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

Abstract

A new tetraazamacrocyclic ligand, L (C₂₄H₁₆N₁₂O₆) and its complexes of type, [MLCl₂] and [CuL]Cl₂ (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, ¹H NMR, ¹³C 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 × 10⁴ M⁻¹, 5.7 × 10⁴ M⁻¹ and 2.6 × 10⁴ M⁻¹, respectively in 5 mM Tris-HCl/50 mM NaCl buffer at pH 7.2. The photo induced cleavage studies revealed that the complexes show photonuclease property against pUC19 DNA under UV-visible irradiation.

Keywords:

• Tetraazamacrocyclic ligand
• metal complexes
• DNA binding and cleavage

Acknowledgment

This work is supported by Major Research Project (F.No.33-322 /2007 (SR) Dated: 28-02-2008) from the University Grants Commission, New Delhi.