New selenites: hydrothermal syntheses, crystal structures, and characterization of Rb3HGa2(OH)2(SeO3)4, Rb3Ga5(SeO3)8(HSeO3)2·0.5H2O, and RbGa(SeO3)2·H2O.

Three new gallium selenites, Rb3HGa2(OH)2(SeO3)4, Rb3Ga5(SeO3)8(HSeO3)2·0.5H2O, and RbGa(SeO3)2·H2O, have been synthesized by hydrothermal reactions using Rb2CO3, Ga(NO3)3·xH2O, and SeO2 as reagents. Rb3HGa2(OH)2(SeO3)4 consists of unidimensional corner-linked chains of GaO4(OH)2 that are connected by a SeO3 group, whereas Rb3Ga5(SeO3)8(HSeO3)2·0.5H2O and RbGa(SeO3)2·H2O exhibit three-dimensional frameworks consisting of three, mutually perpendicular, eight-membered rings (8-MRs). In all three reported materials, Se(4+) is in an asymmetric coordination environment attributable to the stereoactive lone pair. Ion-exchange reactions, infrared spectroscopy, thermal analysis, elemental analysis, and dipole moment calculations for the reported materials are also presented. Crystal data: Rb3HGa2(OH)2(SeO3)4, orthorhombic, space group Cmca (No. 64), with a = 7.17890(10) Å, b = 18.0925(2) Å, c = 12.6972(2) Å, and Z = 4; Rb3Ga5(SeO3)8(HSeO3)2·0.5H2O, triclinic, space group P-1 (No. 2), with a = 10.7727(2) Å, b = 12.5372(3) Å, c = 12.6952(3) Å, α = 87.210(10)°, β = 85.447(10)°, γ = 72.519(10)°, and Z = 2; RbGaSe2O6·H2O, triclinic, space group P-1 (No. 2), with a = 8.7027(6) Å, b = 9.7622(7) Å, c = 15.3347(14) Å, α = 105.622(4)°, β = 90.210(4)°, γ = 116.385(2)°, and Z = 2.