Synthesis of tin containing calixarenes and their anion binding capabilities
Extensive research has been done on the ability of calixarenes to complex cations and neutral species. The electron-rich molecular cavity and lower rim consisting of a cyclic array of oxygen donors makes the structure of the calixarene conducive to this type of complexation. Conversely, the calixarenes represent a synthetically malleable framework upon which charged, Lewis acidic or hydrogen bond donor or acceptor functionalities may be placed in order to design anion binding hosts of very specific dimensions and selectivities. The purpose of this research is to synthesize a ditopic species that has the ability to simultaneously complex anions and cations starting from the calixarene skeleton. Starting with the p-tert-butylcalix[ 4]arene, the lower rim was functionalized with four ethoxy ethyl groups to create a binding site for small cations. Subsequently, the upper rim was functionalized with four tin atoms positioned at the end of n-propyl chains. The Lewis acidic nature of the tin functionalized molecules provided a site for possible binding of anions. Complexation of chloride ions by the new tetratin calixarene was studied by 119Sn NMR titration experiments. The stoichiometry of the host-guest complex was determined using Job's Method of Continuous Variations. Furthermore, the binding constant, Ka, was determined at various temperatures using the Benesi-Hildebrand method, also known as a double reciprocal plot.
calixarenes, synthesis, binding, tin
Herren, M. A. (1999). Synthesis of tin containing calixarenes and their anion binding capabilities (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.