Synthesis, structure determination, and infrared spectroscopy of (NpO2)2(SO4)(H2O)4: Prevalence of cation–cation interactions and cationic nets in neptunyl sulfate compounds

The compound (NpO2)2(SO4)(H2O)4 was synthesized by evaporation of a Np5+ sulfate solution. The crystal structure was determined using single crystal X-ray diffraction and refined to an R1=0.0310. (NpO2)2(SO4)(H2O)4 crystallizes in triclinic space group P-1, a=8.1102(7) Å, b=8.7506(7) Å, c=16.234(1) Å, α=90.242(2)°, β=92.855(2)°, γ=113.067(2)°, V=1058.3(2) Å3, and Z=2. The structure contains neptunyl pentagonal bipyramids that share vertices through cation–cation interactions to form a sheet or cationic net. The sheet is decorated on each side by vertex sharing with sulfate tetrahedra, and adjacent sheets are linked together through hydrogen bonding. A graphical representation of (NpO2)2(SO4)(H2O)4 was constructed to facilitate the structural comparison to similar Np5+ compounds. The prevalence of the cationic nets in neptunyl sulfate compounds related to the overall stability of the structure is also discussed.

Graphical abstract(NpO2)2(SO4)(H2O)4 was synthesized by hydrothermal methods and its structure determined. A graphical representation of the compound was constructed to facilitate the structural comparison to similar Np5+ compounds and the prevalence of the cationic nets in neptunyl sulfate compounds related to the overall stability of the structure is discussed.Figure optionsDownload full-size imageDownload as PowerPoint slide