Synthesis, characterization and biological activity of manganese(II), iron(II), cobalt(II), nickel(II) and copper(II) schiff base complexes against multidrug resistant bacterial and fungal pathogens

A Schiff base was prepared from the interaction of ethanolic solutions of 2-hydroxy-1– naphthaldehyde and butylenediamine. The complexes were synthesized by refluxing the mixture of ethanolic solutions of the Schiff base and respective metal (II) chloride. Their solubility, melting point/decomposition temperature, molar conductance, elemental analysis and IR were carried out. The melting point of the Schiff base and the decomposition temperature of the complexes determined are high. The Schiff base and its metal (II) Schiff base complexes are insoluble in water and most common organic solvents, except methanol, ethanol and DMSO. The molar conductance of the complexes determined falls in the range 9 – 12 Ohm -1 cm 2 mol -1 . Elemental analysis of the complexes for C, N and H revealed 1:1 metal to Schiff base ratio. The IR spectral analysis of the free Schiff shows a band at 1641 cm -1 , which is assigned to v(C=N) stretching vibrations. This band is observed in the complexes but at lower frequencies, indicating coordination of the Schiff base to the metal ion through the azomethine group. The Schiff base and its divalent metal complexes were screened for their antibacterial activity against Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris and Salmonella typhi as well as Rhizopus nigricans. and Mucur specie fungal isolates. It has been found that all the complexes show different activity on the isolates and that the complexes show higher activity than the free ligand.