147triazacyclononane

1,4,7-triazacyclononane, commonly abbreviated TACN, is a nine-membered macrocyclic ligand containing three nitrogen atoms at positions 1, 4 and 7 and six methylene groups. The ring is flexible and can act as a tridentate donor, coordinating metal ions through its three secondary amine nitrogens. As a parent structure, TACN serves as a building block for a variety of more complex chelators used in coordination chemistry and radiopharmaceuticals.

In coordination chemistry TACN forms mono- and multidentate complexes with a range of metal ions, including Cu(II), Zn(II), Ni(II), and lanthanides. The pH-dependent protonation state of the ring influences binding, and the nitrogens can be neutral or protonated, affecting complex stability. Derivatization at the nitrogens yields ligands with enhanced denticity and specificity.

Derivatives of TACN are widely employed in medicine and imaging. Notably, the scaffold is central to NOTA-type chelators (1,4,7-triazacyclononane-1,4,7-triacetic acid), in which three carboxylate arms are appended to give strong, kinetically inert chelation of Ga-68 for PET and Cu-64 radiopharmaceuticals. Other functionalized TACN ligands are used for catalysis and environmental chemistry.

Safety and handling follow standard laboratory practices for amines; TACN and its derivatives are generally handled as solids or solutions and can be irritants. The compound is studied primarily in inorganic and medicinal chemistry rather than in bulk chemical production.