Synthesis and anion recognition of neutral receptors based on multiamide calix[4]arene

Two multiamide calix[4]arenes (5, 6) were synthesized and characterized by IR, ¹H NMR, MS and elemental analysis. The binding properties of receptors with some anions (ρ-O₂NPhOPO₃^2-, ρ-O₂NphO^-, H₂PO₄, Ac^-, Cl^-, Br^- and I^-) were studied by UV-Vis spectra. The results indicate that the tetraamide calix[4]arenes (5, 6) have a good selectivity to the anions containing aromatic ring (τ-O₂NPhOPO₃^2-, τ-O₂NphO^-). The 1:1 complexes between host and guest were formed through multiple hydrogen bonding and π-π interactions. The hosts 5 and 6 also show a definite binding ability for the anions (H₂PO₄^-, Ac^-, Cl^-) that have no ultraviolet absorption, which provides a simple method of spectrum detection for these anions.