Uranyl peroxide pyrophosphate cage clusters with oxalate and nitrate bridges†
Abstract
Two complex cage clusters built from uranyl hexagonal bipyramids and multiple types of bridges between uranyl ions, U30Py10Ox5 and U38Py10Nt4, were crystallized from aqueous solution under ambient conditions. These are built from 30 uranyl hexagonal bipyramids, 10 pyrophosphate groups, and five oxalate bridges in one case, and 38 uranyl hexagonal bipyramids, 10 pyrophosphate groups, and four nitrate groups in the other. The crystal compositions are (H3O)10Li18K22[(UO2)30(O2)30(P2O7)10(C2O4)5](H2O)22 and Li24K36[(UO2)38(O2)40(OH)8(P2O7)10(NO3)4](NO3)4(H2O)n for U30Py10Ox5 and U38Py10Nt4, respectively. Cluster U30Py10Ox5 crystallizes over a narrow range of solution pH that encourages incorporation of both oxalate and pyrophosphate, with incorporation of oxalate only being favored under more acidic conditions, and pyrophosphate only under more alkaline conditions. Cluster U38Py10Nt4 contains two identical lobes consisting of uranyl polyhedra and pyrophosphate groups, with these lobes linked into the larger cluster through four nitrate groups. The synthesis conditions appear to have prevented closure of these lobes, and a relatively high