1,4,7-Triazacyclononane (TACN) is a cyclic triamine compound with the formula C6H15N3. It serves as a classic tridentate macrocyclic ligand in coordination chemistry, known for its strong affinity for binding to various transition metal ions, particularly copper(II), nickel(II), and zinc(II). Its structure provides a pre-organized cavity for metal coordination. The primary application of TACN and its derivatives is in the field of materials science and supramolecular chemistry. It is a fundamental building block for constructing macrocyclic and cage-like complexes used in catalysis, molecular recognition, and as models for metalloenzyme active sites. Functionalized TACN derivatives are key precursors for creating advanced adsorbents, separation materials, and functional molecular devices based on host-guest chemistry. Beyond its role as a material precursor, TACN is also a valuable synthetic intermediate in organic chemistry for the preparation of more complex polyamine ligands and macrocycles. Its properties as a strong organic base and metal chelator make it useful in various research contexts.