Intramolecular dynamics of lanthanide(III) tetraoxadiaza macrocycle complexes in solution as studied by NMR

S. P. Babailov, L. D. Nikulina, J. H. Krieger

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Abstract

1H and 13C NMR and 1H NMR relaxation spectroscopy (RS) measurements are reported for the CDCl3 and CD 2Cl2 solutions of [La(NO3)3 (diaza-18-crown-6)] (I), [Pr(NO3)3 (diaza-18-crown-6)] (II) and [Nd(NO3)3 (diaza-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. Enantiomeric isomer interconversion in II is characterized by ΔH‡ = 21.5 ± 4 kJ mol-1. Studies of the values of the lanthanide-induced shifts and the longitudinal relaxation rate enhancement revealed that the structure of complexes in solution is similar to that reported for the [La(NO3)3(18-crown-6)] complex in the crystal state. Nevertheless, it appears that the principal values of the molar paramagnetic susceptibility tensor (χi) significantly differ in complexes II and III. The possible reasons for the different characteristics of these complexes are discussed.

Original languageEnglish
Pages (from-to)25-29
Number of pages5
JournalJournal of Inclusion Phenomena and Macrocyclic Chemistry
Volume43
Issue number1-2
DOIs
Publication statusPublished - 2002
Externally publishedYes

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Keywords

  • Complexes of lanthanides
  • Crown ethers
  • Dynamic NMR
  • Enthalpy of activation
  • Molecular dynamics

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics

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