A New Class of Potassium-selective Calix[4]arenes in Cone Conformation

Benzoate modified calix[4]arenes 3–8 were synthesized from (o-bromomethyl)benzoate. EA, IR, 1 H and 13 C NMR characterizations showed that compounds 3, 4, 5, 7 and 8 were in cone conformation, while 6 was in a 1,3-alternate conformation. The solvent extraction experiments found that the cone-conformers 3 and 8 have high selectivity for K + as compared to Na + . Compound 3 has an extractability of 69.8% for K + and 7.1% for Na + . Compound 8 has an extractability of 80.9% for K + and 19.1% for Na + . In order to elucidate the results, the complex behavior of compounds 3, 6 and 8 for K + were studied by 1 H NMR and the crystal structures of compounds 3 and 6 were determined.