Theoretical modelling studies of aggregation and molecular interactions

Understanding the interactions between dye molecules and their constituent moieties will lead to an improvement in the design of new molecules with the appropriate properties. Here, we use computational methods to investigate the relative stability of the three tautomers of hydroxy-triazine, and how they interact with themselves in the gas phase, in aqueous solution and in the solid state. Ab initio and density functional theory (DFT) methods were used to establish the relative gas phase stability of the tautomers, showing two of the tautomers to be significantly more stable than the third. Thermodynamic cycles were calculated using ab initio free energies of salvation and gas phase energies. The crystal phase investigation involved data mining of the Cambridge Structural Database and generating hypothetical crystal structures which were subjected to lattice energy minimisations. The interactions were investigated in the gas phase by minimising small clusters of the tautomers, treated as rigid molecules, from a number of random starting conformations. Molecule dynamics simulations looked at the behaviour in solution, while the lattice energy minimisations and the CSD were again used to look at solid phase interactions. The above methods were also incorporated into further investigations of the interactions between these tautomers and another important dye-related molecule, morpholine, both as an additive and as a covalently bonded fraction. Whole dye molecules containing these substructures, were then studied using the above methods, as well as UV-Vis spectroscopic analysis to calculate dimerisation equilibrium constants. Finally the computational methods were applied to look at the effects of substituents on the interactions of zinc phthalocyanine.EThOS - Electronic Theses Online ServiceGBUnited Kingdo