Multidentate ligand kinetics. XIV. Formation and dissociation kinetics of rare earth-cyclohexylenediaminetetraacetate complexes

Nyssen, Gerard A.; Margerum, Dale W.

doi:10.1021/ic50090a007

Cited by 78 publications

(42 citation statements)

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“…It has been noted previously [23] that the relative stability of lanthanide complexes with trans-1,2-diaminocyclohexano-N,N,N',N'-tetraacetic acid is more strongly a function of the complex dissociation rates than of complex formation. We have now ac- cumulated enough data on the kinetics of complexation of dioxoactinide ions by phosphonate and arsenate bearing ligands to assess whether a similar relationship governs the relative stability of actinyl complexes.…”

Section: Discussionmentioning

confidence: 97%

Kinetic Study of the Reactions of Np(V) and U(VI) with Diphosphonic Acids in Acetate Buffer Solutions

Fugate¹,

Nash²,

Sullivan³

1997

Radiochimica Acta

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The results of kinetic investigations for the reactions of Np(V) and U(VI) with methanediphosphonic acid (MDPA), 1-hydroxyethane-1,1-diphosphonic acid (HEDPA), and of Np(V) with Arsenazo III in acetate buffer media (/ = 0.1 M) are presented. Rate and activation parameters have been determined for the complex formation reaction of Np(V) with Arsenazo III, complex formation between U(VI) and the diphosphonate ligands, and for both formation and dissociation reactions of the Np(V)-diphosphonate complexes. The activation parameters are generally consistent with an associative mechanism for complex formation and dissociation reactions in all systems. Isokinetic plots suggest a common mechanism for the actinyl (V and VI) reactions with MDPA and HEDPA. A distinct isokinetic relationship exists for the actinyl derivatives of chromotropic acid derivatives Arsenazo III and Chlorophosphonazo III. In acetate buffer media, Np(V) reacts more rapidly with the diphosphonate ligands than U(VI) despite its lower formal charge and the smaller thermodynamic driving force for complex formation.

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Section: Discussionmentioning

confidence: 97%

Kinetic Study of the Reactions of Np(V) and U(VI) with Diphosphonic Acids in Acetate Buffer Solutions

Fugate¹,

Nash²,

Sullivan³

1997

Radiochimica Acta

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“…The rate-controlling step in the acid-catalysed dissociation path was assigned either to the rupture of a second metal-carboxylate bond of the protonated complex or to the slow transfer of the hydrogen ion from the protonated carboxylate oxygen to the neighboring nitrogen site; thereby causing rupture of the metal-nitrogen bond; This interpretation is supported by the parallel trend of AG* for the acid-dissociation of Ln -DCTA to the difference (Λσ°ηΐοΑ-Λ6χηοοτΑ) where /IG°n IDA and A G°nDCTA are the standard free energies of the formation of the IDA and DCTA complexes, respectively [53] (Fig. 8).…”

Section: Complexation Kineticsmentioning

confidence: 93%

Systematics of Lanthanide Coordination

Rizkalla

1993

Radiochimica Acta

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This article discusses the general trends of lanthanide coordination in solution. The bonding in these compounds is best described by an ionic model. Minor covalent interactions are inferred from spectral measurements; however, these probably involve the 5d or 6s rather than the 4/ orbitals. The enthalpy and entropy of these reactions are largely compensatory. Nevertheless, deviations are observed for systems involving strong metal-donor interactions such as the polyaminocarboxylates. The kinetics of complexation of these polyaminocarboxylates are interpreted in terms of a dissociative interchange mechanism. The rate-determining step probably involves the formation of a distorted LnY* complex (low AH* and negative AS*). The use of NMR and chiroptical methods to study the conformational preference and mode of coordination in these complexes are also discussed.

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“…These values are almost the same as those measured through the ligand and metal-exchange processes in a batch reaction system (4.0±0.5) × 10 -3 s -1 for Ce(III)-Quin2, 10 and 2.1 × 10 -4 s -1 for Ce(III)-cydta chelate). 11 The agreements prove the validity of the rate analysis by CE.…”

Section: Methodsmentioning

confidence: 63%

Dissociation Rate Constant Estimation for the Cerium(III)-O,O′-bis(2-aminoethyl)-ethyleneglycol-N,N,N′,N′-tetraacetate System by Capillary Electrophoresis

2000

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Multidentate ligand kinetics. XIV. Formation and dissociation kinetics of rare earth-cyclohexylenediaminetetraacetate complexes

Cited by 78 publications

References 1 publication

Kinetic Study of the Reactions of Np(V) and U(VI) with Diphosphonic Acids in Acetate Buffer Solutions

Kinetic Study of the Reactions of Np(V) and U(VI) with Diphosphonic Acids in Acetate Buffer Solutions

Systematics of Lanthanide Coordination

Dissociation Rate Constant Estimation for the Cerium(III)-O,O′-bis(2-aminoethyl)-ethyleneglycol-N,N,N′,N′-tetraacetate System by Capillary Electrophoresis

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