Liquid-liquid extraction of transition metal cations by nine new azo derivatives calix[n]arene

Liquid-liquid extraction of various alkali, alkaline-earth, and transition metal cations with o-(4-hydroxydiazophenyldiazophenyl)-p-tert-butylphenol (L1), bisdiazo (1-hydroxy-4-tert-butylphenyl)benzene (L2), p-(2-hydroxy-5-tert-butylphenylazophenylazo)calix[4]arene (L3), and p-(2-hydroxy-5-tert-butylphenylazophenylazo)calix[6]arene (L4), p-(4-butylphenylazo)calix[6]arene (L5), p-[4-(phenylazo)phenylazo]calix[6]arene (L6), p-(4-hydroxyphenylazo)calix[6]arene (L7), p-{4-[N-(thiazol-2-yl)sulfamoyl]phenylazo}calix[6]arene (L8), p-(4-acetamidophenylazo)calix[6]arene (L9), p-(thiazol-2-ylazo)calix[6]arene (L10), and p-(2-sulfanylphenylazo)calix[6]arene (L11) from the aqueous phase into the organic phase was carried out. For comparison, the corresponding azo calix[n]arene derivatives and two phenol derivatives were also examined. Since Ag+, Hg+, and Hg2+ cations form complexes with azo groups strongly, the extraction of these metals was found to be highly effective.