Heteroaromaticity .11. The conjugation energies of annulenes and heteroannulenes from their molecular dimensions

A previously described method for the direct calculation of conjugation energies from molecular dimensions has been applied to a range of monocyclic and bridged annulenes and hetero-annulenes. As might have been anticipated only those compounds having conjugated peripheries with (4n+2)pi electrons and adequate overlap between adjacent p-orbitals display substantial conjugation energies. Where comparison is possible the results reported here are in reasonable agreement with those obtained by other methods. (C) 1997 Elsevier Science Ltd.