Non-template synthesis of ‘N4’ macrocyclic imine ligands with variable ring sizes: the importance of intramolecular hydrogen-bonding. X-Ray crystal structures of three macrocyclic and two open-chain ligands

Abstract

Di-imine tetra-aza macrocycles with an extensive range of ring sizes can be isolated by simple condensations without recourse to ‘metal-ion template’ or ‘high-dilution’ reactions, provided the rings can form intramolecular hydrogen bonds to reduce unfavourable lone-pair–lone-pair interactions between the nitrogen atoms.