Nanotechnologies / Materials
Organic electronic materials, Organic magnetic materials

Synthesis and elucidation of physical properties of a hydrocarbon
molecule with a triplet ground state
Department of Materials Engineering Science, Graduate School of Engineering Science
Associate Professor Akihiro Shimizu

https://researchmap.jp/7000009063

Professor Ryo Shintani

https://researchmap.jp/RMshintani

Abstract

Nanotechnologies / Materials

Since the first reported production in 2004, researchers havebeen hard at work using graphene and similar carbon-basedmaterials to revolutionize electronics, sports, and many other disciplines. Now, we have made a discovery that will advance thelong-elusive field of nanographene magnets.
In a study recently published in Journal of the American Chemical Society, we have synthesized a crystalline nanographene, atriangulene, with magnetic properties that have been predicted
theoretically since the 1950s, but until now have been unconfirmed
experimentally except at extremely low temperatures.

▍ Background & Results
Graphene is a single layer, two-dimensional sheet of carbon
rings arranged in a honeycomb lattice. Why does graphene excite
researchers? Graphene has impressive properties—it exhibits
efficient, long-distance charge transport and has a much higher
strength than similarly thick steel. Nanostructures of graphene
have edges that exhibit magnetic and electronic properties that
researchers would like to exploit. However, graphene nanosheets
are difficult to prepare and it’s difficult to study their zigzag edge
properties. Overcoming these challenges by using a simpler, yetadvanced, model system known as triangulene is something weaimed to address.
Triangulene has long eluded synthesis in a crystalline form because of its uncontrolled polymerization. In this study, this polymerization was prevented by introducing bulky substituent groups that
didn’t affect triangulene’s underlying properties. The triangulene
derivative is stable at room temperature but must be kept in an
inert atmosphere because it slowly degrades when exposed tooxygen. Nevertheless, crystallization was possible, which enabled
confirmation of its theoretically predicted highly symmetric structure
and aromaticity of all six-membered rings. Localization of unpaired
electrons on the zigzag edges of the molecule was confirmed by
ESR measurements. This is an electronic state that can serve as anexperimentally tractable model for zigzag-edged nanographene.
By measuring its magnetic properties, we confirmed that the triangulene derivative is in the triplet ground state with large ferromagnetic interaction of unpaired electrons. Its fundamental optical andelectrochemical properties were also elucidated.

▍ Significance of the research and Future perspective
This is the first study to elucidate the crystal structure of a hydrocarbon molecule with a triplet ground state. We can extend
the long-sought synthetic procedure reported here to increase thenumber of carbon rings in the molecule and perform chemical syntheses of advanced forms of nanographene. In so doing, we may
be able to synthesize materials that are foundational for future advanced electronics and magnets, and supplement the silicon that’subiquitous in modern electronics.
P a t e n t
Arikawa, Shinobu; Shimizu, Akihiro; Shintani, Ryo et al. Synthesis and Isolation of a Kinetically Stabilized Crystalline Triangulene. J. Am. Chem. Soc. 2021;
143(46): 19599-19605. doi: 10.1021/jacs.1c10151
UR
L http://www.chem.es.osaka-u.ac.jp/poc/
K e y w o r d magnets, spins, radicals, hydrocarbons, organic molecules
Tr e a t i s e