On-surface synthesis of nonbenzenoid nanographenes through skeletal rearrangement reactions on Au(111).

Skeletal rearrangement reaction is a class of important chemical reactions to synthesize various constitutional isomers from a given precursor molecule. This approach allows the synthesis of diverse nanographenes incorporating five- and seven-membered rings, thereby tuning their chemical and physical properties. Here, we present formation of five types of closed-shell and two types of open-shell nanographenes on Au(111) via carbon rearrangements of 7-(2,6-dimethylphenyl)-12-[10-(2,6-dimethylphenyl)anthracen-9-yl]tetraphene. The structural, electronic, and magnetic properties of various products composed of pentagonal or pentagonal/heptagonal rings were in-detail investigated with a combination of bond-resolved scanning tunneling microscopy/scanning tunneling spectroscopy at 4.3 K and density functional theory calculations. We found that both zigzag edges and fused pentagonal rings significantly affect the band gap and the spin polarization. This discovery could facilitate the on-surface synthesis of intriguing carbon nanostructures through skeletal rearrangement.