Highly Stable Radical Cations of N,N'-Diarylated Tetrabenzotetraaza[8]circulene.

N,N'-Diarylated tetrabenzotetraaza[8]circulenes 3 a and 3 b were synthesized in good yields by a reaction sequence involving oxidation of tetrabenzodiazadithia[8]circulene 5-Oct and SN Ar reaction with aniline derivatives. The obtained aza[8]circulenes 3 a and 3 b were easily oxidized to give their radical cations 3 a+ and 3 b+ , which are highly stable under ambient conditions. X-ray diffraction analysis of radical cation 3 a+ showed a face-to-face dimer arrangement with an interplanar separation of 3.320 Å. The spin density of 3 a+ was calculated to be delocalized over the whole circulene π-systems with spin-spin exchange integral (J=-144 cm-1 ) in the dimeric part. These radical cations displayed far red-shifted absorption bands reaching to 2000 nm. Thus this study has proved the hetero[8]circulene scaffold to be a new entry of promising electronics and spin materials.