University of Oulu

Cherry, P., Rouf, S., Vaara, J. (2017) Paramagnetic Enhancement of Nuclear Spin–Spin Coupling. Journal of Chemical Theory and Computation, 13 (3), 1275-1283. doi:10.1021/acs.jctc.6b01080

Paramagnetic enhancement of nuclear spin–spin coupling

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Author: Cherry, Peter John; Rouf, Syed Awais1; Vaara, Juha1
Organizations: 1NMR Research Unit, University of Oulu, P.O. Box 3000, FIN-90014 Oulu, Finland
Format: article
Version: accepted version
Access: embargoed
Persistent link: http://urn.fi/urn:nbn:fi-fe201801021026
Language: English
Published: American Chemical Society, 2017
Publish Date: 2018-01-19
Description:

Abstract

We present a derivation and computations of the paramagnetic enhancement of the nuclear magnetic resonance (NMR) spin–spin coupling, which may be expressed in terms of the hyperfine coupling (HFC) and (for systems with multiple unpaired electrons) zero-field splitting (ZFS) tensors. This enhancement is formally analogous to the hyperfine contributions to the NMR shielding tensor as formulated by Kurland and McGarvey. The significance of the spin–spin coupling enhancement is demonstrated by using a combination of density-functional theory and correlated ab initio calculations, to determine the HFC and ZFS tensors, respectively, for two paramagnetic 3d metallocenes, a CrII(acac)2 complex, a Co(II) pyrazolylborate complex, and a lanthanide system, Gd–DOTA. Particular attention is paid to relativistic effects in HFC tensors, which are calculated using two methods: a nonrelativistic method supplemented by perturbational spin–orbit coupling corrections, and a fully relativistic, four-component matrix–Dirac–Kohn–Sham approach. The paramagnetic enhancement lacks a direct dependence on the distance between the coupled nuclei, and represents more the strength and orientation of the individual hyperfine couplings of the two nuclei to the spin density distribution. Therefore, the enhancement gains relative importance as compared to conventional coupling as the distance between the nuclei increases, or generally in the cases where the conventional coupling mechanisms result in a small value. With the development of the experimental techniques of paramagnetic NMR, the more significant enhancements, e.g., of the 13C13C couplings in the Gd–DOTA complex (as large as 9.4 Hz), may eventually become important.

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Series: Journal of chemical theory and computation
ISSN: 1549-9618
ISSN-E: 1549-9626
ISSN-L: 1549-9618
Volume: 13
Issue: 3
Pages: 1275 - 1283
DOI: 10.1021/acs.jctc.6b01080
OADOI: https://oadoi.org/10.1021/acs.jctc.6b01080
Type of Publication: A1 Journal article – refereed
Field of Science: 114 Physical sciences
Subjects:
Funding: The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme FP7/2007-2013/under REA grant agreement no. 317127 (P.J.C. and S.A.R.). S.A.R. and J.V. were additionally supported by the Academy of Finland (projects 258565 and 296292).
EU Grant Number: (317127) PNMR - Pushing the Envelope of Nuclear Magnetic Resonance Spectroscopy for Paramagnetic Systems. A Combined Experimental and Theoretical Approach
Academy of Finland Grant Number: 258565
296292
Detailed Information: 258565 (Academy of Finland Funding decision)
296292 (Academy of Finland Funding decision)
Copyright information: © 2017 American Chemical Society.