Interactions between heterometallic bridged cis-or trans-Pt(II)-Zn(II)complexes and calf thymus DNA

Abstract

More recently scientific attention is paid on non-platinum based drug especially on bio-essential metal ions. Design of the heterometallic complexes is possible way to overcome limitation of platinum-based drugs. The four novel complexes [{cis-PtCl(NH3)(μ-4,4′-bipyridyl)ZnCl(terpy)}](ClO4)2, [{trans-PtCl(NH3)(μ-4,4′-bipyridyl)ZnCl(terpy)}](ClO4)2, [{cis-PtCl(NH3)(μ-pyrazine)ZnCl(terpy)}](ClO4)2 and [{trans-PtCl(NH3)(μ-pyrazine)ZnCl(terpy)}](ClO4)2 (where terpy = 2,2′:6′,2′′-terpyridine) were synthesized and characterized. The binding of the heterometallic bridged cis-or trans-Pt(II)-Zn(II) complexes to calf thymus DNA (CT-DNA) was studied using UV absorption and fluorescence emission spectroscopy. The results indicate that the complexes bind strongly to DNA (Kb, in the order of 104 M−1) through groove binding, hydrogen bonds, and hydrophobic or electrostatic interaction. According to Stern–Volmer quenching constant (KSV) and binding constant (K), the [{cis-PtCl(NH3)(μ-4,4′-bipyridyl)ZnCl(terpy)}](ClO4)2 complex interacts with CT-DNA-EB more strongly than the rest of the studied complexes.