Researchers at Nagoya University have synthesized a unique molecule with a surprising property: it can absorb near infrared light. The molecule is composed only of hydrogen and carbon atoms and offers prospects for the manufacture of organic conductors and batteries. Details were published in the newspaper Nature Communication.
Organic chemist Hiroshi Shinokubo and physical organic chemist Norihito Fukui from Nagoya University are working on the design of interesting new molecules using organic or carbon-containing compounds. In the lab, they synthesized an aromatic hydrocarbon called methoxy-substituted like-indacenoterrylene. This molecule has a unique structure because its methoxy groups are located inside rather than at its periphery.
“Initially, we wanted to see if this hydrocarbon exhibited new phenomena due to its unique structure,” explains Fukui.
But during their investigations, the researchers found that they could convert it into a new bowl-shaped hydrocarbon called like-indacenoterrylene.
“We were surprised to discover that this new molecule exhibits near infrared absorption up to 1,300 nanometers,” explains Shinokubo.
What is unique like-indacenoterrylene is not that it absorbs near infrared light. Other hydrocarbons can also do this. like-indacenoterrylene is interesting because it does so although it is composed of only 34 carbon atoms and 14 hydrogen atoms, without containing other types of stabilizing atoms at its periphery.
When scientists performed electrochemical measurements, theoretical calculations, and other tests, they found that like-indacenoterrylene was surprisingly 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 different subunits, one which donates and another which withdraws electrons. The narrow HOMO-LUMO space facilitates the excitation of electrons in the molecule.
“The study offers an effective guideline for the design of hydrocarbons with a narrow HOMO-LUMO gap, which involves making molecules with coexisting electron donor and attractant subunits,” explains Fukui. “These molecules will be useful for the development of next generation solid state materials, such as organic conductors and organic batteries.”
The team then plans to synthesize other aromatic hydrocarbons absorbing near infrared based on the design concepts collected in this current study.
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