Aza-crown ether

In organic chemistry, an aza-crown ether is an aza analogue of a crown ether (cyclic polyether). That is, it has a nitrogen atom (amine linkage, −NH− or >N−) in place of each oxygen atom (ether linkage, −O−) around the ring. While the parent crown ethers have the formulae (CH₂CH₂O)_n, the parent aza-crown ethers have the formulae (CH₂CH₂NH)_n, where n = 3, 4, 5, 6. Well-studied aza crowns include triazacyclononane (n = 3), cyclen (n = 4), and hexaaza-18-crown-6 (n = 6).

Selected aza-crowns and their complexes
1,4,7-Trimethyl-1,4,7-triazacyclononane, a tridentate ligand used in coordination chemistry.
Cyclam is a tetraaza crown ether with alternating (CH₂)₂ and (CH₂)₃ linkers between amine centers.
Plerixafor, a derivative of cyclam, is used to treat lymphoma and multiple myeloma.
2.2.2-Cryptand is an aza-crown of the mixed ether-amine variety.

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