Successive Crystallization of Organically Templated Uranyl Sulfates: Synthesis and Crystal Structures of [pyH](H3O)[(UO2)3(SO4)4(H2O)2], [pyH]2[(UO2)6(SO4)7(H2O)], and [pyH]2[(UO2)2(SO4)3]

Three new uranyl sulfates, [pyH](H3O)[(UO2)3(SO4)4(H2O)2] (1), [pyH]2[(UO2)6(SO4)7(H2O)] (2), and [pyH]2[(UO2)2(SO4)3] (3), were produced upon hydrothermal treatment and successive isothermal evaporation. 1 is monoclinic, P21/c, a = 14.3640(13), b = 10.0910(9), c = 18.8690(17) A, β = 107.795(2), V = 2604.2(4) A3, R1 = 0.038; 2 is orthorhombic, C2221, a = 10.1992(8), b = 18.5215(14), c = 22.7187(17) A, V = 4291.7(6) A3, R1 = 0.030; 3 is orthorhombic, Pccn, a = 9.7998(8), b = 10.0768(8), c = 20.947(2) A, V = 2068.5(3) A3, R1 = 0.055. In the structures of 1 and 2, the uranium polyhedra and SO4 tetrahedra share vertices to form 3∞[(UO2)3(SO4)4(H2O)2]2− and 3∞[(UO2)6(SO4)7(H2O)]2− frameworks featuring channels (12.2 × 6.7 A in 1 and 12.9 × 6.5 A in 2), which are occupied by pyridinium cations. The structure of 3 is comprised of 2∞[(UO2)2(SO4)3]2− layers linked by hydrogen bonds donated by pyridinium cations. The compounds 1–3 are formed during recrystallization processes, in which the evaporation of mother liquor leads to a stepwise loss of hydration water.