Nitrogen-14 and oxygen-17 hyperfine interactions in perturbed nitroxides

Allan H. Cohen, Brian M Hoffman*

*Corresponding author for this work

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

We have measured the isotropic and anisotropic hyperfine splittings for di-tert-butyl nitroxide (DTBN) and 2,2,6,6-tetramethylpiperidine N-oxyl (TMPN) perturbed by molecular complex formation, by hydrogen bonding, and by solvent effects in aprotic solvents. We use these measurements to obtain the σ-π interaction parameters for a Karplus-Fraenkel equation (a1 = Q11 iρiπ + Qjj iρj π) which relates the 14N and 17O isotropic hyperfine splittings to the spin density in the nitroxide N-O π-electron system; QNN N = 23.9 ± 1.0 G, QOO N = 3.6 ± 0.4 G, QOO O = 31.7 ± 0.7 G, and QNN O = 4.7 ± 0.5 G. In addition for protonated nitroxides QOO N = 13.2 ± 0.3 G. The values of QNN N for TMPN and DTBN are identical and discussion of the angle dependence of the parameter suggests that the radicals in solution do not differ with respect to planarity at nitrogen.

Original languageEnglish (US)
Pages (from-to)1313-1321
Number of pages9
JournalJournal of Physical Chemistry
Volume78
Issue number13
DOIs
StatePublished - Jan 1 1974

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oxygen 17
Nitrogen
Oxygen
nitrogen
Hydrogen bonds
interactions
Electrons
hydrogen
electrons

ASJC Scopus subject areas

  • Engineering(all)
  • Physical and Theoretical Chemistry

Cite this

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title = "Nitrogen-14 and oxygen-17 hyperfine interactions in perturbed nitroxides",
abstract = "We have measured the isotropic and anisotropic hyperfine splittings for di-tert-butyl nitroxide (DTBN) and 2,2,6,6-tetramethylpiperidine N-oxyl (TMPN) perturbed by molecular complex formation, by hydrogen bonding, and by solvent effects in aprotic solvents. We use these measurements to obtain the σ-π interaction parameters for a Karplus-Fraenkel equation (a1 = Q11 iρiπ + Qjj iρj π) which relates the 14N and 17O isotropic hyperfine splittings to the spin density in the nitroxide N-O π-electron system; QNN N = 23.9 ± 1.0 G, QOO N = 3.6 ± 0.4 G, QOO O = 31.7 ± 0.7 G, and QNN O = 4.7 ± 0.5 G. In addition for protonated nitroxides QOO N = 13.2 ± 0.3 G. The values of QNN N for TMPN and DTBN are identical and discussion of the angle dependence of the parameter suggests that the radicals in solution do not differ with respect to planarity at nitrogen.",
author = "Cohen, {Allan H.} and Hoffman, {Brian M}",
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Nitrogen-14 and oxygen-17 hyperfine interactions in perturbed nitroxides. / Cohen, Allan H.; Hoffman, Brian M.

In: Journal of Physical Chemistry, Vol. 78, No. 13, 01.01.1974, p. 1313-1321.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Nitrogen-14 and oxygen-17 hyperfine interactions in perturbed nitroxides

AU - Cohen, Allan H.

AU - Hoffman, Brian M

PY - 1974/1/1

Y1 - 1974/1/1

N2 - We have measured the isotropic and anisotropic hyperfine splittings for di-tert-butyl nitroxide (DTBN) and 2,2,6,6-tetramethylpiperidine N-oxyl (TMPN) perturbed by molecular complex formation, by hydrogen bonding, and by solvent effects in aprotic solvents. We use these measurements to obtain the σ-π interaction parameters for a Karplus-Fraenkel equation (a1 = Q11 iρiπ + Qjj iρj π) which relates the 14N and 17O isotropic hyperfine splittings to the spin density in the nitroxide N-O π-electron system; QNN N = 23.9 ± 1.0 G, QOO N = 3.6 ± 0.4 G, QOO O = 31.7 ± 0.7 G, and QNN O = 4.7 ± 0.5 G. In addition for protonated nitroxides QOO N = 13.2 ± 0.3 G. The values of QNN N for TMPN and DTBN are identical and discussion of the angle dependence of the parameter suggests that the radicals in solution do not differ with respect to planarity at nitrogen.

AB - We have measured the isotropic and anisotropic hyperfine splittings for di-tert-butyl nitroxide (DTBN) and 2,2,6,6-tetramethylpiperidine N-oxyl (TMPN) perturbed by molecular complex formation, by hydrogen bonding, and by solvent effects in aprotic solvents. We use these measurements to obtain the σ-π interaction parameters for a Karplus-Fraenkel equation (a1 = Q11 iρiπ + Qjj iρj π) which relates the 14N and 17O isotropic hyperfine splittings to the spin density in the nitroxide N-O π-electron system; QNN N = 23.9 ± 1.0 G, QOO N = 3.6 ± 0.4 G, QOO O = 31.7 ± 0.7 G, and QNN O = 4.7 ± 0.5 G. In addition for protonated nitroxides QOO N = 13.2 ± 0.3 G. The values of QNN N for TMPN and DTBN are identical and discussion of the angle dependence of the parameter suggests that the radicals in solution do not differ with respect to planarity at nitrogen.

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