We present a design strategy that combines topological frustration and electron-electron interactions to fabricate a large, fully fused ‘butterfly’-shaped tetra radical nanographene on Au(111). We employ bond-resolved scanning tunneling microscopy and spin-excitation spectroscopy to resolve the molecular backbone and reveal the strongly correlated open-shell character, respectively. This nanographene contains four unpaired electrons with both ferromagnetic and anti-ferromagnetic interactions, harboring a many-body singlet ground state and strong multi-spin entanglement, which is well described by many-body calculations. 
https://www.nature.com/articles/s41557-024-01453-9