Thermodynamics of complexation of lanthanides by benzoic and isophthalic acids

Choppin, Gregory R.; Bertrand, P. A.; Hasegawa, Yūko; Rizkalla, Ε. N.

doi:10.1021/ic00140a025

Cited by 74 publications

(32 citation statements)

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“…The toluene phase was dried (Na 2 SO 4 ), filtered and evaporated to dryness. NMR data of intermediate (11) The crude intermediate (11) obtained above was dissolved in diluted HCl (250 mL, 1:1) and the mixture was heated under reflux for 18 h. During this time some precipitate formed. After cooling, the suspension was filtered, and nonpolar impurities were extracted with CHCl 3 (3 î 50 mL).…”

Section: Methodsmentioning

confidence: 99%

Lanthanide(III) Complexes of Novel Mixed Carboxylic‐Phosphorus Acid Derivatives of Diethylenetriamine: A Step towards More Efficient MRI Contrast Agents

Kotek

Lebdušková

Hermann

et al. 2003

Chemistry A European J

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Three novel phosphorus-containing analogues of H(5)DTPA (DTPA = diethylenetriaminepentaacetate) were synthesised (H6L1, H5L2, H5L3). These compounds have a -CH2-P(O)(OH)-R function (R = OH, Ph, CH2NBn2) attached to the central nitrogen atom of the diethylenetriamine backbone. An NMR study reveals that these ligands bind to lanthanide(III) ions in an octadentate fashion through the three nitrogen atoms, a P-O oxygen atom and four carboxylate oxygen atoms. The complexed ligand occurs in several enantiomeric forms due to the chirality of the central nitrogen atom and the phosphorus atom upon coordination. All lanthanide complexes studied have one coordinated water molecule. The residence times (tau(M)298) of the coordinated water molecules in the gadolinium(III) complexes of H6L1 and H5L2 are 88 and 92 ns, respectively, which are close to the optimum. This is particularly important upon covalent and noncovalent attachment of these Gd(3+) chelates to polymers. The relaxivity of the complexes studied is further enhanced by the presence of at least two water molecules in the second coordination sphere of the Gd(3+) ion, which are probably bound to the phosphonate/phosphinate moiety by hydrogen bonds. The complex [Gd(L3)(H2O)](2-) shows strong binding ability to HSA, and the adduct has a relaxivity comparable to MS-325 (40 s(-1) mM(-1) at 40 MHz, 37 degrees C) even though it has a less favourable tau(M) value (685 ns). Transmetallation experiments with Zn(2+) indicate that the complexes have a kinetic stability that is comparable to-or better than-those of [Gd(dtpa)(H2O)](2-) and [Gd(dtpa-bma)(H2O)].

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Section: Methodsmentioning

confidence: 99%

Lanthanide(III) Complexes of Novel Mixed Carboxylic‐Phosphorus Acid Derivatives of Diethylenetriamine: A Step towards More Efficient MRI Contrast Agents

Kotek

Lebdušková

Hermann

et al. 2003

Chemistry A European J

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“…The stability of the Ln 3þ complexes of polyaminopolycarboxylic and polyphosphonic acids is related to the sum of the protonation constants of the free ligand (9)(10)(11). The protonation constants (logK H i ) of the P-DTPA and NP-DTPA ligands, as determined by pH potentiometry, are listed and compared with those of the parent DTPA in Table 1 (standard deviations are shown in parentheses).…”

Section: Complexation and Protonation Properties Of The H 6 Np-dtpa Lmentioning

confidence: 99%

The effects of intramolecular H‐bond formation on the stability constant and water exchange rate of the Gd(III)‐diethylenetriamine‐N′‐(3‐amino‐1,1‐propylenephosphonic)‐N, N,N″,N″‐tetraacetate complex

Baranyai

Gianolio

Ramalingam

et al. 2007

Contrast Media & Molecular

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The binding interaction of metal chelates to biological macromolecules, though driven by properly devoted recognition synthons, may cause dramatic changes in some property associated with the coordination cage such as the thermodynamic stability or the exchange rate of the metal coordinated water. Such changes are due to electrostatic and H-bonding interactions involving atoms of the coordination cage and atoms of the biological molecule at the binding site. To mimic this type of H-bonding interactions, lanthanide(III) complexes with a DTPA-monophosphonate ligand bearing a propylamino moiety (H6NP-DTPA) were synthesized. Their thermodynamic stabilities and the exchange lifetime of the coordinated water molecule (for the Gd-complex) were compared with those of the analog complexes with DTPA and the parent DTPA-monophosphonate derivative (H6P-DTPA). It was found that the intramolecular H-bond between the epsilon-amino group and the phosphonate moiety in NP-DTPA complexes causes displacements of electric charges in their coordination cage that are markedly pH dependent. In turn, this affects the characteristic properties of the coordination cage. In particular it results in a marked elongation of the exchange lifetime of the coordinated water molecule.

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“…Figure 6 shows a comparison of the stability constant values for complexes of rare earth ions with phenoxyacetate obtained from this study and the literature data for benzoate complexes (5). The trend in the stability constants for phenoxyacetate is similar to that for benzoate.…”

Section: Rare Earths-phenoxyacetate Systemsmentioning

confidence: 63%