Ab Initio Density Funtional vs Hartree Fock Predictions for the Structure of [18]Annulene: Evidence for Bond Localization and Diminished Ring Currents in Bicycloannelated [18]Annulenes

Threshold levels for the correct theoretical description of the delocalized [18]annulene (1) have been established with hybrid ab initio density functional computations. Analogous calculations on the bicycloannelated derivative 2 predict a clearly bond-localized structure and earmark this molecule as a new synthetic target for the study of aromaticity.