Uranyl-Peroxide Clusters Incorporating Iron Trimers and Bridging by Bisphosphonate- and Carboxylate-Containing Ligands.

A hybrid uranium-iron cage nanocluster, [(UO2)24(FeOH)24(O2)24(PO4)8(CH(COO)(PO3)2)24]96- (U24Fe24), was synthesized using bridging ligands containing bisphosphonate and carboxylate groups. U24Fe24 contains six tetramers of uranyl hexagonal bipyramids and eight iron trimers, each of which consists of three corner-sharing Fe3+ octahedra and is stabilized by in situ formed phosphate and 2,2-bis(phosphonato)acetate (C2P2) groups. Tetramers and trimers are bridged by 24 C2P2 groups into a cage cluster. Crystals of U24Fe24 present a paramagnetic-like behavior. X-ray scattering showed that U24Fe24 forms in the reactant solution prior to crystallization and is stable upon dissolution in water.