Analysis of the NQR parameters in 2-nitro-5-methylimidazole derivatives by quantum chemical calculations

Abstract

The present study involves nitrogen NMR-NQR measurements and semiempirical as well as ab initio calculations at the different levels in three 2-nitro-5-methylimidazole derivatives. The NMR-NQR data were compared with the results of the quantum chemical calculations with the geometry optimization by seven semiempirical and a few ab initio methods. Since the use of a finite basis set is always a source of uncertainties in the electric field gradient (EFG) tensor components, the calculations were performed in different basis sets, and—regarding the effect of the functional—also at different levels of the theory. The results closest to experimental ones were obtained at the BLYP level of theory.