Fulvalene ions—I: Calculations on calicene ions

Calculations on planar and 90°-twisted calicene and the mono- and di-ions derived from it are reported. Both all-valence-electron and π-electron calculations were performed, utilizing an “all aromatic” geometry throughout. Calculated ionization energies indicate that there should be no appreciable gain in resonance stabilization upon radical formation, however the radicals should be amenable to preparation. Good general agreement was obtained between the π-electron charge and spin distributions predicted by the INDO and PPP methods. In addition, these are generally in good agreement with simple predictions based on Hu¨ckel's (4n + 2) rule.