Three New Silver Uranyl Diphosphonates: Structures and Properties

The
hydrothermal reaction of uranium trioxide and methylenediphosphonic
acid in the presence of silver nitrate resulted in the formation of
three new uranyl coordination polymers: AgUO2[CH2(PO3)­(PO3H)] (Ag-1), [Ag2(H2O)1.5]­{(UO2)2[CH2(PO3)2]­F2}·(H2O)0.5 (Ag-2), and Ag2UO2[CH2(PO3)2] (Ag-3).
All consist of uranyl pentagonal bipyramids that form two-dimensional
layered structures. Ag-1 and Ag-3 possess
the same structural building unit, but the structures are different; Ag-3 is formed through edge-sharing of F atoms to form UO5F2 dimers. The pH and silver cation have significant
effects on the structure that is synthesized. Raman spectra of single
crystals of Ag-1, Ag-2, and Ag-3 reveal v1 UO22+ symmetric stretches of 816 and 829, 822, and 802 cm–1, respectively. Electronic structure calculations were performed
using the projector augmented wave (PAW) method with density functional
theory (DFT) to gain insight into the nature of bonding and electronic
characteristics of the synthesized compounds. Herein, we report the
syntheses, crystal structures, Raman spectroscopy, and luminescent
behavior of these three compounds.