Interaction of Glutathione With Cis-(2-Aminomethylpyridine)diaqua platinum(II) Perchlorate in Aqueous Medium: Their Kinetics and Mechanism

Author： Ghosh Goutam Kr. Misra Koyel Linert Wolfgang Moi Sankar Chandra

Publisher： Taylor & Francis Ltd

ISSN： 1553-3174

Source： Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, Vol.43, Iss.6, 2013-07, pp. : 714-721

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Abstract

The kinetic interaction of glutathione with cis-[Pt(pic)(OH₂)₂] (ClO₄)₂ (pic = 2-Aminomethylpyridine) has been studied spectrophotometrically as a function of cis-[Pt(pic)(OH₂)₂]²⁺, glutathione concentration, and temperature at pH 4.0, where the complex exists predominantly as the diaqua species and glutathione as a zwitter ion. The substitution reaction shows two distinct consecutive steps: the first is the ligand assisted anation and the second is the chelation step. The association equilibrium constant (K_E ) for the outer sphere complex formation has been evaluated with rate constants k₁ (≍10⁻³) for the first step. The activation parameters for both the steps were evaluated using Eyring equation. The low ∆H₁^≠ = (52.37 ± 2.10 kJmol⁻¹) and large negative value of ∆S₁^≠ = (−112.35 ± 2.98 JK⁻¹mol⁻¹) as well as ∆H₂^≠ = (37.29 ± 1.84 kJmol⁻¹) and ∆S₂^≠ = (−130.12 ± 3.16 JK⁻¹mol⁻¹) indicate an associative mode of activation for both the aqua ligand substitution processes.