The template synthesis and characterization of hexaaza 18-membered macrocyclic complexes of cerium(III), praseodymium(III) and neodymium(III) nitrates

Abstract

We have previously described the preparation and characterization of heavier trivalent lanthanide (Tb to Lu) complexes containing 14-membered quadridentate macrocyclic ligands [ 11. The lighter lanthanide ions (La to Gd) have been found to be ineffective as templates for the synthesis of this macrocycle. The important factor which must be taken into account in the planning of the synthesis of macrocyclic compounds with the aid of metal ion is the ratio of cation diameter to ligand cavity size. The cavity of 1Cmembered macrocycle is too small to enclose the lighter lanthanides. It was therefore interesting to investigate the template action of these ions in the synthesis of macrocyclic ligands with greater ring size. We found that the lanthanum ion may act as a template for the synthesis of 18-membered hexaaza sexidentate macrocyclic compounds [2, 31. The formation of the lanthanide complexes of some macrocyclic Schiff bases has recently been reported [4,5] . This paper reports the preparation and characterization of Ce(III), Pr(II1) and Nd(III) macrocyclic complexes derived from 2,6-diacetylpyridine and o-phenylenediamine. The complexes of 2,7,13,18-tetramethyl4,5:15, 16dibenzo-3,6,14,17,23,24-hexaazatricyclo[l7.3.1 l.81’2]fetrakoza-1(23),2,4,6,8,lO,l2(24),l3,15,l7,l9, 21 dodecaene ligand (L) have been prepared by