Potassium cation cooperative anion recognition by heteroditopic calix[4]arene bis(benzo-15-crown-5) receptor molecules

New upper-rim functionalised heteroditopic calix[4]arene receptors containing amide linked bis(benzo-15-crown-5) ether, bis(benzo-15-crown-5)bis(ferrocene) and tetrakis(benzo-15-crown-5) groups have been prepared. 1H NMR titration studies reveal the bis(benzo-15-crown-5) potassium cation complexed calix[4]arene receptors enhance the strength of chloride, benzoate and dihydrogen phosphate binding in polar organic solvents via favourable preorganisation and electrostatic effects. Cyclic and square wave voltammetric investigations demonstrate that the bis(ferrocene) containing calix[4]arene receptor is capable of electrochemical anion recognition. In the presence of potassium cations the electrochemical response to benzoate anions was amplified significantly.