Platinum(II)/palladium(II) complexes with n-propyldithiocarbamate and 2,2′-bipyridine: synthesis, characterization, biological activity and interaction with calf thymus DNA

Two Pd(II) and Pt(II) complexes ([Pt(bpy)(pr-dtc)]Br and [Pd(bpy)(pr-dtc)]Br, where bpy=2, 2′-bipyridine and pr-dtc = n-propyldithiocarbamate) were synthesized and characterized by elemental analysis (CHN), molar conductivity measurements, Fourier transform infrared, 1H nuclear magnetic resonance and UV–visible techniques. In these complexes, the dithiocarbamato ligand coordinates to Pt(II) or Pd(II) center as bidentate with two sulfur atoms. The binding of these complexes to calf thymus DNA (CT-DNA) was investigated using various physicochemical methods such as spectrophotometric, spectrofluorometric and gel filtration technique. The experimental results indicate that Pt(II) and Pd(II) complexes interact with CT-DNA in the intercalative mode. Both complexes unexpectedly denatured DNA at low concentration. Gel filtration studies indicated that the binding of complexes with DNA is strong enough and does not break readily. The cytotoxic activity of these metal complexes has been tested against human cell tumor lines (K562) and revealed much lower 50% cytotoxic concentration (Cc50) less than that of cisplatin. Several binding and thermodynamic parameters are also described.