SYNTHESES AND CRYSTAL STRUCTURES OF TWO NOVEL GALLOARSENATES: Cs2Ga3(AsO4)2(As3O10) and Cs(GaOH)2H(AsO4)2. Kuan-Jiuh Lin and Kwang-Hwa Lii, Institute of Chemistry, Academia Sinica, Taipei, Taiwan, R.O.C
Microporous aluminophosphates have been extensively studied because of their potential sorption and catalytic properties. Numerous gallophosphates have also been synthesized to discover new open framework materials. The replacement of aluminum by gallium has yielded both novel structure types and phases that are analogous to known aluminophosphates and aluminosilicates. In contrast to the phosphates, much less galloarsenates have been reported. This poster presents the results of our exploratory synthesis and single-crystal X-ray structures of two novel galloarsenates, Cs2Ga3(AsO4)2(As3O10) and Cs(GaOH)2H(AsO4)2.
Crystals of Cs2Ga3(AsO4)2(As3O10) were grown from a flux. It crystallizes in the monoclinic space group C2/c with a= 27.0360(7), b= 5.1074(2), c= 12.5112(4) Å, [[beta]]= 93.86(1)deg., V= 1723.7 (2) Å3, Z= 4, R= 0.035 for 1486 independent reflections with I > 3.0 [[sigma]](I). The framework consists of GaO6 octahedra, GaO5 square pyramids, AsO4 tetrahedra and the very rare triarsenate groups As3O10 which together serve as building units to form an intersecting tunnel structure with the Cs+ cations located at the intersections of tunnels. Crystals of Cs(GaOH)2H(AsO4)2 were grown by a high-temperature, high-pressure hydrothermal method. It crystallizes in the monoclinic space group P21/c with a= 4.6479(4), b= 6.051(1), c= 16.457(2) Å, [[beta]] = 92.99(1)deg., V= 462.2(1) Å3, Z= 2, R = 0.045 for 929 independent reflections with I > 2.5 [[sigma]](I). The structure contains infinite chains of GaO6 octahedra sharing trains edges. These chains are connected by arsenate groups to form layers in the ab-plane. The layers are linked by Cs+ cations and hydrogen bonding.