chelate

Chemical compound whose molecules consist of one or more metal atoms or charged ions joined to chains of organic residues by two or more coordinate (or dative covalent) chemical bonds.

The parent organic compound is known as a chelating agent - for example, EDTA (ethylene-diaminetetra-acetic acid), used in chemical analysis. Chelating agents ‘grip’ the metal ion from several sides at once (six in the case of EDTA), making it extremely unlikely that random movements of any of the coordinating groups lead to a detachment of the entire molecule. This is why they are extremely effective at binding and keeping hold of suitably sized metal ions.

Chelates are used in analytical chemistry, in agriculture and horticulture as carriers of essential trace metals, in water softening, and in the treatment of thalassaemia by removing excess iron, which may build up to toxic levels in the body. Metalloproteins (natural chelates) may influence the performance of enzymes or provide a mechanism for the storage of iron in the spleen and plasma of the human body.