A series of transition metal complexes of Co(II), Ni(II), Zn(II), Fe(III) and VO(IV) have been synthesized involving the Schiff base, 2,3-dimethyl-1-phenyl-4-(2-hydroxy-3-methoxy benzylideneamino)-pyrazol-5-one(L), obtained by condensation of 4-aminoantipyrine with 3-methoxy salicylaldehyde. Structural features were obtained from their FT-IR, UV-vis, NMR, ESI Mass, elemental analysis, magnetic moments, molar conductivity and thermal analysis studies. The Schiff base acts as a monovalent bidentate ligand, coordinating through the azomethine nitrogen and phenolic oxygen atom. Based on elemental and spectral studies six coordinated geometry is assigned to Co(II), Ni(II), Fe(III) and VO(IV) complexes and four coordinated geometry is assigned to Zn(II) complex. The interaction of metal complexes with Calf thymus DNA were carried out by UV-VIS titrations, fluorescence spectroscopy and viscosity measurements. The binding constants (K(b)) of the complexes were determined as 5 × 10(5) M(-1) for Co(II) complex, 1.33 × 10(4) M(-1) for Ni(II) complex, 3.33 × 10(5) M(-1) for Zn(II) complex, 1.25 × 10(5) M(-1) for Fe(III) complex and 8 × 10(5) M(-1) for VO(IV) complex. Quenching studies of the complexes indicate that these complexes strongly bind to DNA. Viscosity measurements indicate the binding mode of complexes with CT DNA by intercalation through groove. The ligand and it's metal complexes were screened for their antimicrobial activity against bacteria. The results showed the metal complexes to be biologically active, while the ligand to be inactive.
The mixed ligand complexes MLA of Cu(II) and Co(II) with Schiff base derived from 4-amino antipyrine and 5-NO(2) salicylaldehyde (2,3 -dimethyl-1-phenyl-4-(2-hydroxy-5-nitro benzylideneamino)-pyrazol-5-one) as ONO donor (L) and A = 2,2 bipyridine (bpy),1,10 phenonthroline (1,10 phen) as N, N donor ligands have been prepared, owing to their biological and other applications. The structural features have arrived from their elemental analyses, magnetic susceptibility, molar conductance, Mass, IR, UV-VIS, powdered XRD and ESR spectral studies, that established MLA type of composition for the metal complexes. The electronic absorption spectral data of the complexes suggest an octahedral geometry around the central metal ion. The interaction of the complexes with Calf Thymus (CT) DNA has been studied using absorption spectra, viscosity measurements and fluorescence spectra. The binding constants (K(b)) of the complexes were determined as 2.1 × 10(6) M(-1) for complex 1, 2.5x10(6)M(-1) for complex 2, 1.16 × 10(6) M(-1) for complex 3,1.25x10(6)M(-1) for complex 4, DNA cleavage experiments performed on pBR-322 plasmids using metal complexes in the presence of H(2)O(2) showed that all the complexes afford a pronounced DNA cleavage. Molecular modelling studies were also performed to confirm the geometries of the complexes. The ligand and their metal complexes were screened for their antimicrobial activity against bacteria. The results showed that the metal complexes are biologically active.
Mixed-ligand Cu(II), Co(II) complexes of formulae [Co(NSALT)(A.A)(H2O)](1), [Co(OHAPT)(A.A)H2O](2), and [Cu(ESALT)(ABPH)H2O] (3) were obtained by refluxing methanol solutions of copper, cobalt chlorides with the appropriate ligands. The complexes were characterized by the ESI-MASS, vibrational spectroscopy (Fourier transform-IR), (1)H-NMR spectroscopy, UV-vis spectroscopy, TGA, ESR, SEM and powder XRD. The preliminary DNA-binding activity of the complexes was studied by recording electronic absorption spectra of the complexes in presence of CT-DNA. The binding constants of three complexes towards calf thymus DNA (CT-DNA) [1.2 × 10(4) M(-1) for 1, 2.5 × 10(4) M(-1) for 2, and 3.0 × 10(4) M(-1) for 3] indicate strong interaction of 3. Changes in the fluorescence of ethidium bromide in the presence of DNA suggest intercalation into or electrostatic interactions with CT DNA. The quenching constants, KSV towards-DNA calculated through fluorescence spectra are 2.9 × 10(4) M(-1)for 1, 1.8 × 10(4) M(-1) for 2, and 3.2 × 10(4) M(-1) for 3. Docking studies on DNA complexes confirm the binding of 1 and 2 in the major groove of CT-DNA (CTP-1 Endonuclease). Moreover, the antibacterial effect of 1-3 against the five bacterial species was evaluated. The metal complexes have cleavage affinity towards PBR322 plasmid. Furthermore, the antioxidant activities of the complexes were determined by DPPH scavenging activity method.
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