Azobenzene-Based Macrocyclic Arenes: Synthesis, Crystal Structures, and Light-Controlled Molecular Encapsulation and...

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Photochemistry

Background:

• Azobenzene (azo)-based macrocycles are key components in supramolecular chemistry due to their photo-responsive properties.
• Controlling molecular encapsulation through external stimuli like light is a significant challenge in developing advanced functional materials.

Purpose of the Study:

• To rationally design and synthesize a series of novel azo-based macrocyclic arenes with varying azo group positions.
• To investigate the structural changes and photo-responsive behavior of these macrocycles upon light irradiation.
• To demonstrate light-controlled host-guest complexation using the synthesized azo-macrocycles.

Main Methods:

• Rational design and synthesis of azo-based macrocyclic arenes (compounds 1-4) using a fragment-cyclization method.
• Structural analysis using X-ray crystallography and computational methods for compounds 1-3.
• Photoisomerization studies (E→Z) to observe changes in macrocycle cavity size.
• Host-guest complexation experiments with specific guest molecules (7,7,8,8-tetracyanoquinodimethane, terephthalonitrile).

Main Results:

• Successful synthesis of a series of novel azo-based macrocyclic arenes.
• Observation of a gradual decrease in macrocycle cavity size upon E→Z photoisomerization, confirmed by crystal and computed structures.
• Demonstration of successful light-controlled host-guest complexation between azo-macrocycle 1 and selected guest molecules.

Conclusions:

• A simple and effective method for preparing azo-macrocycles has been established.
• The synthesized azo-macrocycles exhibit tunable cavity sizes in response to light.
• The developed light-responsive molecular-encapsulation systems hold promise for future applications in photo-responsive host-guest chemistry.