Hierarchy of structures in the family of amine templated open-framework gallium arsenates

Five new gallium arsenate compounds [C2N2H10][Ga(H2AsO4)(HAsO4)2]·H2O, I; [C2N2H10][Ga(OH)(AsO4)]2, II; [C2N2H10][GaF(AsO4)]2, III; [C3N2H12][Ga(OH)(AsO4)]2, IV; [Ga2F3(AsO4)(HAsO4)]·2H3O, V, have been synthesized under hydrothermal conditions and the structures determined employing single crystal X-ray diffraction studies. All the structures consist of octahedral gallium and tetrahedral arsenate units connected together forming a hierarchy of structures. Thus, one- (I), two- (II and IV) and three-dimensionally (III and V) extended structures have been observed. The Ga–O(H)/F–Ga connectivity in some of the structures suggests the coordination requirements posed by the octahedral gallium in these compounds. The observation of only one type of secondary building unit in the structures of III (SBU-4) and V (spiro-5) is unique and noteworthy. All the compounds have been characterized by a variety of techniques that include powder XRD, IR, and TGA.