Synthesis, characterization and theoritical study of some pyrazine carbohydrazide derivatives

Abstract

In the current work, we report the synthesis and characterization of some pyrazine carbohydrazide derivatives; namely: N'-(2-hydroxybenzylidene) pyrazine-2-carbohydrazide (Hmbpcz), N'-(2-hydroxy-4-methoxybenzylidene) pyrazine-2-carbohydrazide (Hbpcz), and N'-(2-hydroxy-4-methoxybenzylidene) benzohydrazide (Mbbz). The procedure includes the reaction of 4-methoxy salicaldehyde and pyrazine carbohydrazide in a 1:1 molar ratio. The synthesized compounds were confirmed by NMR and IR. Moreover, the three compounds were theoretically investigated using the Density Functional Theory (DFT) approach with the B3LYP/Def2-TZVP basis set. Each of the three compounds exhibited a planar structure characterised by a strong π-electron resonance across the entire molecule. Among the compounds, compound Mbbz exhibited the greatest HOMO-LUMO energy gap, whilst compound Hmbpcz obtained the lowest. Moreover, the calculations of the natural bond orbital (NBO) revealed that the pyrazine ring surpasses the benzene ring in its ability to transfer electrons to the pi system. The stability values of all compounds were greatly enhanced by the presence of π-electron resonance in the ligands.