PROTON HYPERFINE SPLITTINGS IN ELECTRON SPIN RESONANCE SPECTRA OF HYDROCARBON IONS - A COMPARISON OF COLPA-BOLTON AND GIACOMETTI-NORDIO-PAVAN RELATIONS

The Giacometti-Nordio-Pavan modification of McConnell's relation between proton hyperfine splittings and spin densities has been shown to reduce to a simpler form than that originally proposed. It has been demonstrated further that the Giacometti-Nordio-Pavan modification should not be regarded as arising from a nearest-neighbor effect. A statistical analysis of the available experimental proton hyperfine splittings from even-alternant hydrocarbon ions indicates, however, that the Colpa-Bolton relation is superior to the Giacometti-Nordio-Pavan relation in explaining the differences between proton splittings in corresponding cation and anion radicals. These results are valid within the framework of Huckel molecular-orbital theory.