Green-/NIR-light-controlled rapid photochromism featuring reversible thermally activated delayed fluorescence and photoelectronic switching

• Published in: Chemical science (Cambridge) Vol. 13; no. 32; pp. 9381 - 9386
• Main Authors: Li, Ziyong, Zhang, Ji-Rui, Tian, Xu-Ke, Yang, Shuren, Chen, Si, Zhou, Hui, Yang, Xiao-Gang
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 17-08-2022; The Royal Society of Chemistry
• Subjects: Chemistry; Density ratio; Energy gap; Fluorescence; Irradiation; Memory devices; Optical memory (data storage); Photochromism; Photoelectric effect; Photoelectricity; Polymethyl methacrylate; Storage systems; Switching; Ultraviolet radiation
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d2sc02662g

Fluorescent dithienylethene-based photochromic materials have been attracting considerable attention owing to their wide applications in biological and materials sciences. However, the limitations of detrimental UV irradiation for photocyclization, short emission lifetime, and inefficient photoresponsive speed still need to be addressed. Herein, a novel dithienylethene photochromic molecule,
BFBDTE
, has been prepared by the incorporation of a difluoroboron β-diketonate (BF
2
bdk) unit. The strong electron acceptor BF
2
bdk not only reduces the energy gap of the open isomer, ensuring visible light-controlled fluorescence switching, but also promotes intersystem crossing for the generation of thermally activated delayed fluorescence (TADF). Upon alternating irradiation with green and NIR light,
BFBDTE
presents a rare example of photochromism, fluorescence and TADF switching in various polar solvents and a poly(methyl methacrylate) (PMMA) film. Meanwhile, it shows rapid and well repeatable cyclization (12 s) and cycloreversion reactions (20 s) in PMMA, accompanied by fast TADF switching within 11 s. Furthermore, photo-electrochemical measurements reveal a remarkable on-off photoelectronic response (photocurrent density ratio:
I
light
/
I
dark
= 684) between the open- and closed-form of
BFBDTE
. These remarkable merits make
BFBDTE
promising for photoswitchable molecular devices, optical memory storage systems, NIR detectors, and photoelectric switching.
Controlled by the alternating irradiation of green and NIR light, difluoroboron modifed dithienylethene shows rapid photochromism and photoelectronic switching.