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

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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.

Original language	English
Pages (from-to)	103-109
Number of pages	7
Journal	Journal of Inclusion Phenomena and Macrocyclic Chemistry
Volume	51
Issue number	1
DOIs	https://doi.org/10.1007/s10847-004-4673-5
Publication status	Published - Feb 2005
Externally published	Yes

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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

Babailov, S. P., & Nikulina, L. D. (2005). NMR studies of mixed-ligand lanthanide complexes in solution: Pseudorotation and ring inversion of 18-crown-6 molecule in cerium subgroup chelates. Journal of Inclusion Phenomena and Macrocyclic Chemistry, 51(1), 103-109. https://doi.org/10.1007/s10847-004-4673-5

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title = "NMR studies of mixed-ligand lanthanide complexes in solution: Pseudorotation and ring inversion of 18-crown-6 molecule in cerium subgroup chelates",

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.",

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",

author = "Babailov, {Sergey P.} and Nikulina, {Lubov D.}",

year = "2005",

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doi = "10.1007/s10847-004-4673-5",

language = "English",

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T2 - Pseudorotation and ring inversion of 18-crown-6 molecule in cerium subgroup chelates

AU - Babailov, Sergey P.

AU - Nikulina, Lubov D.

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N2 - 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.

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.

KW - 18-crown-6

KW - Complexes of lanthanides

KW - Crown ethers

KW - Dynamic NMR

KW - Enthalpy of activation

KW - Interconversion of enantiomers

KW - Inversion and pseudorotation of macrocycle molecule

KW - Molecular dynamics

KW - Multi-site exchange

KW - Twelve-site exchange

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10.1007/s10847-004-4673-5