triselenide

Triselenide is a term used in inorganic chemistry to indicate species composed of three selenium atoms. In practice, it most commonly refers to the triselenide anion Se3^2−, which occurs in polyselenide salts together with alkali or alkaline earth metals. The name can also be applied to neutral three-atom selenium molecules in theoretical discussions, but such species are not common under ordinary conditions.

Structure and bonding: In salts containing Se3^2−, the anion is described as a short linear or nearly linear Se–Se–Se chain with delocalized bonding and resonance that distributes electron density over the three atoms. Bond lengths and angles can vary with the countercations and the overall lattice environment.

Formation and occurrence: Se3^2− forms in solutions or melts where selenium is reduced in the presence of suitable cations, as part of the broader family of polyselenide ions Se_n^{2−} (n ≥ 2). In many alkali polyselenide systems, Se3^2− coexists with longer chains such as Se4^{2−} or Se5^{2−}, reflecting the dynamic equilibrium among multiple selenium species.

Reactions and properties: These species participate in redox chemistry characteristic of polyselenides and can interconvert among different Se_n^{2−} forms. They are typically colored in solution, and their stability depends on solvent, temperature, and the nature of the countercation.

Applications and significance: The triselenide motif is of interest for fundamental studies of Se–Se bonding and chain formation, and it features in discussions of redox processes in selenium-containing materials. It also has relevance to research on polyselenides in batteries and related technologies.

Safety: Selenium compounds are toxic; appropriate safety measures and handling procedures are essential.