Although TAM-TAM and TOT-TOT have Kekulé resonance structures, the openshell non-Kekulé diradicals are more stable than the closed-shell Kekulé structure by 8.69 kJ/mol and 32.81 kJ/mol, respectively, due to the recovery of the benzene ring and energy gain of forming aromatic π-sextets as per Clar's rule (Table and Figure ). The molecules of the TRI-series (including TRI-TRI, TRI-CC-TRI, TRI-CCCC-TRI and TRI-Ph-TRI) have four unpaired electrons, while the others have two.