SpinDensity Distribution in Nitrile Anion Radicals
Abstract
Molecularorbital calculations of the pielectron spin densities in a series of aromatic and aliphatic nitrile anion radicals have been performed using the Hückel—LCAO method and the approximate configurationinteraction correction of McLachlan. Coulomb and resonance integrals for the nitrile group were estimated by comparing calculated spin densities with proton and carbon13 hyperfine splittings obtained from electronspin resonance measurements. The predicted spin densities were in generally good agreement with the experimental results, but for some of the compounds it is impossible to get an exact fit between theory and experiment within the framework of the simple valencetheory calculations if the sigma—pi interaction parameters relating splittings to spin densities are taken as fixed quantities. Semiempirical treatments of the N^{14} and C^{13} splittings in the cyano groups give excellent correlations of the experimental splittings with the calculated spin densities, and estimates have been made of some of the sigma—pi interaction parameters relating to the N^{14} splitting. Polarographic halfwave potentials have also been compared with calculated pielectron energies. A discussion is given of the relation between the spin densities predicted by the valencebond and molecularorbital theories.
 Publication:

Journal of Chemical Physics
 Pub Date:
 December 1962
 DOI:
 10.1063/1.1733108
 Bibcode:
 1962JChPh..37.2795R