Length‐Dependent Magnetic Evolution of Anthenes on Au(111)

Nanographenes with zigzag edges, for example, anthenes, exhibit a unique nonbonding π‐electron state, which can be described as a spin‐polarized edge state that yields specific magnetic ground state. However, prior researches on the magnetism of anthenes with varying lengths on a surface is lacking. This study systematically fabricated anthenes with inherent zigzag carbon atoms of different lengths ranging from bisanthene to hexanthene. Their magnetic evolution on the Au(111) surface was analyzed through bond‐resolved scanning probe techniques and density functional theory calculations. The analyses revealed a transition in magnetic properties associated with the length of the anthenes, arising from the imbalance between hybridization energy and the Coulomb repulsion between valence electrons. With the increasing length of the anthenes, the ground state transforms gradually from a closed‐shell to an antiferromagnetic open‐shell singlet, exhibiting a weak exchange coupling of 4 meV and a charge transfer‐induced doublet. Therefore, this study formulated a chemically tunable platform to explore size‐dependent π magnetism at the atomic scale, providing a framework for research in organic spintronics. We successfully fabricated atomically precise anthenes with varying lengths ranging from 2 to 6 anthryls. With increasing lengths, the ground states switch from S=0 (closed‐shell bisanthene) to S=0 (open‐shell teranthene). In longer anthenes, the charge transfer can switch magnetism from S=0 to S=1/2.