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

摘要

The dipolar elements (Bx,By,Bz) of the agr;hyphen;hydrogen hyperfine coupling tensor (agr;A) are used to calculate unpaired spin density (rgr;) and bond lengths (RH) by using the two center dipole equations derived by Gordy (Ref. 1).Bzis used as a measure of rgr; in the equationBz=Qdipzrgr; withQdipz=38.7 MHz. Theagr;Hhyphen;C bond length of electron gain pgr; radicals and alkyl radicals are found to be 0.05ndash;0.10 Aring; shorter than in comparable nonradicals while in electron loss pgr; radicals the bond lengths are longer by 0.04ndash;0.09 Aring;. The two center dipole formalism appears to be useful as an analytical method for distinguishing electron loss pgr; radicals from electron gain pgr; radicals. It is suggested that the isotropic component ofagr;H hfc is affected by spin density bgr; to theagr;H of interest, accounting for a significant portion of the variability inQHCHin the McConnel (Ref. 2) equation,agr;A=QHCHrgr;.