Substitution behaviour of novel dinuclear Pt(ii) complexes with bio-relevant nucleophiles

Abstract

The novel dinuclear Pt(ii) complexes [{trans-Pt(NH 3) 2Cl} 2(μ-pyrazine)](ClO 4) 2 (Pt1), [{trans-Pt(NH 3) 2Cl} 2(μ-4,4′-bipyridyl) ](ClO 4) 2·DMF (Pt2), and [{trans-Pt(NH 3) 2Cl} 2(μ-1,2-bis(4-pyridyl)ethane)] (ClO 4) 2 (Pt3), were synthesized. Acid-base titrations, and temperature and concentration dependent kinetic measurements of the reactions with biologically relevant ligands such as thiourea (Tu), glutathione (GSH) and guanosine-5′-monophosphate (5′-GMP) were studied at pH 2.5 and 7.2. The reactions were followed under pseudo-first-order conditions by stopped-flow and UV-vis spectrophotometry. 1H NMR spectroscopy was used to follow the substitution of chloride in the complex [{trans-Pt(NH 3) 2Cl} 2(μ-4,4′-bipyridyl)](ClO 4) 2·DMF by guanosine-5′-monophosphate (5′-GMP) under second-order conditions. The results indicate that the bridging ligand has an influence on the reactivity of the complexes towards nucleophiles. The order of reactivity of the investigated complexes is Pt1 > Pt2 > Pt3.