Synthesis, Structure Delineation and Antibacterial Activity Study of Metal (II) Complexes of Schiff Base Derived from Kanamycin and Methyl Ester of Amoxicillin

A novel Schiff base ligand was synthesized from Kanamycin and methyl ester of Amoxicillin in stoichiometric ratio. Three metal chlorides viz. CuCl2.2H2O, CoCl2.6H2O and ZnCl2 were used for the synthesis of respective metal complexes from synthesized novel ligand. The proposed structure of the complexes have been established by various microanalytical and spectral techniques like elemental analysis, TG/DTA studies, conductivity measurement, IR, 1H NMR, Electronic and mass spectrometry. Various shifting in the band positions in IR spectra of the complexes suggested coordination of metal ions through azomethine N and O-atoms of the novel ligand. Spectral studies concluded pentadentate nature of ligand. The correct stereochemistry of the complexes was optimized by MM2 calculations programmed in CsChem3D Ultra-11 software. The crystal structures of the complexes have been determined by X-ray powder diffraction techniques. The particle size calculation by Scherrer's formula suggested nanocrystalline nature of the complexes. The Coats-Redfern equation was used to calculate the thermal decomposition kinetic parameters of the metal complexes. Non-spontaneous decomposition of the complexes has been suggested by positive ΔG and negative ΔS values. The pharmacological potentiality of the Schiff base ligand and its metal complexes were assayed in vitro by Kirby Bauer paper disc diffusion method against four bacterial pathogens viz. S. aureus, E. coli, B. subtilis and K. pneumoniae. The results of these studies revealed moderate to better antibacterial potency of the complexed Schiff base against uncomplexed.