A Self-Assembled Metallomacrocycle Singlet Oxygen Sensitizer for Photodynamic Therapy

Although metal‐ion‐directed self‐assembly has been widely used to construct a vast number of macrocycles and cages, it is only recently that the biological properties of these systems have begun to be explored. However, up until now, none of these studies have involved intrinsically photoexcitable self‐assembled structures. Herein we report the first metallomacrocycle that functions as an intracellular singlet oxygen sensitizer. Not only does this Ru2Re2 system possess potent photocytotoxicity at light fluences below those used for current medically employed systems, it offers an entirely new paradigm for the construction of sensitizers for photodynamic therapy. The oxygen (macro)cycle: In cellulo studies show that a self‐assembled Ru2Re2 metallomacrocycle possesses potent photocytotoxicity through singlet oxygen sensitization (see figure).