Synthesis, NMR characterization and ion binding properties of 1,3-bridged p-tert-butyldihomooxacalix[4]crown-6 bearing pyridyl pendant groups

A new dihomooxacalix[4]crown-6 (2) was synthesized and isolated in a cone conformation in solution at rt, as established by NMR (1H, 13C and NOESY). The binding properties of 2 towards alkali, alkaline earth, transition and heavy metal cations have been assessed by phase transfer and proton NMR titration experiments. The results are compared to those obtained with calixcrowns 1 and 3.