A study of some non-covalent functional group π interactions

The present thesis is concerned with the quantification of weak non-covalent interactions between a simple π system and functional groups through dynamic NMR studies of conformational equilibria of specifically designed molecular balance systems. The work begins with an introduction which provides a formal review of the current literature on various aspects of non-covalent π-interactions, starting with an examination of the physical properties of non-covalent arene interactions, including arene-arene interactions, the behaviour of aromatic rings as hydrogen bond acceptors and the interactions between aromatic rings and cationic species. The use of molecular balance systems for studying these weak interactions will then be discussed together with some other important methods used. The introduction concludes with an account of olefinic !-interactions and methods for their study as described in the current chemical literature. The second section presents and discusses the results obtained in the present study and begins with the description of the synthetic routes employed to prepare two series of molecular balance systems, both of which feature a common bicyclo[3.2.2]nona-6,8-diene framework and a flexible three carbon atom bridge, whose central carbon atom can possess two different functional groups. The relative abundance of each of the two possible conformers in solution provides a measure of the relative interaction energies. Dynamic NMR studies in a range of solvents were employed to study each derivative. The results from these studies were then compared in order to gain insight into the relative strengths of both olefinic and aromatic π-interactions. The thesis concludes with a formal description of the experimental procedures used in this study and appendices detailing the data obtained from dynamic NMR studies and crystal structure data