Unsubstituted octacene (n=8) and nonacene (n=9) have been detected in matrix isolation. The first reports of stable nonacene derivatives claimed that due to the electronic effects of the thioaryl substituents the compound is not a diradical but a closed-shell compound with the lowest HOMO-LUMO gap reported for any acene, an observation in violation of Kasha's rule.
Unsubstituted octacene (n=8) and nonacene (n=9) have been found in matrix isolation experiments. Initial findings suggested that nonacenes with thioaryl substituents are not radical species but closed-shell compounds, possessing the lowest HOMO-LUMO gap ever observed for acenes, a finding that contradicts Kasha's rule.