Electrochemical studies for cation recognition with diazo-coupled calix[4]arenes

The electrochemical properties of diazophenylcalix[4]arenes bearing ortho-carboxyl group (o-cac) and ortho-ester group (o-eac),respectively,in the presence of various metal ions were investigated by voltammetry in ch3cn. o-cac and o-eac showed voltammetric changes toward divalent metal ions and no significant changes with monovalent alkali metal ions. however,o-cac preferentially binds with alkaline earth and transition metal ions,whereas no significant changes in voltammetric signals are observed in o-eac with alkaline earth metal ions. o-eac only binds with other transition metal ions. this can be explained on metal ion complexation-induced release of proton from the azophenol to the quinone-hydrazone tautomer followed by internal complexation of the metal ion with aid of nitrogen atoms and ortho-carbonyl groups in the diazophenylazocalix[4]arenes. © 2015 bongsu kim and tae hyun kim.