Kinetics and mechanism of the reduction of (ImH)[trans-RuCl4(dmso)(Im)] by ascorbic acid in acidic aqueous solution
- 15 May 2007
- journal article
- Published by Springer Science and Business Media LLC in JBIC Journal of Biological Inorganic Chemistry
- Vol. 12 (6), 809-818
- https://doi.org/10.1007/s00775-007-0234-x
Abstract
A systematic study of the reduction of (ImH)[trans-RuCl4(dmso)(Im)] (NAMI-A; dmso is dimethyl sulfoxide, Im is imidazole), a promising antimetastasing agent entering phase II clinical trial, by l-ascorbic acid is reported. The rapid reduction of trans-[RuIIICl4(dmso)(Im)]− results in formation of trans-[RuIICl4(dmso)(Im)]2− in acidic medium (pH = 5.0) and is followed by successive dissociation of the chloride ligands, which cannot be suppressed even in the presence of a large excess of chloride ions. The reduction of NAMI-A strongly depends on pH and is accelerated on increasing the pH. Over the small pH range 4.9−5.1, the reaction is quite pH-independent and the influence of temperature and pressure on the reaction could be studied. On the basis of the reported activation parameters and other experimental data, it is suggested that the redox process follows an outer-sphere electron transfer mechanism. A small contribution from a parallel reaction ascribed to inner-sphere reduction of aqua derivatives of NAMI-A, was found to be favored by lower concentrations of the NAMI-A complex and higher temperature. In the absence of an excess of chloride ions, the reduction process is catalyzed by the Ru(II) products being formed. The reduction of NAMI-A is also catalyzed by Cu(II) ions and the apparent catalytic rate constant was found to be 1.5 × 106 M−2 s−1 at 25 °C.Keywords
This publication has 38 references indexed in Scilit:
- Redox behavior of tumor-inhibiting ruthenium(iii) complexes and effects of physiological reductants on their binding to GMPDalton Transactions, 2006
- Inhibition of B16 Melanoma Metastases with the Ruthenium Complex Imidazoliumtrans-Imidazoledimethylsulfoxide-tetrachlororuthenate and Down-Regulation of Tumor Cell InvasionThe Journal of pharmacology and experimental therapeutics, 2005
- Pressure and temperature effects on metal-to-metal charge transfer in cyano-bridged CoIII–FeIIcomplexesDalton Transactions, 2005
- Heterocyclic complexes of ruthenium(III) induce apoptosis in colorectal carcinoma cellsZeitschrift für Krebsforschung und Klinische Onkologie, 2004
- Actin-dependent tumour cell adhesion after short-term exposure to the antimetastasis ruthenium complex NAMI-AEuropean Journal Of Cancer, 2004
- Intratumoral NAMI-A Treatment Triggers Metastasis Reduction, Which Correlates to CD44 Regulation and Tumor Infiltrating Lymphocyte RecruitmentThe Journal of pharmacology and experimental therapeutics, 2004
- Appraisal of the redox behaviour of the antimetastatic ruthenium(iii) complex [ImH][RuCl4(DMSO)(Im)], NAMI-ADalton Transactions, 2004
- Kinetics and mechanism of the reduction of pentacyanonitroferrate(III) by L-ascorbic acid in acidic aqueous solutionJ. Chem. Soc., Dalton Trans., 1998
- Measurement of Redox Reaction Volumes for Iron(III/II) Complexes Using High-Pressure Cyclic Staircase Voltammetry. Half-Cell Contributions to Redox Reaction VolumesInorganic Chemistry, 1994
- Kinetics and mechanism of the reaction of aqueous copper(II) with ascorbic acidInorganic Chemistry, 1990