Ion complexation properties of calix[6]arene derivatives: I. 1,4-calix[6]crown-4 derivatives

A series of 1,4-p-tert-butyl-calix[b]crown-4 tetraesters, tetraamides, tetraacids with defined conformation have been synthesized, and their complexation properties towards metal ions and alkyl ammonium ions were investigated systematically. It was found that 1,4-p-tert-butyl-calix[6]crown-4 tetraethylester (3a) and 1,4-p- tert-butyl-calix[6] benzocrown-4 tetramethylester (4b) show high selectivity towards Na+, Li+, respectively and all of them exhibit high complexation abilities towards Et2NH2+ cation.