Procacci, Barbara orcid.org/0000-0001-7044-0560, Roy, S. S. orcid.org/0000-0002-9193-9712, Norcott, Philip orcid.org/0000-0003-4082-2079 et al. (2 more authors) (2018) Unlocking a diazirine long-lived nuclear singlet state via photochemistry:NMR detection and lifetime of an unstabilized diazo-compound. Journal of the American Chemical Society. pp. 16855-16864. ISSN 1520-5126
Abstract
Diazirines are important for photoaffinity labelling and their photoisomerization is relatively well known. This work shows how hyperpolarized NMR spectroscopy can be used to characterise an unstable diazo-compound formed via photoisomerization of a 15N2-labelled silyl-ether substituted diazirine. This diazirine is prepared in a nuclear spin singlet state via catalytic transfer of spin order from para-hydrogen. The active hyperpolarization catalyst is characterised to provide insight into the mechanism. The photochemical isomerisation of the diazirine into the diazo-analogue allows the NMR invisible nuclear singlet state of the parent compound to be probed. The identity of the diazo-species is confirmed by trapping with N-phenyl maleimide via a cycloaddition reaction to afford bicyclic pyrazolines that also show singlet state character. The presence of singlet states in the diazirine and the diazo-compound are validated by comparison of experimental nutation behaviour with theoretical simulation. The magnetic state lifetime of the diazo-compound is determined as 12 ± 1 s in CD3OD solution at room temperature whereas its chemical lifetime is measured as 100 ± 5 s by related hyperpolarized NMR studies. Indirect evidence for the generation of the photoproduct para-N2 is presented.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2018 American Chemical Society |
Dates: |
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Institution: | The University of York |
Academic Units: | The University of York > Faculty of Sciences (York) > Chemistry (York) |
Funding Information: | Funder Grant number WELLCOME TRUST 098335/Z/12/Z EPSRC EP/R51181X/1 |
Depositing User: | Pure (York) |
Date Deposited: | 09 Nov 2018 12:50 |
Last Modified: | 27 Nov 2024 00:33 |
Published Version: | https://doi.org/10.1021/jacs.8b10923 |
Status: | Published |
Refereed: | Yes |
Identification Number: | 10.1021/jacs.8b10923 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:138409 |