Aromaticity on the edge of chaos: An ab initio study of the bimodal balance between aromatic and non-aromatic structures for 10π-dihetero[8]annulenes

The computed geometries of a class of 10π-annulenes containing two heteroatoms, which exhibit an acutely sensitive balance between π and σ influences upon ring planarity, reveal that the recent KMLYP hybridisation of the exchange functional in the DFT method is qualitatively superior to the more commonly used B3LYP hybrid for modelling the aromaticity of such systems.