Bioactivity of some divalent M(II) complexes of penicillin based Schiff base ligand: Synthesis, spectroscopic characterization, and thermal study

A series of four novel metal complexes of Co(II), Ni(II), Cu(II) and Zn(II) were synthesized from Schiff base derived from amoxicillin (AMX) and picolinaldehyde (PC2). The ligand and metal complexes were fully characterized by physical and spectral techniques such as elemental microanalysis, conductivity, FT-IR, 1H & 13C NMR, UV-vis, mass spectra, EPR, magnetic moment measurement, TGA/DTA, PXRD and antibacterial activity study. The spectroscopic study revealed 1:2 metal ligand ratio and coordination sites in the ligand for metal ions were evaluated by analysis of the spectral results. The surface morphology of the complexes was evaluated by SEM analysis. Molar conductivity implies non-electrolytic nature of the complexes. UV-vis. spectral study nicely supports octahedral geometry for Co(II) and Zn(II) complexes and tetrahedral geometry for Cu(II) complex. The kinetic parameters were extracted from Coats-Redfern equation. The PXRD study revealed nano-crystalline nature of Co(II), Ni(II) & Cu(II) complexes and amorphous nature of Zn(II) complex. The proposed geometry of the complexes was optimized by MM2 calculation supported in Cs-ChemOffice Ultra-11 program. The ligand and metal complexes were screened for antibacterial potency against four human pathogenic clinical strains of bacteria and the data revealed their promising antibacterial activity.