Pyrophosphate and Methylenediphosphonate Incorporated Uranyl Peroxide Cage Clusters

Six uranyl peroxide cage clusters containing 18-54 uranyl ions, as well as 6-27 pyrophosphate or methylenediphosphonate ligands, have been synthesized and characterized. These uranyl peroxide clusters self-assemble and crystallize from aqueous solutions containing uranyl nitrate, hydrogen peroxide, and pyrophosphate or methylenediphosphonate over a pH range from 5.3 to 8.1. In their structures, uranyl hexagonal bipyramids are linked by bridging peroxide, hydroxide, and pyrophosphate or methylenedisphosphonate ligands. The incorporation of pyrophosphate or methylenedisphosphonate results in several interesting features in the coordination of uranyl ions and the topology of the uranyl peroxide clusters.