Uranyl Titanate Silicates: Syntheses, Structures, and Family Relations

Single crystals of four new uranyl titanate silicates were grown from mixed halide fluxes. Cs6(UO2)2Ti3Si5O21 (1) crystallizes in the Cs6(UO2)2Ge8O21 structure type with triclinic space group P1̅ and lattice parameters a = 7.4353(3) Å, b = 7.9228(3) Å, c = 14.6112(6) Å, α = 91.0070(10)°, β = 96.5470(10)°, and γ = 117.6950(10)°; Cs6(UO2)2TiSi8O23 (2) crystallizes in the monoclinic space group P21/m with lattice parameters a = 15.3157(7) Å, b = 14.4660(6) Å, c = 21.8988(10) Å, and β = 110.358(2)°; Cs7[(UO2)­O]3(Ti2.94Si3.06)­O15.5 (3) crystallizes in the hexagonal space group P6/mmm with lattice parameters a = 14.1925(3) Å and c = 4.26090(10) Å; and [Cs2(CsCl)0.07]­[(UO2)­O]­(Ti0.27Si0.73)­O3 (4) crystallizes in the hexagonal space group P6̅m2 with lattice parameters a = 18.3925(9) Å and c = 4.2980(2) Å. (3) and (4) are related to each other and to previously known [Cs6Cs0.71Cl0.71]­[(UO2)3O3(Ge2O7)] through polyhedral insertion. Each compound exhibits yellow–green fluorescence typical of uranyl compounds.