Photoswitchable supramolecular catalysis by interparticle host-guest competitive binding

Area of Science:

• Supramolecular Chemistry
• Nanotechnology
• Catalysis

Background:

• β-cyclodextrin dimers are effective catalysts for ester hydrolysis.
• Controlling catalytic activity with external stimuli is crucial for advanced applications.
• Azobenzene derivatives offer light-responsive molecular switching capabilities.

Purpose of the Study:

• To develop a light-switchable catalytic system for ester hydrolysis.
• To investigate the role of gold nanoparticles functionalized with azobenzene in modulating catalyst activity.
• To demonstrate reversible control over enzymatic-like reactions using visible and UV light.

Main Methods:

• Synthesis of gold nanoparticles functionalized with azobenzene units.
• Preparation of a Zn(II)-coordinated β-cyclodextrin dimer.
• Spectroscopic characterization of nanoparticle-dimer interactions.
• Kinetic studies of ester hydrolysis under varying light conditions (visible and UV).

Main Results:

• Visible light induced a *trans*-azobenzene conformation, leading to tight binding with the dimer and suppressed catalytic activity.
• UV light induced a *cis*-azobenzene conformation, resulting in loose binding and restored/enhanced ester hydrolysis.
• The catalytic system demonstrated reversible on/off switching of ester hydrolysis upon alternating light exposure.

Conclusions:

• Light-controlled gold nanoparticles provide an effective external trigger for modulating the activity of Zn(II)-coordinated β-cyclodextrin dimer catalysts.
• This system offers a novel approach for developing switchable catalytic processes with potential applications in controlled synthesis and drug delivery.
• The interplay between azobenzene photoisomerization, nanoparticle binding, and catalyst accessibility is key to achieving light-responsive catalysis.