Synthesis and complexation studies of 1,3-dialkylated p-tert-butylcalix[4]arene telomers

A series of cone structured lower rim dialkylated p-tert-butylcalix[4]arene (2a-5a) and their relative telomers (2b-5b) have been synthesized to estimate extraction of alkali and transition metal cations from an aqueous phase to an organic phase (dichloromethane). The complexation studies were made by using a liquid-liquid extraction procedure. It has been deduced from the observations that the monomers 2a, 3a and 5a are selective for Hg2+, whereas 4a is not selective but showed higher affinity towards transition metals than the alkali metal cations. The telomer 2b showed more affinity toward Cu2+, Hg2+ and Pb2+ but the telomer 3b is effective for Hg2+ and Pb2+. The telomers 4b and 5b are not selective but they are efficient extractants for the selected transition metal cations. The results indicate that the ligand groups circularly arranged on the lower rim of calixarene cavity form novel binding sites for transition metal cations. (C) 2000 Elsevier Science B.V. All rights reserved.