Voltammetric Study of Nano-baskets of Calix[4]-1,3-crowns-5, -crowns-6 Complexes

Four nano-baskets of calixarene including di(carboxymethoxy)calix[4]arene-crown-5 and -crown-6 in both cone and 1,3-alternate conformations, were synthesized and their binding abilities towards alkali and alkaline earth metals and some lanthanides were studied using differential pulse voltammetry. The novelty of this study is investigation of calixarene complexes by voltammetric behaviors of two acidic moieties during complexation with crown ether ring. Their voltammetric behaviors not only were related to complex formation (by entrapment of cation into crown ether cavity) but also were controlled by ion-dipole interaction between cation and carboxylic acid moieties. The results revealed the selective changes in voltammetric behavior of synthesized scaffolds toward cations. Moreover, the position of crown ether in 1,3-alternate conformations enhanced the domain of binding ability to more cations. Furthermore, carboxylic acid moieties, which were far from the crown ether ring in 1,3-alternate, were not affected by encapsulated cations in the coordination space of crown ether and hence, they showed no voltammetric behavior. (C) 2012 Elsevier Ltd. All rights reserved.