Electrochemistry of a urea-functionalized calix[4]diquinone sulfate-anion selective receptor

A new class of neutral ligands is synthesized and studied for the binding properties with anions by electrochemical methods. The binding of calix[4]diquinone 1 with HSO4− causes a large negative shift of the electrode potentials of the calix[4]diquinone. This novel neutral anion receptor 1 binds anions through hydrogen-bonding and shows high selectivity for HSO4− over H2PO4−, Cl−, and CH3CO2−. The selectivity of HSO4− over H2PO4−, Cl−, and CH3CO2− may be attributed to the stronger hydrogen-bonding with the urea moiety, and also with the quinone moiety of 1 receptor, and also the greater compatibility of the cavity of 1 with tetrahedral HSO4−.