Donor-Acceptor Dihydropyrenes Switchable with Near-Infrared Light

Area of Science:

• Organic Chemistry
• Materials Science
• Photochemistry

Background:

• Low-intensity near-infrared (NIR) light offers advantages for operating molecular switches, including deep tissue penetration and reduced radiation damage.
• Designing bistable systems activated by low-energy NIR photons presents a significant challenge.

Purpose of the Study:

• To develop a general design strategy for direct one-photon NIR photoswitches.
• To synthesize and investigate the photothermal properties of novel dihydropyrene-based photoswitches.

Main Methods:

• Synthesis of 2,7- and 4,9-disubstituted dihydropyrenes with opposing donor-acceptor substituents.
• Investigation of photothermal properties as a function of substituent type, strength, position, and environmental polarity.
• Tuning excitation wavelength into the deep NIR region.

Main Results:

• Achieved a lowest optical transition beyond 900 nm, significantly enhancing NIR one-photon absorption cross-section (by two orders of magnitude).
• Maximized photoisomerization efficiency while maintaining reasonable thermal stability of the cyclophanediene isomer.
• Demonstrated tunable thermal half-lives ranging from milliseconds to hours.

Conclusions:

• Developed a successful strategy for NIR-activated molecular switches based on dihydropyrenes.
• The synthesized photoswitches exhibit excellent NIR absorption and tunable switching properties.
• These findings open avenues for noninvasive, optically addressable materials and systems.