Self-organized monolayers: A route to conformational switching and read-out of functional supramolecular assemblies by scanning probe methods

Self-organized molecular layers provide a promising route to constructing new (switch able) nanodevices and optimizing nanosensors. The design of such molecules involves control of structure and stabilization on the surface, as well as control of functionality. The search for a potentially universal adapter, which can control the self-organization and stabilization on a particular type of surface, is a unique challenge. High-quality nanoscale imaging using scanning tunneling microscopy (STM) provides the means to further such studies. This article reviews our recent STM work on single molecules,self-assembled monolayers, and self-organized monolayers, highlighting our application of a general self-organizer for graphite surfaces, i.e., a Frechet-type dendron. How powerfully this self-organizing motif can affect various central components (catalytic, switchable, redox-active) on a graphite surface is addressed by analyzing self-organized monolayers of nine different molecules, each containing at least one first- or second-generation Frechet-type dendron. In molecular layers containing a switchable core, we can detect a large conformational change upon protonation with HCl gas. Last, but not least, the dynamic surface organization properties of the Frechet-type dendrons are described.