Donor-Acceptor Stenhouse Adducts: Exploring the Effects of Ionic Character

Area of Science:

• Photochemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Donor-acceptor Stenhouse adducts (DASAs) are photochromic molecules with potential applications in molecular switches.
• Understanding the factors influencing their switching properties, such as dielectric effects and intermolecular interactions, is crucial for their rational design.

Purpose of the Study:

• To investigate the impact of solution-state dielectric and intermolecular interactions on charge separation in DASAs.
• To correlate the ionic character of DASAs with their photoswitching behavior and concentration dependence.

Main Methods:

• Solvatochromic analysis of open-form DASAs.
• X-ray diffraction studies.
• Computational theoretical analysis.
• Investigation of photoswitching kinetics and solvent compatibility across different DASA generations.

Main Results:

• First- and third-generation DASAs exhibit significant zwitterionic resonance in both open and closed forms, enhancing charge separation.
• Second-generation DASAs possess less charge-separated open forms and neutral closed forms.
• The zwitterionic nature of first- and third-generation DASAs allows for control of switching kinetics via ion concentration, a phenomenon less pronounced in second-generation DASAs.

Conclusions:

• The concentration dependence of DASAs is not universal and is strongly influenced by the molecular architecture and resulting ionic character.
• DASAs with a more hybrid structure in the open form can achieve efficient photoswitching even at high concentrations.
• This study provides insights into tailoring DASA properties for specific applications by controlling their electronic structure and intermolecular interactions.