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

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.