Complexone

Complexone is a term used in chemistry to denote a class of ligands that form stable coordination complexes with metal ions. In many European languages the term is used interchangeably with chelating or complexing agents, reflecting their role in binding metal centers through multiple donor atoms. Complexones are characterized by their ability to form cyclic or multidentate structures that stabilize metal ions in solution.

Most complexones bind metals through oxygen and nitrogen donor atoms, creating chelate rings that enhance complex stability. The strength and range of binding depend on the ligand structure, the metal ion, and the solution pH. Stability is described by formation constants, which guide the selection of an appropriate complexone for a given application.

Common examples of complexones include EDTA and its salts (such as disodium EDTA), which are among the most widely used chelating agents. Other well-known complexones include EGTA, DTPA, and NTA. These ligands often act as hexadentate or polydentate chelators, capable of sequestering multiple metal ions.

Applications of complexones span analytical chemistry, environmental science, industry, and medicine. In analytical chemistry, complexometric titration uses complexones to determine metal concentrations, most notably calcium and magnesium in water hardness tests. In water treatment and industrial processes, they prevent precipitation of metals and keep ions in solution. In medicine and laboratory research, chelation therapies and metal ion stabilization exploit complexones to bind specific metals.

Safety and handling considerations vary by compound and context; many complexones are widely used in consumer products, laboratories, and industry, but proper handling, disposal, and regulatory compliance are advised. See also chelation, chelating agent, and complexometric titration.