Magnetic properties of hexakis(pyridine N-oxide)cobalt(II) perchlorate

Abstract

The magnetic properties of the title compound have been measured down to 2 K using the Faraday and critical-torque techniques. Agreement has been obtained with literature values at room temperature, but not with a previous study between 1.5 and 20 K using an inductance method. The reason for the discrepancy is not clear. The angular-overlap ligand-field model (a.o.m.) has been used to interpret the results, and the inclusion of the doublet states in the basis set has a marked effect on the nature of the fit obtained. Using the restricted quartet basis set, it is necessary to have the orbital-reduction factor k= 1.10, but a value of k= 1.00 gives the best fit when the complete basis set is used. If ζ is assumed to have the free-ion value (525 cm^–1) and the co-ordinated oxygen is assumed to be sp²-hybridized, then the a.o.m. parameters are found to be approximately e_σ= 4 300 cm^–1 and 2e_πx=e_πy= 1 330 cm^–1. These values agree reasonably well with those obtained for the isomorphous nickel complex. The inclusion of the doublet states in d³ and d⁷ systems is important in trigonal compounds where the ground state is of ⁴A symmetry.