1,4,7-Trimethyl-1,4,7-triazacyclononane is the aza-crown ether with the formula (CH<sub>2</sub>CH<sub>2</sub>NCH<sub>3</sub>)<sub>3</sub>. This colorless liquid is the N-methylated derivative of triazacyclononane (TACN), a face-capping tridentate ligand that is popular in coordination chemistry.
Although TACN is known for forming 2:1 "sandwich" complexes with many metal ions, corresponding 2:1 complexes of Me<sub>3</sub>TACN are only known for Ag<sup>+</sup>, Na<sup>+</sup>, and K<sup>+</sup>. This effect is mainly due to the greater bulk of Me<sub>3</sub>TACN, which requires ions with a larger ionic radius to accommodate two ligands.
Several related derivatives have been prepared with diverse substituents on nitrogen.