Double J-Coupling Strategy for Near Infrared Emitters

Area of Science:

• Organic Chemistry
• Materials Science
• Photophysics

Background:

• Near-infrared (NIR) fluorophores are crucial for advanced applications.
• High nonradiative rates beyond 800 nm lead to significant fluorescence quenching.
• Developing efficient NIR emitters remains a challenge in photochemistry.

Purpose of the Study:

• To design and synthesize a bis(squaraine) dye for enhanced NIR fluorescence.
• To investigate the photophysical properties of the dye in solution and self-assembled states.
• To explore J-type exciton coupling for efficient NIR emission.

Main Methods:

• Synthesis of a novel bis(squaraine) dye with a head-to-tail chromophore arrangement.
• Spectroscopic analysis (absorption and fluorescence) in chloroform and toluene.
• Investigation of self-assembly into nanofibers in less polar solvents.

Main Results:

• The bis(squaraine) dye exhibited intramolecular J-type coupling in chloroform, with absorption at 961 nm and fluorescence at 971 nm (quantum yield 0.33%).
• In toluene, the dye self-assembled into nanofibers, showing intermolecular J-type coupling with a bathochromic shift (absorption at 1095 nm, fluorescence at 1116 nm).
• Demonstrated efficient NIR emission via controlled exciton coupling.

Conclusions:

• The bis(squaraine) dye design effectively overcomes NIR fluorescence quenching.
• J-type exciton coupling, both intramolecular and intermolecular, is a viable strategy for efficient NIR emission.
• Self-assembly offers a pathway to further tune NIR optical properties.