Visible light-triggered gel-to-sol transition in halogen-bond-based supramolecules

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Photochemistry

Background:

• Photoresponsive supramolecular gels are valuable but often rely on harmful UV light.
• Halogen bonds are effective supramolecular assembly drivers but rarely used for visible light responsiveness.
• Developing visible light-triggered gels avoids health and environmental concerns associated with UV light.

Purpose of the Study:

• To create a supramolecular gel responsive to visible light using halogen bonding.
• To investigate the use of azopyridine derivatives and a tetrafluoro-iodophenyl diazene as building blocks.
• To establish an environmentally friendly method for controlling supramolecular material phase transitions.

Main Methods:

• Synthesized azopyridine derivatives (Azopy-Cn) as halogen bond acceptors.
• Utilized 1,2-bis(2,3,5,6-tetrafluoro-4-iodophenyl)diazene (BTFIPD) as a halogen bond donor and photoresponsive unit.
• Investigated the gel-to-sol transition and morphological changes under visible light irradiation.

Main Results:

• Successfully fabricated a visible light-responsive supramolecular gel.
• Observed a distinct gel-to-sol transition upon green light exposure.
• Documented morphological changes from flakes to sheets with increasing light exposure time.
• Demonstrated the photoisomerization of BTFIPD due to n-π* energy level shifts.

Conclusions:

• Presented an environmentally friendly, visible light-triggered method for supramolecular gel phase transition control.
• Highlighted the potential of halogen bonding in conjunction with visible light-responsive moieties.
• Opened avenues for applications in energy conversion and information storage using stimuli-responsive materials.