Coronoids with holes shaped like an odd carbon benzenoid have antiaromatic holes and antiaromatic conjugated
circuits. Another class of concealed diradical coronoids has been identified. They are Hückel molecular orbital diradicals (HOMO = LUMO = 0, each with a single electron occupancy) that have VB (valence-bond) structures (K ≠ 0).This
new class of concealed diradical coronoids have more enhanced antiaromatic contributions. The smallest holes in graphenes are spin polarized and have antiaromatic characteristics.