Density functional theory and ab initio studies of geometry, electronic structure and vibrational spectra of novel benzothiazole and benzotriazole herbicides.

The ground-state geometries, electronic structures and vibrational wavenumbers of S-1,3-benzothiazolyl-4-bromobenzenecarbothioate and S-(5,7-dimethyl-3H-4lambda-5-[1,2,4]triazolo[1,5-a]pyridinyl)4-chlorobenzenecarbothioate were studied by DFT-B3LYP, BLYP and ab initio RHF method with different basis sets. The comparison was performed for optimized geometries, thermodynamic parameters and electronic structures at different levels of theory. Because of the larger repulsion effect in triazole ring, the vibrational wavenumbers of skeleton vibration of triazole ring are significantly lower than that of thiazole ring.