Molecular-strain engineering of chiral redox-active macrocycles

Redox-active macrocycles featuring cyclical through-space conjugation represent an increasingly important class of molecular materials for both fundamental and application-oriented investigations — especially for their abilities to stabilise charge and assemble into porous electroactive nanostructures. In particular, chiral molecular triangles, consisting of three aromatic diimide (ADI) linkers bound together by enantiopure trans-1,2-diaminocyclohexane bridges, have proven to be a popular platformfor accessing a wide range of attractive electronic and energy storage properties, thanks to their globally distributed LUMOs. However, although the effects of different ADI linkers (such as benzene, naphthalene and perylene diimides) on the physical, optical, electronic and self-assembly characteristics of molecular triangles have been explored in depth, diversification of the chiral vertex unit has yet to be investigated. This Thesis explores the consequences of manipulating the vertex chemistry of chiral pyromellitic diimide (PMDI) molecular triangles by systematically introducing modifications to the cyclohexane bridging unit. The first section of this Thesis discusses methods applied to introduce a homologous series of electron-rich trans-1,2-diamines groups, which allows for fundamental investigation of structural and electronic effects on account of aromatic groups. For the first time, the successful synthesis of a molecular triangle with an acyclic trans-1,2-diamine, suggesting that contrary to widely promoted design paradigms, the preorganisation offered by more rigid trans-1,2-diaminocyclohexanes is, in fact, unnecessary. The second section explores the extent at which even subtle changes in the degree of through-space orbital overlap and strain engineering via the aforementioned synthetic modifications can stabilise molecular triangle electron acceptors by lowering the energies required to access their multi-reduced states. This work ultimately serves to promote the advancement of this class of organic molecular materials as prime candidates for future rechargeable energy storage and related organic electronic applications.