Mechanistic aspects of ligand substitution on cis-diaqua(cis-1,2-diaminocyclohexane)platinum(II) by Glycine-l-Leucine

Abstract

The kinetics of the interaction of glycine-Lleucine (Glyleu) with cis-[Pt(cis-dach)(OH 2 ) 2 ] 2? (dach = 1, 2-diaminocyclohexane) has been studied spectrophotometrically as a function of [cis-[Pt(cis-dach)(OH 2 ) 2 ] 2? ], [Glyleu] and temperature at pH 4.0, where the complex exists predominantly as the diaqua species and Glyleu as a zwitterion. The substitution reaction shows two consecutive steps: the first is the ligand-assisted anation and the second is the chelation step. The activation parameters for both the steps were evaluated using Eyring's equation. The low DH 1 = (51.9 ± 2.8 kJmol -1 ) and large negative value of DS 1 = (-152 ± 8 JK -1 mol -1 ) as well as DH 2 = (54.4 ± 1.7 kJmol -1 ) and DS 2 = (-162 ± 5 JK -1 mol -1 ) indicate an associative mode of activation for both the aqua ligand substitution processes.

Ligand substitution reaction on a platinum(ii) complex with bio-relevant thiols: kinetics, mechanism and bioactivity in aqueous medium

“…3), which is probably due to the completion of outer sphere association complex formation. 40,41 In the next step of the reaction, interchange of the ligands from the outer sphere to inner sphere occurs, i.e. ligand attacks at the metal centre through sulfur to give the intermediate complex (B).…”

In vitro model reaction of sulfur containing bio-relevant ligands with Pt(ii) complex: kinetics, mechanism, bioactivity and computational studies

“…2, inset) and k 2(obs) were calculated from extrapolated part of the linear portion of ln(A a À A t ) versus time curve at any time 't'. A similar method of calculation was followed for each ligand concentration from 3.04 Â 10 À3 to 9.12 Â 4), which is probably due to the completion of outer sphere association complex formation 48,49 followed by interchange of the ligands from the outer sphere to inner sphere, i.e. ligand approaches to the metal centre to form inner sphere complex.…”