Thermo-Bistable Red and Sensitized Near-Infrared Photoswitches

Area of Science:

• Materials Science
• Photochemistry
• Organic Chemistry

Background:

• Molecular photoswitching in the red/near-infrared (NIR) spectrum is crucial for minimizing photodamage and enabling deep-tissue penetration in biological and optoelectronic applications.
• Developing photoswitches with both long-wavelength responsiveness and high thermal stability remains a significant challenge.

Purpose of the Study:

• To report a novel, intrinsically thermo-bistable, red-light-responsive photochromic motif based on a perylene bisimide (PBI) scaffold.
• To achieve sensitized NIR photoisomerization and enhance photochemical/thermal performance for advanced applications.

Main Methods:

• Rational side-chain engineering of the PBI scaffold with aryl substituents to tune the transition-state energy barrier.
• Investigating photoisomerization pathways, including a triplet pathway for sensitized NIR photoisomerization.
• Characterizing thermal stability, photoisomerization quantum yield, fluorescence, and photoconversion efficiency.

Main Results:

• Developed a red-light-responsive (605 nm/730 nm) PBI photoswitch with intrinsic thermo-bistability.
• Achieved sensitized NIR photoisomerization (808 nm/730 nm) via a triplet pathway.
• Demonstrated exceptional thermal stability (ΔG‡ = 45.07 kcal mol⁻¹) and a long-lived closed isomer.
• Obtained high photoisomerization quantum yield, bright fluorescence, and near-quantitative photoconversion efficiency.

Conclusions:

• The novel PBI photochromic motif significantly enhances molecular photoswitching performance in the red-light spectrum.
• These PBI-based photoswitches offer a promising platform for advanced biomedical and optoelectronic applications, including dynamic cell-membrane imaging.