Although the signal intensities differ, the LS species exhibit similar g values and hyperfine splitting for all complexes, where an eight-line hyperfine splitting on gz, due to the interaction of the unpaired electron with the Co II nucleus (I = 7/2), is visible (Figure , see Table for simulation parameters). The 10 K EPR spectra (Figure ) span a very broad field range, indicating significant magnetic anisotropy in the HS state, for which two distinct sets of signals are visible in all three complexes. Although the transition at low fields occurs at the same effective g value (geff = 7.9, only 2 significant figures are given due to the broadness of the signal) in all complexes, the high-field signals are remarkably dependent on the nature of the ligand. The signal at geff = 7.9 can only arise from a transition in the Ms = ± 3/2 manifold, characterized by gz > 2.5, demonstrating that that the zero-field splitting term D is negative (see also ESI). EPR spectra of frozen solutions (Figure ) were broadly similar to those of polycrystalline samples, showing that no coupling of the complexes occurs in the solid state, presumably due to the steric bulk of the ligands that prevents close approach of the Co II ions.