A theoretical study on the aromaticity of thiadiazoles and related compounds

Three different approaches have been considered to determinate the aromatic character of isomeric thiadiazoles. Several indices have been obtained fro m calculations made in the context of nonlocal (B3LYP) density functional c alculations. The results were compared with the existing experimental evide nce for analog heterocycles. It is concluded that the thiadiazoles are arom atic compounds, with a larger aromatic character than pyrrole, thiophene an d furan. The monoxide and dioxide derivatives are shown to be non-aromatic or antiaromatic molecules. (C) 2001 Elsevier Science BN. All rights reserve d.