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

Brücher, Ernő

doi:10.1016/0022-1902(81)80555-6

Cited by 27 publications

(5 citation statements)

References 8 publications

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“…An acid-catalyzed dissociation pathway is typically the preferred mode at lower pH. 12,17,[41][42][43][44][45] The second pathway is thought to proceed through a dinuclear intermediate that has not been identified. Brücher and coworkers 44 compared the derived rate parameters with order of magnitude estimates of the lanthanide hydration rates and concluded that the rate determining step of the complex formation between Ln(III) and H(EDTA) 3− must be a chelate ring closure reaction (rather than solvent exchange).…”

Section: Discussionmentioning

confidence: 99%

The kinetics of lanthanide complexation by EDTA and DTPA in lactate media

et al. 2012

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The interaction of trivalent lanthanide and actinide cations with polyaminopolycarboxylic acid complexing agents in lactic acid buffer systems is an important feature of the chemistry of the TALSPEAK process for the separation of trivalent actinides from lanthanides. To improve understanding of metal ion coordination chemistry in this process, the results of an investigation of the kinetics of lanthanide complexation by ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) and diethylenetriamine-N,N,N',N'',N''-pentaacetic acid (DTPA) in 0.3 M lactic acid/0.3 M ionic strength solution are reported. Progress of the reaction was monitored using the distinctive visible spectral changes attendant to lanthanide complexation by the colorimetric indicator ligand Arsenazo III, which enables the experiment but plays no mechanistic role. Under the conditions of these experiments, the reactions occur in a time regime suitable for study by stopped-flow spectrophotometric techniques. Experiments have been conducted as a function of EDTA/DTPA ligand concentration, total lactic acid concentration, and pH. The equilibrium perturbation reaction proceeds as a first order approach to equilibrium over a wide range of conditions, allowing the simultaneous determination of complex formation and dissociation rate constants. The rate of the complexation reaction has been determined for the entire lanthanide series (except Pm(3+)). The predominant pathway for lanthanide-EDTA and lanthanide-DTPA dissociation is inversely dependent on the total lactate concentration; the complex formation reaction demonstrates a direct dependence on [H(+)]. Unexpectedly, the rate of the complex formation reaction is seen in both ligand systems to be fastest for Gd(3+). Correlation of these results indicates that in 0.3 M lactate solutions the exchange of lanthanide ions between lactate complexes and the polyaminopolycarboxylate govern the process.

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Section: Discussionmentioning

confidence: 99%

The kinetics of lanthanide complexation by EDTA and DTPA in lactate media

et al. 2012

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“…(2)], is characterized by the stability constant log K Zn2L 4.48. [16] Thus, the equilibrium constant for the Equation (3) with Eu 3 [13] and also in the reaction between [Cd(CDTA)]…”

Section: à5mentioning

confidence: 99%

“…However, both k 0 and k' increase with an increase in the concentration of Eu 3 , which is characteristic of direct attack of Eu 3 on the complex, by the formation of dinuclear complexes. The formation of dinuclear [Ln(DTPA)]Eu complexes was assumed earlier, [13] and the complex [Nd 2 (DTPA)] was detected by 1 H NMR spectroscopy. [19] The concentration of dinuclear species increases with an increase in the concentration of Eu 3 , when the concentration of the monoprotonated species…”

Section: àmentioning

confidence: 99%

The Rates of the Exchange Reactions between [Gd(DTPA)]2− and the Endogenous Ions Cu2+ and Zn2+: A Kinetic Model for the Prediction of the In Vivo Stability of [Gd(DTPA)]2−, Used as a Contrast Agent in Magnetic Resonance Imaging

2000

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The kinetic stability of the complex [Gd(DTPA)]2- (H5DTPA = diethylenetriamine-N,N,N',N",N"-pentaacetic acid), used as a contrast-enhancing agent in magnetic resonance imaging (MRI), is characterised by the rates of the exchange reactions that take place with the endogenous ions Cu2+ and Zn2+. The reactions predominantly occur through the direct attack of Cu2+ and Zn2+ on the complex (rate constants are 0.93+/-0.17 M(-1) s(-1) and (5.6+/-0.4) x 10(-2)M(-1) S(-1), respectively). The proton-assisted dissociation of [Gd(DTPA)]2- is relatively slow (k1 = 0.58+/-0.22 M(-1) s(-1)), and under physiological conditions the release of Gd3+ predominantly occurs through the reactions of the complex with the Cu2+ and Zn2+ ions. To interpret the rate data, the rate-controlling role of a dinuclear intermediate was assumed in which a glycinate fragment of DTPA is coordinated to Cu2+ or Zn2+. In the exchange reactions between [Gd-(DTPA)]2- and Eu3+, smaller amounts of Cu2+ and Zn2+ and their complexes with the amino acids glycine and cysteine have a catalytic effect. In a model of the fate of the complex in the body fluids, the excretion and the "dissociation" of [Gd(DTPA)]2- are regarded as parallel first-order processes, and by 10 h after the intravenous administration the ratio of the amounts of "dissociated" and excreted [Gd(DTPA)]2- is constant. From about this time, 1.71% of the injected dose of [Gd(DTPA)]2- is "dissociated". The results of equilibrium calculations indicate that the Gd3+ released from the complex is in the form of Gd3+-citrate.

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“…The reactions of the LnA C H T U N G T R E N N U N G (DTPA) 2À complexes take also place with the direct attack of the exchanging metals on the complex, via the formation of dinuclear intermediates. [2][3][4][5][6][7][8] The proton assisted dissociation rates have been compared in HCl (0.1 m), where the complexes are thermodynamically not stable. The half-life of dissociation (t 1/2 ) of GdA C H T U N G T R E N N U N G (DOTA) À was found to be 338 h, while that of GdA C H T U N G T R E N N U N G (DTPA) 2À was < 5 s, indicating that the macrocyclic complex is much more inert than the linear one.…”

Section: Introductionmentioning

confidence: 99%

Dissociation Kinetics of Open‐Chain and Macrocyclic Gadolinium(III)‐Aminopolycarboxylate Complexes Related to Magnetic Resonance Imaging: Catalytic Effect of Endogenous Ligands

Baranyai

Pálinkás

Uggeri

et al. 2012

Chemistry A European J

101

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The kinetics of the metal exchange reactions between open-chain Gd(DTPA)(2-) and Gd(DTPA-BMA), macrocyclic Gd(DOTA)(-) and Gd(HP-DO3A) complexes, and Cu(2+) ions were investigated in the presence of endogenous citrate, phosphate, carbonate and histidinate ligands in the pH range 6-8 in NaCl (0.15 M) at 25 °C. The rates of the exchange reactions of Gd(DTPA)(2-) and Gd(DTPA-BMA) are independent of the Cu(2+) concentration in the presence of citrate and the reactions occur via the dissociation of Gd(3+) complexes catalyzed by the citrate ions. The HCO(3)(-)/CO(3)(2-) and H(2)PO(4)(-) ions also catalyze the dissociation of complexes. The rates of the dissociation of Gd(DTPA-BMA), catalyzed by the endogenous ligands, are about two orders of magnitude higher than those of the Gd(DTPA)(2-). In fact near to physiological conditions the bicarbonate and carbonate ions show the largest catalytic effect, that significantly increase the dissociation rate of Gd(DTPA-BMA) and make the higher pH values (when the carbonate ion concentration is higher) a risk-factor for the dissociation of complexes in body fluids. The exchange reactions of Gd(DOTA)(-) and Gd(HP-DO3A) with Cu(2+) occur through the proton assisted dissociation of complexes in the pH range 3.5-5 and the endogenous ligands do not affect the dissociation rates of complexes. More insights into the interaction scheme between Gd(DTPA-BMA) and Gd(DTPA)(2-) and endogenous ligands have been obtained by acquiring the (13)C NMR spectra of the corresponding diamagnetic Y(III)-complexes, indicating the increase of the rates of the intramolecular rearrangements in the presence of carbonate and citrate ions. The herein reported results may have implications in the understanding of the etiology of nephrogenic systemic fibrosis, a rare disease that has been associated to the administration of Gd-containing agents to patients with impaired renal function.

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

Cited by 27 publications

References 8 publications

The kinetics of lanthanide complexation by EDTA and DTPA in lactate media

The kinetics of lanthanide complexation by EDTA and DTPA in lactate media

The Rates of the Exchange Reactions between [Gd(DTPA)]2− and the Endogenous Ions Cu2+ and Zn2+: A Kinetic Model for the Prediction of the In Vivo Stability of [Gd(DTPA)]2−, Used as a Contrast Agent in Magnetic Resonance Imaging

Dissociation Kinetics of Open‐Chain and Macrocyclic Gadolinium(III)‐Aminopolycarboxylate Complexes Related to Magnetic Resonance Imaging: Catalytic Effect of Endogenous Ligands

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