Nanoscale molecular systems : designed phenyl-acetylene architectures

Abstract

Molecular design should be about fulfilling function. However designing molecular structures that will fulfill a particular function is incredibly difficult. The delicate interplay of structure-property relationships and further emergent phenomena that arise when molecules come together are very unpredictable. This thesis sets out tools to guide the budding molecular architect in successfully making the transition in mindset from structure-property relationships to structure-function relationships. In chapter 1, after covering briefly the tools currently used to investigate the nano world, we explore the chemistry of acetylenes applied in coupling reactions to form phenyl-acetylene bonds. We then turn our attention to supramolecular chemistry as a driver for the formation of self-assembled networks, allowing for a bottom-up approach to achieve nanopatterned, functional surfaces. In chapter 2, the concept of phenyl-acetylene building blocks is presented. This modular approach to the assembly nano scale architectures makes the ‘mass production’ of a library of interesting building materials viable through organic synthesis. Both aryl and carbazole building blocks are explored, with a focus on their scope for further assembly to larger architectures. Chapter 3 discusses applications of the building block approach to molecular electronics. Computing devices could become much faster, smaller, and cheaper to run if we move away from the silicon-based transistor towards functional single molecules. We have synthesised a series of linear, fully conjugated nano-rods and stars to act as molecular wires in an attempt to fabricate the first functional three-terminal device. In chapter 4 we investigate the synthetic route towards an organic metamaterial. The building block methodology is applied an refined in the 26 step synthesis of a giant, fully conjugated carbazole based macrocyle. Finally, in Chapter 5 we look to the synthesis and STM investigations of a family of star-shaped molecular rods demonstrating an unprecedented level of control of single molecular organisation in an extended array.