K. Nakamura, Q.-Q. Li, O. Krejčí, A. S. Foster,* K. Sun, S. Kawai,* S. Ito*
J. Am. Chem. Soc. 2020, 142, 11363–11369. DOI: 10.1021/jacs.0c02534
Abstract: Heterocyclic circulenes are an important class of polycyclic aromatic hydrocarbon molecules because of their unique structural properties and promising applications. However, synthesis of heterocyclic circulenes is still limited and thus is an important synthetic challenge. Here we describe the first example of a π-extended diazacirculene bearing six hexagons and two pentagons, which was successfully synthesized only by a combined in-solution and on-surface synthetic strategy. State-of-the-art scanning tunneling microscopy with a CO functionalized tip and density functional theory calculations revealed its planar confor-mation and a unique electronic structure.