Circuits integrating molecular-scale components may ultimately allow the replacement of silicon-based electronics by high speed systems with low energy consumption. Because of the prominent use of magnetization-based information storage technologies in our daily life, Single-Molecule-Magnets (SMM), which are able to interconvert between two states with opposite magnetization directions receive a great deal of attention. In this proposal, we detail a new strategy to reversibly switch such molecular magnetic behavior with light. It relies on a ligand-centered light driven process within a metal complex containing photoswitchable ligands. Such strategy will be efficiently applied to the otherwise light insensitive 4f based SMM systems because their high sensitivity to minute changes in their coordination environment will maximize the impact of the photo-isomerization event on the resulting magnetic behavior.