Complexes of lanthanide(III) ions with macrocyclic ligands containing pyridine head units

Lanthanide(III) salts were found to act as templates for the cyclic condensation of organic dicarbonyl compounds with primary diamines to yield complexes of macrocyclic Schiff-base ligands in moderate to good yield. Three types of macrocyclic lanthanide(III) complexes were obtained: (i) mononuclear complexes of an 18-membered sexidentate N3O3 macrocycle derived from the reaction of 2,6-diacetylpyridine with 1,5-bis(2-aminophenoxy)-3-oxapentane; (ii) mononuclear complexes of 15-membered pentadentate N3O2 macrocycles derived from the reactions of 2,6-diacetyl- or 2,6-diformyl-pyridine with 1,2-bis(2-aminophenoxy)ethane. The complexes were characterised by elemental analyses, molar conductivity, mass, IR and H-1 NMR spectroscopy and thermogravimetric and magnetic measurements.