A Novel C3v-Symmetrical Calix[6](aza)cryptand with a Remarkably High and Selective Affinity for Small Ammoniums
- 11 March 2004
- journal article
- research article
- Published by American Chemical Society (ACS) in The Journal of Organic Chemistry
- Vol. 69 (15) , 4879-4884
- https://doi.org/10.1021/jo035859o
Abstract
The three-step synthesis of a calix[6]arene capped with a TAC unit is presented. The novel C(3v)-symmetrical calix[6](aza)cryptand displayed an exceptionally high affinity for small ammoniums. NMR and X-ray diffraction analyses demonstrated the formation of endo-complexes. These complexes are stabilized thanks to (i) hydrogen bonding to both the aza cap and one phenolic unit of the calixarene and to (ii) cationic and CH-pi interactions between the ammonium and the aromatic walls of the host. Combined extraction and competitive binding experiments yielded the free energies of bindings DeltaG degrees in chloroform. The values are the highest ever obtained with a calixarene-type host. Calix[6]TAC displayed the best affinity for EtNH(3)(+). Comparison with other small ammoniums emphasizes the high selectivity of the recognition process.Journal ArticleArticle faisant la couverture du numéro du 23 juillet 2004info:eu-repo/semantics/publisheKeywords
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