In Vitro Antimicrobial Screening of Metal Complexes of Schiff Base derived from Streptomycin and Amoxicillin: Synthesis, Characterization and Molecular Modelling

摘要

A series of three new metal (II) complexes of Schiff base were synthesized from the novel ligand derived from Streptomycin and Amoxicillin in stoichiometric ratio. They were characterized by elemental analysis and spectral techniques like IR, 1H NMR, electronic spectrum and mass spectrum. IR spectral data suggested that the tetradentate ligand has coordination to metal ions through azomethine nitrogen, glycosidic oxygen and two amine nitrogens. Electronic spectral measurement indicated square planar geometry of Ni and Zn-complexes and tetrahedral geometry of Cu-complex with diamagnetic behavior. Molar conductivity measurements revealed non-electrolyte nature of the complexes where metal ions have coordination through doubly negative charged anions of the Schiff base. The thermal behavior (TGA/DTA) of the complexes was studied and kinetic parameters were determined by Coats-Redfern method. XRPD technique revealed monoclinic crystal systems for Ni- and Zn-complexes and hexagonal crystal system for Cu-complex. The possible geometries of the metal complexes with their bond length were optimized by MM2 calculations using CsChem3D Ultra-11 program package software. Antibacterial sensitivity of the ligand and its metal complexes were assayed in vitro against four bacterial pathogens viz. E. coli, B. subtilis, S. aureus and K. pneumonia by Kirby Bauer paper disc diffusion method and showed moderate to better potency.