Theoretical studies of novel aromatic molecules and transition states

Abstract

Monocyclic conjugated molecules have stabilities, bond lengths, and magnetic properties following expectations from Hückel's Rule. Two hydrocarbons which seem to deviate from these generalizations, s-indacene and cyclohepta[def]fluorene, were studied with density functional theory. The former has characteristics expected for both aromatic and antiaromatic molecules; the latter is a ground state triplet. Potentially aromatic transition states with 10 electrons were also investigated. The mechanism of the 5,5-sigmatropic shift is predicted to be stepwise involving diradical intermediates. © 1999 IUPAC.