Stability and Reactivity of Two Benzimidazole Hydrazide-Hydrazone Compounds: A Theoretical Study by DFT Method

Abstract

This work contributes to theoretical chemistry’s knowledge of benzimidazole-hydrazide-hydrazone. Indeed, hydrazides-hydrazones-benzimidazoles have shown anticancer, antibacterial, antiparasitic activities, and many other activities. A benzimidazole-hydrazide-hydrazone compound can exhibit four conformers: E/Z synperiplanar (Esp, Zsp) and E/Z antiperiplanar (Eap, Zap). Studies have indicated that the prevalence of these compounds is attributed to their stability and their tendency to readily bind to DNA. A theoretical study with advanced methods would make it possible to evaluate the stability of benzimidazole-hydrazide-hydrazone conformers. Therefore, we carried out this theoretical study on the conformers of two benzimidazoles-hydrazides-hydrazones denoted C<sub>1</sub> and C<sub>2</sub> wich differ by the presence of fluorine atom in the structure of C<sub>2.</sub> Specifically, we analyze the stability and the reactivity of the compounds based on the dipole moment, Gibbs free energy, HOMO and LUMO energies and UV-visible. For this purpose, calculations were performed in gas phase and DMSO using DFT and TD-DFT methods at the B3LYP/6-311+G(d, p) level theory. The dipole moment values show that Zap conformer is the most polar for both compounds. The Gibbs free energy indicate that Esp conformer emerges as the most stable for both compounds in both phases. The energy gap (E<SUB>LUMO</SUB>-E<SUB>HOMO</SUB>) and TD-DFT results suggest that Esp conformer is the most reactive conformer for the two compounds.