Two 1,3-calix[4]azacrowns-5 in the 1,3-alternate conformation have been constructed from calix[4]arene. They formed 1:1 endo and 1:2 endo-endo complexes with NH4+ in CDCl3. Comparison with 1,3-calix[4]-bis-crown-5 lead us to conclude a better binding by replacement of the central O atom by NH group in the crown. (C) 2000 Elsevier Science Ltd. All rights reserved.
Two 1,3-calix[4]azacrowns-5 in the 1,3-alternate conformation have been constructed from calix[4]arene. They formed 1:1 endo and 1:2 endo-endo complexes with NH4+ in CDCl3. Comparison with 1,3-calix[4]-bis-crown-5 lead us to conclude a better binding by replacement of the central O atom by NH group in the crown. (C) 2000 Elsevier Science Ltd. All rights reserved.