Reversible Manipulation of Supramolecular Chirality using Host–Guest Dynamics between β‐Cyclodextrin and Alkyl Amines

Abstract

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 β-cyclodextrin (β-CD) and alkyl amines (CH(CH)NH), we report that faster host-guest dynamics induces a dipole located above the cavity of β-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 β-CD. Excitingly, enzyme responsive supramolecular chirality is obtained as a result of shifting the molar ratio by enzyme triggered hydrolysis of β-CD. We expect that this strategy may open up an area of rationally designed chiral supramolecular materials based on host-guest chemistry.

Self-assembly of chiral supra-amphiphiles

“…Huang, Yan ad co-workers reported a chiral supra-amphiphile based on b-cyclodextrin and a long alkyl amine. 106 Under vortex mixing, achiral organic amines CH 3 (CH 2 ) nÀ1 NH 2 (n = 6-10) were added into the saturated solution of b-cyclodextrin. For shorter chain amines of CH 3 (CH 2 ) nÀ1 NH 2 (n = 6, 7), NMR and FT-MS spectra indicated that a host-guest complex was not formed, which was also co-evidenced by no Tyndall effect.…”

α-Cyclodextrin-Catalyzed Symmetry Breaking and Precise Regulation of Supramolecular Self-Assembly Handedness with Harata–Kodaka’s Rule

“…To further confirm the above postulation, we decided to measure the host–guest dynamics-dependent ICD of the cone-shell self-assemblies since the host–guest dynamics has a great impact on the threading position of the guest in the cavity of α-CyD, which may reverse the ICD at properly designed host dynamics . Both concentrations and host-to-guest ratios are effective protocols to achieve dynamic control . In principle, at lower concentrations, the exchanging rate between the C4AZO molecules in and out of the α-CyD is slower, so that the C4AZO molecules have time to thread deeper in α-CyD.…”

“…On the contrary, if the chromophore is outside of the cavity of CyDs, a negative ICD should be expected . In the past half century, the above Harata–Kodaka rule was extensively utilized to predict the absolute configuration of the achiral guest in the cavity of CyDs − but has never been considered in symmetry breaking in racemic self-assembled structures and controls the handedness of supramolecular structures.…”

Chirality at the Nanoparticle Surface: Functionalization and Applications

“…Chiral recognition also plays a key part in the field of chemical, biological, and pharmaceutical sciences because of the precise orientation of functional groups in chiral molecules [6][7][8][9]. Many active pharmaceutical ingredients (APIs) are chiral and the two enantiomers often present different pharmacokinetic, therapeutic, and toxicological profiles.…”