Kinetic studies on substitution of cis-diaqua-chloro-tris-(dimethyl sulphoxide)-ruthenium(II) complex with some dipeptides in aqueous medium

Abstract

The kinetics of interaction between cis-[RuCl(Me 2 SO) 3 (H 2 O) 2 ] + and some selected dipeptides such as glycyl glycine(gly gly), glycyl alanine(Gly-L-ala) and glycyl-L-leucine(gly leu) has been studied spectrophotometrically as a function of [RuCl(Me 2 SO) 3 (H 2 O) + 2 ], [dipeptide] and temperature at a particular pH(5.0), where the substrate complex exists predominantly as a diaqua species (in aqueous solution) and dipeptides as the zwitter ions. The reaction has been found to proceed via two distinct consecutive steps i.e., it shows a non-linear dependence on the concentration of dipeptide: first process is dependent and the second step is independent of ligand concentration respectively. The rate constants for the processes are: k 1 ∼ 10 −3 s −1 and k 2 ∼ 10 −5 s −1. The activation parameters were calculated from Eyring plots suggests an associative mechanism for the interaction process. From the temperature dependence of the outer sphere association equilibrium constants, the thermodynamic parameters were also calculated, which gives a negative G 0 value at all temperatures studied, supporting the spontaneous formation of an outer sphere association complex. Keywords. Ligand substitution; dipeptides; cis-[RuCl(Me 2 SO) 3 (H 2 O) 2 ] + ; kinetics.

The Role of an Alkyl-Phenyl Spacer on the Reactivity of Novel Platinum(II) Complexes with Thiourea Nucleophiles

“…The small but positive enthalpy and large negative entropy confirm the associative mode of mechanism for all the investigated complexes. This is an indication that the mechanistic reactions of these complexes are characterized by bond formation in the transition state . The activation parameters also imply a good degree of ligand participation in the transition state and a more compact transition state than that of the starting reactants .…”

Mechanistic Aspects of Ligand Substitution oncis-diaqua-chloro-tris(Dimethyl Sulfoxide) Ruthenium(II) Complex by Adenosine and Cytidine in Aqueous Medium

“…Studies on the bioactivities and kinetic aspects of ruthenium(II/III) complexes are still a developing area. With this background we planned to study the interaction of cis-[RuCl(Me 2 SO) 3 (H 2 O) 2 ] + with different ligands such as some dipeptides and azide [20,21]. We felt that more studies are required to explain our general conclusion.…”