The prospect of mastering and exploiting the motion of molecules is a fundamental challenge related to the development of molecular architectures featuring tunable properties. In this context, the ElectroMagnet project aims at developing metal-organic molecular systems for which large amplitude reorganizations can be used to control the spin state of magnetically active metallic centers. According to this strategy, the magnetic state of the metal will be defined by its coordinated ligands whose number can be controlled by electron transfer centered on key organic fragments. The proposed concept relies in particular on the pi-dimerization of viologen cation radicals as the driving force of structural reorganizations.