“…In contrast, Mn 3+ , which is also a non-Kramers ion and for which thermal SCO is now well-established, ,,− switches between the fully unpaired spin quintet and partially paired spin triplet forms; therefore, a considerable ZFS is expected to persist at low temperature. Spin triplet Mn 3+ is generally not common, with about 20 examples at room temperature, ,− and the ZFS interactions have been quantified via the D and E parameters in just two cases. , These studies have however demonstrated that spin triplet Mn 3+ has the highest ZFS parameters for any manganese ion, with D values in the range +15 to +20 cm –1 , while the axially elongated spin quintet form shows small but negative values in the range of −4.5 to −1.2 cm –1 with only a small number of published spin quintet Mn 3+ examples with positive D values, i.e., axial compression of the Jahn–Teller ion. ,− In these examples, the sign and magnitude of the ZFS parameters have been examined in selected examples by Tregenna-Piggott, , Krzystek and Telser, ,− and Duboc and Neese, ,,, who have built on the earlier studies of Gregson in probing the electronic structure . Thermally induced switching to a different spin state in Mn 3+ can therefore be expected to profoundly affect the magnitude and possibly also the sign of D .…”