Electron spin–lattice relaxation of nitroxyl radicals in temperature ranges that span glassy solutions to low-viscosity liquids

Sato, Hideo, Bottle, Steven E., Blinco, James P., Micallef, Aaron S., Eaton, Gareth R. and Eaton, Sandra S. (2008) Electron spin–lattice relaxation of nitroxyl radicals in temperature ranges that span glassy solutions to low-viscosity liquids. Journal of Magnetic Resonance, 191 1: 66-77.


Author Sato, Hideo
Bottle, Steven E.
Blinco, James P.
Micallef, Aaron S.
Eaton, Gareth R.
Eaton, Sandra S.
Title Electron spin–lattice relaxation of nitroxyl radicals in temperature ranges that span glassy solutions to low-viscosity liquids
Journal name Journal of Magnetic Resonance   Check publisher's open access policy
ISSN 1090-7807
1096-0856
Publication date 2008-03
Year available 2007
Sub-type Article (original research)
DOI 10.1016/j.jmr.2007.12.003
Volume 191
Issue 1
Start page 66
End page 77
Total pages 12
Place of publication Orlando, Fla., U.S.A.
Publisher Academic Press
Language eng
Subject 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics
Formatted abstract Electron spin–lattice relaxation rates, 1/T1, at X-band of nitroxyl radicals (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidin-1-oxyl, 3-carbamoyl-2,2,5,5-tetramethylpyrrolidin-1-oxyl and 3-carbamoyl-2,2,5,5-tetramethylpyrrolin-1-oxyl) in glass-forming solvents (decalin, glycerol, 3-methylpentane, o-terphenyl, 1-propanol, sorbitol, sucrose octaacetate, and 1:1 water:glycerol) at temperatures between 100 and 300 K were measured by long-pulse saturation recovery to investigate the relaxation processes in slow-to-fast tumbling regimes. A subset of samples was also studied at lower temperatures or at Q-band. Tumbling correlation times were calculated from continuous wave lineshapes. Temperature dependence and isotope substitution (2H and 15N) were used to distinguish the contributions of various processes. Below about 100 K relaxation is dominated by the Raman process. At higher temperatures, but below the glass transition temperature, a local mode process makes significant contributions. Above the glass transition temperature, increased rates of molecular tumbling modulate nuclear hyperfine and g anisotropy. The contribution from spin rotation is very small. Relaxation rates at X-band and Q-band are similar. The dependence of 1/T1 on tumbling correlation times fits better with the Cole–Davidson spectral density function than with the Bloembergen–Purcell–Pound model.
© 2007 Elsevier Inc. All rights reserved.
Keyword Cole–Davidson spectral density function
Nitroxyl radical
Spin–lattice relaxation
Tumbling
Q-Index Code C1
Additional Notes Available online 14 December 2007

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
Centre for Advanced Imaging Publications
 
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