Newly synthesized organic molecules can be tuned to emit different colors depending on their molecular structure in crystalline form. Molecular switches are chemicals with a molecular structure that can switch between two or more stable configurations in response to changes in the environment. They are of great interest in the development of molecular computers, molecular machines, and drug delivery systems. Compounds with conformational isomers (same molecular formulas but different molecular structures) can make very efficient molecular transitions.
Researchers at Hokkaido University and Kyushu University have developed a technique to synthesize potential molecular switches from anthraquinodimethanes (AQDs), a group of crowded organic molecules. The research, led by Associate Professor Yusuke Ishigaki of Hokkaido University and Associate Professor Toshikazu Ono of Kyushu University, is published in the journal Science. Limits of Materials Chemistry.
“AQD is a crowded type of ethylene, which is a molecule with carbon-carbon double bonds surrounded by large chemical groups,” explains Ohno. “They have two common isomers, folded and twisted forms. They are particularly interesting as molecular switches because sterically hindered double bonds can provide isomers that absorb and emit at different wavelengths.”
AQDs are usually in the most stable folded or twisted form, making it difficult to isolate pure samples of any other isomer to study their properties. The researchers overcame this hurdle by creating flexible AQD derivatives that can form different isomers more easily and stably.
The synthesized derivatives were able to stably form not only twisted and folded isomers, but also other isomeric forms upon recrystallization in various solvents. The researchers conducted a detailed analysis of the derivatives to fully understand their properties. In the crystalline state, each of these isomers absorbs and emits light at different frequencies due to differences in the distribution of electrons in the molecules of the isomers. Interestingly, the absorption and emission of light changed when the crystals were crushed into an amorphous solid, and other crystals with original or different colors can be obtained after treatment with suitable solvents.
“This study is the first report on the isolation of multiple isomeric forms of AQD,” said Ishigaki. “Their ability to absorb and emit different frequencies of light and, more importantly, to modulate absorption and emission by external stimuli, makes these compounds excellent candidates for the development of molecular switches.”
Source: Port Altele
