Use of alpha hyperfine coupling tensors as a measure of unpaired spin density and free radical geometry

Journal Article · Thu Dec 20 04:00:00 EST 1984 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.447594· OSTI ID:6213153

Bernhard, W A

The dipolar elements (B/sub x/, B/sub y/, B/sub z/) of the ..cap alpha..-hydrogen hyperfine coupling tensor (/sup ..cap alpha../A) are used to calculate unpaired spin density (rho) and bond lengths (R/sub H/) by using the two center dipole equations derived by Gordy (Ref. 1). B/sub z/ is used as a measure of rho in the equation B/sub z/ = Q/sup dip//sub z/ rho with Q/sup dip//sub z/ = 38.7 MHz. The /sup ..cap alpha../H-C bond length of electron gain ..pi.. radicals and alkyl radicals are found to be 0.05--0.10 A shorter than in comparable nonradicals while in electron loss ..pi.. radicals the bond lengths are longer by 0.04--0.09 A. The two center dipole formalism appears to be useful as an analytical method for distinguishing electron loss ..pi.. radicals from electron gain ..pi.. radicals. It is suggested that the isotropic component of /sup ..cap alpha../H hfc is affected by spin density ..beta.. to the /sup ..cap alpha../H of interest, accounting for a significant portion of the variability in Q/sup H//sub CH/ in the McConnel (Ref. 2) equation, /sup ..cap alpha../A = Q/sup H//sub CH/rho.

• Research Organization: Department of Radiation Biology and Biophysics, University of Rochester, Rochester, New York 14642
• OSTI ID: 6213153
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 81:12; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640302* -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
ALKYL RADICALS
ANGULAR MOMENTUM
BOND LENGTHS
COUPLING
DIMENSIONS
HYPERFINE STRUCTURE
INTERACTIONS
LENGTH
MOLECULAR STRUCTURE
PARTICLE PROPERTIES
RADICALS
SPIN
TENSORS