A new I3O93− group constructed from IO3− and IO55− anion units in Cs3[Ga2O(I3O9)(IO3)4(HIO3)]

Abstract

An alkali metal gallium iodate, Cs₃[Ga₂O(I₃O₉)(IO₃)₄(HIO₃)] (CGIO), was synthesized by the traditional hydrothermal method. Interestingly, CGIO revealed a novel I₃O₉³⁻ fundamental building block (FBB) constituted by two IO₃ tetrahedrons and one IO₅ polyhedron through sharing O atoms. The new I₃O₉³⁻ trimer forms a 0D [Ga₂O(I₃O₉)(IO₃)₄(HIO₃)]³⁻ anion cluster together with the [Ga₂O₁₁]¹⁶⁻ dimer and isolated IO₃⁻ units. The UV-vis-NIR diffuse reflectance spectrum of CGIO shows a wide bandgap of 4.05 eV, and the thermal stability could reach above 400 °C. First-principles calculations explicated that the optical properties of CGIO mainly originated from the iodate anion units with a calculated birefringence of 0.04 at 1064 nm.