Synthesis and Characterization of peri-Heptacene on a Metallic Surface

The synthesis of long n-peri-acenes (n-PAs) is challenging as a result of their inherent open-shell radical character, which arises from the presence of parallel zigzag edges beyond a certain n value. They are considered as pi-electron model systems to study magnetism in graphene nanostructures; being potential candidates in the fabrication of optoelectronic and spintronic devices. Here, we report the on-surface formation of the largest pristine member of the n-PA family, i.e. peri-heptacene (n=7, 7-PA), obtained on an Au(111) substrate under ultra-high vacuum conditions. Our high-resolution scanning tunneling microscopy investigations, complemented by theoretical simulations, provide insight into the chemical structure of this previously elusive compound. In addition, scanning tunneling spectroscopy reveals the antiferromagnetic open-shell singlet ground state of 7-PA, exhibiting singlet-triplet spin-flip inelastic excitations with an effective exchange coupling (J(eff )) of 49 meV.

Automated summary

This study reports the successful on-surface synthesis of the largest pristine member of the n-PA family, peri-heptacene, on an Au(111) substrate under ultra-high vacuum conditions. High-resolution scanning tunneling microscopy and theoretical simulations provide insights into the chemical structure of this previously elusive compound. Scanning tunneling spectroscopy reveals that peri-heptacene exhibits an antiferromagnetic open-shell singlet ground state and a singlet-triplet spin-flip inelastic excitation with an effective exchange coupling of 49 meV.