New Topological Indices for Alternant Polycyclic Aromatic Hydrocarbons

Pairwise orthogonal topological indices A and Woo derived from the characteristic graphs of alternant polycyclic aromatic hydrocarbons (kata-annellated and peri-condensed systems) correlate with resonance energy per electron, energy of the HOMO and total ;i: electron energy respectively. For topological indices a high discrimination power is necessary but not sufficient to correlate with molecular properties. However, the indices and properties must be related similarly to topology and the size of the systems. Accordingly Type-A indices and properties which depend comparably strongly on both topology and size (e.g. A and resonance energy per electron) and Type - B indices and properties which depend predominantly on size (e. g. Woo and total ;i: electron energy) are distinguished