Synthesis, physical characterization and antimicrobial activity of trivalent metal Schiff base complexes

M(III) complexes of Cr, Mn and Fe with a Schiff base derived from 2-amino-4-ethyl-5-hydroxybenzaldehyde and thiocarbohydrazide were synthesized and characterized by several techniques, including elemental analysis (C,H,N), molar conductance measurements, magnetic measurements, and electronic, mass and IR spectral studies. Based on these studies, a five-coordinated square pyramidal geometry for all the complexes was proposed. The Schiff base ligand and the complexes were also tested for their antimicrobial activity (against the bacteria Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus megaterium, and the fungi Kluyveromyces fragilis, Rhodotorula rubra, Candida albicans and Trichoderma reesei) to assess their inhibiting potential. An attempt was also made to correlate the antimicrobial activity with the geometry of the complexes. All complexes were found to be less active against the pathogens E. coli, S. aureus and P. aeruginosa. The Cr(III) complex showed the best antimicrobial activity, but the ligand alone was found to be active against the fungus T. reesei.