Cu clusters and chalcogenchalcogen bonds in various copper polychalcogenides

Several new barium copper polychalcogenides were discovered during the last years. Their structures were all unprecedented, displaying a variety of different cationic copper clusters along with dimeric, trimeric, or infinite anionic polychalcogen units. Te22− pairs, bent V-shaped Te32− trimers, linear, hypervalently bonded Se34− trimers, and infinite, almost linear chains of Te atoms occur in BaCu6−xSTe6, BaCu6−xSeTe6 and Ba3Cu14−xTe12, Ba6.76Cu2.42Te14, Ba2(Cu,Ag)4Se5 and Ba2Cu4−xSeyTe5−y, respectively.All Cu-based examples exhibit significant copper deficiencies, and are thus p-doped semiconductors or metals. On the other hand, the few isostructural representatives with silver and gold, namely Ba2Ag4Se5 and Ba7Au2Te14, are stoichiometric materials. The Cu deficiencies are deduced to arise from the tendency to mixed-valent compounds.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (96 K)Download as PowerPoint slideHighlights► A series of polychalcogenides exhibit various anionic, in part nonclassical bonded SeSe and TeTe oligomers as well as infinite chains. ► The same compounds contain cationic Cu atom clusters with Cu deficiencies of different extent. ► Seemingly analogous Ag and Au chalcogenides are without Ag or Au deficiencies.