Carbon-13 hyperfine splittings in the electron paramagnetic resonance spectra of .beta.-substituted ethyl radicals

1976 ◽  
Vol 80 (3) ◽  
pp. 275-278 ◽  
Author(s):  
J. C. Scaiano ◽  
K. U. Ingold
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Paramagnetic Resonance ◽  
Hyperfine Splittings ◽  
Ethyl Radicals ◽  
Electron Paramagnetic

An Electrolytically Generated, Localized Hole Center in Quartz

1989 ◽  
Vol 44 (4) ◽  
pp. 278-282
Author(s):  
A. B. Vassilikou-Dova ◽  
K. Eftaxias ◽  
G. Lehmann
Keyword(s):  
Activation Energy ◽  
Electron Paramagnetic Resonance ◽  
Temperature Dependence ◽  
Free Electron ◽  
Room Temperature ◽  
Hole Center ◽  
Paramagnetic Resonance ◽  
Tentative Model ◽  
Hyperfine Splittings ◽  
Electron Paramagnetic

Abstract In natural smoky quartz and neutron-irradiated, initially colorless quartz a new hole center was formed electrolytically at temperatures near 1100 K in addition to the well-known smoky quartz center. Unlike the latter its electron paramagnetic resonance spectra can already be measured at room temperature due to firm localization of the hole on one oxygen. It is characterized by fairly small hyperfine splittings due to Al impurity and significant deviations of all three principal g factors from that of a free electron. A tentative model for the structure of this center is proposed.An activation energy of 215 kJ/mol was determined for this electrolytic coloration from the temperature dependence of the electrolysis currents.

The first 1H and 14N ENDOR spectra of an oxygen-centered radical adduct of DMPO-type nitrones

1988 ◽  
Vol 66 (9) ◽  
pp. 2395-2402 ◽  
Author(s):  
D. Larry Haire ◽  
Uwe M. Oehler ◽  
H. Duane Goldman ◽  
Robert L. Dudley ◽  
Edward G. Janzen
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Long Range ◽  
Double Resonance ◽  
Electron Nuclear Double Resonance ◽  
Paramagnetic Resonance ◽  
Spectral Signatures ◽  
Radical Adduct ◽  
Sequence Patterns ◽  
Hyperfine Splittings ◽  
Electron Paramagnetic

We report the first 1H and 14N electron nuclear double resonance (ENDOR) spectra of oxygen-centered radical adducts (i.e., derived from the addition of tert-butoxyl radicals) of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as well as the related cyclic nitrones: 4-phenyl-5,5-dimethyl-1-pyrroline-N-oxide (4-Ph-DMPO) and 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO). Features of the electron paramagnetic resonance (EPR) and ENDOR spectra of these cyclic (pyrrolidine) aminoxyl (nitroxide) species along with some deuterated analogues in liquid toluene solutions are highlighted. For instance, we found several long-range γ-H hyperfine splittings (HFS's) detectable by ENDOR that provide unique spectral signatures for these radical adducts. Conformational assignments of the pyrrolidine aminoxyl structures based upon the EPR and ENDOR findings are also discussed. Signs of the various hyperfine splittings (i.e., aN, [Formula: see text]) investigated by cross-relaxation intensity sequence patterns (CRISP) in the ENDOR spectra are also presented.

scholarly journals Electron paramagnetic resonance studies on Pseudomonas nitrosyl nitrite reductase. Evidence for multiple species in the electron paramagnetic resonance spectra of nitrosyl haemoproteins

1980 ◽  
Vol 189 (2) ◽  
pp. 285-294 ◽  
Author(s):  
M K Johnson ◽  
A J Thomson ◽  
T A Walsh ◽  
D Barber ◽  
C Greenwood
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Absorption Spectra ◽  
High Temperatures ◽  
Nitrite Reductase ◽  
Axial Ligand ◽  
Coupling Constants ◽  
Paramagnetic Resonance ◽  
Temperature Spectra ◽  
Hyperfine Splittings ◽  
Electron Paramagnetic

The e.p.r. spectra of reduced 14NO- and 15NO-bound Pseudomonas nitrite reductase have been investigated at pH 5.8 and 8.0 in four buffer systems. At pH 8.0, absorption spectra indicated that only the haem d1 was NO-bound, but, although quantification of the e.p.r. signals in all cases accounted for NO bound the the haem d1 in both subunits of the enzyme, the precise form of the signals varied with buffer and temperature. A rhombic species, with gx = 2.07, gz = 2.01 and gy = 1.96, represented in the low-temperature spectra seen in all the buffers was converted at high temperatures (approx. 200K) into a form showing a reduced anisotropy. Hyperfine splitting on the gz component of this rhombic signal indicated a nitrogen atom trans to NO and it is proposed that histidine provides the endogenous axial ligand for haem d1. At pH 5.8, absorption spectra indicated NO binding to both haems c and d1 and e.p.r. quantifications accounted for NO-bound haems c and d1 in both enzyme subunits. The e.p.r. spectra at pH 5.8 were generally similar to those at pH 8.0 with respect to g-values and hyperfine coupling constants, but were broader with less well defined hyperfine splittings. As at pH 8, rhombic signals present in spectra at low temperatures were converted to less anisotropic forms at high temperatures. The results are discussed in relation to work on model nitrosyl-protohaem complexes [Yoshimura, Ozaki, Shintani & Watanabe (1979) Arch. Biochem, Biophys. 193, 301-313]. No. e.p.r. signal was observed from oxidized NO-bound Pseudomonas nitrite reductase at pH 6.0, over the temperature range 6-100K.

ALICYCLIC KETYLS: I. ANGULAR DEPENDENCE OF HYPERFINE COUPLING AND CONFORMATIONAL MOBILITY OF CYCLOHEXANONE KETYLS

1965 ◽  
Vol 43 (9) ◽  
pp. 2571-2575 ◽  
Author(s):  
J. W. Lown
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Angular Dependence ◽  
Room Temperature ◽  
Hyperfine Coupling ◽  
Conformational Mobility ◽  
Paramagnetic Resonance ◽  
Methyl Group ◽  
Tert Butyl ◽  
Hyperfine Splittings ◽  
Electron Paramagnetic

The electron paramagnetic resonance (e.p.r.) spectra of ketyls derived from cyclopentanone and 4-tert-butyl, 4-methyl, 3-methyl, and unsubstituted cyclohexanone have been recorded in dimethoxymethane at room temperature. The proton hyperfine splittings (aH) observed with rigid ketyls are consistent with a dihedral angular (θ) dependence of hyperfine coupling of the form, aH = 4.8 + 9.6 cos2 θ. Conformational averaging of the hyperfine coupling is observed with 4-methyl, 3-methyl, and unsubstituted cyclohexanone ketyls. The conformer populations calculated from the e.p.r. spectra are in accordance with A values for the methyl group derived from non-radical cyclohexane compounds.

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