π-Conjugated Radical Cations Stabilized by Surrounding Bicyclic σ-Frameworks (ORGANIC MATERIALS CHEMISTRY-High-Pressure Organic Chemistry)

Abstract

Benzene 1, naphthalene 2, biphenylene 3, and anthracene 4, fully annelated with bicyclo[2.2.2]octene were transformed into the corresponding radical cations, and their structures were clarified by X-ray crystallography. The remarkable stability of these salts are ascribed to the electronic and steric effects of the bicyclic frameworks. 1, 4-Dithiin 5 annelated with the same bicyclic units was also oxidized into the stable salt of the radical cation, and the structure examined by X-ray crystallography. The ESR study indicated that the spin is effectively delocalized into the bicyclic frameworks. Dithiin 5 was further oxidized into the dication, which was shown to be 6π aromatic by the NMR and theoretical studies.