Because of its larger wavelength than visible light, near-infrared light is invisible and can penetrate a variety of materials. For technical advancements that effectively absorb near-infrared light, such as the dyes in the infrared blocking filters of smartphone cameras and security inks, organic compounds are crucial.
The development of novel dyes that can absorb longer wavelengths of near-infrared light is desirable for these and numerous other technical uses.
Organic compounds that absorb near-infrared radiation were formerly thought of being closed-shell molecules lacking unpaired electrons.
However, a joint research group led by Associate Professor Takeshi Maeda, Assistant Professor Daisuke Sakamaki, and Professor Hideki Fujiwara from Osaka Metropolitan University discovered that near-infrared absorbing oxocarbon-based dyes have an intermediate state between closed-shell and open-shell electronic configurations. They also discovered that the contribution of open-shell dye forms increases along with the wavelengths of near-infrared light absorbed.
“We have clarified the proper electronic structure of near-infrared absorbing oxocarbon-based dyes that are regarded as pure closed-shell molecules. We hope that this will lead to advances in the molecular design, properties, functions, and applications of near-infrared absorbing dyes and to the development of new near-infrared absorbing organic materials that be used in society,” Professor Takeshi Maeda concluded.
The results were published in Chemical Science on January 16, 2023, and were selected as 2023 Chemical Science HOT Article Collection.
Other authors on the paper include: graduate student Taishi Oka, Assistant Professor Naoya Suzuki, Professor Shigeyuki Yagi from Osaka Metropolitan University, Dr. Kenji Kamada from National Institute of Advanced Industrial Science and Technology, and Mr. Tatsuki Konishi.
