Tumbling of methyl radicals adsorbed on a silica gel surface studied by electron spin resonance

1968 ◽  
Vol 46 (2) ◽  
pp. 207-210 ◽  
Author(s):  
C. L. Gardner ◽  
E. J. Casey
Keyword(s):  
Electron Spin Resonance ◽  
Silica Gel ◽  
Electron Spin ◽  
Relaxation Mechanism ◽  
Quantitative Comparison ◽  
Methyl Radicals ◽  
Spin Quantum ◽  
Spin Quantum Number ◽  
Spin Resonance ◽  
Marked Dependence

The electron spin resonance spectra of CH3 and CD3 adsorbed on a silica gel surface at 77 °K are characterized by a marked dependence of the line width on nuclear spin quantum number. This dependence can be interpreted in terms of the tumbling of the radicals on the surface, anisotropies in the hyperfine and g tensors giving rise to a relaxation mechanism dependent on MI. A quantitative comparison of the spectra with the theory of this relaxation mechanism developed by McConnell, Kivelson, and Freed and Fraenkel enables the tumbling frequencies, 2.0 × 107 s−1 and 1.3 × 107 s−1 for CH3 and CD3 respectively, to be determined.

Methyl "radicals" on doped silica gel surfaces

1969 ◽  
Vol 47 (18) ◽  
pp. 3367-3369 ◽  
Author(s):  
E. J. Casey ◽  
C. W. M. Grant ◽  
C. L. Gardner
Keyword(s):  
Electron Spin Resonance ◽  
Silica Gel ◽  
Electron Spin ◽  
Line Intensity ◽  
Free Electron ◽  
Hyperfine Splitting ◽  
Silica Gels ◽  
Methyl Radicals ◽  
Spin Resonance ◽  
Hot Oxygen

Methyl radicals adsorbed on silica gels containing dopings of the semiconductor ZnO were investigated by electron spin resonance at 77 °K. In addition to the normal 4-line "a"-spectrum, with hyperfine splitting of 23.3 ± 0.2 G, a second broader 4-line spectrum "b" with splitting 18.8 ± 0.6 G appears. Variations in line intensity with extent of doping were measured. Disappearance of the b-spectrum when the doped gels were dried under hot oxygen was observed. Partial delocalization of the radical's free electron and mixing into the doped surface were clearly indicated.Satellites ("c") to the a-spectrum were observed and are discussed.

Light-induced reversible ionization of tetramethylphenylenediamine in an inorganic polymer of n-butyl orthotitanate

1988 ◽  
Vol 66 (8) ◽  
pp. 1931-1935
Author(s):  
Hisashi Ueda ◽  
Masahiro Kaise
Keyword(s):  
Relaxation Time ◽  
Electron Spin Resonance ◽  
Visible Light ◽  
Relative Intensity ◽  
Hyperfine Splitting ◽  
Resonance Absorption ◽  
Spin Quantum ◽  
Spin Quantum Number ◽  
Spin Resonance ◽  
Intensity Ratios

n-Butyl orthotitanate, BT, polymerized in tetrahydrofuran, if irradiated by visible light, gives a new electron spin resonance absorption that is not found before irradiation. In the present work, three different polymers of BT were synthesized by adding tetramethyl phenylenediamine (TMPD), dimethyl phenylenediamine (DMPD), or phenylenediamine (PD), to the solution of BT. The polymers thus prepared were tested to see if they give a new esr signal when irradiated by visible light. The polymer to which 1 mol% of TMPD was added gave TMPD•+ when irradiated by visible light, but the TMPD•+ signal decayed after the irradiation was discontinued. This change, therefore, is reversible. The resonant position of every hyperfine splitting line of the TMPD•+ found in this polymer coincided with that of TMPD•+ in solution, but the relative intensity ratios and the line width of each line depended on the nuclear spin quantum number of the coupling nuclei. This can be interpreted by the restricted rotational motion of TMPD•+ in the polymer matrix. The contribution of the non-diagonal term to the spin relaxation time would explain this phenomenon. In the case of the polymer to which DMPD was added, a small amount of DMPD•+ seemed to be formed, but no radical was detected in the case of the polymer to which PD was added.

The Detection of Alkoxy and Other Radicals in the Gamma Radiolysis of Alcohols by an Electron Spin Resonance and Spin Trapping Method

1974 ◽  
Vol 52 (21) ◽  
pp. 3645-3650 ◽  
Author(s):  
Frederick Peter Sargent ◽  
Edward Michael Gardy
Keyword(s):  
Electron Spin Resonance ◽  
Carbon Atom ◽  
Electron Spin ◽  
Spin Trapping ◽  
Methyl Radicals ◽  
Alkoxy Radicals ◽  
Spin Resonance ◽  
Gamma Radiolysis ◽  
Trapping Method

The radicals produced during γ radiolysis of methanol, ethanol, 1-propanol, 2-propanol, and t-butanol have been trapped by reaction with 2-nitroso-2-methylpropane (t-nitrosobutane) to give nitroxides which are detected by e.s.r.[Formula: see text]All the alcohols gave alkoxy radicals and, with the exception of t-butanol, radicals derived by the loss of an H atom from the carbon atom adjacent to the OH group. Methyl radicals were detected in t-butanol.

Electron spin resonance study of γ-irradiated tetraethylammonium iodide

1968 ◽  
Vol 46 (16) ◽  
pp. 2749-2752 ◽  
Author(s):  
L. Fabes ◽  
J. K. S. Wan
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Secondary Reaction ◽  
Electron Spin Resonance Study ◽  
Methyl Radicals ◽  
Γ Irradiation ◽  
Spin Resonance ◽  
Secondary Radical ◽  
Tetraethylammonium Iodide ◽  
Spin Resonance Study

γ-Irradiation of polycrystalline tetraethylammonium iodide at 77°K leads to the breaking of a C—C bond and the primary radicals ĊH3 and [Formula: see text] were detected by electron spin resonance. The methyl radicals were found to disappear readily at 120°K. In the range of 263–273°K a secondary reaction between [Formula: see text] and the parent ion [Formula: see text] was observed; the resulting secondary radical [Formula: see text] was found to be stable up to 373°K.

Sign in / Sign up

Export Citation Format

Share Document