Mewis, Ryan E., Green, Richard A., Cockett, Martin C R orcid.org/0000-0001-5580-7408 et al. (6 more authors) (2015) Strategies for the hyperpolarization of acetonitrile and related Ligands by SABRE. Journal of Physical Chemistry B. pp. 1416-1424. ISSN 1520-5207
Abstract
(Chemical Equation Presented) We report on a strategy for using SABRE (signal amplification by reversible exchange) for polarizing 1H and 13C nuclei of weakly interacting ligands which possess biologically relevant and nonaromatic motifs. We first demonstrate this via the polarization of acetonitrile, using Ir(IMes)(COD)Cl as the catalyst precursor, and confirm that the route to hyperpolarization transfer is via the J-coupling network. We extend this work to the polarization of propionitrile, benzylnitrile, benzonitrile, and trans-3-hexenedinitrile in order to assess its generality. In the 1H NMR spectrum, the signal for acetonitrile is enhanced 8-fold over its thermal counterpart when [Ir(H)2(IMes)(MeCN)3]+ is the catalyst. Upon addition of pyridine or pyridine-d5, the active catalyst changes to [Ir(H)2(IMes)- (py)2(MeCN)]+ and the resulting acetonitrile 1H signal enhancement increases to 20- and 60-fold, respectively. In 13C NMR studies, polarization transfers optimally to the quaternary 13C nucleus of MeCN while the methyl 13C is hardly polarized. Transfer to 13C is shown to occur first via the 1H - 1H coupling between the hydrides and the methyl protons and then via either the 2J or 1J couplings to the respective 13Cs, of which the 2J route is more efficient. These experimental results are rationalized through a theoretical treatment which shows excellent agreement with experiment. In the case of MeCN, longitudinal two-spin orders between pairs of 1H nuclei in the three-spin methyl group are created. Two-spin order states, between the 1H and 13C nuclei, are also created, and their existence is confirmed for Me13CN in both the 1H and 13C NMR spectra using the Only Parahydrogen Spectroscopy protocol.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2014 American Chemical Society. This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited. |
Dates: |
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Institution: | The University of York |
Academic Units: | The University of York > Faculty of Sciences (York) > Chemistry (York) The University of York The University of York > Faculty of Sciences (York) > Psychology (York) |
Funding Information: | Funder Grant number WELLCOME TRUST 098335/Z/12/Z EPSRC EP/G009546/1 |
Depositing User: | Pure (York) |
Date Deposited: | 09 Mar 2015 15:55 |
Last Modified: | 26 Nov 2024 00:29 |
Published Version: | https://doi.org/10.1021/jp511492q |
Status: | Published |
Refereed: | Yes |
Identification Number: | 10.1021/jp511492q |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:84052 |
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Description: Strategies for the Hyperpolarization of Acetonitrile and Related Ligands by SABRE
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Description: MeCN_Final_revised2