The lessons of an absorbing, shell-shaped near-infrared molecule made up only of hydrogen and carbon atoms offer insights for future organic conductors.
Nagoya University researchers have synthesized a unique molecule with a surprising property: it can absorb near infrared light. The molecule consists only of hydrogen and carbon atoms and offers insights into the manufacture of organic conductors and batteries. The details were published in the magazine Communication with nature.
Organic chemist Hiroshi Shinokubo and physical organic chemist Norihito Fukui from Nagoya University are working to develop new, interesting molecules using organic or carbonaceous compounds. In the laboratory, they synthesized an aromatic hydrocarbon called methoxy-substituted how-indacenoterrylen. This molecule has a unique structure in that its methoxy groups are internal rather than on its periphery.
“First of all, we wanted to find out whether this hydrocarbon had new phenomena due to its unique structure,” says Fukui.
However, during their research, the researchers found that they could convert it into a new cup-shaped hydrocarbon called how-indacenoterrylen.
“We were surprised that this new molecule has an absorption in the near infrared of up to 1300 nanometers,” explains Shinokubo.
What’s unique about how-indacenoterrylen is not that it absorbs near infrared light. Other hydrocarbons can do the same. how-indacenoterrylen is interesting because it does so despite only having 34 carbon and 14 hydrogen atoms with no other types of stabilizing atoms on its periphery.
When the scientists performed electrochemical measurements, theoretical calculations, and other tests, they found this out how-Indacenoterrylen was intriguingly stable and also had a remarkably narrow gap between its highest occupied molecular orbital (HOMO) and its lowest unoccupied molecular orbital (LUMO). This means that the molecule has two electronically distinct subunits, one that donates and one that withdraws electrons. The narrow HOMO-LUMO gap facilitates the excitation of electrons in the molecule.
“The study provides an effective guideline for the design of hydrocarbons with a narrow HOMO-LUMO gap, with which molecules with concurrent electron-donating and electron-withdrawing subunits can be produced,” says Fukui. “These molecules will be useful in the development of next-generation solid-state materials such as organic conductors and organic batteries.”
The team next plans to synthesize other aromatic hydrocarbons that absorb the near infrared based on the design concepts gathered in this current study.
Reference: “as-Indaceno[3,2,1,8,7,6-ghijklm]Terrylen as a near-infrared absorbing C70 fragment “by Yuki Tanaka, Norihito Fukui and Hiroshi Shinokubo, August 3, 2020, Communication with nature.
DOI: 10.1038 / s41467-020-17684-6