Detailed electronic structure of a high-spin cobalt(II) complex determined from NMR and THz-EPR spectroscopy

Here we report a combined use of THz-EPR and NMR spectroscopy for obtaining a detailed electronic structure of a long-known high-spin complex, cobalt(II) bis[tris(pyrazolyl)borate]. The lowest inter-Kramers transition was directly measured by THz-EPR spectroscopy, while the energies of higher Kramers doublets were estimated by a recently proposed NMR-based approach. Together, they produced magnetic parameters for a full model that explicitly includes spin–orbit coupling. This approach is applicable to all transition metal ions for which the spin–orbit coupling cannot be treated perturbatively.