Biscalixarenes: Synthesis and investigation of the extraction behavior of biscalix[4]arene derivatives in a two-phase extraction system

A series of different bridged biscalix[4]arenes in which the lower rims are linked via a single site on each calixarene were synthesized and converted to their alcoholic, ketonic, and esteric derivatives. Their complexing abilities were studied by the liquid-liquid extraction of selected alkali (Li+ Na+, K+, Cs+) and transition (Cu2+, Co2+, Cd2+, Ni2+, and Hg2+) metal cations. Through extraction examination it has been deduced from the observations that the alcoholic derivatives are very poor extractants as compared to the ketonic and esteric derivatives. The ketonic derivative is selective for Hg2+, whereas the esteric derivative is not selective but a good extractant and showed higher affinity towards Na+, Cu2+, Co2+, and Hg2+. The results indicate that the ligands containing pi -system functional groups and having a proper conformation of calixarene cavity form novel binding sites for the comlexation of metal cations.