The aromaticity and Möbius characteristics of carbeno[8]heteroannulenes and triplet state annulenesElectronic supplementary information (ESI) available: due to the two printed page length restriction on this communication, energies and coordinates for all the systems studied can be viewed via the ESI. See http://www.rsc.org/suppdata/cc/b1/b110626k/

Two types of annulene which may show significant Möbius aromatic character and bond and twist delocalisation are proposed; triplet states with 4n + 2 occupancy of the p pi array of atomic orbitals and a novel 8-pi carbeno[8]heteroannulene ring system 1 where the Hückel highly antiaromatic nature as a planar system can be attenuated or even reversed by the C2 symmetric Möbius distortion.