Cucurbiturils in Microscopic Complexes and Cooperative Host-host Systems

This dissertation presents some of our interesting findings, both from a thermodynamic and kinetic point of view, of supramolecular systems in which cucurbit[7]uril is a component. The goal in chapter one is to put our results in perspective, using a selection of related scholarly work done by others. In chapter two we studied the formation of inclusion complexes between the cucurbit[7]uril host and a cationic guest containing ferrocenylmethyl and adamantyl residues connected to an ammonium nitrogen. The initial state of the system is a ~1:1 mixture of two isomeric microscopic complexes, which evolves as a function of time towards the thermodynamically stable mixture, dominated by the adamantyl-included complex. Detection of isomeric complexes using relatively slow methods, like NMR spectroscopy, is rare in the literature. The slow evolution of the system in a matter of hours which leads to segregation of different chemical species through time is another facet of this work. Chapter three deals with a supramolecular system in which multiple components assemble cooperatively. The study involves the self-assembly in aqueous solution of the well-known cyclophane, cyclobis(paraquat-p-phenylene), and two cucurbit[7]uril hosts around a simple hydroquinol-based, diamine guest. Formation of a quaternary complex was shown to be a very efficient process, which takes place not only because of the attractive forces between each of the hosts and the guest, but also because of the interactions between the hosts in the final molecular assembly. The present system adds not only to our knowledge of cooperative self-assembly, but also offers new building blocks for construction of complex molecular structures