The complex formation equilibria of [Pt(SMC)(H₂O)₂]⁺ and [Pt(terpy)H₂O]²⁺, where SMC = S-methyl-L-cysteine and terpy = 2,2′:6′,2″-terpyridine, with some biologically relevant ligands such as inosine (INO), inosine-5′-monophosphate (5′-IMP), guanosine-5′-monophosphate (5′-GMP) and glutathione (GSH) were studied. The stoichiometry and stability constants of the complexes formed are reported, and the concentration distribution of the various complex species have been evaluated as a function of pH. Also the kinetics and mechanism of the complex formation reactions were studied as a function of nucleophile concentration and temperature. For the complex [Pt(SMC)(H₂O)₂]⁺, two consecutive reaction steps, which both depend on the nucleophile concentration, were observed under all conditions. The negative entropies of activation support an associative complex formation mechanism. Reaction of guanosine-5′-monophosphate (5′-GMP) with Pt(II) complexes was carried out in the presence and absence of glutathione (GSH) at neutral pH. The rate constants clearly showed a kinetic preference toward GSH at neutral pH. The reactions were also monitored by HPLC. However, only a small amount of coordinated 5′-GMP was detected in the HPLC trace. The products were isolated and characterized by MALDI-TOF mass spectrometry.

The novel dinuclear Pt(II) complexes [{trans-Pt(NH₃)₂Cl}₂(μ-pyrazine)](ClO₄)₂ (Pt1), [{trans-Pt(NH₃)₂Cl}₂(μ-4,4′-bipyridyl)](ClO₄)₂·DMF (Pt2), and [{trans-Pt(NH₃)₂Cl}₂(μ-1,2-bis(4-pyridyl)ethane)](ClO₄)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(NH₃)₂Cl}₂(μ-4,4′-bipyridyl)](ClO₄)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.