NMR studies of mixed-ligand lanthanide complexes in solution

Pseudorotation and ring inversion of 18-crown-6 molecule in cerium subgroup chelates

Sergey P. Babailov, Lubov D. Nikulina

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

1H and 13C NMR measurements are reported for the CDCl3 and CD2Cl2 solutions of [La(NO 3)3(18-crown-6)] (I), [Pr(NO3) 3(18-crown-6)] (II) and [Ce(NO3)3(18-crown-6)] (III) complexes. Temperature dependencies of the 1H NMR spectra of II have been analyzed using the dynamic NMR methods for multi-site exchange. Two types of conformational dynamic processes in II were identified (the first one with activation enthalpy ΔH=26 ± 4 kJ/mol is conditioned by interconversion of complex enantiomeric form and pseudorotation of macrocycle molecule upon the C2 symmetry axis, the second one with ΔH=46 ± 5 kJ/mol is conditioned by macrocycle molecule inversion). Studies of the values of the lanthanide-induced shifts revealed that the structure of complexes in solution is similar to that reported for the complex I in the crystal state.

Original languageEnglish
Pages (from-to)103-109
Number of pages7
JournalJournal of Inclusion Phenomena and Macrocyclic Chemistry
Volume51
Issue number1
DOIs
Publication statusPublished - Feb 2005
Externally publishedYes

Fingerprint

cerium
Cerium
Lanthanoid Series Elements
rare earth elements
chelates
subgroups
Nuclear magnetic resonance
inversions
Ligands
nuclear magnetic resonance
ligands
Molecules
rings
enthalpy
crystals
molecules
Enthalpy
Chemical activation
activation
temperature

Keywords

  • 18-crown-6
  • Complexes of lanthanides
  • Crown ethers
  • Dynamic NMR
  • Enthalpy of activation
  • Interconversion of enantiomers
  • Inversion and pseudorotation of macrocycle molecule
  • Molecular dynamics
  • Multi-site exchange
  • Twelve-site exchange

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics

Cite this

NMR studies of mixed-ligand lanthanide complexes in solution : Pseudorotation and ring inversion of 18-crown-6 molecule in cerium subgroup chelates. / Babailov, Sergey P.; Nikulina, Lubov D.

In: Journal of Inclusion Phenomena and Macrocyclic Chemistry, Vol. 51, No. 1, 02.2005, p. 103-109.

Research output: Contribution to journalArticle

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abstract = "1H and 13C NMR measurements are reported for the CDCl3 and CD2Cl2 solutions of [La(NO 3)3(18-crown-6)] (I), [Pr(NO3) 3(18-crown-6)] (II) and [Ce(NO3)3(18-crown-6)] (III) complexes. Temperature dependencies of the 1H NMR spectra of II have been analyzed using the dynamic NMR methods for multi-site exchange. Two types of conformational dynamic processes in II were identified (the first one with activation enthalpy ΔH‡=26 ± 4 kJ/mol is conditioned by interconversion of complex enantiomeric form and pseudorotation of macrocycle molecule upon the C2 symmetry axis, the second one with ΔH‡=46 ± 5 kJ/mol is conditioned by macrocycle molecule inversion). Studies of the values of the lanthanide-induced shifts revealed that the structure of complexes in solution is similar to that reported for the complex I in the crystal state.",
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AB - 1H and 13C NMR measurements are reported for the CDCl3 and CD2Cl2 solutions of [La(NO 3)3(18-crown-6)] (I), [Pr(NO3) 3(18-crown-6)] (II) and [Ce(NO3)3(18-crown-6)] (III) complexes. Temperature dependencies of the 1H NMR spectra of II have been analyzed using the dynamic NMR methods for multi-site exchange. Two types of conformational dynamic processes in II were identified (the first one with activation enthalpy ΔH‡=26 ± 4 kJ/mol is conditioned by interconversion of complex enantiomeric form and pseudorotation of macrocycle molecule upon the C2 symmetry axis, the second one with ΔH‡=46 ± 5 kJ/mol is conditioned by macrocycle molecule inversion). Studies of the values of the lanthanide-induced shifts revealed that the structure of complexes in solution is similar to that reported for the complex I in the crystal state.

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