Aminopolycarboxylates of rare earths-VIII. Kinetic study of exchange reactions between Eu3+ ions and lanthanide(III) diethylenetriaminepentaacetate complexes

E. Brücher, Gábor Laurenczy

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Abstract

The kinetics of the exchange reactions between Ln(III)-diethylenetriaminepentaacetate complexes (Lndtpa; Ln La, Nd, Ho and Lu) were studied by a spectrophotometric method. At higher pH values, the exchange takes place mainly via the direct encounter of the complexes Lndtpa and Eu3+ ions, while at lower pH values the rate-determining step is the proton-catalyzed dissociation of the complexes, at a rate proportional to the square of the H+ ion concentration. At higher H+ ion concentrations, the rate of the exchange is decreased by increase of the Eu3+ concentration, presumably because of the formation of the binuclear complexes LndtpaEu+, which undergo further transformation only slowly, The sequence of rate constants as a function of the atomic number is just the opposite to the sequence of complex stability constants; the rate constants exhibit a minimum at Ho.

Original languageEnglish
Pages (from-to)2089-2096
Number of pages8
JournalJournal of Inorganic and Nuclear Chemistry
Volume43
Issue number9
DOIs
Publication statusPublished - 1981

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Lanthanoid Series Elements
Rare earth elements
Rare earths
Ion exchange
rare earth elements
Ions
Kinetics
Rate constants
kinetics
ion concentration
ions
Protons
encounters
dissociation
protons

Cite this

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title = "Aminopolycarboxylates of rare earths-VIII. Kinetic study of exchange reactions between Eu3+ ions and lanthanide(III) diethylenetriaminepentaacetate complexes",
abstract = "The kinetics of the exchange reactions between Ln(III)-diethylenetriaminepentaacetate complexes (Lndtpa; Ln La, Nd, Ho and Lu) were studied by a spectrophotometric method. At higher pH values, the exchange takes place mainly via the direct encounter of the complexes Lndtpa and Eu3+ ions, while at lower pH values the rate-determining step is the proton-catalyzed dissociation of the complexes, at a rate proportional to the square of the H+ ion concentration. At higher H+ ion concentrations, the rate of the exchange is decreased by increase of the Eu3+ concentration, presumably because of the formation of the binuclear complexes LndtpaEu+, which undergo further transformation only slowly, The sequence of rate constants as a function of the atomic number is just the opposite to the sequence of complex stability constants; the rate constants exhibit a minimum at Ho.",
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T1 - Aminopolycarboxylates of rare earths-VIII. Kinetic study of exchange reactions between Eu3+ ions and lanthanide(III) diethylenetriaminepentaacetate complexes

AU - Brücher, E.

AU - Laurenczy, Gábor

PY - 1981

Y1 - 1981

N2 - The kinetics of the exchange reactions between Ln(III)-diethylenetriaminepentaacetate complexes (Lndtpa; Ln La, Nd, Ho and Lu) were studied by a spectrophotometric method. At higher pH values, the exchange takes place mainly via the direct encounter of the complexes Lndtpa and Eu3+ ions, while at lower pH values the rate-determining step is the proton-catalyzed dissociation of the complexes, at a rate proportional to the square of the H+ ion concentration. At higher H+ ion concentrations, the rate of the exchange is decreased by increase of the Eu3+ concentration, presumably because of the formation of the binuclear complexes LndtpaEu+, which undergo further transformation only slowly, The sequence of rate constants as a function of the atomic number is just the opposite to the sequence of complex stability constants; the rate constants exhibit a minimum at Ho.

AB - The kinetics of the exchange reactions between Ln(III)-diethylenetriaminepentaacetate complexes (Lndtpa; Ln La, Nd, Ho and Lu) were studied by a spectrophotometric method. At higher pH values, the exchange takes place mainly via the direct encounter of the complexes Lndtpa and Eu3+ ions, while at lower pH values the rate-determining step is the proton-catalyzed dissociation of the complexes, at a rate proportional to the square of the H+ ion concentration. At higher H+ ion concentrations, the rate of the exchange is decreased by increase of the Eu3+ concentration, presumably because of the formation of the binuclear complexes LndtpaEu+, which undergo further transformation only slowly, The sequence of rate constants as a function of the atomic number is just the opposite to the sequence of complex stability constants; the rate constants exhibit a minimum at Ho.

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