Core-shell magnetic nanoparticles deliver singlet oxygen for mild oxidations: rechargeable, removable, reusable

Singlet oxygen is a useful reactive species. In addition to its role in photodynamic therapy, a variety of synthetically useful reactions can be carried out using singlet oxygen generated by photosensitization. In this work, we present a novel approach for synthetic applications, where singlet oxygen can be generated both via photosensitization and by thermal cycloreversion reaction of a singlet oxygen storage/photo-sensitizer compound on nanoparticles. With this goal in mind, a BODIPY photosensitizer-pyridone conjugate was covalently tethered to silica-iron oxide core-shell nanoparticles. The modified nanoparticles serve as singlet oxygen sources through photosensitization of the BODIPY core, or alternatively, once the pyridone module is transformed into an endoperoxide, they can be used as a chemical source of singlet oxygen under mild conditions in the dark. The nanoparticle-based agent can easily be recovered with a magnet and can be reused repeatedly. We expect ready and convenient availability of singlet oxygen to broaden the scope of reactions for this reactive oxygen species.