Photoswitchable anion recognition via synergy between chalcogen bonding and hydrogen bonding

Abstract

Exploring photoresponsive noncovalent interactions with controllable tunability is of great significance for advancing supramolecular recognition and smart dynamic materials. Herein, we report light-responsive hydrazone-based receptors incorporating a telluroazole-derived chalcogen bond donor for photoswitchable anion binding. This system undergoes bidirectional E/Z photoisomerization, which modulates an intramolecular NH⋯N hydrogen bond and hence enhances the electrophilicity of the tellurium center in the Z-isomer for chalcogen bonding. This structural change leads to a significant increase in the binding affinity of the Z-isomer toward halide anions (Cl⁻, Br⁻, and I⁻), with binding constants up to 20 times higher than the E-isomer. The incorporation of electron-withdrawing substituents amplifies the polarization, allowing the control over binding strength and selectivity. Moreover, anion binding facilitates Z → E photoisomerization, offering a feedback mechanism between recognition and structural switching. This study demonstrates a new strategy combining reversible photochemical control and synergistic noncovalent interaction modulation, offering an effective approach for the development of stimuli-responsive supramolecular systems.