Single molecule electronics in ionic liquid media

The field of single molecule electronics, where the charge transport properties of a variety of single molecular systems are investigated, has vastly increased in popularity over the last decade. This thesis in particular explores the single molecule conductance and electron transfer over a range of molecules in a room temperature ionic liquid medium. Prior to the work contained in this thesis, no conductance measurements of a single molecule had been recorded in a room temperature ionic liquid medium, to the best of our knowledge. Due to the novelty of room temperature ionic liquids in this field, it was decided that alkanedithiols would be an ideal starting point, largely due to their simplicity and reputation as a model system in single molecule electronics. Ionic liquids have several notable advantages as a medium in such measurements and the aim of the research contained in this thesis is first to show that ionic liquids are indeed a viable medium and secondly, to demonstrate their advantages over more widely used, conventional aqueous or organic media. The redox active molecular wire pyrrolo-tetrathiafulvalene is a particular molecule which would highlight the benefits of an ionic liquid medium, as it has a redox transition which is outside of the potential window available to aqueous electrolytes. Single molecule conductance measurements were obtained using a scanning tunnelling microscope (STM), in particular, the current-distance I(s) technique, and for alkanedithiols also the STM break junction technique. The electrochemistry of pyrrolo-tetrathiafulvalene was investigated using cyclic voltammetry and a monolayer of pyrrolo-tetrathiafulvalene was characterised using polarisation modulation infrared reflection absorption spectroscopy (PM-IRRAS).