The electronic structure of iron in (pseudo-)molecular environments is notoriously complex due to different spin states that are easily energetically accessible within the same oxidation state. Moreover, different oxidation states can be attained readily, including by intramolecular redox events with so-called redox non-innocent ligands. Even within the same oxidation and spin state, details of the electronic structure can differ due to the orbital occupation pattern, which is dictated by the ligand field splitting and thus ultimately the local geometry around the iron ion. For an FeN 4 -system with an iron(II) ion, six electrons are expected to occupy the dorbitals. In addition, the conjugated π-system of the equatorial ligand can play a role by hosting unpaired electrons, either by intramolecular redox events (formally oxidising the iron ion to Fe(III)) or by being in a triplet configuration that couples ferromagnetically or antiferromagnetically with the unpaired electrons of the iron ion.