Variable dimensionality in the uranium fluoride 2-methyl-piperazine system: Syntheses and structures of UFO-5, 6, and 7; Zero, one, and two dimensional materials with unprecedented topologies

The hydrothermal syntheses and structures of a new series of organically templated Ulv materials are presented. The materials, UFO-5 (C5N2H14)2(H3O)U 2F13, UFO-6 (C5N2H14)2U2F 12.H2O and UFO-7 (C5N2H14)(H3O)U2F 11, exhibit unprecedented topologies as well as represent 0-D (UFO-5), 1-D (UFO-6), and 2-D (UFO-7) phases. By systematic experimentation and utilizing a composition prism, wherein the reagents including H2O are graphically depicted, we have determined stability regions in which UFO-5, 6, and 7 can be synthesized as phase pure products. In addition, through pH measurements we observe a direct relationship between the acidity of the reaction and the dimensionality of the product. We suggest that the increased acidity facilitates condensation of the molecular uranium units in UFO-5, to produce the 1-D UFO-6 and at higher acidity the 2-D UFO-7. ©1999 Materials Research Society