Some Cobalt O Radical Anions

The 59Co hyperfine matrix components must have identical signs in order that the average values match the observed isotropic couplings we assume the signs are negative since the isotropic couplings almost certainly arise from polarization of inner shell s orbitals (see below). 

The SOMO in these radicals is expected from extended Hiickel MO calculations27-29 to be primarily cobalt 3dyz in character. In the Cs symmetry of the radicals, dyz belongs to the a representation and d-hybridization is possible only with dxy. Assuming that such hybridization is negligible, the g-matrix 

Since 3dyz/4s admixture is symmetry-forbidden for these radicals, the Fermi contact contribution to the isotropic coupling, As, must be entirely from spin polarization, 

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