Synthesis, crystal structures and DNA-binding properties of two new mononuclear copper(II) complexes

Two mononuclear copper(II) complexes, [Cu(bpy)(2)(CH3OH)](pic)(2) (1) and [Cu(Me(2)bpy)(2)(H2O)](pic)(2) (2) (bpy = 2,2'-bipyridine; Me(2)bpy = 4,4'-dimethyl-2,2'-bipyridine; Hpic = 2,4,6-trinitrophenol), were synthesized and characterized by elemental analyses, conductivity measurements, IR, UV-Visible spectroscopy and single crystal X-ray analyses. Both complexes 1 and 2 are mononuclear compounds. The copper atom in complex 1 is in a distorted square pyramidal geometry with a CuN4O chromophore as revealed from the tau value (0.25), while the Cu(II) ion in complex 2 displays a distorted trigonal bipyramidal stereochemistry with tau = 0.72. Hydrogen bonding interactions and pi-pi stacking interactions link the mononuclear copper complex 1 or 2 into a 1D infinite chain. The interactions of the two mononuclear complexes with herring sperm DNA (HS-DNA) have been studied by UV-visible absorption titration, fluorescence titration and ethidium bromide (EB) displacement experiments. The results suggest that both complexes might bind to DNA by intercalation.