Abstrakt
A novel type of anion receptor, based on the intramolecularly bridged calix[4]arene immobilized in the cone conformation, is described. The reductive coupling of a distal dialdoxime using Zn/T/Cl-4 led to calix [4]arene with a meso-1,2-diaminoethane-1,2-diyl bridge that was transformed into the corresponding receptors by reaction with aryl isocyanates.
H-1 NMR titration experiments revealed that the combination of a unique structural feature (bridge) with arylureido functional groups led to the formation of very potent anion receptors. Contrary to model non-bridged compounds, these well-preorganized receptors can efficiently bind selected anions (H2PO4-, AcO-, BzO(-)) via hydrogen bonding interactions even in highly competitive solvent (DMSO-d(6)).