BaZn₂(HAs₂O₇)AsO₄:  A Novel Barium Zinc Arsenate Containing Zn₄O₁₆ Clusters and Hydrogen Diarsenate Groups

Abstract

A novel barium zinc arsenate has been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, IR spectroscopy, and thermogravimetric analysis. Being the first compound in the Ba−Zn−AsV−O system, the structure contains tetramers of ZnO5 square pyramids which have not been seen in the Zn/X/O lattices, where X = P or As. Diffraction measurements were performed on a CCD area detector system. Crystal data: BaZn2(HAs2O7)AsO4, monoclinic, P21/c, a = 11.5773(3) Å, b = 8.0975(2) Å, c = 10.0511(3) Å, β = 93.862(2)°, Z = 4. The framework consists of Zn4O16 cluster units, AsO4 tetrahedra, and HAs2O7 groups. The cluster units, each formed by four ZnO5 pyramids sharing alternate corners and edges, are cross-linked by AsO4 tetrahedra to form an infinite sheet [Zn2AsO4]. The sheets are held together via HAs2O7 groups to form a three-dimensional network. Barium cations are located in the cavities surrounded by HAs2O7 anions. BaZn2(HAs2O7)AsO4 is the first structurally characterized compound which contains the hydrogen diarsenate group, HAs2O7 2-.

Insights into Formation Conditions, Crystal Structures, and Thermal Behavior of Hydrous and Anhydrous Barium Arsenates

“…Such partly deprotonated diarsenate units in crystalline solids are scarcely described whereas a plethora of fully deprotonated diarsenate units has been known for a long time. The only other example of a (HAs 2 O 7 ) 3– group reported so far is present in the crystal structure of BaZn 2 (HAs 2 O 7 )­AsO 4 . The (HAs 2 O 7 ) 3– diarsenate anions in the two structures show similar bond lengths and angles.…”

Novel Gallium Phosphate Framework Encapsulating Trinuclear Mn3(H2O)6O8 Cluster: Hydrothermal Synthesis and Characterization of Mn3(H2O)6Ga4(PO4)6

“…We have been interested in the synthesis of novel open-frameworks of transition metal phosphates and arsenates by incorporating both inorganic and organic cations as structure-directing reagents . Because not many manganese-substituted gallium phosphates are known, we thought of exploring the possibility of synthesizing new phases in the system.…”