Revolutionary Material Triangulene Synthesized after 70 Years

Crystalline Trianguline

Researchers from Osaka University and collaborating partners have synthesized a crystalline triangulene. Triangulene have been predicted theoretically since the 1950s, but until now have been unconfirmed experimentally except at extremely low temperatures. Graphene is a flat, two-dimensional sheet of carbon atoms bonded together to form a strong but flexible honeycomb network. Graphene conducts heat and electricity very efficiently along its plane. The material strongly absorbs light of all visible wavelengths, which accounts for the black color of graphite; yet a single graphene sheet is nearly transparent because of its extreme thinness. Graphene chips are analysed using optical profilometry to measure its surface topography. The material is also about 100 times stronger than would be the strongest steel of the same thickness. 

Graphene has edges that exhibit magnetic and electronic properties that could potentially be exploited. But graphene nanosheets are difficult to prepare. Their zigzag edge properties, difficult to study. The researchers at Osaka University aimed to address these issues by using a simpler, yet advanced, model system known as triangulene.

Triangulene is a triangular shaped molecule, but it is also a close relative of graphene. It has been around for decades on fume sashes and chalkboards, but no one has ever been able to synthesize, and test it in a material testing lab. It’s theoretically stable but should be extremely reactive.

“Triangulene has long eluded synthesis in a crystalline form because of its uncontrolled polymerization,” say both Shinobu Arikawa and Akihiro Shimizu, two key authors of the study.

“We prevented this polymerization by steric protection—bulking up the molecule—and did so in a way that didn’t affect its underlying properties.”

Triangulene derivative synthesized in the metrology lab by this team is stable at room temperature but it slowly degrades when exposed to oxygen. Therefore, it must be kept in an inert atmosphere; crystallization was possible, however, and the researchers were able to confirm its theoretically predicted properties.

“By measuring its optical and magnetic properties, we confirmed that our molecule is in the triplet ground state,” explains Ryo Shintani, senior author. “This is an electronic state that can serve as an experimentally tractable model for zigzag-edged nanographene.”

Research reported here has crucial implications and applications. Researchers can synthesize new forms of nanographene using the long-sought synthetic procedure reported here. Researchers from across the globe may be able to synthesize materials that are foundational for future advanced electronics and magnets.