Synthesis, structure and characterization of M(IO3)2(HIO3) (M = Ca, Sr) as new anhydrous alkaline earth metal bis-iodate hydrogeniodate compounds

Abstract

Two new metal iodates, namely, M(IO₃)₂(HIO₃) (M = Ca, Sr), were successfully synthesized by the hydrothermal method, and their structures were determined by single-crystal X-ray diffraction. They were found to be isostructural, and crystallized in the monoclinic space group P2₁/n with the lattice parameters: a = 6.9647(14) Å, b = 15.719(3) Å, c = 7.2042(14) Å, β = 92.76(3)°, Z = 4 for Ca(IO₃)₂(HIO₃), and a = 7.0697(14) Å, b = 15.986(3) Å, c = 7.3802(15) Å, β = 93.13(3)°, Z = 4 for Sr(IO₃)₂(HIO₃). The structure featured a [HIO₃]·[IO₃]⁻ complex with strong intermolecular interactions, and it was composed of [IO₃]⁻ anions and [HIO₃]·[IO₃]⁻ complexes interconnected by Ca²⁺ or Sr²⁺ cations. The two compounds were characterized by X-ray diffraction, IR and Raman spectroscopies, UV–Vis diffuse reflectance spectroscopy, thermogravimetry and differential scanning calorimetry as well as by theoretical calculations.