Lanthanide(III) macroacyclic and macrocyclic Schiff base complexes containing oxamidic groups

Abstract

The macroacylic Schiff bases containing oxamidic groups have been prepared by [2+1] condensation of N, N′-bis-(2-aminoethyl)oxamido (H 2L A, respectively, with 2-hydroxybenzaldehyde (H 4L B) or 2,6-diformyl-4-chlorophenol (H 4L C) and their properties studied by IR, NMR and mass spectrometry. The complexation behaviour of the formyl and amino-amide precursors H 2L A and of the Schiff bases H 4L B and H 4L C towards lanthanide(III) salts was studied and the resulting mononuclear or polynuclear complexes characterised by IR and NMR spectroscopy. H 4L B forms, when reacted with copper(II) salts in a methanol/dimethylformamide solution, the more soluble green mononuclear Cu(H 2L B) and the less soluble violet homodinuclear Cu 2(L B) complexes, which have been separated by subsequent crystallization. Magnetic susceptibility measurements evidence a strong antiferromagnetic interaction between the two copper ions in the dinuclear complex. The macrocyclic Schiff bases H 6L DH 6L G were also synthesised by [2+2] condensation of N, N′-bis(2-aminoethyl)oxiamido or N, N′-bis(2-amino-1,1-dimethylethyl)oxamido with 2,6-diformyl-4-chlorophenol or 2,6-diformyl-4-methylphenol. H 6L DH 6L G have been characterised by elemental analyses, IR, NMR; their cyclic nature was inferred especially by FAB mass spectrometry. They form homodinuclear or polynuclear lanthanide(III) and yttrium(III) complexes when reacted with Ln(NO 3) 3· nH 2O (Ln = Dy 3+, Gd 3+, La 3+, Y 3+). The homodinuclear complexes Ln 2(HL)(NO 3) can give rise to heteropolynuclear copper(II)-lanthanide(III) complexes when reacted with copper(II) salts.