Synthesis, structure and paramagnetic NMR analysis of a series of lanthanide-containing [LnTi6O3(OiPr)9(salicylate)6] cages
Royal Society of Chemistry
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Li, N., García-Rodríguez, R., Matthews, P. D., Luo, H., & Wright, D. (2017). Synthesis, structure and paramagnetic NMR analysis of a series of lanthanide-containing [LnTi6O3(OiPr)9(salicylate)6] cages. Dalton Transactions, 46 (13), 4287-4295. https://doi.org/10.1039/c7dt00049a
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.
External DOI: https://doi.org/10.1039/c7dt00049a
This record's URL: https://www.repository.cam.ac.uk/handle/1810/271173