Unstable intermediates. Part XLV. Hyperfine coupling and spin-polarisation for inorganic and organic radicals
Abstract
In order to facilitate comparison of spin-polarisations in a wide range of π-radicals, a new expression (UX) is proposed, to replace the familiar QX-values. The expression UX is defined as the ratio of QX to the isotropic hyperfine coupling, AX, calculated for one electron in the appropriate valence s-orbital for atom X. This ratio, which has been used effectively in describing hybridisation in σ-radicals, has been calculated from electron spin resonance results for a wide range of inorganic and organic π-radicals and is found to follow well defined trends. These lead to empirical generalisations which indicate that spin polarisation is dominated by the valence s-electrons, especially those involved in σ-bonding.