Kantola, A., Lantto, P., Heinmaa, I., Vaara, J., Jokisaari, J. (2020) Direct magnetic-field dependence of NMR chemical shift. Physical Chemistry Chemical Physics, 22 (16), 8485-8490. https://doi.org/10.1039/D0CP01372B
Direct magnetic-field dependence of NMR chemical shift
|Author:||Kantola, Anu M.1; Lantto, Perttu1; Heinmaa, Ivo2;|
1NMR Research Unit, University of Oulu, P.O. Box 3000, FI-90014, Finland
2National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, EE-12618 Tallinn, Estonia
|Online Access:||PDF Full Text (PDF, 2 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe2020043024668
Royal Society of Chemistry,
|Publish Date:|| 2020-04-30
Nuclear shielding and chemical shift are considered independent of the magnetic-field strength. Ramsey proposed on theoretical grounds in 1970 that this may not be valid for heavy nuclei. Here we present experimental evidence for the direct field dependence of shielding, using 59Co shielding in Co(acac)3 [tris(acetylacetonate)cobalt(III)] as an example. We carry out NMR experiments in four field strengths for this low-spin diamagnetic Co(III) complex, which features a very large and negative nuclear shielding constant of the central Co nucleus. This is due to a magnetically accessible, low-energy eg ← t2g orbital excitation of the d6 system. The experiments result in temperature-dependent magnetic-field dependence of −5.7 to −5.2 ppb T−2 of the 59Co shielding constant, arising from the direct modification of the electron cloud of the complex by the field. First-principles multiconfigurational non-linear response theory calculations verify the sign and order of magnitude of the experimental results.
PCCP. Physical chemistry chemical physics
|Pages:||8485 - 8490|
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
114 Physical sciences
116 Chemical sciences
Financial support has been obtained from the University of Oulu (Kvantum Institute), and the Academy of Finland (projects 285666 and 296292). Computational resources due to CSC (Espoo, Finland) and the Finnish Grid and Cloud Infrastructure project (persistent identifier urn:nbn:fi:research-infras-2016072533), were used. IH was supported by European Regional Development Fund (TK134).
|Academy of Finland Grant Number:||
285666 (Academy of Finland Funding decision)
296292 (Academy of Finland Funding decision)
© The Authors 2020. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.