Biologically vital metal-based antimicrobial active mixed ligand complexes: synthesis, characterization, DNA binding and cleavage studies

Few novel cobalt(II) and copper(II) complexes [M(fmp)3]Cl2, [M(fmp)(bpy)2]Cl2, [M(fmp)(phen)2]Cl2 and [M(fmp)(phen)(bpy)]Cl2 (fmp = 3-furan-2-ylmethylene-pentane-2,4- dione, phen = 1,10-phenanthroline, bpy = 2,2'-bipyridine) have been synthesized and characterized by elemental analyses, molar conductance, magnetic susceptibility measurements, IR, electronic, EPR, mass spectra and cyclic voltammetric studies. The synthesized complexes are found to be monomeric and electrolytic nature. The UV-Vis., magnetic susceptibility and EPR spectral data of the complexes suggest a distorted octahedral geometry for Cu(II) complexes and octahedral geometry for Co(II) complexes around the central metal ion. The CV profile of the complexes shows a quasi-reversible peak which indicates that the metal-ligand linkage is more covalent in nature. Spectroscopic and viscosity measurements prove that the [M(fmp)(phen)2]Cl2 complexes bind more efficiently with DNA than other complexes through intercalative mode. The difference of peak potential and electrochemical parameters between free and DNA-bound complexes shows the formation of an electrochemical active complex between synthesized complexes and DNA. All the complexes cleave the Supercoiled pUC19 DNA in vitro under the presence of reducing agent (3-mercaptopropionic acid). The in vitro antimicrobial activities of the compounds have been tested against the bacterial and fungal strains using the disc diffusion method. The minimum inhibitory concentration (MIC) values against the growth of microorganisms are much larger for metal chelates than the individual ligands.