Antiferromagnetic Chains in a Monolayer of Molecular Qubits Assembled on Graphene

The neutral Cu 2+ complex [Cu(dttt) 2 ], in which dttt − is the 1,3,2‐dithiazole‐4‐thione‐5‐thiolate ligand, is a promising molecular spin qubit where a hydrogen‐free and sulfur‐rich scaffold has been designed to enhance the spin coherence. In bulk, the structural organization induces strong intermolecular antiferromagnetic exchange couplings up to about 100 cm −1 , mediated by van der Waals interactions and propagated along 1D chains of molecules within the crystal structure. Here, the deposition by sublimation in ultra‐high vacuum conditions of [Cu(dttt) 2 ] on a graphene surface is studied, focusing on investigating the topology and magnetism of ultrathin films. These deposits are characterized by combining X‐ray photoelectron spectroscopy and scanning tunneling microscopy; the latter indicates an ordered chain‐like arrangement of the assembled monolayer. Synchrotron‐based X‐ray absorption techniques flanked by density functional theory and wavefunction‐based simulations confirm the molecular ordering. These reveal that the magnetic coupling observed in bulk is also present at the monolayer level, highlighting the persistence of a 1D antiferromagnetic intermolecular coupling of about 50 cm −1 with a non‐negligible contribution coming from a through‐surface exchange path.