We describe the synthesis and characterization of a hydroxylated aza-adamantyl nitroxide radical Z-3, with the solubility in water of 170 mM at room temperature. We find that the hydroxylation has no significant effect on the electronic structure and stability of aza-adamantyl nitroxides. We prepare a series of β-cyclodextrin (β-CD) derivatives which can form stoichiometric 1:1 inclusion complexes with Z-3, to investigate their effects on water solubility and stability of the radical upon complexation. The results indicate that water solubility of Z-3 increases by 1.4 – 3 times, while radical stability somewhat decreases, depending on different β-CD substituents. Overall, sodium disulfobutylether-β-CD shows the best result in complexation with Z-3, providing water solubility > 0.35 mol L‒1, while maintaining stability of the nitroxide radical with a half-life at room temperature of 13.5 days in water.

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