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UV/Vis Spectroscopy Studies of the Photoisomerization Kinetics in Self-Assembled Azobenzene-Containing Adlayers
N R Krekiehn1, M Müller1, U Jung1
1†Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, Leibnizstr. 19, 24118 Kiel, Germany.
Langmuir : the ACS Journal of Surfaces and Colloids
|July 3, 2015
Summary
Photoisomerization of azobenzene derivatives in self-assembled adlayers on gold surfaces was studied. Azobenzenes on molecular platforms showed uninhibited photoswitching, unlike those in thiol monolayers.
Area of Science:
- Photochemistry
- Surface Science
- Molecular Engineering
Background:
- Azobenzene derivatives are widely used in molecular switches and photoresponsive materials.
- Self-assembled monolayers (SAMs) on surfaces offer a platform for controlling molecular behavior.
- Understanding photoisomerization in confined environments is crucial for designing advanced materials.
Purpose of the Study:
- To directly compare the photoisomerization of azobenzene derivatives in self-assembled adlayers on gold with their behavior in solution.
- To investigate the influence of surface confinement and molecular architecture on azobenzene photoswitching.
- To elucidate the role of excitonic coupling in surface-bound azobenzene systems.
Main Methods:
- UV/vis spectroscopy was employed to study the trans-cis photoisomerization.
- Comparative analysis of azobenzene derivatives in dichloromethane solution and as self-assembled adlayers on gold.
- Investigation of azobenzene derivatives immobilized on triazatriangulene-based molecular platforms and in thiol SAMs.
Main Results:
- Highly reversible trans-cis isomerization was observed for all studied azobenzene systems in adlayers.
- Azobenzenes on triazatriangulene platforms exhibited nearly uninhibited photoswitching, similar to free molecules.
- Azobenzene-containing thiol SAMs showed significantly reduced photoswitching fractions and kinetics compared to free molecules.
- A blue-shift in the π-π* transition for adlayers agreed with theoretical studies on excitonic coupling.
Conclusions:
- Molecular architecture significantly impacts azobenzene photoisomerization in self-assembled adlayers.
- Triazatriangulene-based platforms enable efficient photoswitching of azobenzenes on surfaces.
- Thiol SAMs can hinder azobenzene photoisomerization due to environmental constraints.
- Excitonic coupling plays a role in the optical properties of azobenzene adlayers.
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