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

Abstract

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 ΔH 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 ∼3.0 nm. We presume that these cylinder are twisted because of chiral transfer from the chiral galactose moiety and show ICD.