Spectra and DNA-binding properties of two novel mixed-ligand complexes containing organosulfonate

Abstract

Two novel mixed-ligand complexes, [M(phen)2(ans)2]·H2O (M = Cd(II) 1, Zn(II) 2; phen is 1, 10-phenanthroline, and ans is 4-aminonaphthalene-1-sulfonate), were obtained from the reaction of 1, 10-phenanthroline, sodium 4-aminonaphthalene-1-sulfonate tetrahydrate and acetate in mixed solvents. Interaction of the complexes with calf thymus DNA (ctDNA) were investigated using UV-vis absorption spectra, luminescence titrations, steady-state emission quenching by [Fe(CN)6]4−, DNA competitive binding with ethidium bromide (EB) and viscosity measurements. The experimental results indicate that there exist two interaction modes between the complexes and DNA, namely the electrostatic interaction and intercalation, with the binding constants of 1.82 × 105 M−1 for 1 and 4.78 × 104 M−1 for 2 in buffer of 50 mM NaCl and 5 mM Tris-HCl (pH 7.0).