demetalation

Demetalation is the process of removing metal ions or a central metal atom from a compound, complex, or material. In coordination chemistry and organometallic chemistry it describes the loss of the metal center from a ligated framework, yielding the free ligand or an apo-metal complex. In biochemistry and cell biology it refers to the removal of metal cofactors from metalloproteins, producing apoenzymes, which often alters activity and stability. In materials science and metallurgy, demetalation describes the leaching or dissolution of metals from alloys, catalysts, or composite materials, or from corrosion products, under conditions such as acidic environments or elevated temperatures.

Mechanisms of demetalation vary by system. Acid-promoted demetalation involves protonation that weakens metal–ligand bonds. Chelation by strong ligands (for example, EDTA or citrate) can sequester the metal and drive its removal. Redox-driven demetalation occurs when a change in oxidation state reduces the metal’s affinity for its ligands. Hydrolytic or oxidative processes can also release metal ions from complexes, porphyrin rings, or mineral matrices.

Contexts and implications. In porphyrin chemistry, demetalation of metalloporphyrins is a routine transformation used to obtain free-base porphyrins. In biology, demetallation can deactivate or modify metalloproteins and affect metal homeostasis. In catalysis and materials engineering, demetalation contributes to catalyst deactivation and metal leaching, impacting longevity and environmental mobility of metals. Detection and quantification typically rely on ICP-MS or atomic absorption spectroscopy for metal content, along with UV-Vis or spectroscopic methods to monitor metal-containing species.

See also: demetallation, dealloying, metal ion leaching, chelation therapy.