Anion Extraction Properties of a New "Proton-Switchable" Terpyridin-Conjugated Calix[4]arene

A new terpyridin-conjugated calix[4]arene derivative has been synthesized via selectively substitution of p-tert-butylcalix[4]arene. The synthesized ligand was characterized by FTIR, H-1 NMR, C-13 NMR, C-13-DEPT-135 and elemental analysis. Moreover, the dichromate extraction capability of the compound regarding the removal of toxic oxyanion from aqueous solutions was discussed in a liquid-liquid extraction system. The results indicated that the pH of the solution is a key parameter for the efficient extraction of Cr(VI) and that compound 6 is partially protonated in acidic conditions. Hence, facilitating binding of dichromate results from both electrostatic interactions and hydrogen bonding. To understand the selectivity of 6, the retention of dichromate anions in the presence of NO3-, Cl-, and SO42- anions at pH 1.5 was also discussed.