Calix[4]pyrrole-based molecular self-assembly

Abstract

Over the last two decades, calix[4]pyrroles – teterapyrrolic macrocycle linked through α or meso-like positions by sp³-hybridized carbon atoms – have been exploited as strong and selective receptors and as extractants for both anions and ion pairs. In particular, complexation of an anion to calix[4]pyrrole via four hydrogen bonds drives conformational changes from the 1,3- alternate to the cone conformation. This conversion provides a concave, bowl-like cavity that permits recognition of charge diffuse cations, such as cesium and imidazolium, through cation–𝜋 interactions. This structural flexibility is a characteristic of calix[4]pyrrole chemistry. The work described in this dissertation takes advantage of molecular switching phenomena. In particular, it details efforts to realize self-assembly using functionalized calix[4]pyrroles. In the context of theses efforts, a variety of secondary forces, such as hydrogen bonding interaction, 𝜋 - 𝜋 (CH-𝜋) interactions, and charge transfer (CT) interactions are exploited and studied in detail. Also included in this dissertation is a summary of studies of stimulus-responsive behavior, wherein systems constructed from calix[4]pyrroles are exposed to external stimuli that includes anions, acid/base, and electrochemical triggers. Chapter 1 gives a brief overview of the use of calix[4]pyrroles as molecular carriers stressing the transport of ion pairs. Chapter 2 details a multi-stage molecular equilibrium system that exploits two kinds of cali[4]pyrroles as well as appropriately chosen chemical inputs, and the conseqyent construction of a NAND logic gate. Chapter 3 describes factors that affect the self-assembly process under condition where the interactions are relatively weak. Chapter 4 focuses on orthogonal self-assembly from calix[4]pyrrole and a functionalized fullerene. Chapter 5 details formation of metal-containing 1D arrays and molecular capsules. Lastly, chapter 6 demonstrates the syntheses and the characterization data of all compounds used in these studies.