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O: Fachverband Oberflächenphysik

O 61: Organic molecules on inorganic substrates: electronic, optical and other properties II

O 61.4: Vortrag

Mittwoch, 11. März 2026, 15:45–16:00, HSZ/0201

Synthesis and Characterization of a Polyradical Hexaazacycloarene — •Zilin Ruan, Olaf A. Kleykamp, Tim Naumann, Faming Kang, Jörg Sundermeyer, and J. Michael Gottfried — Department of Chemistry, Philipps University Marburg, 35037 Marburg, Germany

Cycloarenes have drawn considerable research interest owing to their unique electronic and topological features. The synthesis of large zigzag-edged cycloarenes, which are predicted to exhibit exotic polyradical ground states, has remained elusive. Here, we report the synthesis of a zigzag-edged hexaazacycloarene incorporating six graphitic nitrogen atoms within its macrocyclic backbone, achieved through a combined in-solution cyclization and on-surface cyclodehydrogenation on a Au(111) surface. The structural and electronic properties of the resulting macrocycle were investigated by STM/STS, nc-AFM and KPFM. DFT and multireference CASSCF calculations reveal that the isolated molecule has an open-shell singlet ground state with six unpaired electrons and undergoes a spontaneous symmetry breaking from C6 to C2, driven by strong electron-electron correlations and a pseudo-Jahn-Teller instability. Notably, the expected low-energy spin excitations are absent on Au(111), which is rationalized by the hybridization between the molecular π-system and the substrate, effectively quenching the intrinsic magnetism. These results provide crucial insight into correlation-driven magnetism and represent a significant advance toward the realization of cycloarenes with π-magnetism.

Keywords: On-surface synthesis; Scanning probe microscopy; Polyradical molecule