New tetrafunctionalized cone calix[4]arenes as neutral hosts for anion recognition

The synthesis and anion binding properties of several new cone calix[4]aren es having different flexibility and tetrafunctionalized at the upper rim wi th various type of hydrogen bonding donor groups such as thioureas (1-3), t rifluoroacetamides (4, 5) and perfluorinated alcohols (6) are reported. The results obtained show that thiourea receptors are the most effective in th e complexation of all anions and that the rigid cone compound 2 is more eff icient than the mobile cone analog 1 in the binding of spherical anions, wh ereas the reverse is true for the complexation of tetrahedral H2PO4- anion.