Liquid-liquid extraction of transition metal cations by diazo coupling calix[4]arene derivatives

The selective liquid-liquid extraction of various alkaline, alkaline-earth and transition metal cations from the aqueous phase to the organic phase was carried out by using diazo coupling calix[4]arenes [p-(4-n-butyl-phenylazo)calix[4]arene(L1), p-(4-phenylazophenylazo)calix[4]arene(L2), p-(4-acetamlidazo)calix[4]arene(L3), p-(N′-2-thiazol-2-ylsulphanylazo)calix[4]arene(L4) and p-(2-thiazolazo)calix[4]arene(L5)] and the phenol derivatives [2-(5-bromo-2-pyridylazo)-5-diethylaminophenol(L6) and (2-chloro-4-nitrophenylazo)-5-secbutyl-2-phenol(L7)]. It was found that compounds L1-L6 showed some selectivity towards Ag+, Hg+ and Hg2+, while extractability of all cations was observed with compound L2 containing double diazo groups