Functionalized Calixpyrroles: Building Blocks for Self-Assembly

This chapter covers advances in the development of anion and ion pair recognition systems based on calix[4]pyrrole. The intention of this manuscript is to provide of an overview of promising systems for the sensing of relevant analytes, such as the toxic fluoride anion, phosphate anions, as well as the extraction and transport of anionic species and ion pairs including cesium halide and sulfate salts. It is divided into seven sections. The first section describes the synthetic methods employed to functionalized calix[4]pyrrole. The second section focuses on functionalized calix[4]pyrroles that display enhanced anion binding properties compared to the non-functionalized parent system, octamethylcalix[4]pyrrole. The use of functionalized calix[4]pyrroles containing a fluorescent group or functionalized calix[4]pyrroles as building blocks for the preparation of stimulus-responsive materials is discussed in Sect. 12.3. Receptors that are able to recognize and selectively extract ionic species from aqueous media into organic environments are the topic of Sect. 12.4. Anion and ion pair receptors based on calix[4]pyrroles that are designed to achieve the transmembrane transport of ions are the focus of the fifth section. Finally, the last section will summarize work devoted on calix[4]pyrrole systems capable of forming higher order supramolecular aggregates and capsules, as well as studies of their response to external stimuli. Potential applications, including the possible removal of deleterious anions and the eventual development of therapeutics that function via the transport of anions across cell membranes, are discussed.