Reversible and Efficient Light-Induced Molecular Switching on an Insulator Surface

Area of Science:

• Surface Science
• Molecular Switches
• Photochemistry

Background:

• Azobenzene derivatives are prototypical molecular switches with distinct trans and cis states.
• Investigating these switches on metallic surfaces is common, but bulk insulators offer advantages like electronic decoupling.
• Electronic decoupling is crucial for controlling the switching properties of molecular switches.

Purpose of the Study:

• To investigate the light-induced isomerization of an azobenzene derivative on a bulk insulator surface.
• To explore the advantages of using bulk insulators, specifically calcite (101̅4), as a substrate for molecular switches.
• To understand the influence of the substrate on the switching behavior and molecular assembly.

Main Methods:

• Atomic Force Microscopy (AFM) with submolecular resolution was employed.
• The study focused on an azobenzene derivative supported by a calcite (101̅4) surface.
• Light sources were used to induce and control photoisomerization.

Main Results:

• The azobenzene derivative exhibited light-induced isomerization on the calcite surface.
• Unexpectedly, cis isomers were observed immediately after preparation, suggesting kinetic trapping.
• The photoisomerization process was reversible, with different light sources leading to distinct molecular assemblies.
• The isomerization efficiency was comparable to that in solution, attributed to weak molecule-surface interactions.

Conclusions:

• Bulk insulators like calcite provide a viable platform for studying molecular switches.
• Kinetic trapping can influence the initial state of molecular switches on surfaces.
• The weak interaction between azobenzene derivatives and insulator surfaces enables efficient and reversible photoisomerization.