Clay complexes arenes

Fig. 10a-f Examples of the structural motifs of p-ferf-butylcalix[4] arene derivatives a guest-free structure b 1 1 complex c 2 1 host-guest complex d hydrogen-bonded structure with an amine guest e self-inclusion structure f 1 1 host-guest clay mimic structure. (Adopted from [44] with permission)... 

The sulfonate derivatives (Fig. 4A), in which introduction of suitable ligand functions takes place at the para-position of the aromatic ring, are the most widely studied of the w ater-soluble calixarenes. Their solid-state binding to a wide range of metallic cations and complexes was reviewed by Raston and Atwood. The ability of these molecules to intercalate cations in expandable layers between bilayers of para-sulfonato-calix[4]arene led Atwood and Coleman in 1988 to name these systems Organic Clays." (Fig. 4C). Since then. Atwood extended the structural types observed to include liposomal analogues, tubes, and various Archimedian and Platonic solids."... 

The chemical behavior of clays is also mimicked by the title complexes in two respects the presence of cation-exhange capabilities and the reduced water content in the ammonium salt [20]. Currently, other similarities between clays and the water-soluble calixarenes are being probed. In particular, the size- and polarity-selective cavity of the calix[4]arene sulfonates is finding utility in the separation of organic substances, cations, anions, and neutral molecules, from aqueous feed streams. 

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