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新たに合成されたアントラキノジメタン誘導体の結晶で、分子構造によって色が異なります。 クレジット: 石垣祐介


分子スイッチは、環境の変化に応じて 2 つ以上の安定した配置間で変化する分子構造を持つ化学物質です。 彼らは、分子コンピューター、分子機械、および薬物送達システムの開発に大きな関心を寄せています。 配座異性体 (分子式は同じだが分子構造が異なる) を持つ化合物は、非常に効果的な分子スイッチを作ることができます。


折り畳み異性体とねじれ異性体は、異なる波長の光を吸収します。 クレジット:菅原一真ほか材料化学フロンティア。 2023 年 2 月 8 日

の研究者[{” attribute=””>Hokkaido University and Kyushu University have developed a technique to synthesize potential molecular switches from anthraquinodimethanes (AQDs), a group of overcrowded organic molecules. The study, led by Associate Professor Yusuke Ishigaki at Hokkaido University and Associate Professor Toshikazu Ono at Kyushu University, was published in the journal Materials Chemistry Frontiers.

Methyl Derivative Four Different Isomers

The methyl derivative of the new compound has four different isomers, with different crystal structures each. Credit: Kazuma Sugawara, et al. Materials Chemistry Frontiers. February 8, 2023

“AQDs are a type of overcrowded ethylene, molecules with carbon-carbon double bonds surrounded by large chemical groups,” explains Ono. “They have two common isomers, the folded and twisted forms. They are especially interesting as molecular switches, as their sterically hindered double bond can provide isomers absorbing and emitting different wavelengths of light.”

AQDs generally adopt the most stable folded or twisted form, making it difficult to isolate pure samples of any other isomer to study their properties. The researchers surmounted this obstacle by designing flexible AQD derivatives that can more easily and stably form different isomers.

Amorphous Solid Light Absorption and Emission Changes

When ground into amorphous solid and treated with appropriate solvents the light absorption and emission changes. Credit: Kazuma Sugawara, et al. Materials Chemistry Frontiers. February 8, 2023

The synthesized derivatives were not only able to stably form twisted and folded isomers, but also other isomeric forms, when recrystallized in different solvents. The researchers performed detailed analysis of the derivatives to fully understand their properties.

Takanori Suzuki, Kazuma Sugawara, and Yusuke Ishigaki

Takanori Suzuki (left) Kazuma Sugawara (center) and Yusuke Ishigaki (right), authors from Hokkaido University. Credit: Yusuke Ishigaki

In a crystalline state, each of these isomers absorbs and emits distinct frequencies of light, which is due to the differences in the distribution of electrons in the isomer molecules. Interestingly, the light absorption and emission changed when the crystals were ground into amorphous solid, and following treatment with appropriate solvents can produce original or other crystals with a variety of colors.

Yoshio Yano and Toshikazu Ono

Yoshio Yano (left) and Toshikazu Ono (right), authors from Kyushu University. Credit: Toshikazu Ono

“This work is the first report on the isolation of multiple isomeric forms of AQD,” Ishigaki concluded. “Their absorption and emission of different light frequencies, and more importantly, the ability to modulate the absorption and emission by external stimuli, make these compounds excellent candidates for the development of molecular switches.”

Reference: “Exceptionally flexible quinodimethanes with multiple conformations: polymorph-dependent colour tone and emission of crystals” by Kazuma Sugawara, Toshikazu Ono, Yoshio Yano, Takanori Suzuki and Yusuke Ishigaki, 8 February 2023, Materials Chemistry Frontiers.
DOI: 10.1039/D2QM01199A

Funding: This work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI and Grant-in-Aid for Research Fellows (JP20H02719, JP20K21184, JP21H01912, JP21H05468, JP20J20972); Toyota Riken Scholar; and a 2020 DIC Award in Synthetic Organic Chemistry, Japan.

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