NMR studies of mixed-ligand lanthanide (III) complexes. Peculiarities of molecular structure, dynamics and paramagnetic properties for cerium subgroup chelates with crown ethers

Sergey P. Babailov, Dmitry A. Mainichev

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Abstract

The molecular structure, dynamics and paramagnetic properties of the complex cations [Ln(ptfa)2 (18-crown-6)]+ in deuterated toluene were studied for Ln = La, Ce, Pr and Nd. The activation enthalpy values of 68 ± 5, 55 ± 15 and 60 ± 13 kJ mol-1 for the 18-crown-6 conformational inversion processes for the complex cations of Ce, Pr and Nd, respectively, were obtained. Quantitative investigation of the lanthanide-induced chemical shifts shows a monotonic change of a spatial structure and magnetic susceptibility in comparison with the Bleaney predicted dependence. The free energy of molecular inversion activation for 18-crown-6 molecules in the complex cation [Ln(fod)2(18-crown-6)]+ is 74 ± 9 kJ mol-1 at 363 K, which is a little more than the value of the free energy of activation 64 ± 9 kJ mol-1 at 363 K in the complex cation [Ln(ptfa)2(18-crown-6)]+.

Original languageEnglish
Pages (from-to)187-193
Number of pages7
JournalJournal of Inclusion Phenomena and Macrocyclic Chemistry
Volume43
Issue number3-4
DOIs
Publication statusPublished - 2002
Externally publishedYes

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Keywords

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

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics

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