Surfactant-induced chirality transfer, amplification and inversion in a cucurbit[8]uril–viologen host–guest supramolecular system

Abstract

Chirality manipulation in supramolecules, especially in multicomponent supramolecular structures, is crucially desired. Herein, we report a feasible approach to achieve the chirality transfer, amplification, and inversion in a ternary supramolecular system consisting of new chiral molecules L4, which contain two positively charged viologen units and express an R configuration, cucurbit[8]uril (CB[8]) molecules, and surfactant molecules sodium dodecyl sulfate (SDS). A series of experimental techniques and measurements were used to investigate the mechanism of chirality changes, including circular dichroism (CD) spectroscopy, absorption spectroscopy, isothermal titration calorimetry (ITC), and small-angle X-ray scattering (SAXS). The achiral SDS molecules were found to facilitate the transformation of chirality from the molecular level to the supramolecular level. The CD signals could be regulated precisely as the coassembled ternary supramolecular structure of the L4/SDS/CB[8] system strongly depended on the quantity of each component. When the molar ratio of L4, SDS, and CB[8] reached 3 : 2 : 2, a significant chirality inversion from the positive upward CD signals to the negative downward CD signals was observed. The combination effects of non-covalent interactions which involve electrostatic and host–guest interactions caused a supramolecular structure packing change from the lamellar to the rectangular stacking pattern and resulted in a large chirality inversion at the supramolecular level. Our results may provide a facile approach to regulate multiple chiral activities in multicomponent supramolecular systems.