Two novel [1+1] Schiff base macrocyclic compounds 4 and 5 have been synthesized from Precursor 1 [1,7-bis(2'-formylphenyl)-4-aza-1,7-dioxa-4-(4'-toluenesulfonyl)heptane] and Precursor 2 [1,7-bis(2'-formylphenyl)-1,4,7- trioxaheptane] with diamine 3 [N,N'-(2-aminophenyl)pyridine-2,6-dicarboxamide] via condensation and cyclizaction in acid-catalyzed condition, respectively, and the structures were characterized by elemental analysis, ¹H NMR, IR and MS techniques. Simultaneously, the crystal structures of two compounds 4 and 5 were determined by X-ray diffraction analysis. The X-ray single crystal analysis reveals that each of the two macrocycles 4 and 5 exhibits twisted “figure eight” conformation due to the strong intramolecular hydrogen bonding interactions, and the stabilized structure in part by the intramolecular π-π stacking interactions between the two benzene rings. The studies on the UV-vis absorption spectra show that the two macrocycles 4 and 5 have a selective recognition for La³⁺ ion.

Key words: Schiff base, macrocyclic compound, synthesis, crystal structure