Supramolecular Chirality: Vesicle-to-Chiral Helix Transition of the Micelles Consisting of a Sugar-Bearing Calix[4]arene Surfactant

Supramolecular self-assembly and the resulting chiral transfer from the molecular level to the nanoscale is a major topic in modern supramolecular chemistry. We synthesized a galactose-bearing calix[4]arene surfactant (chiral) and mixed it with a primary amine-bearing analogue (achiral). The mixture showed strong induced circular dichroism (ICD) at an almost 3:2 molar ratio of the two surfactants, and exothermic heat was observed upon mixing. The magnitude of Delta H was comparable to that of van der Waals interactions. This phenomenon indicated that the ICD can be ascribed to the formation of a new supramolecular assembly in which the stoichiometric interaction between the two molecules leads to complexation and the resultant complex has chiral morphology. Transmission electron microscopy and small-angle X-ray scattering showed that the galactose-bearing surfactant forms vesicles, and the mixing induces a transition from the vesicles to threadlike cylinders with a diameter of similar to 3.0 nm. We presume that these cylinder are twisted because of chiral transfer from the chiral galactose moiety and show ICD.