Organic Functionalization of Uranyl Peroxide Clusters to Impact Solubility.

Benzene-1,2-diphosphonic acid (Ppb) was introduced into the uranyl peroxide cluster system, resulting in three Ppb-functionalized uranyl peroxide clusters, (UO2)20(O2)20(C6H4P2O6)1040- (U20Ppb10), (UO2)26(O2)33(C6H4P2O6)638- (U26Ppb6), and (UO2)20(O2)24(C6H4P2O6)632- (U20Ppb6). Dissolution experiments were performed for the potassium salts of U20Ppb10 and U26Ppb6, which revealed the capacity of U20Ppb10 to dissolve in the organic solvent dimethyl sulfoxide (DMSO). Unlike U20Ppb10, the K salt of U26Ppb6 did not dissolve in DMSO but was more soluble in water, perhaps due to the lower proportion of Ppb ligands in its structure. In this work, U20Ppb10 and U20Ppb6 formed as potassium salts and both adopt the fullerene topology of previously reported U20. U20 contains 20 uranyl peroxide units and encapsulates 12 Na cations. It is not possible for unfunctionalized U20 to incorporate 12 K cations owing to space constraints, as is the case in the new clusters reported here. Transformation of U20Ppb10 in water over time to produce U24 was observed, possibly owing to its ability to incorporate K cations, which have been associated with the formation of U24.