Issue 13, 2017

Synthesis, structure and paramagnetic NMR analysis of a series of lanthanide-containing [LnTi6O3(OiPr)9(salicylate)6] cages

Abstract

The influence of paramagnetic Ln3+ ions on the NMR behaviour is investigated via a series of new isostructural lanthanide-containing cages with the general formula [LnTi6O3(OiPr)9(salicylate)6] (Ln-1, Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Er). Compared to conventional coordination compounds containing Ln3+ ions, the peripheral ligands in Ln-1 are separated from the paramagnetic lanthanide centres by oxo-Ti4+ linkages, and therefore experience a weaker paramagnetic influence. As a result, all of the 1H and 13C NMR signals of these Ln-1 cages (except for Gd-1) are observed and can be unambiguously assigned, which provides an excellent platform for the in-depth study of the NMR behaviour of paramagnetic Ln3+ ions. Further analysis of the fully assigned paramagnetic signals suggests that the pseudo-contact component dominates the 1H NMR shifts, whereas both the pseudo-contact and Fermi-contact contributions affect the 13C shifts, although the majority of the resonance environments are at least four bonds distant from the central Ln3+ ion. Our results also show that the use of Bleaney's factors to describe the pseudo-contact shift is inadequate for this Ln-1 cage series.

Graphical abstract: Synthesis, structure and paramagnetic NMR analysis of a series of lanthanide-containing [LnTi6O3(OiPr)9(salicylate)6] cages

Supplementary files

Article information

Article type
Paper
Submitted
05 Jan 2017
Accepted
01 Mar 2017
First published
01 Mar 2017

Dalton Trans., 2017,46, 4287-4295

Synthesis, structure and paramagnetic NMR analysis of a series of lanthanide-containing [LnTi6O3(OiPr)9(salicylate)6] cages

N. Li, R. García-Rodríguez, P. D. Matthews, H. Luo and D. S. Wright, Dalton Trans., 2017, 46, 4287 DOI: 10.1039/C7DT00049A

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