Stability and aromaticity of charged Möbius[4n]annulenes.

A number of parent aromatic Möbius annulenes that violate the Hückel rule have been proposed theoretically. Unfortunately, these species are thermodynamically and kinetically unstable and probably impossible to synthesize. We therefore systematically screened a large number of annulene anions, dianions, and dications and predict that a Möbius [14]annulene dication is not only the most stable isomer among these monocyclic structures but also the global minimum on the (CH)(14)(2+) hypersurface including bicyclic and tricyclic isomers. Thus, under stable ion conditions the Möbius [14]annulene dication should be stable toward cis-trans isomerizations and electrocyclic reactions which are the most probable pathways limiting the lifetime of Möbius annulenes.