Preparation, characterization, antimicrobial and anticancer activities of Schiff base mixed ligand complexes

A new Schiff base ligand (HL) derived from quinoline-2-carboxaldehyde with 2-aminophenol (1:1 molar ratio) and its mixed ligand complexes, viz. 2,2′-bipyridine (1:1:1 molar ratio), have been synthesized and characterized by elemental analysis, spectroscopic studies, X-ray diffraction, ESR, magnetic and thermal analysis. The molar conductance measurement of mixed ligand complexes in DMF showed that Zn(II) and Cd(II) complexes were nonelectrolytes; however, Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) complexes were electrolytes. The transition metal complexes had octahedral geometry with a general molecular formulae [M(L)(2,2′-bipy)(H 2 O)]Cl x · n H 2 O (M = Cr(III) ( x = n = 2), Mn(II) and Co(II) ( x = 1, n = 0), Ni(II) and Cu(II) ( x = n = 1) and [M(L)(2,2′-bipy)Cl]Cl x · n H 2 O (M = Fe(III) ( x = 1, n = 3), Zn(II) ( x = 0, n = 1) and Cd(II) ( x = 0, n = 2)). Also, Schiff base ligand and its mixed ligand complexes were screened against Gram-positive bacteria ( Streptococcus pneumoniae , Bacillus subtilis ), Gram-negative bacteria ( Pseudomonas aeruginosa , Escherichia coli ) and fungal species ( Aspergillus fumigatus , Candida albicans ). Gentamicin, ampicillin and amphotericin B were used as standard drugs for Gram positive, Gram negative and antifungal activity, respectively. The results showed that all mixed ligand complexes have antimicrobial activity higher than free Schiff base ligand. In addition, anticancer activity of Schiff base ligand and its mixed ligand metal complexes were also tested against breast cancer cell line (MCF-7) and colon cancer cell line (HCT-116). Cd(II) complex showed the highest IC 50 against two cell lines.