Investigating the edge state of graphene nanoribbons by a chemical approach: Synthesis and magnetic properties of zigzag-edged nanographene molecules

• Periacenes are investigated to elucidate the origin of the edge state of ZGNR.
• The edge state becomes obvious from the molecular size of teranthene.
• The edge state is strongly associated with the formation of aromatic sextets.

The edge state, which is a peculiar magnetic state in zigzag-edged graphene nanoribbons (GNRs) originating from an electron–electron correlation in an edge-localized π-state, has promising applications for magnetic and spintronics devices and has attracted much attention of physicists, chemists, and engineers. For deeper understanding the edge state, precise fabrication of edge structures in GNRs has been highly demanded. We focus on [a.b]periacene, which are polycyclic aromatic hydrocarbons (PAHs) that have zigzag and armchair edges on molecular periphery, as a model compound for the understanding and actually prepare and characterize them. This review summarizes our recent studies on the origin of the edge state by investigating [a.b]periacene in terms of the relationship between the molecular structure and spin-localizing character.