Many main group chalcogenides are useful functional materials with possible applications as, e.g., magnetic or optical materials. Group 14 chalcogenides, i.e., silicium or germanium sulfides, selenides, or tellurides, are particularly interesting in this context. Those compounds often contain alkali metal cations, mostly sodium and potassium. In the Li/Ge/Se system, no compounds had been found so far.

Zhongxiang Zhou and colleagues, Harbin Institute of Technology, China, have synthesized the first ternary lithium germanium selenide, Li₃Ge₃Se₆ (pictured). The team mixed Li metal, Ge powder, and Se powder in a 1:1:2 ratio, placed the mixture into a graphite crucible under an Ar atmosphere, and then sealed the crucible into a silica tube under a high vacuum. The tube was then heated at temperatures up to 850 °C.

The product was characterized using X-ray crystallography as well as infrared (IR), Raman, and UV-Vis spectroscopy. The team found that the structure contains “tunnels” formed by connected LiSe₆ octahedra. Some of these tunnels contain one-dimensional [Ge₄Se₈]_n chains, which consist of [Ge₂Se₆]^6– clusters. The existence of Ge-Ge bonds in these ethane-like clusters was supported by the Raman spectra of the compound. According to the researchers, the previously unknown chain-like structures are a consequence of the space constraints within the tunnels.

• Li₃Ge₃Se₆: The First Ternary Lithium Germanium Selenide with Interesting _∞[Ge₆Se₁₂]_n Chains Constructed by Ethane-like [Ge₂Se₆]⁶– Clusters,
  Guangmao Li, Ni Zhen, Yu Chu, Zhongxiang Zhou,
  Dalton Trans. 2017.
  DOI: 10.1039/c7dt03781c