title: Thermodynamics of the interaction of ruthenium(III) polyaminecarboxylate complexes with bio-relevant ligands. Deactivation of the complexes as NO scavengers by thiol ligands.
abstract: The acid-base and complex-formation equilibria of [Ru(H(2)dtpa)(H(2)O)], where dtpa = diethylenetriaminepentaacetate, with a series of bio-relevant ligands having various functional groups, viz. thiol, amine, imidazole and carboxylate, were investigated using potentiometric and spectrophotometric techniques. The pK(a) values for [Ru(H(2)dtpa)(H(2)O)] were found to be 2.28 and 3.48 for the uncoordinated carboxylic acid groups and 8.83 for the coordinated water molecule. The complexes formed are of 1:1 stoichiometry and their formation-constants were determined. The effect of dioxane on the acid-base and complex-formation equilibria of the Ru(III) complex was studied. The displacement reaction of coordinated NO by the investigated ligands showed that thiols can compete with NO in their reaction with [Ru(III)(dtpa)(H(2)O)](2-). The results reveal that the Ru(III) complex is deactivated as a NO scavenger by thiolate ligands.
authors.affiliation: Department of Chemistry, Faculty of Science, Cairo University, Giza, Egypt.
authors.forename: Safaa S
authors.initials: SS
authors.lastname: Hassan
authors.forename: Mohamed M
authors.initials: MM
authors.lastname: Shoukry
authors.forename: Rudi
authors.initials: R
authors.lastname: van Eldik
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry*; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D007700:Kinetics; D008024:Ligands; D009569:Nitric Oxide / Q000737:chemistry*; D011073:Polyamines / Q000737:chemistry; D012428:Ruthenium / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D002264:Carboxylic Acids; D056831:Coordination Complexes; D008024:Ligands; D011073:Polyamines; D012997:Solvents; D013438:Sulfhydryl Compounds; D009569:Nitric Oxide; D012428:Ruthenium