The kinetics of exchange between a lanthanide ion and the gadolinium complex of N, N″-bis(2-methoxyethylamide-carbamoylmethyl)-diethylenetriamine- N, N′, N″-triacetate

The exchange kinetics of Gd(DTPA-BMEA) with the radioactive tracer Eu(III) have been studied in aqueous solution of 0.15 M ionic strength and 25°C. The exchange is a first-order reaction with the rate expression containing both acid-dependent and acid-independent terms. At pH>6, the exchange is g...

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Bibliographic Details
Published in:Inorganica Chimica Acta 1997-10, Vol.262 (2), p.133-138
Main Authors: Rothermel, G.L, Rizkalla, E.N, Choppin, G.R
Format: Article
Language:English
Subjects:
Aminopolycarboxylate complexes
Gadolinium complexes
Kinetics and mechanisms
Lanthanide complexes
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Summary:The exchange kinetics of Gd(DTPA-BMEA) with the radioactive tracer Eu(III) have been studied in aqueous solution of 0.15 M ionic strength and 25°C. The exchange is a first-order reaction with the rate expression containing both acid-dependent and acid-independent terms. At pH>6, the exchange is governed by direct reaction of Eu(III) ions with Gd(DTPA-BMEA), while below pH 6, the rate determining step is proton-catalyzed dissociation of the complex with a first-order dependence on [H +]. The relatively slow association and dissociation of the Ln(DTPA-BMEA) complexes can be attributed to steric effects related to the binding of the two methoxyethylamide groups.
ISSN:0020-1693
1873-3255
DOI:10.1016/S0020-1693(97)05513-8