Stimuli-Responsive Resorcin[4]arene Cavitands: Toward Visible-Light-Activated Molecular Grippers

Area of Science:

• Supramolecular Chemistry
• Photochemistry
• Materials Science

Background:

• Resorcin[4]arene cavitands are versatile molecular scaffolds with tunable properties.
• Photosensitizers like [Ru(bpy)₂ dppz]²⁺ can initiate photochemical reactions.
• Controlling molecular conformation is key for developing responsive materials.

Purpose of the Study:

• To synthesize resorcin[4]arene cavitands functionalized with quinone and ruthenium photosensitizers.
• To investigate light-induced electron transfer and subsequent conformational switching in these systems.
• To explore the potential of these switching cavitands in stimuli-responsive nanodevices.

Main Methods:

• Synthesis of functionalized resorcin[4]arene cavitands.
• Visible-light irradiation (420 nm) to trigger electron transfer.
• Spectroscopic analysis to monitor radical anion formation and conformational changes.
• Guest encapsulation studies with small molecules.

Main Results:

• Visible-light irradiation induced electron transfer from [Ru(bpy)₂ dppz]²⁺ to quinone, forming a stable semiquinone (SQ) radical anion.
• The SQ radical anion triggered a conformational switch from a kite to a vase shape, creating an encapsulation cavity.
• The vase state was generated without sacrificial electron donors, and switching was also induced by solvent changes and host-guest complexation.

Conclusions:

• Light-activated electron transfer in functionalized cavitands drives significant conformational changes.
• The generated vase-shaped cavitands can encapsulate small molecules.
• These findings pave the way for developing advanced stimuli-responsive nanodevices, including light-activated molecular grippers.