Aromaticity in Heteronins

Abstract

Hybrid density functional theory (B3LYP) calculations are performed on some of the heteronines (azonine, oxonine and thionine) in order to carry out a systematic estimation of aromaticity using structural, energetic and magnetic criteria. Optimized geometries predict a planer and puckered structures with no bond alternation for azonine and oxonine rings, respectively. A nonplaner structure is obtained for thionine with bond alternation. A comparison has also been made between the difference of frontier molecular orbital energies of the cyclic and the chain-form analog of these molecules (ΔΔFMO). According to this quantity all of the proposed heteronines are aromatic. Results based on the Mulliken population analysis and computed NICS values predict the azonine, oxonine and thionine as aromatic, non-aromatic and antiaromatic, respectively.