Extended Bis(anthraoxa)quinodimethanes with Nine and Ten Consecutively Fused Six-Membered Rings: Neutral Diradicaloids and Charged Diradical Dianions/Dications

We report the challenging synthesis of two very long bis(anthraoxa)quinodimethanes with nine (ABA) and ten (ANA) consecutively fused six-membered rings. The former is stable with negligible diradical character, while the latter with a moderate diradical character (y(0) = 25.0%) is reactive and an unexpected trifluoroacetic substituted product (ANA-TFA) was isolated. X-ray crystallographic analysis revealed a planar backbone with a typical quinoidal character for both. Their dications can be regarded as the isoelectronic structures of the respective nonacene and decacene. The dication ABA(2+) and dianion ABA(2-) are open-shell singlet diradicaloids, while the longer dication ANA-TFA(2+) and dianion ANA(2-) have closed-shell ground state, which can be explained by the different intramolecular Coulomb interactions. Both dianions have a bent backbone and can be considered as an isoelectronic structure of the tetraanion of nonacene and decacene, respectively.