dc.contributor.author
Savitsky, Anton
dc.contributor.author
Nalepa, Anna
dc.contributor.author
Petrenko, Taras
dc.contributor.author
Plato, Martin
dc.contributor.author
Möbius, Klaus
dc.date.accessioned
2022-08-31T12:22:11Z
dc.date.available
2022-08-31T12:22:11Z
dc.identifier.uri
https://refubium.fu-berlin.de/handle/fub188/33401
dc.identifier.uri
http://dx.doi.org/10.17169/refubium-33122
dc.description.abstract
The hydrogen bond plays a key role in weak directional intermolecular interactions. It is operative in determining molecular conformation and aggregation, and controls the function of many chemical systems, ranging from inorganic, organic to biological molecules. Although an enormous amount of spectroscopic information has been collected about hydrogen-bond formation between molecules with closed-shell electronic configuration, the details of such interactions between open-shell radicals and closed-shell molecules are still rare. Here we report on an investigation of hydrogen-bonded complexes between pyrroline-type as well as piperidine-type neutral nitroxide radicals and an alcohol, i.e., 2-propanol. These nitroxide radicals are commonly used as EPR spin labels and probes. To obtain information on the geometry of the complexes and their electronic structure, multi-resonance EPR techniques at various microwave frequencies (X-, Q-, W-band, 244 GHz) have been employed in conjunction with DFT calculations. The planar five-membered ring system of the pyrroline-type nitroxide radical was found to form exclusively well-defined in-plane σ-type hydrogen-bonded complexes with one 2-propanol molecule in the first solvation shell in frozen solution. The measured hyperfine parameters of the hydrogen-bridge proton and the internal magnetic parameters describing the electron Zeeman and the electron-nuclear hyperfine and nuclear quadrupole interactions are in good agreement with values predicted by state-of-the-art DFT calculations. In contrast, multi-resonance EPR on the non-planar six-membered ring system of the piperidine-type nitroxide radical (TEMPOL) reveals a more complex situation, i.e., a mixture of a σ-type with, presumably, an out-of-plane π-type complex, both present in comparable fraction in frozen solution. For TEMPOL, the DFT calculations failed to predict magnetic interaction parameters that are in good agreement with experiment, apparently due to the considerable flexibility of the nitroxide and hydrogen-bonded complex. The detailed information about nitroxide/solvent complexes is of particular importance for Dynamic Nuclear Polarization (DNP) and site-directed spin-labeling EPR studies that employ nitroxides as polarizing agents or spin labels, respectively.
en
dc.format.extent
25 Seiten
dc.rights.uri
https://creativecommons.org/licenses/by/4.0/
dc.subject
hydrogen-bonded complexes
en
dc.subject
neutral nitroxide radicals
en
dc.subject
multifrequency EPR/ENDOR
en
dc.subject.ddc
500 Naturwissenschaften und Mathematik::530 Physik::530 Physik
dc.title
Hydrogen-Bonded Complexes of Neutral Nitroxide Radicals with 2-Propanol Studied by Multifrequency EPR/ENDOR
dc.type
Wissenschaftlicher Artikel
dcterms.bibliographicCitation.doi
10.1007/s00723-021-01442-y
dcterms.bibliographicCitation.journaltitle
Applied Magnetic Resonance
dcterms.bibliographicCitation.number
7-9
dcterms.bibliographicCitation.pagestart
1239
dcterms.bibliographicCitation.pageend
1263
dcterms.bibliographicCitation.volume
53
dcterms.bibliographicCitation.url
https://doi.org/10.1007/s00723-021-01442-y
refubium.affiliation
Physik
refubium.resourceType.isindependentpub
no
dcterms.accessRights.openaire
open access
dcterms.isPartOf.eissn
1613-7507
refubium.resourceType.provider
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