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.

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.

Substituent effects on benzyl radical hydrogen hyperfine coupling constants (hfc's).: Part 5. The comparison of electron spin resonance hfc's and the stabilization energy of π-radicals due to spin delocalization

1986 ◽  
Vol 64 (2) ◽  
pp. 270-276 ◽  
Author(s):  
A. Martin de P. Nicholas ◽  
Donald R. Arnold
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Substituent Effects ◽  
Energy Scale ◽  
Spin Systems ◽  
Stabilization Energy ◽  
Coupling Constants ◽  
Spin Resonance ◽  
Benzyl Radicals ◽  
Spin Delocalization

Electron spin resonance (esr) hfc values of π-radicals are found to be linearly related to the stabilization energy due to spin delocalization. Application of this relationship to benzyl radicals permits the representation of σ•α values on an energy scale. Mulliken charges in the α- and β-spin systems are found to provide valuable information about factors governing the effects of substituents on spin delocalization in benzyl radicals. These effects can be rationalized by considering four types of spin–spin interactions involving σ- and π-electrons in the α- and β-spin systems. The Mulliken analysis shows that all substituents are stronger π α-acceptors (or weaker π α-donors) at the para position relative to the meta position. Similarly, in the 3 system the meta derivatives are the better acceptors. This may be understood in terms of the excess of π α-spin at the para-carbon and the excess of π β-spin at the meta-carbon. Similar effects are observed in the a framework.

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