Supramolecular Capsules Derived from Calixpyrrole Scaffolds |
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Authors: | Pablo Ballester |
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Affiliation: | Institute of Chemical Research of Catalonia (ICIQ), Avda. Països Catalans 16, 43007 Tarragona (Spain) phone: +34 977 920200 (ext. 316) fax: +34 977 920224 |
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Abstract: | This review article describes recent results obtained in the self-assembly of supramolecular capsules derived from calixpyrrole components. Due to their ease of synthesis, calix4]pyrroles are by far the most typically used units in these systems. A clear conformational and structural analogy exists between calix4]arenes and calix4]pyrroles. However, to date, the number of examples in the literature that use calix4]pyrrole scaffolds instead of calix4]arenes for the construction of supramolecular capsules is still meager. Four different approaches are considered for the use of calix4]pyrrole derivatives in the assembly of molecular capsules. Firstly, in an analogous manner to resorcin4]arenes and pyrogallol4]arenes, aryl-extended calix4]pyrroles with hydroxyl groups in their upper rim self-assemble through direct or mediated rim-to-rim interactions into capsular aggregates. Secondly, aryl-extended calix4]pyrroles having non-complementary hydrogen-bonding groups in their upper rim form dimeric templated capsules with suitable substrates. Thirdly, the elaboration of the upper rim of the calix4]pyrroles with urea groups affords dimeric capsules with polar functionalized interiors that closely resemble their tetraurea calix4]arene analogs. Finally, the chemical modification of the pyrrole units of octamethyl calix4]pyrrole into tetrathiafulvalene derivatives yields dimeric capsules induced by anion coordination that display interesting properties in the binding of electron-poor guests. |
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Keywords: | calix[4]pyrrole molecular capsules reversible encapsulation self-assembly self-sorting supramolecular chemistry |
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