Multidentát

Multidentát, also known as multidentate in English, refers to ligands in coordination chemistry that can bind to a metal center through multiple donor atoms. The denticity, the number of donor sites that coordinate to the metal, can range from two (bidentate) to several; common categories include bidentate, tridentate, tetradentate, and hexadentate. Monodentate ligands bind through a single atom, whereas multidentát ligands form several coordination bonds, often creating chelate rings or macrocycles that affect complex properties.

In practice, multidentát ligands can either bind a single metal center at multiple sites (chelation) or bridge two or more metal centers to form polynuclear complexes. The chelate effect, a tendency for chelate-containing complexes to be more thermodynamically stable than similar complexes with equivalent monodentate donors, is a key consequence of multidentát binding.

Common examples include ethylenediamine (en), a classic bidentate ligand; terpyridine, which is tridentate; and ethylenediaminetetraacetic acid (EDTA), a hexadentate ligand that can bind through six donor atoms. Macrocyclic ligands such as porphyrins and phthalocyanines coordinate through several nitrogens in a rigid ring system, often acting as tetradentate or higher dentate ligands. Crown ethers and related polyether ligands also coordinate metal ions via multiple donor oxygens, though their binding motifs are sometimes described within broader supramolecular contexts.

Applications span catalysis, bioinorganic chemistry, and medicine. EDTA is widely used to sequester metal ions in analytical chemistry and chelation therapy, while natural multidentate ligands play central roles in metalloproteins and enzyme active sites.