Synthesis, Characterization and Antimicrobial Activities of Cu(II), Ni(II) and Co(II) Complexes with N–O Donor Ligand.

The complexes of Cu (II), Ni (II) and Co (II) with a Schiff base derived from 5-bromo-3-fluorosalicylaldehyde with 4, 4'-diaminodiphenyl methane in the molar ratio 2:1 were synthesized and characterized by several techniques, including elemental analysis, IR, electronic, conductivity, LC-MS, 1H NMR, and magnetic susceptibility measurements were used to characterize the isolated ligand and its metal complexes. The ligand behaves as dibasic with N2O2 tetra dentate sites and two ligands coordinate with two metal ions to form binuclear complexes. The 1H-NMR data reveal that the Schiff base found in enol-iminic form. The binding site is nitrogen atoms of azomethine groups and oxygen atoms of the phenolic groups. The substitution in phenyl ring of the complexes produces shift in the azomethine υ(C=N) stretching vibrational frequency. The non-electrolytic behavior of complexes indicates the absence of counter ions. EPR spectra provided further information to confirm the binuclear structure. On the behalf of electronic spectral data and magnetic susceptibility measurements, the suitable geometry has been proposed for each complex. The Schiff base ligand and metal complexes were tested against four pathogenic bacteria (E. coli and K. pneumoniae) as Gram-negative, (S. aureus and B. subtilis) as Gram+positive, and pathogenic fungi (A. fumigatus) to assess their antimicrobial properties.