Open-shell nanographenes (NGs), also known as molecular π-magnets, have recently garnered attention for their potential in spintronics and quantum computing. Tailoring of such NGs at the atomic level allows the control of their magnetic interactions. We report here the on-surface synthesis of a dibenzo-fused rhomboidal NG with predominant zigzag edges featuring an open-shell (antiferromagnetic) character and a high value of magnetic exchange coupling (MEC) on Au(111) surfaces. Scanning tunneling microscopy (STM) and noncontact atomic force microscopy (nc-AFM) confirm its chemical structure. Scanning tunneling spectroscopy (STS) measurements, complemented by state-of-the-art theoretical calculations, reveal the open-shell character of the NG, observed as singlet-triplet inelastic excitations. Furthermore, molecular chains consisting of these NGs were fabricated with tunable periodicities through the functionalization of the precursor, showing the absence of MEC between adjacent units, which provides deeper insights into the behavior of open-shell systems and preservation of individual magnetic entities within π-conjugated structures.

Department of Condensed Matter Physics Faculty of Mathematics and Physics Charles University Prague 2 CZ 12116 Czech Republic

IMDEA Nanoscience C Faraday 9 Campus de Cantoblanco 28049 Madrid Spain

Institute of Physics of the Czech Academy of Science Cukrovarnická 10 16200 Prague 6 Czech Republic

Instituto de Ciencia de Materiales de Madrid CSIC Cantoblanco 28049 Madrid Spain

Organic and Carbon Nanomaterials Unit Okinawa Institute of Science and Technology Graduate University 1919 1 Tancha Onna son Kunigami gun Okinawa 904 0495 Japan

Unidad de Nanomateriales avanzados Imdea Nanoscience Unidad asociada al CSIC por el ICMM 28049 Madrid Spain

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