Synthesis, spectroscopic characterization, biological activity and theoretical studies of (E)-N3-(2-chlorobenzylidene)-H-1,2,4-triazole-3,5-diamine

Abstract

The Schiff base (E)-N3-(2-chlorobenzylidene)-H-1,2,4-triazole-3,5-diamine was synthesised and characterized by FT-IR, Raman, 1H &13C NMR, UV–Vis and mass spectrometry. A density functional theory based quantum chemical calculations were performed at B3LYP/6-311++G(d,p) level of theory. A comparative analysis of calculated vibrational frequencies with experimental vibrational frequencies was carried out and prominent bands were assigned. The theoretical UV–Vis spectral studies were carried out using time dependent-DFT method in gas phase and IEFPCM model with solvent field calculation. Atomic charges at selected atoms were calculated by Mulliken population analyses (MPA), Hirshfeld population analyses (HPA) and Natural population analyses (NPA) schemes. The molecular electrostatic potential (MEP) map was calculated to assign reactive site on the surface of the molecule. The conceptual DFT based global and local reactivity descriptors were calculated to obtain an insight into the structure-activity relationship. For instance, the results indicate that the C11 of compound is more prone to nucleophilic attack as it has found maximum value of electrophilic reactivity descriptors and thus favours the formation of new heterocyclic compounds. The frontier molecular orbital analysis was carried out to study the charge transfer within the molecule. The NBO analysis was performed to get an insight into the intramolecular conjugative electronic interactions. The titled compound was screened for in vitro antimicrobial activity against four bacterial and five fungal strains.