Synthesis, spectral characterization, DFT computational studies and inhibitory activity of novel N2S2 tetradentates Schiff bases on metallo-beta-lactamases of Acinetobacter baumannii

Abstract Tetradentates N 2 S 2 Schiff base ligands H 2 L 1 and H 2 L 2 were synthesized respectively from orthophenylenediamine and 1,3-diaminopropane which were condensed on thioacetic acid in ethanolic solutions. These synthesized chelating agents were structurally characterized by the routine physicochemical methods such as FT-IR, 1 H and 13 C NMR, molar conductance and UV–Vis spectrophotometry. The both Schiff bases H 2 L 1 and H 2 L 2 were used as inhibitors agents towards the metallo-beta-lactamases enzymes (MBLs). These enzymes were extracted from Acinetobacter baumannii . It revealed that they have a significant inhibitory effect basing on their IC 50 values, compared to the standard inhibitor like EDTA. Accordingly, these ligands were found to be efficient inhibitors towards MBLs activity. Molecular structures of the obtained compounds with their electronic properties were also investigated using density functional theory (DFT) via B3LYP/6-31G (d,p) method. The essential results obtained from this method have been found to be in good correlation with the decreasing of the energetic gap values (HOMO, LUMO) seeing that as these gap values of H 2 L 1 and H 2 L 2 decrease, their IC 50 decrease. As a consequence, the resulting inhibitory effects become consequently increased.