Ligand-Field Calculations on Pseudo-Tetragonal Ni(II) Compounds

Magnetic susceptibility, magnetic saturation, ligand field and EPR measurements are reported for the compounds Ni(5-methyl pyrazole) 4X2, (X = Cl, Br, I). All data are interpreted using ligand-field calculations, yielding parameters D q, D s, D t, B, C, g∥, g⊥,D, ζ∥, ζ⊥, and k. All data fit with a single set of parameters. The zero-field splittings and g values are determined from the magnetic measurements, whereas the excited state splittings are determined from the ligand-field spectra. In studying the relation between the zero-field splitting of the Ni(II) ion and both the spinorbit coupling and spectroscopic energy parameters, a description using an anisotropic spin-orbit coupling gave the most reliable fit. In addition, known ligand-field spectra and D values of Ni (pyrazole) 4X2, (X = Cl, Br, I) were considered. The derived energy parameters of the corresponding pyrazole and 5-methyl pyrazole compounds are very similar.