Syntheses, Structures, and Ion-Exchange Properties of the Three-Dimensional Framework Uranyl Gallium Phosphates, Cs₄[(UO₂)₂(GaOH)₂(PO₄)₄]·H₂O and Cs[UO₂Ga(PO₄)₂]

Abstract

The reaction of UO(2)(NO(3))(2).6H(2)O with Cs(2)CO(3) or CsCl, H(3)PO(4), and Ga(2)O(3) under mild hydrothermal conditions results in the formation of Cs(4)[(UO(2))(2)(GaOH)(2)(PO(4))(4)].H(2)O (UGaP-1) or Cs[UO(2)Ga(PO(4))(2)] (UGaP-2). The structure of UGaP-1 was solved from a twinned crystal revealing a three-dimensional framework structure consisting of one-dimensional (1)(infinity)[Ga(OH)(PO(4))(2)](4-) chains composed of corner-sharing GaO(6) octahedra and bridging PO(4) tetrahedra that extend along the c axis. The phosphate anions bind the UO(2)(2+) cations to form UO(7) pentagonal bipyramids. The UO(7) moieties edge-share to create dimers that link the gallium phosphate substructure into a three-dimensional (3)(infinity)[(UO(2))(2)(GaOH)(2)(PO(4))(4)](4-) anionic lattice that has intersecting channels running down the b and c axes. Cs(+) cations and water molecules occupy these channels. The structure of UGaP-2 is also three-dimensional and contains one-dimensional (1)(infinity)[Ga(PO(4))(2)](3-) gallium phosphate chains that extend down the a axis. These chains are formed from fused eight-membered rings of corner-sharing GaO(4) and PO(4) tetrahedra. The chains are in turn linked together into a three-dimensional (3)(infinity)[UO(2)Ga(PO(4))(2)](1-) framework by edge-sharing UO(7) dimers as occurs in UGaP-1. There are channels that run down the a and b axes through the framework. These channels contain the Cs(+) cations. Ion-exchange studies indicate that the Cs(+) cations in UGaP-1 and UGaP-2 can be exchanged for Ca(2+) and Ba(2+). Crystallographic data: UGaP-1, monoclinic, space group P2(1)/c, a = 18.872(1), b = 9.5105(7), c = 14.007(1) A, beta = 109.65(3)(o) , Z = 4 (T = 295 K); UGaP-2, triclinic, space group P, a = 7.7765(6), b = 8.5043(7), c = 8.9115(7) A, alpha = 66.642(1)(o), beta = 70.563(1)(o), gamma = 84.003(2)(o), Z = 2 (T = 193 K).

Binuclear Uranium(VI) Complexes with a “Pacman” Expanded Porphyrin: Computational Evidence for Highly Unusual Bis‐Actinyl Structures

“…For the complexes reported in the experiments, a parallel structure of two uranyl ions connected by oxygen bridges in polynuclear complexes is the most common. [8,14,15,30,33,[83][84][85] Recently, two T-shaped tetrameric cation-cation complexes with pentavalent [10] and hexavalent [11] uranyls have been reported. Additionally, there are some uranyl metallates with the combined Tshaped and parallel polyuranyl structures found in solidstate chemistry, [13,16] which usually exhibit one-to three-dimensional arrangements.…”

Barium uranyl diphosphonates

“…Based on these new structures, the topological relations can be discerned [5] and used as a basis for materials design yielding solids with specific properties: e.g. selective ion-exchange [6][7][8][9][10][11][12], mixed-valency [13,14], ionic conductivity [15][16][17][18][19][20], enhanced fluorescence [21][22][23], magnetic ordering [11,24], non-linear optical properties [12,25], and differential gas absorption [26,27].…”

[Hg5O2(OH)4][(UO2)2(AsO4)2]: A complex mercury(II) uranyl arsenate

“…Of late there has been interest in expanding structural diversity and physico-chemical properties of uranyl phosphates and arsenates through the incorporation of main group elements and transition metals [12][13][14]. One possibility is that the second metal center could display mixed-valence on a stoichiometric level, but this has yet to be observed in compounds in this class.…”