Breaking Bonds and Forming Nanographene Diradicals with Pressure

New anthanthrone‐based polycyclic scaffolds possessing peripheral crowded quinodimethanes have been prepared. While the compounds adopt a closed‐shell butterfly‐shaped structure in the ground state, a curved‐to‐planar fluxional inversion is accessible with a low energy barrier through a biradicaloid transition state. Inversion is primarily driven by the release of strain associated with steric hindrance at the peri position of the anthanthrone core; a low‐lying diradical state is accessible through planarization of the core, which is attained in solution at moderate temperatures. The most significant aspect of this transformation is that planarization is also achieved by application of mild pressure in the solid state, wherein the diradical remains kinetically trapped. Complementary information from quantum chemistry, 1H NMR, and Raman spectroscopies, together with magnetic experiments, is consistent with the formation of a nanographene‐like structure that possesses radical centers localized at the exo‐anthanthrone carbons bearing phenyl substituents. π‐Bindungsbruch mit bloßen Händen: Geschlossenschalige Chinodimethan‐Nanographene passieren beim fluxionalen Übergang zwischen ihren gewölbten Strukturen ein planares Diradikal‐Intermediat, das abgefangen werden kann. Das Diradikal ist durch einen energiearmen Triplettzustand charakterisiert. P=Druck, S=Lösungsmittel.