Understanding the Structural Modulations in Twisted Donor-Acceptor-Donor (D-A-D) Systems for Boosting Type I...

Area of Science:

• Supramolecular Chemistry
• Photochemistry
• Organic Synthesis

Background:

• Donor-acceptor-donor (D-A-D) building blocks are crucial for developing functional supramolecular assemblies.
• Crystallization-induced emission (CIE) and intermolecular charge transfer significantly influence photophysical properties.
• Type I photosensitizers are valuable for catalytic applications, including organic synthesis.

Purpose of the Study:

• To design and synthesize novel D-A-D based supramolecular assemblies with tailored photophysical properties.
• To investigate the impact of the angle of twist and intermolecular charge transfer on luminescence and photosensitizing activity.
• To demonstrate the application of these supramolecular assemblies as efficient type I photosensitizers in organic synthesis.

Main Methods:

• Synthesis of twisted D-A-D building blocks (Qx-Ind and Qx-Indaz).
• Spectroscopic studies (absorption, emission) to analyze photophysical behavior in aggregated states.
• Evaluation of type I photosensitizing activity through aerobic oxidative synthesis of quinazolin-4(3H)-ones.

Main Results:

• Supramolecular assemblies of Qx-Ind exhibit high molar absorptivity, long-lived excited states, and CIE characteristics due to a balanced angle of twist and high intermolecular charge transfer.
• Modulation of the angle of twist and charge transfer in Qx-Indaz leads to altered photophysical behavior.
• Qx-Ind assemblies demonstrate superior type I photosensitizing activity, efficiently catalyzing quinazolin-4(3H)-one synthesis without additional additives.
• Qx-Ind assemblies, due to CIE, can be directly used in solid state without pre-preparation.

Conclusions:

• The angle of twist and intermolecular charge transfer are critical parameters for controlling the photophysical behavior and photosensitizing activity of D-A-D supramolecular assemblies.
• Qx-Ind based supramolecular assemblies represent a promising class of efficient and readily usable type I photosensitizers for organic synthesis.
• This study provides a facile strategy for enhancing type I photosensitizing activity through rational molecular design.