A new family of N_xO_x pyridine-containing macrocycles: Synthesis and characterization of their Y(III), Ln(III), Zn(II), and Cd(II) coordination compounds

Reaction between 2,6-bis(2-formylphenoxymethyl)pyridine and N,N-bis(3-aminopropyl)methylamine or tris(2-aminoethyl)amine has been used as the starting point for the synthesis of seven oxa-aza macrocyclic ligands, five of them never reported previously. They all feature different pendant arms, which provide a wide range of coordination possibilities. The Schiff base macrocycles L¹ and L⁴ and their reduced ligands L ² and L⁵ are derived from 2,6-bis(2-formylphenoxymethyl) pyridine and tris(2-aminoethyl)amine or N,N-bis(3-aminopropyl)methylamine, respectively. The reaction of L¹ with salicylaldehyde forms L ³, which features an imine bond in the pendant arm. The ligand L ⁵ has been the precursor for the pendant-armed L⁶ and L⁷, by alkylation of the free NH groups with methyl-imidazole or methyl-indole. By a template or a nontemplate approach, we have synthesized different mono- and dinuclear complexes with Y(III), Ln(III), Zn(II), and Cd(II) cations. Both the free macrocyclic ligands and their corresponding metal complexes have been characterized by microanalysis, IR, UV-vis, ¹H and ¹³C NMR spectroscopy, FAB mass spectrometry, MS electrospray, and conductivity measurements.