Synthesis and characterisation of four novel NxOy-Schiff-base macrocyclic ligands and their metal complexes

Macrocyclic Schiff-bases, L-1 and L-2, and bis-macrocyclic ligands, L-3 and L-4, have been prepared by [1+1] and [2+1] cyclocondensation of 1,7-bis(2'-formylphenyl)-1,4,7-trioxaheptane or 2,6-bis(2-formylphenoxymethyl)pyridine with 2,6-bis(o-aminophenoxymethyl)pyridine or 1,2,4,5-tetraaminebenzene.4HCl, respectively. The related Y-III, M-II (M=Co, Ni, Zn, Cd or Pb) and Ln(III) nitrate or perchlorate complexes have been synthesised following a template procedure, demonstrating the effectiveness of these metal ions to promote the assembly of these four symmetric Schiff-base macrocycles. The complexes were characterised by elemental analyses, molar conductivity, mass spectrometry, i.r., u.v.-vis, and H-1-n.m.r spectroscopy.