Hexaaza and octaaza macrocycles with 2-hydroxy-3,5-dimethylbenzyl pendant arms

Abstract

New 18-membered hexaaza (3 and 4) and 24-membered octaaza (7 and 8) macrocycles with 2-hydroxy-3,5-dimethylbenzyl pendant arms have been prepared via a Mannich type reaction of the corresponding macrocycles [(1 and 2) and (5 and 6) respectively] with 2,4-dimethylphenol in the presence of methanal in a methanolic solution. X-Ray structure analysis shows the tetramethyl substituted hexaaza macrocycle with 2-hydroxy-3,5-dimethylbenzyl pendant arms 4 and its precursor [H₄2]⁴⁺ both have centrosymmetric molecules with step conformation. Differences in conformation arise from hydrogen bonding interactions; in [H₄2]⁴⁺ bonding between amino nitrogen atoms and water molecules appears to tie the backbone chain of the macrocycle together, and in 4 strong intramolecular hydrogen bonding with each 2-hydroxybenzylamino unit dictates the orientation of the pendant arms.