Supramolecular control of fluorescence through reversible encapsulation

Area of Science:

• Supramolecular Chemistry
• Photochemistry
• Molecular Switches

Background:

• 4,4'-dimethylazobenzene undergoes trans-cis isomerization upon light or heat stimuli.
• This isomerization alters molecular binding properties, enabling control over guest encapsulation.
• This phenomenon can be harnessed for developing responsive molecular systems.

Purpose of the Study:

• To investigate the use of light- and heat-induced azobenzene isomerization for remote control of reversible encapsulation.
• To establish a supramolecular fluorescence on/off switch based on controlled encapsulation.
• To correlate fluorescence changes with the encapsulation state of a guest molecule.

Main Methods:

• Utilizing trans to cis isomerization of 4,4'-dimethylazobenzene triggered by light and heat.
• Employing trans-4-ethyl-4'-methylstilbene as a fluorescent guest molecule.
• Correlating fluorescence spectroscopy with proton nuclear magnetic resonance ((1)H NMR) data to confirm encapsulation states.

Main Results:

• Demonstrated remote control over the encapsulation of trans-4-ethyl-4'-methylstilbene using azobenzene isomerization.
• Observed altered fluorescence of the stilbene guest when encapsulated versus free in solution.
• Confirmed the direct relationship between encapsulation state and fluorescence modulation through spectroscopic analysis.

Conclusions:

• The trans-cis isomerization of azobenzene provides a viable mechanism for reversible control of guest encapsulation.
• This system effectively functions as a supramolecular fluorescence on/off switch.
• The combination of fluorescence and NMR spectroscopy is crucial for validating the controlled encapsulation process.