Criteria for aromaticity of mesoionic heterocycles

Abstract

The quantum chemical calculations of the basic criteria for aromaticity (nucleus-independent chemical shift (NICS), aromatic stabilization energy (ASE), and parameters of harmonic oscillator model of aromaticity (HOMA), and geometric indices (I 5)) of 54 mesoionic heterocycles in the 6-31G*split-valence basis set were performed in terms of the density functional theory (DFT) with the B3LYP exchange-correlation hybrid functional. The aromatic nature of the mesoionic heterocycles containing the pyridinium N atom was shown. © 2012 Springer Science+Business Media New York.