Reactivity of Aquadiethylenetriamineplatinum(II) Ion with Disulfide Moiety Cystine: A Kinetic and Mechanistic Approach

Abstract

Substitution reactions of the complex [Pt(dien)H2O]2+ (where dien = diethylentriamine or 1,5-diamino-3-azapentane) with sulfur-containing L-cystine have been studied in a 1.0 × 10−1 mol dm−3 aqueous perchlorate medium at various temperatures (298–323 K) and 4.45 ≤ pH ≤ 2.15 using UV-vis spectroscopy. The products obtained have been characterized by their infrared and 1H NMR datasets at various pH levels and temperatures. From infrared and 1H NMR data, products have indicated that [Pt(dien)H2O]2+ reacted with L-cystine forming a Pt–S bond at low pH. At high pH, a product complex through the Pt–N bond has been formed. All rate constants have been evaluated from nonlinear double exponential plots. The activation parameters ΔH# and ΔS# have been determined using the Eyring equation. The products, SNi, and reversible rate constants have been evaluated. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT