The synthesis and anion binding studies of scorpiand-type calix[5]- and calix[10]phyrins as well as a cryptand-like bicyclic calix[15]phyrin system

The field of anion recognition in supramolecular chemistry has grown significantly in the past decade. The design challenges that are faced in targeting and sensing anions require a greater level of sophistication than is needed for cations. This reflects the greater diversity in geometry, directionality and lower charge density of the larger anions. Many of the existing systems for anion sensing are designed to wrap around the anion creating many points of contact. Some receptors are preorganized while others are more flexible. Often a balance between competing factors is needed to obtain high specificity. An important aspect of anion recognition is sensing, wherein the binding event triggers a change that can be readily monitored. Having a good receptor is again critical. This dissertation presents a set of pyrrole-based macromolecules related to the calix[n]phyrins that interact with guest anions via hydrogen bonding interactions that extend beyond one plane, electrostatic attraction from protonation, and pi-anion interactions. Of the anions tested with the hosts reported in this dissertation, the sulfate anion proved to be bound most strongly. It also produced distinct colorimetric changes that were visible to the naked eye.