Solvent extraction of metal cations by chemically modified biscalix[4]arenes

The 2 lower-rim functionalized biscalix[4]arenes, 2,2'-bis-[5,11, 17,23-tet ra-tert-butyl-25,26,27-trihydroxycalix [4] arenyloxy] diethyl ether and 1, 3-bis-[5,11,17,23-tetra-tert-butyl-25,26,27-trihydroxycalix[4]arenyloxyl pr opanone have been converted to their ester and ketone derivatives. The comp lexation properties of the synthesized ionophores toward selected alkali an d transition metal cations are reported. Hexaester derivatives of 2,2'-bis- [5,11,17,2 3-tetra-tert-butyl-25,26,27-trihydroxycalix[4]arenyloxyl] diethy l ether and 1,3-bis-[5,11,17,23-tetra-tert-butyl-25,26,27-trihydroxycalix[4 ]arenyloxyl propanone are not selective but are good extractants for all of the metal ions studied. However, the 2,2-bis-[5,11,17,23-tetra-tert-butyl- 25,26,27-trihydroxycalix[4]arenyloxyl diethyl ether and 1,3-bis-[5,11,17,23 -tetra-tert-butyl-25,26,27-trihydroxycalix[4]arenyloxyl propanone as well a s their hexaketone derivatives extract Hg2+ selectively. We deduced that th ese ligands display high selectivities that depend on different factors, su ch as the conformation, polarizability, and the nature of the substituents on the lower rim of the biscalixarenes.