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Calix[6]arene based molecular boxes

par Lavendomme, Roy ; [et al.]
Référence Journée Scientifique Annuelle de la Société Royale de Chimie (2013: Mons, Belgium)
Publication Non publié, 2013

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Résumé :

Calix[n]arenes are polyphenolic platforms which have been studied over decades as receptors in host-guest chemistry. Calix[4]arenes are the most studied despite their small cavity which is unable to include guests except small linear molecules. Comparatively, calix[6]arenes have a larger cavity (Ø = 8-10Å) which is well-adapted for the selective inclusion of organic molecules. Usually calix[6]arene based receptors are constrained in the cone conformation in order to present a concave cavity suitable to include a guest. In this conformation, the calix[6]arene cavity is open to outside at the large rim and thus the guest is not fully encapsulated. Only one example of calix[6]arene based receptors that adopts a major 1,3,5-alternate conformation was reported. This calix[6]arene (X6Boc6) is decorated with 6 bulky Boc groups on the phenolic position and constitutes a very rare example of molecular box for organic molecules. Indeed, thanks to (i) its highly encumbered structure (i.e. 12 tert-Butyl groups around its cavity) and (ii) its original conformation, this calix[6]arene can lead to completely closed inclusion complexes. Inclusion complexes have been characterized by NMR spectroscopy and X-ray diffraction. In order to obtain molecular boxes with reinforced complexation properties toward guests, we synthesized related calix[6]arenes displaying hydrogen bond donor groups in place of some of the Boc groups.