Synthesis, spectroscopic characterization and antimicrobial activity of binuclear metal complexes of a new asymmetrical Schiff base ligand: DNA binding affinity of copper(II) complexes

The 1:1 condensation of o-acetoacetylphenol and 1,2-diaminopropane under condition of high dilution gives the mono-condensed Schiff base, (E)-3-(1-aminopropan-2-ylimino)-1-(2-hydroxyphenyl)butan-1-one. The mono-condensed Schiff base has been used for further condensation with isatin to obtain the new asymmetrical dicompartmental Schiff base ligand, (E)-3-(2-((E)-4-(2-hydroxyphenyl)-4-oxobutan2-ylideneamino) propylimino)indolin-2-one (H3L) with a N2O3 donor set. Reactions of the ligand with metal salts give a series of new binuclear complexes. The ligand and its metal complexes were characterized by elemental analyses, IR. H-1 and C-13 NMR, electronic, ESR and mass spectra, conductivity and magnetic susceptibility measurements as well as thermal analyses. The analytical and spectroscopic tools showed that the complexes can be formulated as: [(HL)(VO)(2)(SO4)(H2O)]center dot 4H(2)O,[(HL)Fe2O4(H2O)(3)]center dot EtOH. [(HL)Fe-2(ox)Cl-2(H2O)(3)]center dot 2H(2)O, [(L)M-2(OAc)(H2O)(m)]center dot nH(2)O; M = Co, Ni or Cu, m = 4, 0 and n = 2, 3, [(HL)Cu2-Cl]Cl center dot 6H(2)O and [(L)(UO2)(2)(OAc)(H2O)(3)]center dot 6H(2)O. The metal complexes exhibited octahedral geometrical arrangements except copper complexes that exhibited tetrahedral geometries and uranyl complex in which the metal ion is octa-coordinated. The Schiff base and its metal complexes were evaluated for antimicrobial activity against Gram positive bacteria (Staphylococcus aureus), Gram negative bacteria (Escherichia coli) and fungi (Candida albicans and Aspergillus flavus). The ligand and some of its complexes were found to be biologically active. The DNA-binding properties of the copper complexes (6 and 7) have been investigated by electronic absorption, fluorescence and viscosity measurements. The results obtained indicate that these complexes bind to DNA via an intercalation binding mode with an intrinsic binding constant. K-b of 1.34 x 10(4) and 2.5 x 10(4) M-1, respectively. (C) 2013 Elsevier B.V. All rights reserved.