We analyze here the nuclear motion during the nonadiabatic dynamics simulations, focusing on the motion involving the central iron atom and the directly coordinating ligand atoms. The evolution of the six different Fe-N bond lengths during the dynamics is displayed in Figure (a/b) (blue curves) along with the reference bond length at the Franck-Condon geometry (red line). For set A, the average Fe-N bond lengths stays close to the reference values at the Franck-Condon geometry (Figure ). This is a direct consequence of the MLCT electronic states that control this simulation. These states involve an excitation from a non-bonding t 2g orbital of the d 6 iron configuration to the π system of the organic ligands, leaving the bonding between the iron center and its ligating nitrogen atoms unaffected. In addition, Figure (a) shows the average Fe-N bond distances at the geometries where intersystem crossing occurs (green line). As can be seen, also during intersystem crossing the Fe-N bond lengths remain nearly constant. By contrast, in the simulation using set B, large displacements of the average Fe-N bond lengths along the trajectories are visible with respect to their Franck-Condon reference (Figure ). This is the result of populating 1 MC and 3 MC states. MC states of closed-shell iron(II) compounds involve the excitation of an electron from a nonbonding t 2g orbital to an antibonding e * g orbital, which directly affects the metal-ligand bond lengths. The changes in the Fe-N bond lengths are up to 0.10-0.15 Å, a typical value for hexaaza iron(II) compounds. Additionally, also during intersystem crossing, some Fe-N bonds display pronounced differences of up to 0.05 Å compared to the Franck-Condon values. These differences are likely due to the admixture of MC character to the set B trajectories (recall Figure (f)). In general, there is substantial motion required to reach intersystem crossing geometries as is shown by the superposition of all intersystem crossing geometries of the set B simulation in Figure (c).