Electron Paramagnetic Resonance of X-Ray-Irradiated Single Crystals of Potassium Cobalticyanide, K3Co(CN)6

X-ray irradiation of single crystals of undoped diamagnetic potassium cobalticyanide K3Co(CN) has been shown to produce paramagnetic species. The electron paramagnetic spectra indicate that the eight-line hyperfine interactions observed (I = 72for59Co) collapse into one set when the magnetic field is parallel to any one of the three crystallographic axes labeled a, b, or c. The widths of the hyperfine lines vary and the linewidths increase as the values of the nuclear magnetic spin quantum number (MI) decreases. The experimental results have been interpreted in terms of an appropriate spin Hamiltonian to yield the principal values of the axially symmetric g and hyperfine interaction tensor A. The results obtained are g‖ = 2.010 ± 0.005, g⊥ = 2.170 ± 0.005; A‖ = 83.5 ± 2 G, and A⊥ = 26.9 ± 2 G. A theoretical estimate of the g values obtained by using the method described by Pryce leads to the conclusion that the paramagnetic center is most likely due to a species with d7 configuration formed by the odd electron going into a dz2 orbital followed by a weak tetragonal distortion to symmetry D4h of the ensuing structure as the result of the Jahn–Teller effect. An alternative possibility is that the original anion loses a CN group to form a paramagnetic species with symmetry C4v.