Synthesis and Characterization of a Luminescent Cyclic Poly(ethylene oxide)-Polypyridyl Ruthenium Complex

We report the synthesis of a macrocyclic poly(ethylene oxide) (PEO) connected by one [Ru(bpy)3]2+ unit (where bpy = 2,2′-bipyridine), a photoactive metal complex that provides photosensitivity and potential biomedical applications to this polymer structure. The PEO chain provides biocompatibility, water solubility, and topological play. The macrocycles were successfully synthesized by copper-free click cycloaddition between a bifunctional dibenzocyclooctyne (DBCO)-PEO precursor and 4,4′-diazido-2,2′-bipyridine, followed by complexation with [Ru(bpy)2Cl2]. The cyclic product accumulated efficiently in MCF7 cancer cells and exhibited a longer fluorescence lifetime than its linear analogue, likely due to differences in the accessibility of the ligand-centered/intraligand states of Ru polypyridyls in both topologies.