Effects of Micelles on the Complex Formation of [PtCl(dien)]+ with Biologically Relevant Ligands

Abstract

Abstract Substitution reactions of [PtCl(dien)]+ (dien = diethylenetriamine) with some biologically relevant ligands, such as l-methionine ((l)-Met), glutathione (GSH), and guanosine 5′-monophosphate (5′-GMP), were studied in aqueous 0.10, 0.05, and 0.01 M NaClO4 solutions at pH 2.5 using UV–vis spectrophotometry. The kinetics and mechanism of the complex-formation reactions were studied as a function of nucleophile concentration and temperature. These reactions were also studied in the presence and absence of micelles of sodium dodecyl sulfate (SDS). The presence of anionic micelles accelerated complex-formation. The largest effect of micelles has been observed in the case of l-methionine. On the other hand, an increase in the ionic strength in the presence of micelles caused a decrease in the rate. The negative entropies of activation support an associative complex-formation mechanism.