Molecular-based ferrimagnetic thin films with high critical temperatures (Tc) composed of mixed-valence chromium cyanides were synthesized by means of a simple electrochemical route. The highest Tc was 270 K, obtained for Cr2.12(CN)6. The Tc values were easily controlled by changing the preparation conditions. Moreover, a reversible shift of Tc could be electrochemically induced. As a result of such electrochemical control, these cyanides can be switched reversibly back and forth between ferrimagnetism and paramagnetism. These magnets thus represent materials in which magnetic properties are combined with electrical functions.