Alkyl ammonium ion selectivity of hexahomotrioxacalix[3]arene triamide derivative having the intramolecular hydrogen-bonding group

The lower rim functionalized hexahomotrioxacalix[3] arene triamide 4 with cone-conformation was synthesized from triol 1 by a stepwise reaction. The different extractability for alkali metal ions, transition metal ions, and alkyl ammonium ions from water into dichloromethane is discussed. Due to the strong intramolecular hydrogen bonding between the neighboring NH and CO groups in triamide 4, its affinity to metal cations was weakened. Triamide 4 shows a single selectivity to n-BuNH3+. The anion complexation of triamide 4 was also studied by H-1 NMR titration experiments. Triamide 4 binds halides through the intermolecular hydrogen bonding among the NH hydrogens of amide in a 1: 1 fashion in CDCl3. The association constants calculated from these changes in chemical shifts of the amide protons are K-a = 223 M-1 for Cl- and K-a = 71.7 M-1 for Br-. Triamide 4 shows a preference for Cl- complexation than Br- complexation.