Design, Synthesis, Structural Investigation and Photo Induced Biological Investigations of Co(II), Ni(II) and Cu(II) Complexes Derived from N,O Donor Schiff Bases.

A series of chelated metal complexes, [Co(LI)2] (1), [Ni(LI)2] (2), [Cu(LI)2] (3) [Co(LII)2] (4), [Ni(LII)2] (5) and [Cu(LII)2] (6) were designed and synthesized from newly synthesized Schiff bases, LI = 2-((E)-(5-(4-fluorophenyl)isoxazol-3-ylimino)methyl)-5-methylphenol and LII = 2-((E)-(5-(4-fluorophenyl)isoxazol-3-ylimino)methyl)-4-chlorophenol. The synthesized compounds were characterized by elemental analysis, nuclear magnetic resonance spectroscopy (NMR), electronic spectroscopy (UV-Vis), infrared spectroscopy (FT-IR), magnetic susceptibility (µeff), electron spin resonance spectroscopy (ESR), Thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and powder X-ray diffraction analysis (P-XRD). The spectral investigations have been clearly suggested 1:2 (metal: ligand) stoichiometric complexes with square planar geometrical arrangement around the metal ion. The thermal gravimmetric analysis (TGA) of these complexes indicates greater thermal stability and various steps involved in thermal decomposition of metal complexes. The binding ability between these metal complexes and calf thymus DNA (CT-DNA) was investigated by UV-Vis, fluorescence spectroscopy and viscometric experiments, which disclosed that, the complexes interacted to CT-DNA via an intercalation binding mode. The cleavage property of metal complexes against pBR322 DNA has been explored by gel electrophoresis technique mediated by UV-illumination and H2O2, showed momentous cleavage activity. Antioxidant activity of all complexes was determined by DPPH free radical scavenging experiment and showed prominent antioxidant activity. Further, the antibacterial and antifungal activities of all compounds were screened against bacterial and fungal strains via in-vitro disc diffusion method. These studies revealed that the complexes showed comparatively more antimicrobial activity than free ligands against tested microbial strains.

An Investigation on DNA Binding, Cleavage and Antimicrobial Properties of Mononuclear Co(II), Ni(II) and Cu(II) Complexes Derived from N, O Donor Schiff Bases.

Two sets of mononuclear N, O-chelate complexes, 1a [Co(L1)2(H2O)2], 1b [Ni(L1)2] and 1c [Cu(L1)2], and 2a [Co(L2)2(H2O)2], 2b [Ni(L2)2] and 2c [Cu(L2)2], from respective Schiff base ligands, HL1: 2-((E)-(6-(trifluoromethoxy)phenylimino)methyl)-5-methylphenol, C15H12F3NO2) and HL2: 2-((E)-(4-(trifluoromethoxy)phenylimino)methyl)-4,6-dichlorophenol, C14H8Cl2F3NO2) have been synthesized and well-characterized by analytical and various spectroscopic techniques like mass spectrometry, FT-IR, UV-visible, magnetic susceptibility, ESR and thermogravimetric studies. The geometries are proposed as octahedral for complexes 1a and 2a, whereas square planar for complexes 1b, 1c, and 2b, 2c. DNA binding study was investigated against calf thymus DNA for synthesized complexes comparing with parent ligands and resulted in intercalation mode of binding which was further supported by fluorescence quenching and viscometric titrations. Nuclease efficacy was also investigated against supercoiled pBR322 DNA and a good cleavage pattern was shown by metal complexes. The complexes were found to possess good antimicrobial activity compared to free ligands against bacterial species, Bacillus amyloliquefaciens and Escherichia coli as well as fungal species, Macrophomina phaseolina and Sclerotium rolfsii.

DNA incision evaluation, binding investigation and biocidal screening of Cu(II), Ni(II) and Co(II) complexes with isoxazole Schiff bases.

Two new series of binary metal complexes [M(L1)2] and [M(L2)2] where, M=Cu(II), Ni(II) & Co(II) and L1=4-((3,4-dimethylisoxazol-5-ylimino)methyl)benzene-1,3-diol; L2=2-((3,4-dimethylisoxazol-5-ylimino)methyl)-5-methoxyphenol were synthesized and characterized by elemental analysis, 1H NMR, 13C NMR, FT-IR, ESI mass, UV-Visible, magnetic moment, ESR, SEM and powder XRD studies. Based on these results, a square planar geometry is assigned for all the metal complexes where the Schiff base acts as uninegatively charged bidentate chelating agent via the hydroxyl oxygen and azomethine nitrogen atoms. DNA binding studies of all the complexes with calf thymus DNA have been comprehensively investigated using electronic absorption spectroscopy, fluorescence quenching and viscosity studies. The oxidative and photo cleavage affinity of metal complexes towards supercoiled pBR322 DNA has been ascertained by agarose gel electrophoresis assay. From the results, it is observed that all the metal complexes bind effectively to CT-DNA via an intercalative mode of binding and also cleave pBR322 DNA in a promising manner. Further the Cu(II) complexes have shown better binding and cleavage properties towards DNA. The antimicrobial activities of the Schiff bases and their metal complexes were studied on bacterial and fungal strains and the results denoted that the complexes are more potent than their Schiff base ligands.