1,4,7-Trimethyl-1,4,7-triazacyclononane is the aza-crown ether with the formula (CH2CH2NCH3)3.

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,[1] corresponding 2:1 complexes of Me3TACN are only known for Ag+,[2] Na+,[3] and K+.

[4] This effect is mainly due to the greater bulk of Me3TACN, which requires ions with a larger ionic radius to accommodate two ligands.

Several related derivatives have been prepared with diverse substituents on nitrogen.