Connect – Catch – Couple: Metal-Molecule Interactions in Catalytic Coupling

• Applicant: Privatdozent Dr. Friedrich Esch
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 444946100

This project aims at establishing a fundamental understanding of the chemical interaction between organic molecules and metallic Palladium nanostructures during heterogeneous C–C coupling reactions. Using Scanning Tunneling Microscopy (STM) in vacuum and in solution, we will gain detailed insight into the metal-molecule interaction at the atomic scale, by studying individual molecules in combination with a systematic variation of structure and size of the metal. Pd nanocatalysts will range from stepped single-crystal surfaces over size-selected clusters to single atoms.The coupling process will be investigated along the three main steps: (i) CONNECT: Formation of metal-molecule bonds to the Pd nanostructures; (ii) CATCH: Impact of the metal-molecule interaction on the nanostructure morphology and dynamics; (iii) COUPLE: Formation of reaction products, concomitant to the release of the Pd nanoparticles for further catalytic cycles. By reacting arylhalides with alkenes and boronic acids, catalyst stability and activity will be correlated with structural properties and dynamics. Based on these systematic observations, we want to answer various key questions: How do molecules interact with Pd surfaces of different morphology? How are the reactants activated? How is the catalyst stability affected by single reaction steps? How can the Pd particle size, support, oxidation state and solvent systematically be tuned to increase the catalyst stability?Experiments will be pursued both under ultrahigh vacuum as well as in solution, taking the best of two worlds via complementary environments and techniques: (I) Low temperature STM can attain very high spatial resolution of the metal-molecule bond, giving local insight into favorable molecule-metal arrangements and transformations. Moreover, it can use spectroscopy to locally study electronic properties and manipulation to induce catalytic cycles. (II) Electrochemical STM works at the solid/liquid interface and gives direct insight into the role of solvation and the influence of the redox state of the Pd nanostructure under realistic mild coupling conditions. By implementing the FAST imaging technique, we will furthermore be able to address local particle dynamics, crucial to understand deactivation mechanisms. The partners will use the same molecules and comparable samples, and exchanging the very same samples where required.The novelty of this project lies in the atomic-scale investigation of cross-coupling in various ambients, taking advantage of the complementary expertise and instrumentation of the two project partners. Moreover, the ability to prepare extremely well-defined Pd nanostructures and thereby tune the metal-molecule interaction, in combination with a systematic variation of the molecular precursors, provides a tool for steering fundamental catalytic properties by rational design, with implications in many fields, from sensors to molecular electronics and beyond.

• DFG Programme: Research Grants
• International Connection: Austria
• Partner Organisation: Fonds zur Förderung der wissenschaftlichen Forschung (FWF)
• Cooperation Partner: Professor Dr. Leonhard Grill