Abstract
The supramolecular interactions of small organic molecules with different host molecules are investigated in this dissertation. Additionally, the author also describes the self-assembly mechanisms in hydrogen bonding motif. These studies were carried out by many techniques including, NMR, cyclic voltammetry, steady state voltammetry, mass spectroscopy, UV-visible spectroscopy and fluorescence spectroscopy. Chapter 1 introduces the science of supramolecular chemistry and the background of cucurbiturils, one of the most important host molecules studied in this research work. It describes the structures and binding behaviors of each host molecule. Additionally, the selectivity and binding properties in the host-guest interactions involved cucurbiturils are discussed. Chapter 2 compares the electrochemical properties of cationic and neutral ferrocene derivatives upon addition of cucurbiturils. It is observed that the cationic ferrocene compounds bind to cucurbit[7]uril much stronger compared to the neutral ferrocene compounds. The positive charged side chains favor to interact with cucurbit[7]uril portals and thus stabilize the complexes. Besides, the author describes a simple analytical method to determine the binding constants by a competitive binding with a standard reference compound, cobaltocenium, which is reported to bind strongly to cucurbit[7]uril. Chapter 3 described the research of the pH-dependent binding affinity between cucurbit[7]uril and ferrocene guests. The electrochemical behavior of ferrocene moiety in aqueous solution was investigated by cyclic voltammetry in the presence of cucurbit[7]uril in acidic and basic environment respectively. The protonation and deprotonation processes affect the binding behaviors of the ferrocene residues with cucurbit[7]uril. Chapter 4 describes the synthesis and characterization of a new series of 4-phenyl-pyridinium derivatives. These compounds contain a phenyl-pyridinium residue which is favorable to be bound by cucurbit[8]uril. The 1:1 and 1:2 host-guest binding stoichiometries are both observed by UV-visible spectroscopy. These new compounds can be dimerized encapsulated inside the cucurbit[8]uril portals without being electrochemical reduced. Chapter 5 is a brief introduction into the science of hydrogen bonding. This chapter investigates the application of multiple hydrogen-bonding in supramolecular chemistry extensively. Multiple hydrogen bonds with their directionality and reversibility are of great interest and importance in the design and investigations of well-defined supramolecular assemblies. The potential of hydrogen bonding is limitless and is still developing. Chapter 6 describes the synthesis and photochemical behaviors of a series of ureido-pyrimidione derivatives. All of the DDAA derivatives form stable, non-covalent dimers in non-polar solvents. The dimeric molecular assemblies of these hydrogen bonding motifs in their DDAA pyrimidinedione units are investigated by NMR, X-ray crystallography, fluorescence spectroscopy and computations. Additionally, their hetero-dimerization is well studied by fluorescence spectroscopy. The observation and comparison of fluorescence quenching on the photochemical fluorophore for each compound by ferrocene-DDAA and isopropyl-DDAA reveal the electron transfer process through the quadruple hydrogen bonding motifs.