Bifunctional Recognition: Simultaneous Transport of Cations and Anions through a Supported Liquid Membrane

摘要

The design and synthesis of macrocyclic cation receptors is very well documented in supramolecular chemistry. Despite anion recognition being a relatively new area of research, both positively charged and neutral receptors for anionic species have been prepared in the last few years. Recently we described the synthesis of neutral bifunctional receptors for the simultaneous complexation of hydrophilic anions and cations in organic media. In these receptors, the appropriate binding sites for both anionic and cationic species are covalently combined in a neutral molecule. In this Communication, we report our preliminary results on simultaneous transport of cations and anions through a supported liquid membrane (SLM) assisted by a novel type of neutral bifunctional receptor. To the best of our knowledge, this is the first example of carrier-assisted cotransport, in which the anion and cation of a hydrophilic salt are bound and transported simultaneously through a membrane. Our synthetic strategy is based on the attachment of both cation and anion binding sites to the rigid lipophilic calix[4]-phosphate (H_2PO_4~- ) and chloride (Cl~-) anions and that the calix[4]arene crown-6 (1,3-alternate) fragment is capable of selective complexation of cesium ion (Cs~+).