polyaminocarboxylic

Polyaminocarboxylic acids are a class of ligands in coordination chemistry characterized by multiple amine groups and carboxylate groups arranged to bind metal ions. They act as chelating agents, meaning they form complexes in which a single ligand wraps around a metal center with several donor atoms, increasing complex stability. The class includes both acyclic ligands (for example, ethylenediaminetetraacetic acid, EDTA) and macrocyclic ligands (for example, DOTA and related compounds). Common members are EDTA, DTPA (diethylenetriaminepentaacetic acid), EGTA (ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid), and NTA (nitrilotriacetic acid). They typically bind metal ions via nitrogen atoms from amine groups and oxygen atoms from carboxylate groups, often in multiple coordination sites. The resulting metal–ligand complexes are among the most stable and are sensitive to pH due to the protonation states of the amines and carboxylates.

Applications span medicine, chemistry, and industry. In medicine, polyaminocarboxylates are used for chelation therapy to treat metal poisoning and as chelating agents in radiopharmaceuticals for imaging and therapy. In the laboratory, they serve to sequester metal ions and to purify proteins through affinity methods (for example, Ni-NTA for His-tagged proteins). In industry, they act as sequestering agents to remove metal ions from solutions, aid in cleaning, and act as scale inhibitors.

Safety and environmental considerations include the potential for essential metal depletion and possibly nephrotoxicity at high doses, so use is controlled and targeted. The field continues to develop new ligands with improved selectivity and stability for specific metals.