Reversible Light-Induced Dimerization of Secondary Face Azobenzene-Functionalized β-Cyclodextrin Derivatives

& beta;-cyclodextrin(& beta;CyD) derivatives equippedwith aromaticappendages at the secondary face exhibit tailorable self-assemblingcapabilities. The aromatic modules can participate in inclusion phenomenaand/or aromatic-aromatic interactions. Supramolecular speciescan thus form that, at their turn, can engage in further co-assemblingwith third components in a highly regulated manner; the design ofnonviral gene delivery systems is an illustrative example. Endowingsuch systems with stimuli responsiveness while keeping diastereomericpurity and a low synthetic effort is a highly wanted advancement.Here, we show that an azobenzene moiety can be "clicked"to a single secondary O-2 position of & beta;CyD affording 1,2,3-triazole-linked & beta;CyD-azobenzene derivatives that undergo reversible light-controlledself-organization into dimers where the monomer components face theirsecondary rims. Their photoswitching and supramolecular propertieshave been thoroughly characterized by UV-vis absorption, inducedcircular dichroism, nuclear magnetic resonance, and computationaltechniques. As model processes, the formation of inclusion complexesbetween a water-soluble triazolylazobenzene derivative and & beta;CyDas well as the assembly of native & beta;CyD/& beta;CyD-azobenzenederivative heterodimers have been investigated in parallel. The stabilityof the host-guest supramolecules has been challenged againstthe competitor guest adamantylamine and the decrease of the mediumpolarity using methanol-water mixtures. The collective datasupport that the E-configured & beta;CyD-azobenzenederivatives, in aqueous solution, form dimers stabilized by the interplayof aromatic-aromatic and aromatic-& beta;CyD cavity interactionsafter partial reciprocal inclusion. Photoswitching to the Z-isomer disrupts the dimers into monomeric species, offeringopportunity for the spatiotemporal control of the organizational statusby light.