Guest-induced chain folding in amphiphilic calixarene structures

Abstract

Amphiphilic calixarenes represent a promising class of derivatives, potentially useful for transporting molecules because of their ability to self-organize as Solid Lipid Nanoparticles in water. The current study shows that after derivatization of the para-H-calix[4]arene with hexanoyl chains, the resultant amphiphilic calixarenes retain their properties to complex small organic molecules. The solid structures of the complexes of para-hexanoyl-calix[4]arene with methanol, dimethylformamide–methanol, dimethyl sulfoxide–methanol and nitrobenzene are reported. As for the p-tert-butyl calix[4]arene, aliphatic guests are stabilized by a variety of short-range interactions including C–H⋯π or π−π interactions. Moreover, the presence of the grafted hydrophobic chains generates an extension of the hydrophobic calixarene cavity and thus provides another site where complexation can take place. The structures show that the geometry of the hexanoyl chains is modified by the presence of the guest molecules and that the chains fold over to aid encapsulation of the guest.