SFB 658:  Elementary Processes in Molecular Switches at Surfaces

Subject Area Physics
Chemistry
Term from 2005 to 2017
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 12489635
 

Final Report

Final Report Year 2017

Final Report Abstract

Molecular switches came to the attention of the wider public at the latest with the award of the Nobel Prize for Chemistry 2016 to Jean-Pierre Sauvage, Fraser Stoddart und Ben Feringa – for inventing and synthesizing artificial molecular machines. External stimuli change the conformation or the configuration of molecular switches which can therefore realize complex functions on the shortest length scales and with a high degree of reproducibility. Nature exploits molecular switching in human vision which relies on the isomerization of retinal between microscopically distinct cis- and trans-states. The Collaborative Research Center Sfb 658 ”Elementary processes in molecular switches at surfaces“ aimed at anchoring molecular switches at surfaces and developing new methods to control the functionalities of these anchored molecules. A major challenge was that the molecules’ switching properties were strongly affected or even completely suppressed by the surface. This led us to develop strategies for optimizing the coupling between switch and surface. Specifically, we synthesized new molecular switches with various spacers which allowed us to tailor the interaction between switch and surface both in planar and in vertical adsorption geometries. As a result of an intense cooperation between chemical synthesis and surface physics, we could ultimately realize a large variety of switching processes on surfaces. This includes transcis-isomerization, tautomerization, ring-opening/ring-closing reactions and switching in magnetic molecules on metal and semiconductor surfaces as well as on graphene and carbon nanotube substrates. After overcoming substantial initial difficulties, switching molecules at surfaces became routine. Through intensive collaboration between experiment and theory, this allowed us to unravel and optimize the elementary processes of switching events in considerable detail both in individual molecules and molecular ensembles. Specific configurations of molecular switches could be realized and stabilized through atomic scale manipulation, and contacted both in vertical and lateral configurations, for instance for realizing a single-molecule transistor. Self-organization was exploited to realize molecular layers whose optical and electric properties could be effectively switched through light with minimal aging. Switching could be enhanced in networks through cooperativity. The spin state of magnetic molecules could be stabilized and switched through the coupling to the substrate. Moreover, switching processes were exploited to manipulate the physical and chemical properties of carbon nanotubes such as solubility, biocompatibility, light emission, or carrier density. A crucial condition for the success of Sfb 658 was the intense collaboration across disciplines which persisted through all funding periods. Of the total of about 430 publications in peer-reviewed journals, more thab 25% resulted from a cooperation of two or more subprojects. Over the course of the project, seven project leaders received and followed outside offers, reflecting the impact and the quality of our research. We are proud that within Sfb 658, 85 students completed their dissertations in this cutting edge research field. Last but not least, Sfb 658 will have a lasting impact on the Focus Area Nanoscale at Freie Universität Berlin and the wider Berlin research landscape through its role in four new professorial appointments.

Publications

DFG Programme Collaborative Research Centres

Completed projects

Applicant Institution Freie Universität Berlin
Participating University Humboldt-Universität zu Berlin; Technische Universität Berlin; Universität Potsdam
Participating Institution Fritz-Haber-Institut der Max-Planck-Gesellschaft (FHI); Paul-Drude-Institut für Festkörperelektronik (PDI)
Spokespersons Professor Dr. Felix von Oppen, until 7/2015; Professor Dr. Martin Weinelt, since 7/2015