Theoretical simple estimation and accurate evaluation of local aromaticity for polycyclic conjugated hydrocarbons

Stationary point structures (or stable structures) and the electronic states of polycyclic conjugated hydrocarbons are estimated by an extended combination method between two Kekule structures(ECMK). The estimation by the ECMK required two postulation conditions. (i) Stationary point structures can be represented with one Kekule structure or the combination of two Kekule structures. (ii) Structures including element Kekule structures of the structures with lower energy are not candidates for structures with higher energy. The structures and electronic states of 13 compounds composed of six-cyclic and four-cyclic rings were estimated by the ECMK, and corresponded to their geometries and the local aromaticity obtained by complete active space self-consistent field molecular orbital and B3LYP methods. Copyright (c) 2014 John Wiley & Sons, Ltd.