A New Index for the Estimation of the Aromatic Character - VIII

A new aromaticity index is proposed based on the energy of π orbitals D={[π1+Σn2(π1-πn)]0 /[π1 + Σn2(π1-πn)]} x a, where n are the number of occupied π orbitals and a is the number of cycles in the molecule. Calculations have been performed on aromatic and heteroaromatic compounds by using DFT method at B3LYP/6-311G+(d,p) level. This new index has been tested on a large number of 6π electron compounds, on bicyclic and polycyclic aromatic compounds and compared with HOMA and the aromatic stabilization energy (ASE). In all the cases, a good correlation has been found. In the case of HOMA, for monocyclic pentaatomic compounds different correlations was found depending on the nature, the number, and the position of the heteroatoms.