Advanced carbon-based magnetic material was eventually created after 70 years


Fig.1 Structure and spin density distribution of triangulene. Credit: Shinobu Arikawa et al.
Fig.1 Structure and spin density distribution of triangulene. Credit: Shinobu Arikawa et al.

Since its first reported manufacture in 2004, researchers have been hard at work exploiting graphene and other carbon-based materials to improve electronics, sports, and a variety of other fields. Now, Japanese researchers have made a breakthrough in the long-elusive field of nanographene magnets.


In a study published recently in the Journal of the American Chemical Society, researchers from Osaka University and collaborators synthesized crystalline nanographene with magnetic properties predicted theoretically since the 1950s but unconfirmed experimentally except at extremely low temperatures.


Graphene is a two-dimensional, single-layer sheet of carbon rings organized in a honeycomb lattice. What piques the interest of researchers in graphene?


Graphene has remarkable characteristics. It transports charges efficiently over long distances and has a substantially higher strength than comparably thick steel. Graphene nanostructures have magnetic and electrical features that researchers would want to utilize. Graphene nanosheets, on the other hand, are challenging to manufacture and investigate due to their zigzag edge characteristics. The researchers at Osaka University attempted to overcome these obstacles by employing a simpler, yet the sophisticated, model system is known as triangulene.

Fig.2 Spin density distribution of triangulene and space-filling model and crystal structure of triangulene derivatives. Credit: Shinobu Arikawa et al.
Fig.2 Spin density distribution of triangulene and space-filling model and crystal structure of triangulene derivatives. Credit: Shinobu Arikawa et al.

Triangulene has long resisted crystalline synthesis due to uncontrolled polymerization, according to the study's two lead scientists, Shinobu Arikawa and Akihiro Shimizu. We avoided polymerization by sterically protecting the molecule and bulking it out in a way that did not impact its underlying characteristics.


The triangulene derivative developed by the researchers is stable at room temperature but must be stored in an inert environment since it degrades slowly when exposed to oxygen. Nonetheless, crystallization was achievable, allowing confirmation of theoretically expected features such as unpaired electron localization on the zigzag edges of the molecule.


According to Ryo Shintani, senior author, "we established that our molecule is in the triplet ground state by testing its optical and magnetic characteristics." This is an electronic state that may be used as a testable model for zigzag-edged nanographene.


These findings have far-reaching implications. Researchers can use the long-desired synthetic process described here to increase the number of carbon rings in the molecule and execute chemical synthesis of advanced forms of nanographene. In doing so, researchers at Osaka University and Osaka City University may be able to synthesis materials that will serve as the foundation for future sophisticated electronics and magnets, as well as substitute the silicon that is prevalent in contemporary electronics.


Journal Information: Shinobu Arikawa et al, Synthesis and Isolation of a Kinetically Stabilized Crystalline Triangulene, Journal of the American Chemical Society (2021). DOI: 10.1021/jacs.1c10151

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