Molecular design strategy reveals near infrared-absorbing hydrocarbon


Date:
October 17, 2020
Source:
Nagoya University
Summary:
The lessons learned from a near infrared absorbing, bowl-shaped
molecule made only from hydrogen and carbon atoms offers insights
for future organic conductors.



FULL STORY ========================================================================== Nagoya University researchers have synthesized a unique molecule with a surprising property: it can absorb near infrared light. The molecule is
made only of hydrogen and carbon atoms and offers insights for making
organic conductors and batteries. The details were published in the
journal Nature Communications.


========================================================================== Organic chemist Hiroshi Shinokubo and physical organic chemist
Norihito Fukui of Nagoya University work on designing new, interesting molecules using organic, or carbon-containing, compounds. In the lab,
they synthesized an aromatic hydrocarbon called methoxy-substituted as-indacenoterrylene. This molecule has a unique structure, as its
methoxy groups are located internally rather than at its periphery.

"Initially, we wanted to see if this hydrocarbon demonstrated novel
phenomena due to its unique structure," says Fukui.

But during their investigations, the researchers discovered they could
convert it into a new bowl-shaped hydrocarbon called as-indacenoterrylene.

"We were surprised to find that this new molecule exhibits near infrared absorption up to 1300 nanometers," Shinokubo explains.

What's unique about as-indacenoterrylene is not that it
absorbs near infrared light. Other hydrocarbons can do this as
well. as-indacenoterrylene is interesting because it does this despite
being made of only 34 carbon and 14 hydrogen atoms, without containing
other kinds of stabilizing atoms at its periphery.

When the scientists conducted electrochemical measurements, theoretical calculations, and other tests, they found that as-indacenoterrylene 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 different subunits, one that donates and another that
withdraws electrons. The narrow HOMO-LUMO gap makes it easier for
electrons to become excited within the molecule.

"The study offers an effective guideline for the design of hydrocarbons
with a narrow HOMO-LUMO gap, which is to fabricate molecules with
coexisting electron- donating and electron-withdrawing subunits,"
says Fukui. "These molecules will be useful for the development of next-generation solid-state materials, such as organic conductors
and organic batteries." The team next plans to synthesize other near infrared-absorbing aromatic hydrocarbons based on the design concepts
garnered in this current study.


========================================================================== Story Source: Materials provided by Nagoya_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Yuki Tanaka, Norihito Fukui, Hiroshi
Shinokubo. as-Indaceno[3,2,1,8,7,6-
ghijklm]terrylene as a near-infrared absorbing C70-fragment. Nature
Communications, 2020; 11 (1) DOI: 10.1038/s41467-020-17684-6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201017194219.htm

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