Copper and silver heterometallic iodoantimonates: structure, thermal stability, and optical properties†

Seven heterometallic iodoantimonates with the general formula (Cat)₂{[Sb₂M₂I₁₀]} (M = Cu(I) (1–6), Ag(I) (7)) were prepared. X-ray diffraction data indicate that these compounds are the first Sb(III) representatives of the structural type previously known only for heterometallic iodobismuthates(III). In 3 and 4, halogen-substituted cations form halogen bonds with the heterometallic halometalate chain. 1–7 show prominent thermal stability. The estimated optical band gaps lie between 2.16 and 2.40 eV. As in heterometallic iodobismuthates, incorporation of Cu⁺ rather than Ag⁺ provides a much lower band gap.