Lead(II) Schiff Base Complexes: Design, Synthesis, Theoretical, Antibacterial and Docking Studies

Abstract

This study presented the bioactive lead(II) compounds of oxazine and thiazine Schiff-bases using NMR (1H, 13C), FT-infrared spectroscopy, UV-visible, molar conductance, elemental analysis and molecular weight. The molecular parameters e.g. bond length, bond angle, HOMO/LUMO energy gap and softness/hardness was calculated by DFT-B3LYP/Lanl2dz basis set. According to the spectral data, the Schiff-base coordinated to the lead atom in bidentate mode. A theoretical DFT computational investigation was conducted to supplement the experimental data. The antibacterial activity of lead complexes against E. coli (–) and S. aureus (+) bacteria was determined by disc-diffusion method. Lead complexes of thiazine derivatives are more active than oxazine derivatives. In order to better understand the molecular interaction and binding mode of the drugs, a molecular docking study has been carried out on the protein 3q8u (NDK) from S. aureus. A docking investigation with the NDK protein (S. aureus) revealed that compound 1h has the highest binding affinity (-8.18 Kcal/mol) among the eight ligands (1a-h).