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.

Copper- and Silver-Containing Heterometallic Iodobismuthates: Features of Thermochromic Behavior

Nine heterometallic iodobismuthates with the general formula Cat₂{[Bi₂M₂I₁₀}] (M = Cu(I), Ag(I), Cat = organic cation) were synthesized. According to X-ray diffraction data, their crystal structures consisted of {Bi₂I₁₀} units interconnected with Cu(I) or Ag(I) atoms through I-bridging ligands, forming one-dimensional polymers. The compounds are thermally stable up to 200 °C. Optical band gaps (E_g), estimated at room temperature via diffuse reflectance measurements, range from 1.81 to 2.03 eV. Thermally induced changes in optical behavior (thermochromism) for compounds 1-9 were recorded, and general correlations were established. The thermal dependence of E_g appears to be close to linear for all studied compounds.