Molecular balances

Abstract

Predicting and quantifying solvent effects on non-covalent interactions is often very challenging, as they are influenced and modulated by multiple factors. In this thesis, a series of molecular torsion balances is used as a tool to tackle the complexities of noncovalent interactions in solution.

Chapter 1 presents an up-to-date literature review on solvent effects on non-covalent interactions, with a particular focus on solvent effects on conformational equilibria and molecular torsion balances. Chapter 2 demonstrates the use of molecular torsion balances and a simple explicit solvation computational model to show that the electrostatic potential of the substituted aromatic rings is largely dependent on the explicit solvation of the substituent. The contribution of both bond polarisation and through-space field effects is also covered.

Chapter 3 provides a literature review on the deuterium isotope effects on non-covalent interactions, presenting a range of contradictory findings. Molecular torsion balances are used here as a probe of H/D isotope effects on the conformational equilibria, solvent isotope effects and the solvophobic effect in aqueous mixtures. The balances are studied from thermodynamic and kinetic viewpoints, through which both intra- and intermolecular interactions are examined. It is shown here that H/D isotope effects on the presented system are either non-existent or negligibly small.

Chapter 4 presents the use of molecular torsion balances to investigate carbonylcarbonyl interactions, taking into account steric and solvent effects. This is compared experimentally and computationally against two existing theories rationalising these interactions.

In Chapter 5, a background of metal-ligand interactions is outlined, along the most widely utilised theories rationalising them. The electronic effects of Pt complexation by a pyridyl-substituted molecular torsion balance is analysed both experimentally and computationally, and the arising discrepancies are addressed. The applicability limits of the previously presented simple solvation models are determined using systems displaying extreme electronic effects.