Exploring novel molecular photoswitches plays a crucial role in photo-functional materials chemistry. Photoswitching molecules change their properties when irradiated, and the materials have potential applications ranging from phytopharmacology to data storage.
A new study by the Osaka Metropolitan University Graduate School of Engineering reports about new molecules that reversibly change with light and heat.
Aza-diarylethenes have nitrogen instead of carbon in a molecular structure similar to photoswitching diarylethenes. Scientists synthesized aza-diarylethenes with benzothiophene-S and S-dioxide as a part of the hexatriene structure and investigated their photochromic properties.
Previously reported aza-diarylethenes to exhibit fast thermally reversible photochromism. However, the new aza-diarylethenes exhibit not only photoswitching but thermal switching as well.
UV light writes the Chinese character for “light” on treated paper, which then gets erased after irradiation with visible light. A soldering iron then makes marks on treated paper that are erased with visible light irradiation.
Credit: Osaka Metropolitan University
Thanks to their thermal stability, scientists successfully isolated the colored isomer that adopts a closed-ring structure with a bond between carbon and nitrogen atoms.
These aza-diarylethenes are unique because they can change shape in two ways: light (photochemical reactions) and heat (thermal reactions). This means they can open and close like a ring in response to temperature changes, which most diarylethenes cannot do. Researchers studied this behavior closely and created a diagram showing how the energy levels balance these compounds’ open and closed forms.
Additionally, 1H NMR spectroscopy showed that both types of closed-ring isomers—made with light and heat—have the same structure. This was explained by how the photochemical and thermal ring-closing reactions work. These discoveries improve our understanding of aza-diarylethenes and encourage future research into creating new photoswitches.
According to researchers, the new photoswitching molecules can be used as a rewritable recording medium, writing with light or heat and erasing with light.
Dr. Daichi Kitagawa, a lecturer at the Osaka Metropolitan University, Department of Chemistry and Bioengineering Graduate School of Engineering, said, “Our findings are very useful for the development of switching molecules that can be reversibly altered by light and heat. They may also lead to the development of new functional materials.”
Journal Reference:
- Shota Hamatani, Daichi Kitagawa, and Seiya Kobatake. Aza-Diarylethenes Undergoing Both Photochemically and Thermally Reversible Electrocyclic Reactions. Angewandte Chemie International Edition. DOI: 10.1002/anie.202414121