Photo-Electroswitchable Arylaminoazobenzenes.

Area of Science:

• Organic Chemistry
• Photochemistry
• Electrochemistry
• Materials Science

Background:

• Azobenzenes are known for their photoisomerization properties.
• Controlling azobenzene isomerization catalytically and reversibly remains a challenge.
• Redox-active groups can influence molecular properties and reactivity.

Purpose of the Study:

• To synthesize and characterize azobenzenes appended with redox-active arylamino groups (redox auxiliary, RA).
• To investigate the catalytic Z→E azo isomerization of RA-azo compounds upon electron loss.
• To explore the reversible cycling of RA-azo structures using photo- and electrostimulation.

Main Methods:

• Synthesis of RA-appended azobenzenes.
• Catalytic Z→E isomerization studies using chemical, electrochemical, and photochemical oxidation.
• Density Functional Theory (DFT) calculations to elucidate the mechanism.
• Investigation of nanomechanical properties and stimuli-responsive behavior.

Main Results:

• Fast, complete, and catalytic Z→E isomerization was achieved upon electron loss from the RA unit.
• RA-azo structures demonstrated reversible E→Z→E cycling via sequential photo- and electrostimulation.
• Catalytic electron transfer (ET) was effective at low loadings (0.04-1.0 mol %) and high dilutions (10⁻⁴-10⁻⁵ M), yielding high turnover numbers (TONs) of 100-2300.
• A Z→E acceleration factor of at least 2 × 10⁹-fold was observed for RA-azo 5.
• DFT calculations revealed that the RA radical cation stabilizes the transition state for Z→E isomerization.

Conclusions:

• The developed RA-azo structure class provides a robust platform for efficient, catalytic, and reversible azobenzene isomerization.
• Photo- and electrostimulation offer tunable control over the nanomechanical features of these molecules.
• This work presents a novel approach for controlling molecular switches with potential applications in advanced materials and nanotechnology.