Turning to the Mössbauer parameters of energetically relevant configurations, see Figure , it is clear that IS3, HS3 and LS2 behave similarly. This is not surprising given their similar electronic structures at the iron atom; the unpaired electrons on the ring have a limited influence on the Mössbauer parameters. The isomer shifts of the three IS configurations lie within the uncertainty range of the calibration study, which is consistent with their nearly identical structural parameters. Their quadrupole splitting values differ more significantly, which is expected due to the different orbital occupations and hence different symmetries of the electric field gradient. For A 2+ /B, the electronically distinct configurations LS1/LS1 and HS1, respectively, fall close to the IS3 reference value. For B, the HS2 configuration arising from the intramolecular redox event has a clearly distinguishable Mössbauer signature.