Reversible Manipulation of Supramolecular Chirality using Host-Guest Dynamics between β-Cyclodextrin and Alkyl Amines.

Host-guest interactions are widely employed in constructing responsive materials, although less is known to manipulate the chiral property of materials using such host-guest dynamics. With the supramolecular self-assembly based on beta-cyclodextrin (beta-CD) and alkyl amines (CH3(CH2)(n-1)NH2), we report that faster host-guest dynamics induces a dipole located above the cavity of beta-CD, whereas slower dynamics create in-cavity dipole. These two scenarios correspond to negative and positive chiral signals, respectively. Considering that a larger fraction of amines facilitates faster exchange between the threaded and unthreaded amines, the chiral signal for the right-handed helical ribbons can be manipulated simply by alternatively increasing the fraction of amines and beta-CD. Excitingly, enzyme responsive supramolecular chirality is obtained as a result of shifting the molar ratio by enzyme triggered hydrolysis of beta-CD. We expect that this strategy may open up an area of rationally designed chiral supramolecular materials based on host-guest chemistry.