Multifunctional Fluorenyl-Embedded Helicenes

Fluorene – an electron-rich organic polyaromatic molecule containing a central 5-membered ring – has been well-established in the literature as being a versatile, multifunctional building block with tuneable and robust optoelectronic and redox properties. For example, its relatively high photoluminescence quantum yield, its ability to support neutral organic radicals and its ambipolar charge transporting capabilities has warranted its use in the development of advanced light-emitting and charge transporting applications. However, benzannulated derivatives of fluorene are less well-known, despite retaining the optoelectronic behaviours inherent to fluorene, that are boosted by enhanced conjugation through the polyaromatic backbone. In fact, the few examples of ortho fused benzannulated derivatives of fluorene that have been published are shown to possess a non planar screw shaped backbone enabling access to properties relating to their inherent chirality.
This Thesis focuses on investigating the fundamental properties of tetra annulated tetrabenzo[a,c,g,i]fluorene (TBF) and its derivatives in order to draw attention to its multifaceted optical and charge conductive behaviours. Particular emphasis is placed on scrutinising the structures that the materials synthesised adopt in the solution- and solid state and relating these structural findings to their emergent properties. For example, Chapter 2 and Chapter 3 relate how the structures of TBFs appended with a bulky, rigid anthracene substituent, affect their emissive and redox properties, respectively. Then, in Chapter 4, the dynamic interconversion of the polyaromatic backbone of TBFs are interrogated by DFT calculations to inform the design of configurationally stable TBF helicenes for the isolation of chiroptically-active molecules. Finally, Chapter 5 explores how the incorporation of heteroatoms into the TBF framework impacts optical and redox properties. Such chiral fluorescent closed- and open shell helicenes can lead to a deeper understanding of fundamental spin electronics and molecular magnetics that may benefit the development of advanced light-emitting and memory technologies and hence lead us to a more advanced and sustainable future.