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Rationalization of Anomalous Pseudocontact Shifts and Their Solvent Dependence in a Series of C3-Symmetric Lanthanide Complexes

Vonci, Michele; Mason, Kevin; Suturina, Elizaveta A.; Frawley, Andrew T.; Worswick, Steven G.; Kuprov, Ilya; Parker, David; McInnes, Eric J.L.; Chilton, Nicholas F.

Rationalization of Anomalous Pseudocontact Shifts and Their Solvent Dependence in a Series of C3-Symmetric Lanthanide Complexes Thumbnail


Authors

Michele Vonci

Kevin Mason

Elizaveta A. Suturina

Andrew T. Frawley

Steven G. Worswick

Ilya Kuprov

Eric J.L. McInnes

Nicholas F. Chilton



Abstract

Bleaney’s long-standing theory of magnetic anisotropy has been employed with some success for many decades to explain paramagnetic NMR pseudocontact shifts, and has been the subject of many subsequent approximations. Here, we present a detailed experimental and theoretical investigation accounting for the anomalous solvent dependence of NMR shifts for a series of lanthanide(III) complexes, namely [LnL1] (Ln = Eu, Tb, Dy, Ho, Er, Tm, and Yb; L1: 1,4,7-tris[(6-carboxypyridin-2-yl)methyl]-1,4,7-triazacyclononane), taking into account the effect of subtle ligand flexibility on the electronic structure. We show that the anisotropy of the room temperature magnetic susceptibility tensor, which in turn affects the sign and magnitude of the pseudocontact chemical shift, is extremely sensitive to minimal structural changes in the first coordination sphere of L1. We show that DFT structural optimizations do not give accurate structural models, as assessed by the experimental chemical shifts, and thus we determine a magnetostructural correlation and employ this to evaluate the accurate solution structure for each [LnL1]. This approach allows us to explain the counterintuitive pseudocontact shift behavior, as well as a striking solvent dependence. These results have important consequences for the analysis and design of novel magnetic resonance shift and optical emission probes that are sensitive to the local solution environment and polarity.

Citation

Vonci, M., Mason, K., Suturina, E. A., Frawley, A. T., Worswick, S. G., Kuprov, I., …Chilton, N. F. (2017). Rationalization of Anomalous Pseudocontact Shifts and Their Solvent Dependence in a Series of C3-Symmetric Lanthanide Complexes. Journal of the American Chemical Society, 139(40), 14166-14172. https://doi.org/10.1021/jacs.7b07094

Journal Article Type Article
Acceptance Date Jul 7, 2017
Online Publication Date Sep 8, 2017
Publication Date Sep 8, 2017
Deposit Date Oct 20, 2017
Publicly Available Date Sep 8, 2018
Journal Journal of the American Chemical Society
Print ISSN 0002-7863
Electronic ISSN 1520-5126
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 139
Issue 40
Pages 14166-14172
DOI https://doi.org/10.1021/jacs.7b07094

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Copyright Statement
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of the American Chemical Society, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/jacs.7b07094


Accepted Journal Article (Supporting information) (1.5 Mb)
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