Synthesis, Conformation and Metal-binding Properties of Calix[6]arene Derivatives

A novel 1,3,5-trimethoxy-2,4,6-tribromoethoxycalix[6]arene (2) as a useful intermediate for the design of new host–guest-type receptors of calix[6]arene with C3v symmetrical conformation and two ‘biscalix[6]arenes’ (3–4) has been synthesized by reacting 1,3,5-trimethoxy-p-tert-butylcalix[6]arene (1) with 1,2-dibromoethane in THF in the presence of NaH. Furthermore, several calix[6]arene derivatives 5–7 were then prepared from 2 and their conformational characteristics were studied by dynamic 1H NMR spectroscopy. The complexing properties toward heavy metal ions of the prepared compound 5 are also reported in this paper with the help of fluorescence spectra and UV-visible spectra. It is shown that this ligand can form relatively stable complexes with Cu2+ and Sn2+.