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 detected in matrix isolation experiments. The initial reports of stable nonacene derivatives suggested that the thioaryl substituents lead to closed-shell structures with a lower HOMO-LUMO gap than expected, contradicting Kasha's rule.