demetallation

Demetallation is the chemical or biological process by which a central metal ion is removed from a complex, compound, or material. It contrasts with metallation, the incorporation of a metal into a structure. The term is used across chemistry, biochemistry, and materials science to describe loss of metal from coordination spheres, porphyrins, enzymes, or catalysts. Demetallation can be driven by changes in pH, redox conditions, or the presence of strong chelating agents, and may result in a metal-free ligand or in an apo-structure in biology.

In coordination chemistry and pigment chemistry, demetallation often occurs when the metal–ligand bond becomes unstable: for example, acidic hydrolysis of metalloporphyrins such as chlorophyll, where Mg2+ is removed to form pheophytin, or metal removal from other porphyrins under chelating conditions. In catalysis and materials science, demetallation refers to leaching or deactivation where active metal centers disassociate from supports or frameworks, undermining performance.

In biology, demetallation can deactivate metalloproteins or apoenzymes, either accidentally under stress or as part of turnover and metal homeostasis. The loss of metal ions such as iron, zinc, or copper can alter structure and function, and in some systems is followed by metal re-association processes during maturation or repair. Detection and study of demetallation employ spectroscopy, mass spectrometry, and elemental analysis, often with monitoring of activity changes.