Anisotropy of the Carbon-13 and Proton Hyperfine Coupling Constants in Organic Radicals

Publisher Website
Google Scholar
Abstract
A theoretical study of the anisotropy of the carbon‐13 and proton hyperfine coupling constants in organic radicals is presented in terms of a spin density formulation which uses the generalized product approximation specialized to valence‐bond wavefunctions. Both isotropic and anisotropic components of the 13C and 1H hyperfine coupling tensors are obtained for the methyl and ethyl radicals with inclusion of all valence electrons. Theoretical results for the methyl radical are also based on spin densities from self‐consistent‐field (SCF) molecular‐orbital theory in the approximation of intermediate neglect of differential overlap and from nonempirical spin‐restricted SCF calculations with configuration interaction. The calculated results are compared with the available experimental data, and they indicate that inclusion of contributions from the σ‐electron framework is essential. But in contrast to isotropic hyperfine coupling constants, components of the anisotropic hyperfine tensor are relatively insensitive to the spin density distribution. Factors which are also discussed are the importance of variation of the effective nuclear charge, radical geometry, contributions from inner shells, and off‐diagonal elements of the spin density matrix.

This publication has 44 references indexed in Scilit: