Neutron diffraction study of RbHSeO₄and NH₄HSeO₄single crystals

New Vanadium Selenites: Centrosymmetric Ca2(VO2)2(SeO3)3(H2O)2, Sr2(VO2)2(SeO3)3, and Ba(V2O5)(SeO3), and Noncentrosymmetric and Polar A4(VO2)2(SeO3)4(Se2O5) (A = Sr2+ or Pb2+)

“…The most interesting structural feature is that isolated Se 2 O 5 groups are found in the crystal structure. In fact, the Se 2 O 5 group usually acts as a bridging ligand between the MO x polyhedra. − In our effort to find the materials containing this isolated Se 2 O 5 group, only a few compounds, for example, A 2 (Se 2 O 5 ) (A = K + , or NH 4 + ) , or B­(Se 2 O 5 ) (B = alkaline earth metals or Pb 2+ ), − could be found. Thus, A 4 (VO 2 ) 2 (SeO 3 ) 4 (Se 2 O 5 ) (A = Sr 2+ or Pb 2+ ) are very rare examples in the solid-state oxide materials that possess an isolated Se 2 O 5 group.…”

Selenium Oxoanion Compounds of Palladium(II)

“…MSe 2 O 5 (M = Pb, Cd, Mn) and Cr 2 (Se 2 O 5 ) 3 are also known and have been characterized by vibrational spectroscopy . The ammonium salt of diselenite, (NH 4 ) 2 Se 2 O 5 , has been studied by neutron diffraction and shown to undergo a phase transition at 312 K. − Despite the presence of two lone-pairs of electrons on the diselenite anion, most compounds are centrosymmetric; notable exceptions include LiFe(Se 2 O 5 ) 2 , Nb 2 Se 4 O 13 , Nd 2 (Se 2 O 5 ) 3 ·H 2 SeO 3 ·2H 2 O, and In 2 (Se 2 O 5 ) 3 . Small second-harmonic generation responses have been observed for the frequency-doubling of 1064 nm light by In 2 (Se 2 O 5 ) 3 .…”

Synthesis and Crystal Structures of Hydrogen Monofluorophosphates with N-containing Organic Cations. The Influence of Fluorine on their Hydrogen Bond SystemsDedicated to Professor Dieter Naumann on the Occasion of his 60th Birthday

“…Hydrogen-bonded chains have also been observed in the hydrogen sulfates and selenates of larger cations: Rb ϩ [17,18] and Cs ϩ [19,20]. [C(NH 2 ) 3 ]HSO 4 [21] also forms chains of HSO 4 tetrahedra.…”