On-Surface Synthesis of a Ferromagnetic Molecular Spin Trimer

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Abstract
Triangulenes are prototypical examples of open-shell nanographenes. Their magnetic properties, arising from the presence of unpaired π electrons, can be extensively tuned by modifying their size and shape or by introducing heteroatoms. Different triangulene derivatives have been designed and synthesized in recent years thanks to the development of on-surface synthesis strategies. Triangulene-based nanostructures with polyradical character, hosting several interacting spin units, can be challenging to fabricate but are particularly interesting for potential applications in carbon-based spintronics. Here, we combine pristine and N-doped triangulenes into a more complex nanographene, TTAT, predicted to possess three unpaired π electrons delocalized along the zigzag periphery. We generate the molecule on a Au(111) surface and detect direct fingerprints of multiradical coupling and high-spin state using scanning tunneling microscopy and spectroscopy. With the support of theoretical calculations, we show that its three radical units are localized at distinct parts of the molecule and couple via symmetric ferromagnetic interactions, which result in a S = 3/2 ground state, thus demonstrating the realization of a molecular ferromagnetic Heisenberg spin trimer.
Funding Information
  • HORIZON EUROPE European Research Council (101097693)
  • European Regional Development Fund
  • Ministerio de Educaci?n y Formaci?n Profesional (FPU20/03305)
  • Xunta de Galicia (ED431G 2019/03)
  • Diputaci?n Foral de Gipuzkoa (2022-QUAN-000030-01, 2023-QUAN-000028-01)
  • Engineering and Physical Sciences Research Council (EP/V062654/1)
  • European Research Council (ERC Synergy Grant MolDAM (no. 951519), ERCAdG CONSPIRA (101097693))
  • Ministerio de Ciencia, Innovaci?n y Universidades (CEX2020-001038-M, PID2022-139776NB-C65, PID2022-140845OBC61, PID2022-140845OBC62, PID2023-146694NB-I00, RYC2021-034304-I)
  • Grantov? Agentura Cesk? Republiky (23-0548)
  • H2020 Future and Emerging Technologies (863098)
  • Euskal Herriko Unibertsitatea
  • Hezkuntza, Hizkuntza Politika Eta Kultura Saila, Eusko Jaurlaritza
  • NextGenerationEU (PRTR-C17.I1)
  • H2020 European Research Council (951519)
  • HORIZON EUROPE Digital, Industry and Space (101093374)

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