ELECTRON SPIN RESONANCE STUDIES OF PHOTOLYTICALLY GENERATED AROMATIC KETYLS

1966 ◽  
Vol 44 (5) ◽  
pp. 551-559 ◽  
Author(s):  
Raymond Wilson
Keyword(s):  
Hydrogen Bonding ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Aprotic Solvent ◽  
Coupling Constants ◽  
Proton Coupling ◽  
Protic Solvents ◽  
Spin Resonance ◽  
Semi Empirical ◽  
Spin Densities

Electron spin resonance observations on the photolytically generated ketyls of benzaldehyde, acetophenone, and benzophenone in protic solvents are reported. Proton coupling constants differ considerably from those reported by other workers for the same ketyls generated by other methods in aprotic solvents.Molecular orbital calculations of unpaired electron spin densities, in which the effective electronegativities of the oxygen atoms on the ketyls are assumed to be increased by hydrogen bonding in protic solvents, are reported. The calculated changes in spin densities agree qualitatively with the semi-empirical changes calculated by the McConnell relationship.Observations on the dynamics of solvation of the benzaldehyde ketyl in a mixture of a protic and an aprotic solvent are reported and discussed.

Matrix dependence of the electron spin resonance spectra of the radical trapped in different single crystals

1977 ◽  
Vol 55 (20) ◽  
pp. 3554-3558 ◽  
Author(s):  
J. P. Michaut ◽  
J. Roncin
Keyword(s):  
Electron Spin Resonance ◽  
Single Crystal ◽  
Single Crystals ◽  
Electron Spin ◽  
Experimental Error ◽  
Field Effect ◽  
Coupling Constants ◽  
Crystal Field Effect ◽  
Proton Coupling ◽  
Spin Resonance

Nitrogen and proton coupling tensors have been measured for the [Formula: see text] radical trapped in five different single crystal matrices. As all isotropic coupling constants are the same within experimental error (aN = 21.2 G, aH = 28.4 G), no measurable crystal field effect is found. In these solids the motions of the radical depend on the dimension of the trapping cage and the motions of the surrounding molecules.

THE ELECTRON SPIN RESONANCE SPECTRA OF DINITRONAPHTHALENE ANION RADICALS

1965 ◽  
Vol 43 (12) ◽  
pp. 3400-3406 ◽  
Author(s):  
P. H. H. Fischer ◽  
C. A. McDowell
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Coupling Constants ◽  
Radical Anions ◽  
Proton Coupling ◽  
Spin Resonance ◽  
Full Symmetry ◽  
Nitrogen Coupling ◽  
Anion Radicals

The radical anions of 1,4-dinitronaphthalene, 1,5-dinitronaphthalene, and 1,8-dinitronaphthalene have been generated by electrolytic means, and their e.s.r. spectra recorded. The spectra consist of 61, 111, and 85 lines respectively, and can be analyzed in terms of one nitrogen and three proton coupling constants, consistent with the full symmetry of the species giving rise to them. These constants are, for 1,4-dinitronaphthalene: aN = 0.97 G, aH2 = 1.69 G, aH5 = 0.53 G, and aH6 = 0.41 G; for 1,5-dinitronaphthalene: aN = 2.30 G, aH2 = 2.42 G, aH3 = 0.44 G, and aH4 = 2.82 G; for 1,8-dinitronaphthalene: aN = 3.03 G, aH2 = 3.63 G, aH3 = 0.95 G, and aH4 = 3.73 G. Whereas the nitrogen coupling constants can be unambiguously assigned, this, in the absence of deuteration studies say, is not the case for the three sets of equivalent protons. As an aid in the assignment of proton coupling constants, Hückel LCAO calculations and simplified SCFMO calculations by the method of McLachlan have been performed. The first mentioned of the above proton constants could thus be assigned with reasonable certainty, the remaining two aHi remain ambiguous.

A comparison of electron spin resonance α- and β-hyperfine coupling constants in para-substituted α-phenethyl radicals

1986 ◽  
Vol 64 (4) ◽  
pp. 769-772 ◽  
Author(s):  
Donald R. Arnold ◽  
A. Martin de P. Nicholas ◽  
Kent M. Young
Keyword(s):  
Electron Spin Resonance ◽  
Experimental Evidence ◽  
Linear Relationship ◽  
Electron Spin ◽  
Hyperfine Coupling ◽  
Coupling Constants ◽  
Hyperfine Coupling Constants ◽  
Spin Resonance ◽  
Benzyl Radicals ◽  
Spin Delocalization

The linear relationship between the electron spin resonance hyperfine coupling constants (hfc) of the α- and β-hydrogens of para-substituted α-phenethyl radicals provides experimental evidence that the magnitude of both the α- and β -hfc is determined largely by the extent of spin delocalization in these benzylic systems. The [Formula: see text] scale, developed using substituted benzyl radicals, is shown to apply to phenethyl radicals as well.

Nitroxide derivatives of acetylacetone as spin-labelled ligands

1981 ◽  
Vol 59 (1) ◽  
pp. 156-163 ◽  
Author(s):  
D. Plancherel ◽  
D. R. Eaton
Keyword(s):  
Electron Spin Resonance ◽  
Metal Complex ◽  
Electron Spin ◽  
Hyperfine Coupling ◽  
Esr Spectra ◽  
Enol Form ◽  
Coupling Constants ◽  
Spin Resonance ◽  
Steric Factors ◽  
Derivatives Of

Electron spin resonance spectra are reported from a number of radicals derived from 2,4-pentadione substituted at the 3 position with nitroxide-containing groups. If the substituent is t-butyl nitroxide no metal complexes are formed. This is attributed to steric factors which prevent the formation of the enol form of the β-diketone. If the substituent is trifluoromethyl nitroxide two types of metal complex have been observed. The esr spectra of the first type are very similar to that of the uncomplexed radical. Such complexes are formed with Co(III) and Al(III). The esr spectra of the second type show considerably increased 14N and 19F hyperfine coupling constants and in some cases large couplings to the metal nucleus. Complexes for the second type have been observed with Pd(II), Pt(II), and Rh(III). The possible structures of these radicals are discussed.

A PARAMAGNETIC RESONANCE STUDY OF HINDERED DIARYLMETHYL RADICALS AND RELATED COMPOUNDS: I. ANALYSIS OF THE SPECTRA

1966 ◽  
Vol 44 (12) ◽  
pp. 1387-1395 ◽  
Author(s):  
H. R. Falle ◽  
F. C. Adam
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Ion Pair ◽  
Coupling Constants ◽  
Methyl Groups ◽  
Steric Repulsion ◽  
Paramagnetic Resonance ◽  
Spin Resonance ◽  
Phenyl Rings ◽  
Related Compounds

Several ortho-substituted radicals of the benzhydryl type and a variety of diaryl ketyls have been studied through the nuclear hyperfine structure of their electron spin resonance spectra. A strong similarity is found between the spectra of a given ketyl and its hydrocarbon analogue. This suggests that when ketones are reduced, a very tight ion pair is formed between the ketyl anion and its cation. Although the coupling constants of the protons vary with different reducing agents, larger variations are observed when bulky groups are substituted into ortho positions. These larger changes are attributed to a forced internal rotation of the phenyl rings. The distortion results from the steric repulsion between the ortho groups. The effect of 'buttressing' of ortho methyl groups is also studied. Deuterium and 13C substitutions have been effected in some of the compounds.

E.P.R. studies of the anions of some peri-alkylnaphthalenes

1972 ◽  
Vol 25 (11) ◽  
pp. 2353 ◽  
Author(s):  
RFC Claridge ◽  
BM Peake
Keyword(s):  
Electron Spin Resonance ◽  
Molecular Orbital ◽  
Electron Spin ◽  
Hyperfine Coupling ◽  
Inductive Effect ◽  
Coupling Constants ◽  
Radical Anions ◽  
Hyperfine Coupling Constants ◽  
Spin Resonance ◽  
Aliphatic Substituent

The hyperfine coupling constants for the radical anions of 2,3-dihydro- phenalene (perinaphthane) and 7,8,9,l0-tetrahydrocyclohepta[de]naphthalene have been determined from analysis of the electron spin resonance spectra in solution. The results are compared with data from other mono- and di-peri- substituted naphthalenes. A simple H�ckel molecular orbital treatment is used to describe the inductive effect of the aliphatic substituent.

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