Synthesis, characterization and antimicrobial activity of transition metal complexes with the Schiff base derived from imidazole-2-carboxaldehyde and glycylglycine

The Co(II), Ni(II) and Cu(II) complexes of the Schiff base derived from imidazole-2-carboxaldehyde and glycylglycine were synthesized and characterized by elemental analysis, PMR, molar conductance, IR, electronic, magnetic measurements, ESR, redox properties, thermal studies, XRD and SEM. Conductance measurements indicate that the complexes are 1 : 1 electrolytes. IR data show that the ligand is tetradentate with imidazole nitrogen, azomethine nitrogen, amide nitrogen and carboxylato oxygen donor groups. Electronic spectral measurements indicate tetrahedral geometry for Co(II) and Ni(II) complexes and square-planar geometry for Cu(II). Magnetic measurements show weak ferromagnetic behavior for Co(II) and Ni(II) complexes, and paramagnetic for Cu(II) complex. The X-band ESR spectral data indicate a covalent link between metal and ligand. The complexes were found to be stabilized in unusual oxidation states of metal during electrolysis. Thermal analysis of the complexes indicate that decomposition takes place in three steps. XRD shows that Ni(II) and Cu(II) complexes have the respective crystallite size of 42 and 34 nm, while the Co(II) complex is amorphous. The surface morphology of the complexes was studied by SEM. The antimicrobial activities of the ligand and its complexes indicate that the metal complexes possess high antibacterial and antifungal activities towards the bacterial species S. aureus, E. coli, K. pneumaniae, P. vulgaris and P. aeruginosa and the fungal species A. niger, R. stolonifer, A. flavus, R. bataicola and C. albicans.