Electron spin polarization transfer from a nitroxide incarcerated within a nanocapsule to a nitroxide in the bulk aqueous solution

A thioxanthone derivative containing a covalently attached ¹⁵N-labeled nitroxide was incarcerated into an octaacid nanocapsule. Photoexcitation of the thioxanthone chromophore generated electron spin polarization of the nitroxide. This spin polarization of the ¹⁵N-labeled nitroxide was transferred through the walls of the carcerand to a ¹⁴N-labeled nitroxide in external bulk solvent, a process that was directly observed by time-resolved EPR spectroscopy. The efficiency of the communication between the incarcerated guest and molecules in the bulk solvent was shown to be controlled by supramolecular factors such as Coulombic attraction and repulsion between the guest@host complex and charged molecules in the bulk solvent phase.