Mishra, ShantanuShantanuMishraLohr, Thorsten G.Thorsten G.LohrPignedoli, Carlo A.Carlo A.PignedoliLiu, JunzhiJunzhiLiuBerger, ReinhardReinhardBergerUrgel, José I.José I.UrgelMüllen, KlausKlausMüllenFeng, XinliangXinliangFengRuffieux, PascalPascalRuffieuxFasel, RomanRomanFasel2024-10-072024-10-072018https://boris-portal.unibe.ch/handle/20.500.12422/60704Polycyclic aromatic hydrocarbons exhibit a rich spectrum of physicochemical properties depending on the size and, more critically, on the edge and bond topologies. Among them, open-shell systems—molecules hosting unpaired electron densities—represent an important class of materials for organic electronic, spintronic, and optoelectronic devices, but remain challenging to synthesize in solution. We report the on-surface synthesis and scanning tunneling microscopy- and spectroscopy-based study of two ultralow-gap open-shell molecules, namely peri-tetracene, a benzenoid graphene fragment with zigzag edge topology, and dibenzo[a,m]dicyclohepta[bcde,nopq]rubicene, a nonbenzenoid nonalternant structural isomer of peri-tetracene with two embedded azulene units. Our results provide an understanding of the ramifications of altered bond topologies at the single-molecule scale, with the prospect of designing functionalities in carbon-based nanostructures via engineering of bond topology.en500 - Science::530 - Physics500 - Science::540 - Chemistryarticle10.7892/boris.12140510.1021/acsnano.8b07225