Oligopyrrole-based anion receptor
Anions are important species in the natural world and are critically involved in almost the full range of known chemical process. Also, anions are among the most pervasive of all known pollutants (e.g., nitrate, phosphate). Therefore, the synthesis and study of synthetic receptors for the purpose of anion recognition continues to attract increasing attention within the supramolecular community. This dissertation focuses on both the synthesis of neutral and positively charged pyrrole-based anion receptors and the analysis of their anion binding affinities. The first section of this dissertation will provide a background involving the chemistry and biochemistry of anions and a brief overview of various classical synthetic anion receptors, such as those based on high charge (i.e., ammonium, guanidium, and protonated pyrrole), alternative hydrogen bond donor schemes (i.e., amide and urea), and the use of metal centers. The second part, consisting of chapters 2-5, will discuss the synthesis, characterization, and analysis of the anion binding abilities of neutral pyrrolebased anion receptors whose basis for anion recognition involves almost exclusively hydrogen bonding interactions. Specifically, the main focus of chapter 2 is the analysis of the anion binding properties of meso-octamethylcalixpyrrole. Chapters 3-5 then cover the modification of the basic calixpyrrole skeleton with the goal of generating receptors with improved anion binding affinities and selectivities. The third part of the dissertation, covering chapters 6 and 7, will center around a discussion of positively charged, pyrrole-based synthetic receptors that rely on a combination of hydrogen bonds and electrostatic interactions to effect anion binding. The fourth part will present the results of studies involving systems, wherein anion binding to an elaborated calixpyrrole system is used to control the recognition of a second neutral guest. Chapter 9 does not detail experimental results per se but presents an overview of the various analytical techniques that commonly used to measure anion binding affinities in the case of synthetic receptors. Finally, the last chapter is the experimental section for this dissertation; in it is found a detailed description of the synthetic and analytic procedures used to characterize the systems discussed in chapters 2-8.