Photosensitive molecular switch, having a chelate ligand, a metal ion bonded coordinatively to the chelate ligand, the metal ion being selected from the group of metal ions consisting of Mn2+, Mn3+, Fe2+, Fe3+, Co2+ and Ni2+, a photochromic system which is bonded covalently to the chelate ligand and can be isomerized by irradiation, this system being bonded coordinatively to the metal ion in one configuration and not bonded to the metal ion in the other configuration.