H4octapa: Highly stable complexation of lanthanide(III) ions and copper(II)

Ferenc Krisztián Kálmán, Andrea Végh, Martín Regueiro-Figueroa, Éva Tóth, Carlos Platas-Iglesias, G. Tircsó

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

The acyclic ligand octapa4- (H4octapa = 6,6′-((ethane-1,2-diylbis((carboxymethyl)azanediyl))bis(methylene))dipicolinic acid) forms stable complexes with the Ln3+ ions in aqueous solution. The stability constants determined for the complexes with La3+, Gd3+, and Lu3+ using relaxometric methods are log KLaL = 20.13(7), log KGdL = 20.23(4), and log KLuL = 20.49(5) (I = 0.15 M NaCl). High stability constants were also determined for the complexes formed with divalent metal ions such as Zn2+ and Cu2+ (log KZnL = 18.91(3) and log KCuL = 22.08(2)). UV-visible and NMR spectroscopic studies and density functional theory (DFT) calculations point to hexadentate binding of the ligand to Zn2+ and Cu2+, the donor atoms of the acetate groups of the ligand remaining uncoordinated. The complexes formed with the Ln3+ ions are nine-coordinated thanks to the octadentate binding of the ligand and the presence of a coordinated water molecule. The stability constants of the complexes formed with the Ln3+ ions do not change significantly across the lanthanide series. A DFT investigation shows that this is the result of a subtle balance between the increased binding energies across the 4f period, which contribute to an increasing complex stability, and the parallel increase of the absolute values of the hydration free energies of the Ln3+ ions. In the case of the [Ln(octapa)(H2O)]- complexes the interaction between the amine nitrogen atoms of the ligand and the Ln3+ ions is weakened along the lanthanide series, and therefore the increased electrostatic interaction does not overcome the increasing hydration energies. A detailed kinetic study of the dissociation of the [Gd(octapa)(H2O)]- complex in the presence of Cu2+ shows that the metal-assisted pathway is the main responsible for complex dissociation at pH 7.4 and physiological [Cu2+] concentration (1 μM).

Original languageEnglish
Pages (from-to)2345-2356
Number of pages12
JournalInorganic Chemistry
Volume54
Issue number5
DOIs
Publication statusPublished - Mar 2 2015

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Lanthanoid Series Elements
Complexation
Copper
Ions
Ligands
copper
ligands
ions
Hydration
Density functional theory
hydration
dissociation
density functional theory
Metals
Atoms
Ethane
Coulomb interactions
Binding energy
methylene
ethane

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry
  • Medicine(all)

Cite this

Kálmán, F. K., Végh, A., Regueiro-Figueroa, M., Tóth, É., Platas-Iglesias, C., & Tircsó, G. (2015). H4octapa: Highly stable complexation of lanthanide(III) ions and copper(II). Inorganic Chemistry, 54(5), 2345-2356. https://doi.org/10.1021/ic502966m

H4octapa : Highly stable complexation of lanthanide(III) ions and copper(II). / Kálmán, Ferenc Krisztián; Végh, Andrea; Regueiro-Figueroa, Martín; Tóth, Éva; Platas-Iglesias, Carlos; Tircsó, G.

In: Inorganic Chemistry, Vol. 54, No. 5, 02.03.2015, p. 2345-2356.

Research output: Contribution to journalArticle

Kálmán, FK, Végh, A, Regueiro-Figueroa, M, Tóth, É, Platas-Iglesias, C & Tircsó, G 2015, 'H4octapa: Highly stable complexation of lanthanide(III) ions and copper(II)', Inorganic Chemistry, vol. 54, no. 5, pp. 2345-2356. https://doi.org/10.1021/ic502966m
Kálmán FK, Végh A, Regueiro-Figueroa M, Tóth É, Platas-Iglesias C, Tircsó G. H4octapa: Highly stable complexation of lanthanide(III) ions and copper(II). Inorganic Chemistry. 2015 Mar 2;54(5):2345-2356. https://doi.org/10.1021/ic502966m
Kálmán, Ferenc Krisztián ; Végh, Andrea ; Regueiro-Figueroa, Martín ; Tóth, Éva ; Platas-Iglesias, Carlos ; Tircsó, G. / H4octapa : Highly stable complexation of lanthanide(III) ions and copper(II). In: Inorganic Chemistry. 2015 ; Vol. 54, No. 5. pp. 2345-2356.
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