Semi-empirical pi-electron calculations of proton, nitrogen and fluorine hyperfine-coupling constants

The application of the parameterization scheme of Beveridge and Hinze for pi-electron molecular orbital calculations to spin density calculations is examined for a series of radicals including anions derived from pyridine derivatives. substituted styrenes, aromatic cazboxylic acids, benzonitriles and fluoronitrobenzene derivatives and azabenzyl and fluorobenzyl radicals. The method correlates proton hyperfine coupling constants satisfactorily and gives a reasonable correlation of nitrogen coupling constants. The application to fluorine couplings is less satisfactory.