Strong Magnetic Exchange Coupling of a Dibenzo-fused Rhomboidal Nanographene and its Homocoupling with Tunable Periodicities on a Metal Surface

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.