Koordinationszahl und nephelauxetischer Effekt von Komplexen der Lanthaniden

Geier, G. Richard; Karlen, U.; Zelewsky, Alex von

doi:10.1002/hlca.19690520721

Cited by 49 publications

(41 citation statements)

References 26 publications

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“…Additional evidence evidence in support of Geier's proposed for the existence of an equilibrium such as [3] hydration equilibria [3 j. A maximum in the plot has been obtained at least for the europium of the heat capacity change (AC,,) for the forcomplex from s~ectro~hotometric (18)(19)(20) and mation of the 1 :2 Ln-diglycolate complexes us. ~o l a r o g r a~h i c studies (21) of aqueous solutions atomic number was interpreted as due to the of the ]Eu-EDTA complex.…”

Section: Introductionsupporting

confidence: 57%

“…~o l a r o g r a~h i c studies (21) of aqueous solutions atomic number was interpreted as due to the of the ]Eu-EDTA complex. The equilibrium presence of hydration equilibria which (acconstants, K,, evaluated from s~e c t r o~h o t o -cording to an expected similarity in the geometry metric studies (18)(19)(20) were in good agreement of the Ln-EDTA complex (1 1) and the complex with the values derived from thermodynamic formed by the coordination of two (terdentate) data (17). diglycolate ligands to the Ln3 + ions) are expected As regards the aqua ions, conflicting opinions to be similar to those proposed by Geier (17) for have arisen.…”

Section: Introductionmentioning

confidence: 95%

“…In the region between Sm and Tb an equilibrium is proposed (17) between two types of EDTA complexes differing in their degree of hydration which in the series ions show a non-monotonic development (becoming smaller from La to Nd, becoming larger from Nd to Tb, and then decreasing once more from Tb to Yb). On the other hand, Geier et al (17)(18)(19) and Anderegg (14) are not convinced that the C.N. of the aquo ions changes.…”

Section: Introductionmentioning

confidence: 96%

“…Various authors have expressed the opinion that owing to the "lanthanide contraction" partially hydrated complexes (12)(13)(14) and in particular the EDTA complexes (11,(15)(16)(17) are expected to undergo a change in coordination number somewhere in the middle of the lanthanide series. Such a change is also considered to be revealed in the irregular progression of the enthalpy (AH) and entropy (AS, see Flg.…”

Section: Introductionmentioning

confidence: 99%

“…1) changes associated with the complex formation reaction (eq. 2) (11,(15)(16)(17). The explanation offered proceeds somewhat as follows.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Studies of Oxygen Exchange Between Trivalent Lanthanide – EDTA Complexes and Solvent Water: Evidence for a Structural Change Within the Series

Betts¹,

Voss²

1973

Can. J. Chem.

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Oxygen-18 labelled EDTA, dissolved in normal water. has been used to examine the kinetics of oxygen transfer between the solvent and a variety of metal-EDTA complexes, including most of the lanthanides, Ca and Th. The lability of the oxygens is profoundly affected by the ionic charge of the metal in the chelate. Thus oxygen exchange in the Th-EDTA-Hz0 system shows a half-life of 10 lnin at 100 O C , while for comparable conditions. Ca-EDTA-Hz0 shows a half-life in excess of 100 days. The lanthanides as agroup show behavior intermediate between these extremes. Within the latter group the lability varies systematically with atomic number, Pr-EDTA (element 59) being the most reactive and Yb-EDTA (element 70) the least reactive. The maximum variation across the group is about 10-fold. Interpretation of these results is presented in terms of the polarizing effect of the metal ion on the electron density at the acetate groups. The variation in lability within the lanthanide group can be accounted for quantitatively by changes in coordination number of the central metal ion.De 1'EDTA marque par de l'oxygene-18, dissous dans l'eau normale. a ete utilise pour examiner la cinetique du transfert d'oxygene entre le solvant et une serie de complexes metal-EDTA, conprenant la plupart des lanthanides, Ca et Th. La labilite des oxygenes est profondement affectee par la charge ionique du metal dans le chelate. Par suite I'echange de I'oxygene dans le systeme Th-EDTA-Hz0 possede une demi-vie de 10 min a 100 "C, alors que dans des conditions comparables, Ca-EDTA-Hz0 possede une demivie superieure a 100 jours. Les lanthanides, comme un groupe, possedent un comportement intermediaire entre ces 2 extrimes. A l'interieur de ce dernier groupe, la labilit6 varie systematiquement avec le numero atomique, Pr-EDTA (element no. 59) ttant le plus rkactif et Yb-EDTA (element no. 70) le moins reactif. La variation maximum a travers le groupe se situe dans un intervalle de 10 environ. L'interpretation de ces resultats est present6 en terme d'effet polarisant de l'ion metallique sur la densite electrique des groupes acetales. La variation dans la labilite a I'interieur du groupe des lanthanides peut itre explique quantitativement par des changements dans le nombre de coordination de l'ion metallique central.

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Section: Introductionsupporting

confidence: 57%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

“…1) changes associated with the complex formation reaction (eq. 2) (11,(15)(16)(17). The explanation offered proceeds somewhat as follows.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Studies of Oxygen Exchange Between Trivalent Lanthanide – EDTA Complexes and Solvent Water: Evidence for a Structural Change Within the Series

Betts¹,

Voss²

1973

Can. J. Chem.

View full text Add to dashboard Cite

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Stability and Toxicity of Contrast Agents

Brücher

Tircsó

Baranyai

et al. 2013

The Chemistry of Contrast Agents in Medical Magnetic Resonance Imaging

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Magnetic Resonance Imaging (MRI) derives directly from the phenomenon of Nuclear Magnetic Resonance (NMR [1][2][3][4]), which is widely used by chemists to determine molecular structure. The word "nuclear" was dropped in the switch to imaging to avoid alarming patients as NMR has nothing to do with radioactivity. This book is intended mainly for chemists, who are generally familiar with the NMR spectra. After a brief overview of the technique explaining the notion of relaxation time and saturation transfer used in MRI, we will describe localization techniques, which are less well-known in chemistry. The purpose of this short chapter is not to provide a complete theory of MRI [5][6][7][8], but to understand the rest of the book concerning the action of contrast agents. We will not go into the theoretical background of the phenomena, and while it is important to have some understanding of quantum mechanics, it is not our purpose to develop this aspect. This is a "nuts and bolts" description of MRI. Whenever possible, we refer to chemists' knowledge of NMR (for example, "2D NMR"). Theoretical basis of NMR Short description of NMRIn most cases, MRI focuses on one type of atomic nucleus, that of hydrogen in H 2 O. We will therefore only use this nucleus, termed the " 1 H proton."The physical phenomenon of NMR lies at the boundary between "conventional" and "quantum" treatment due to the small transition energies involved. Traditionally, the 1 H proton can be considered as a charged

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Structure, Stability, Dynamics, High‐Field Relaxivity and Ternary‐Complex Formation of a New Tris(aquo) Gadolinium Complex

Nonat

Fries

Pécaut

et al. 2007

Chemistry A European J

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The tripodal hexadentate picolinate ligand dpaa3- (H3dpaa=N,N'-bis[(6-carboxypyridin-2-yl)methyl]glycine) has been synthesised. It can form 1:1 and 1:2 lanthanide/ligand complexes. The crystal structure of the bis(aquo) lutetium complex [Lu(dpaa)(H2O)2] has been determined by X-ray diffraction studies. The number of water molecules was determined by luminescence lifetime studies of the terbium and europium complexes. The tris(aquo) terbium complex shows a fairly high luminescence quantum yield (22 %). The [Gd(dpaa)(H2O)3] complex displays a high water solubility and an increased stability (pGd=12.3) with respect to the analogous bis(aquo) complex [Gd(tpaa)(H2O)2] (pGd=11.2). Potentiometric and relaxometric studies show the formation of a soluble GdIII hydroxo complex at high pH values. A unique aquohydroxo gadolinium complex has been isolated and its crystal structure determined. This complex crystallises as a 1D polymeric chain consisting of square-shaped tetrameric units. In heavy water, the [Gd(dpaa)-(D2O)3] complex shows a quite high HOD proton relaxivity at high field (11.93 s(-1) mM(-1) at 200 MHz and 298 K) because of the three inner-sphere water molecules. The formation of ternary complexes with physiological anions has been monitored by relaxometric studies, which indicate that even under conditions favourable to the formation of adducts with oxyanions, the mean relaxivity remains higher than those of most of the currently used commercial contrast agents except for the citrate. However, the measured relaxivity (r1=7.9 s(-1) mM(-1)) in a solution containing equimolar concentrations of [Gd(dpaa)(D2O)3] and citrate is still high. The interaction with albumin has been investigated by relaxometric and luminescence studies. Finally, a new versatile method to unravel the geometric and dynamic molecular factors that explain the high-field relaxivities has been developed. This approach uses a small, uncharged non-coordinating probe solute, the outer-sphere relaxivity of which mimics that of the water proton. Only a routine NMR spectrometer and simple mathematical analysis are required.

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Koordinationszahl und nephelauxetischer Effekt von Komplexen der Lanthaniden

Cited by 49 publications

References 26 publications

Studies of Oxygen Exchange Between Trivalent Lanthanide – EDTA Complexes and Solvent Water: Evidence for a Structural Change Within the Series

Studies of Oxygen Exchange Between Trivalent Lanthanide – EDTA Complexes and Solvent Water: Evidence for a Structural Change Within the Series

Stability and Toxicity of Contrast Agents

Structure, Stability, Dynamics, High‐Field Relaxivity and Ternary‐Complex Formation of a New Tris(aquo) Gadolinium Complex

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