The use of functional molecules and their assembly into pre-defined architectures are key challenges in nanotechnology and of interest in various fields from molecular electronics over novel materials to molecular machines. We study chemical processes of single functional molecules on surfaces by scanning tunneling microscopy under ultrahigh vacuum conditions and at low temperatures, thus allowing submolecular resolution analysis. The central objectives are (i) to control and understand these functions at the single-molecule level, (ii) the controlled molecular assembly in two dimensions, and (iii) to investigate the influence of the atomic-scale environment, i.e. interactions of the molecules with other adsorbates and the surface.Various examples of how to control chemical processes will be discussed, ranging from covalent molecular linking to intramolecular reactions. The first is realized by on-surface polymerization [1] where specifically designed molecular building blocks are connected to two-dimensional networks or one-dimensional chains, which can act as molecular wires [2,3]. The polymerization process can be catalytically controlled via the surface material and precise structure [4]. Furthermore, a hierarchical growth mode could be achieved by the sequential creation of reactive sites within the molecules on demand [5]. On the other hand, chemical processes within individual molecular can be controlled via their environment. This was observed for molecular switches, where the atomic-scale surroundings cause drastic changes in their switching probability and lead to a spatially periodic switching pattern [6]. Recently, we could show that the rate of an intramolecular hydrogen transfer reaction can be tuned up and down by single atoms in the vicinity of the molecule [7].[1] Nature Nanotech. 2, 687 (2007); [2] Science 323, 1193 (2009); [3] Nature Nanotech. 7, 712 (2012); [4] Angew. Chem. Int. Ed. 51, 5096 (2012); [5] Nature Chem. 4, 215 (2012); [6] Nature Nanotech. 3, 649 (2008); [7] Nature Chem., in press.

Controlling chemical processes at the level of single molecules

247th National Meeting (2014)

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