Mn2+ complexes of open-chain ligands with a pyridine backbone: Less donor atoms lead to higher kinetic inertness

Sophie Laine, Célia S. Bonnet, Ferenc K. Kálmán, Zoltán Garda, Agnès Pallier, Fabien Caillé, Franck Suzenet, G. Tircsó, Éva Tóth

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

The kinetic inertness of Mn2+ complexes is an important parameter for the in vivo safety of potential MRI contrast agents. Rigidifying the ligand structure typically leads to reinforced kinetic inertness. In this context, we studied the Mn2+ complexes of three linear poly(amino carboxylate) ligands containing a pyridine moiety in their skeleton and bearing four (L1, L2) or three carboxylates (L3). The thermodynamic stability constants of the complexes formed with Mn2+, Ca2+, Mg2+, Zn2+ and Cu2+ have been determined using pH-potentiometry, 1H relaxometry and UV/Vis spectrophotometry and are close to those of the EDTA analogues. In contrast, and despite the presence of the pyridine in the ligand backbone, the dissociation rates of the complexes are several orders of magnitude higher than that of [Mn(EDTA)]2-, resulting from a very efficient dissociation pathway catalyzed by the direct attack of Cu2+ or Cu(OH)+. Due to the fewer carboxylate functions, ligand L3 is less favorable for metal-assisted dissociation and provides higher kinetic inertness for its Mn2+ chelate than the L1 and L2 analogues. The water exchange of the monohydrated MnL3 complex has been studied in a variable temperature 17O NMR study. The exchange rate is very high, k298ex = 2.8 × 109 s-1, which is among the highest values reported for a Mn2+ complex. The NMRD profiles are typical of small molecular weight Mn2+ chelates (r1p = 2.44 mM-1 s-1 at 25 °C and 20 MHz).

Original languageEnglish
Pages (from-to)8012-8020
Number of pages9
JournalNew Journal of Chemistry
Volume42
Issue number10
DOIs
Publication statusPublished - Jan 1 2018

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Pyridine
Ligands
Atoms
Kinetics
Ethylenediaminetetraacetic acid
Edetic Acid
Bearings (structural)
Spectrophotometry
Magnetic resonance imaging
Contrast Media
Thermodynamic stability
Metals
Molecular weight
Nuclear magnetic resonance
pyridine
Water
Temperature

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Materials Chemistry

Cite this

Laine, S., Bonnet, C. S., Kálmán, F. K., Garda, Z., Pallier, A., Caillé, F., ... Tóth, É. (2018). Mn2+ complexes of open-chain ligands with a pyridine backbone: Less donor atoms lead to higher kinetic inertness. New Journal of Chemistry, 42(10), 8012-8020. https://doi.org/10.1039/c8nj00648b

Mn2+ complexes of open-chain ligands with a pyridine backbone : Less donor atoms lead to higher kinetic inertness. / Laine, Sophie; Bonnet, Célia S.; Kálmán, Ferenc K.; Garda, Zoltán; Pallier, Agnès; Caillé, Fabien; Suzenet, Franck; Tircsó, G.; Tóth, Éva.

In: New Journal of Chemistry, Vol. 42, No. 10, 01.01.2018, p. 8012-8020.

Research output: Contribution to journalArticle

Laine, S, Bonnet, CS, Kálmán, FK, Garda, Z, Pallier, A, Caillé, F, Suzenet, F, Tircsó, G & Tóth, É 2018, 'Mn2+ complexes of open-chain ligands with a pyridine backbone: Less donor atoms lead to higher kinetic inertness', New Journal of Chemistry, vol. 42, no. 10, pp. 8012-8020. https://doi.org/10.1039/c8nj00648b
Laine, Sophie ; Bonnet, Célia S. ; Kálmán, Ferenc K. ; Garda, Zoltán ; Pallier, Agnès ; Caillé, Fabien ; Suzenet, Franck ; Tircsó, G. ; Tóth, Éva. / Mn2+ complexes of open-chain ligands with a pyridine backbone : Less donor atoms lead to higher kinetic inertness. In: New Journal of Chemistry. 2018 ; Vol. 42, No. 10. pp. 8012-8020.
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AU - Garda, Zoltán

AU - Pallier, Agnès

AU - Caillé, Fabien

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AB - The kinetic inertness of Mn2+ complexes is an important parameter for the in vivo safety of potential MRI contrast agents. Rigidifying the ligand structure typically leads to reinforced kinetic inertness. In this context, we studied the Mn2+ complexes of three linear poly(amino carboxylate) ligands containing a pyridine moiety in their skeleton and bearing four (L1, L2) or three carboxylates (L3). The thermodynamic stability constants of the complexes formed with Mn2+, Ca2+, Mg2+, Zn2+ and Cu2+ have been determined using pH-potentiometry, 1H relaxometry and UV/Vis spectrophotometry and are close to those of the EDTA analogues. In contrast, and despite the presence of the pyridine in the ligand backbone, the dissociation rates of the complexes are several orders of magnitude higher than that of [Mn(EDTA)]2-, resulting from a very efficient dissociation pathway catalyzed by the direct attack of Cu2+ or Cu(OH)+. Due to the fewer carboxylate functions, ligand L3 is less favorable for metal-assisted dissociation and provides higher kinetic inertness for its Mn2+ chelate than the L1 and L2 analogues. The water exchange of the monohydrated MnL3 complex has been studied in a variable temperature 17O NMR study. The exchange rate is very high, k298ex = 2.8 × 109 s-1, which is among the highest values reported for a Mn2+ complex. The NMRD profiles are typical of small molecular weight Mn2+ chelates (r1p = 2.44 mM-1 s-1 at 25 °C and 20 MHz).

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