Synthesis and characterization of three novel azocalix[4]arene Schiff base derivatives and their selective copper extraction

The synthesis and characterization of three novel Schiff bases of azocalix4]arene and their selective copper extraction are described. The preparation of azocalix4]arenes (1c, 2c and 3c) has been achieved by the condensation of 2-hydroxy-3-methoxybenzaldehyde with the amine group of upper rim mono-, di- and tetra-(aminophenylazo) calix4]arene in ethanol. The synthesized products (1c, 2c and 3c) are characterized by both ¹H and ¹³C NMR techniques, IR spectroscopy and elemental analysis. Extraction capabilities of interested derivatives of azocalix4]arene from aqueous phase into organic phase are also examined. While extraction of Ag⁺, Hg⁺ and Hg²⁺ cations gave strong complexes with azo groups, extraction of Cu²⁺ cation is found to be highly effective with ?CCH=N?C and neighboring ?COH groups.