Synthesis of two calix[4]arene diamide derivatives for extraction of chromium(VI)

The synthesis of four diamide derivatives of the p-tert-butylcalix[4]arenes from the reaction of 5,11,17,23-tetra-tert-butyl-25,27-diethoxycarbonylmethoxy-26,28-dihydroxycalix[4]arene 2 with various primary amines were reported. The 1H and 13C NMR, data showed that the synthesized compounds exist in the cone conformation. The complexing properties of these compounds toward Cr2O72−/HCr2O7− anions are also studied. It has been observed that receptors and are better extractant than the compounds and . The protonated alkyl ammonium form of and is an effective extractant for transferring HCr2O7−/Cr2O72− anions from an aqueous phase into a dichloromethane layer.