The generation of nanostructures via a bottom-up process involving taylor-made molecular building blocks offers great promise to the field of nanoscience and its application in future nanotechnology. However, several scientific challenges await clever chemistry solutions. While self-assembly is certainly a powerful strategy to form periodic patterns, the connection via covalent bonds is key to overcome their fragility and access stable 1D and 2D nanostructures.Over the past few years, we have developed an �on-surface synthesis� of 1D and 2D covalent nanostructures involving chemical reactions between thermally activated monomer building blocks in the confinement of a metallic substrate. When deposited on Au(111), appropriately substituted porphyrin or oligofluorene monomers could be polymerized to one-dimensional and two-dimensional polyporphyrin chains and networks, respectively as well as polyfluorene strands, carrying no solubilizing groups. We could recently improve our method substantially by realizing the first hierarchical covalent connection sequence using monomers with programmed reactivity, which allow for sequential activation at specific temperatures, and by directing the growth process via the underlaying substrate surface.In addition to an increased stability of the structures, as demonstrated by manipulation experiments, the aryl-aryl connection allows for efficient charge transport along polyfluorene wires. Therefore, for the first time the current flow through a single lengthy molecular wire could be measured as a continuous function of its length up to 20 nm, providing details into fundamental questions of charge transport through individual molecules over large distances. Furthermore, this synthetic technique could be extended to other surfaces, for example insulating NaCl films on Au(111) as well as semiconducting substrates such as TiO2, allowing the decoupling from the underlying metallic substrates and hybridization of the organic and inorganic semiconductors, respectively.Here, the genesis of our on-surface polymerization will be presented and the most recent developments will be highlighted.

On-surface synthesis of covalent 1D and 2D polymers

248th National Meeting (2014)

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