Hyperfine coupling constants and their dependence on charge densities |
| |
Authors: | J.P. Colpa J.R. Bolton |
| |
Affiliation: | Department of Theoretical Chemistry , University of Cambridge |
| |
Abstract: | In paramagnetic aromatic systems the relation between the hyperfine coupling constants a H for the protons and the spin density ρ on the adjacent carbon atom is usually given by the relation a H = -Qρ (McConnell) in which Q is a constant characteristic for the C-H bond. In the paramagnetic ions of aromatic molecules the carbon atoms have in general besides a non-zero spin density also a non-zero excess charge density. If one takes into account both the effect of the spin density ρ and the excess charge density ε on the C-H bond, the following formula is obtained for the proton hyperfine coupling constant: in which Q and K are predicted to be positive constants of the same order of magnitude. Comparison with experimental data gives Q = 31·2 gauss; K = 17 gauss. |
| |
Keywords: | |
|
|