Photo switchable activation of sigma-hole

Governing intermolecular interactions is crucial for i) controlling how molecules communicate within a molecular assembly, and ii) fine-tuning the physical and chemical properties of ordered materials.

Halogen bonds (XB) and chalcogen bonds (ChB) are two sigma-hole interactions that are garnering significant attention across various fields such as supramolecular chemistry, crystal engineering, anion recognition, and catalysis, owing to their directionality and strong predictability.

Among the numerous factors influencing the molecular organization of interacting partners, interaction strength plays a significant role. Its increase or decrease is pivotal in activating or deactivating recognition phenomena. Current strategies to optimize the recognition process are limited to strongly activated XB/ChB donors.

The switching on/off (reversible control) of XB and ChB interactions has never been explored and could have valuable implications in virtually all fields where these interactions occur. This seems to be the next essential challenge in the realm of sigma-hole interactions and will be addressed by HALO.

HALO aims to: (a) Photo-induced manipulation of the inherent electrostatics of heavier halogen/chalcogen atoms to toggle their involvement in electrophilenucleophile interactions on or off, (b) Exploit this control over interactions to develop new strategies for time-honored recognition processes, e.g., sensing of toxic anions like CN, NO2, AsO43.

While sigma-hole interactions have been known for decades, their photochemical activation has not been addressed until now.

Notably, the hydrogen bond, the most utilized molecular interaction across interdisciplinary fields, does not offer any means for such electrostatic control.

The breakthrough of this project lies in introducing reversibility to the state-of-the-art XB/ChB-based recognition strategies, paving the way for a new generation of XB/ChB-based light-responsive materials for green processes and devices.