An approach to the synthesis of chemically modified bisazocalix[4] arenes and their extraction properties

Bisazocalix[4]arenas [N,N′-bis(5-azo-25,26,27-tribenzoyloxy-28- hydroxycalix[4]arene)benzene (1), N,N′-bis(5-azo-25,26,27-tribenzoyloxy- 28-hydroxycalix [4]arene)biphenyl (2) and N,N′-bis(5-azo-25,26,27- tribenzoyloxy-28-hydroxycalix[4]arene)-2,2′-dinitro biphenyl (3)] have been synthesized from 25,26,27-tribenzoyloxy-28-hydroxycalix[4]arene by diazocoupling with the corresponding aromatic diamines (p-phenylenediamine, 4,4′-diamino biphenyl and 4,4′-diamino-2,2′-dinitrobiphenyl). Extraction studies of bisazocalix [4]arenes 1, 2, and 3 show no difference in their extraction behavior and selectivity, whereas azocalix[4]arenes are a poor extradant for heavy metal cations. The absorption spectra of the prepared bisazocalix[4]arenes are discussed, both the effect of varying pH and solvent upon the absorption ability of bisazocalix[4]arenes. © 2005 Elsevier Ltd. All rights reserved