Abstract: The present invention relates to novel organometallic compounds for use as a medicine, in particular in photodynamic therapy against various diseases, such as cancer or inflammatory and/or immune disorders. The compounds comprise a central porphyrin or phtalocyanine backbone to which ligand linkers coordinated to at least one transition metal are attached. Eta-5 or eta-6 arenes further bind to the transition metal. According to a preferred embodiment, the compound is a tetranuclear Ruthenium (+II) complex.