamethylcalix4]pyrrole, which acts as an effective carrier for cesium chloride but does not operates through a nitrate‐for‐chloride anion exchange mechanism. |
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| Keywords: | binding sites calixarenes crown compounds ion pairs ion transport structure‐activity relationships |
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