polyiodinen

Polyiodine refers to a class of chemical compounds containing chains or networks of iodine atoms. These structures are formed when diatomic iodine molecules (I2) interact with iodide ions (I-) or other polyiodide species. The most common and simplest polyiodine species is the triiodide ion, I3-. This ion consists of a central iodine atom bonded to two iodide ions. The structure of the triiodide ion is linear.

Polyiodine species can exist in various forms, with varying numbers of iodine atoms and different charge states. For example, I5-, I7-, and I9- ions have been characterized. These larger polyiodine ions typically adopt more complex geometries, often with linear or slightly bent arrangements of iodine atoms. The stability of these species depends on the specific structure and the surrounding chemical environment.

Polyiodine compounds are often formed in solutions containing iodine and iodide salts. They play a crucial role in various chemical processes, including analytical chemistry. For instance, the starch-iodine test, used to detect the presence of starch, relies on the formation of a deep blue-black complex between starch and polyiodine species, primarily triiodide. The intense color arises from charge transfer within the polyiodine-starch complex. In some cases, polyiodine compounds can also be encountered in solid-state materials, forming extended frameworks.