The ability to engineer geometrically well-defined antidots in large triangulene homologues allows for creating an entire family of triangulene quantum rings (TQRs) with tunable high-spin ground state, crucial for next-generation molecular spintronic devices. Herein, we report the synthesis of an open-shell [7]triangulene quantum ring ([7]TQR) molecule on Au(111) through the surface-assisted cyclodehydrogenation of a rationally designed kekulene derivative. Bond-resolved scanning tunneling microscopy (BR-STM) unambiguously imaged the molecular backbone of a single [7]TQR with a triangular zigzag edge topology, which can be viewed as [7]triangulene decorated with a coronene-like antidot in the center. Additionally, dI/dV mapping reveals that both inner and outer zigzag edges contribute to the edge-localized and spin-polarized electronic states of [7]TQR. Both experimental results and spin-polarized density functional theory calculations indicate that [7]TQR retains its open-shell septuple ground state (S = 3) on Au(111). This work demonstrates a new route for the design of high-spin graphene quantum rings for future quantum devices.

Centre for Advanced 2D Materials National University of Singapore 6 Science Drive 2 Singapore 117546 Singapore

Department of Chemistry National University of Singapore 3 Science Drive 3 Singapore 117543 Singapore

Institute of Physics Czech Academy of Sciences Prague 16200 Czech Republic

J Heyrovský Institute of Physical Chemistry Czech Academy of Sciences v v i Dolejškova 3 18223 Prague 8 Czech Republic

Regional Centre of Advanced Technologies and Materials Palacký University Olomouc 78371 Czech Republic

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