Metal Complexes of New Tetraazamacrocyclic Constrained Oxadiazole Ring as Subunits: Synthesis, DNA Binding and Photonuclease Activity

A new tetraazamacrocyclic ligand, L (C24H16N12O6) and its complexes of type, [MLCl2] and [CuL]Cl-2 (Where M = Co(II), Fe(II); L =N,N'-(benzene-1,3-diyldi-1,3,4-oxadiazole-5,2-diyl)bis{2-[(5-benzene-1,3-diyl-1,3,4-oxadiazol-2-yl) amino] acetamide}) were synthesized and characterized by elemental analysis including IR, H-1 NMR, C-13 NMR, mass and electronic spectral data. An octahedral geometry has been proposed for Fe(II) and Co(II) complexes except the Cu(II) complex which have a square planar environment. The binding property of the complexes with CT-DNA was studied by absorption spectra, viscosity measurement and thermal denaturation studies. The absorption spectral results indicate that the complexes binds with the base pairs of DNA with an intrinsic binding constant K-b of Cu(II), Co(II) and Fe(II) complexes were found to be 4.5 x 10(4) M-1, 5.7 x 10(4) M-1 and 2.6 x 10(4) M-1, respectively in 5 mM Tris-HCl/50 mMNaCl buffer at pH 7.2. The photo induced cleavage studies revealed that the complexes show photonuclease property against pUC19 DNA under UV-visible irradiation.