For model 1 and its variants with axial ligands, at least intermediate quadrupole splittings are predicted, which are higher than would be expected for the D1 doublet. As discussed above, quadrupole splittings cannot be predicted reliably for electronic structures where multireference character can be expected, as is the case for e.g. models 1, 1 Large and 2 Large with square-planar Fe(II) sites, or models with axial O 2 ligands, whereas the isomer shift can be predicted reliably.