Department of Chemistry
The University of Texas at Dallas
800 W Campbell Road
Richardson, TX 75080-3021
phone: (972) 883-2918
fax: (972) 883-2925
The Wurster's Crowns
Macrocyclic ligands that contain additional functionality as either an appended group or within the macrocyclic framework have been the subject of intense study in recent years. Those that contain redox-active moieties are particularly noteworthy as they are classes of ligands whose coordinating ability (binding strength and/or selectivity) can be altered by physical or chemical means. We have developed synthetic routes to representative members of a new class of redox-active macrocyclic receptors. The common structural component which distinguishes these macrocycles is the incorporation of the N,N,N',N'-tetraalkyl-1,4-phenylenediamine unit within the macrocyclic framework. Because these redox-active groups can be viewed as derivatives of Wurster's Reagent, the trivial name "Wurster's crowns" are suggested for these ligands.
Our synthetic methods are general and allow for the synthesis of any N, O or S-containing Wurster's crown, cryptand or bis(macrocycle). Thus, hosts for nearly all metal ions in the periodic table are available for study. Among a number of applications, these crowns are under investigation as cation, anion and neutral molecule sensors and transport agents, redox-switchable catalysts and molecular magnets. As proof of concept, specific Wurster's crowns were developed for electrochemically sensing Li+, Na+ and K+ ions; improvement of the selectivity was observed using a macrobicycle topology. In addition, we have developed synthetic routes for the synthesis of macrocyclic arrays containing multiple redox centers in both cyclophane and traditional crown topologies.
In collaboration with Dr. Andrew Sargent (East Carolina University) ab initio theoretical studies have provided a fundamental understanding of the properties of representative members of this class of compounds and their metal complexes.