A Density Functional Theory Study of the Structural Preferences of Type B Heteropentalene Mesomeric Betaines and Their Non‐Aromatic Azacyclooctatetraene Isomers

ABSTRACT Density Functional Theory (DFT) has been used to explore the relative thermodynamic stabilities of a series of Type B heteropentalene mesomeric betaines (HMBs) 1a‐c and their corresponding azacyclooctatetraene isomers 2a‐c . The results of these calculations suggest that (a) the interconversion of most pairs of isomers is unlikely to occur and (b) the HOMO/LUMO energy difference in the HMBs suggests they might have a role in reducing the band gaps of known Type B HMB conducting polymers.