Controlling Molecular Properties with Light

The work in this thesis explores photoactive units and self-assembly, both individually and at the intersection of these fields. The various approaches are unified by the interaction between molecules and light irradiation, with a special focus on visible-light photoswitching. Chapter 2 explores the incorporation of the photoactive unit tetraphenylethene (TPE) into larger self-assembled architectures using iron pyridyl-imine templation. A [Fe2L3]4+ triple helicate assembly was thoroughly characterised and derivatised through amide formation. Unsymmetrical TPE derivatives were isolated and their emission and self-assembly properties were studied. Chapter 3 discusses the problems of accurately determining photostationary state (PSS) composition. Methodologies are discussed, with specific reference to known and assumed quantities. Examples are presented where the PSS composition can be estimated, and these methodologies are also used in Chapters 4 and 5. A guide to the measurements required in more difficult cases is presented. Chapter 4 reports on new visible light photoswitches, based on azobenzazoles. Their photoswitching properties are thoroughly studied, and the effect of protonation on the switching properties is explored. Photoswitching is possible using yellow light, and high-level ab initio calculations validate the proposed protonation of the ring nitrogen. Chapter 5 describes the derivatisation of o-fluoroazobenzenes, with specific reference to incorporation into larger structures. A macrocyclic architecture is described, based on imine condensation reactions. The combination of a pyridyl functionalised ligand with palladium(II) gives a mixture of self-assembled species, which were individually characterised. Visible light irradiation leads to reversible configurational change, and out-of-equilibrium behaviour