Generalized Polansky Index as an Aromaticity Measure in Polycyclic Aromatic Hydrocarbons

In this work, the ideas of molecular quantum similarity are used to generalize the Polansky similarity index. The newly developed index gauges the aromaticity of individual benzenoid rings in polyaromatic hydrocarbons by its similarity to benzene beyond the scope of simple Hückel theory on which it was originally based. The reported generalization allows the new index to be calculated at a realistic contemporary ab initio level of theory, opening the possibility of its use as a new measure of aromaticity. As will be shown, the new index correlates very well not only with the original Polansky index but also with the Generalized Population Analysis based multicenter index