Single molecule reactivity studies in a liquid-STM

Single molecule reactivity studies in a liquid-STM

Hans Elemans
Radboud University Nijmegen
Institute for Molecules and Materials
Scanning Probe Microscopy group

Many chemical reactions are catalyzed by metal complexes, and insight in their reaction mechanisms is of fundamental importance for the design of new chemical processes. A wealth of conventional spectroscopic techniques is available to study reaction mechanisms at the ensemble level, but with the emergence of single molecule microscopy and spectroscopy research it has become possible to obtain unique information about reactivity at subnanometer scale.

My group aims at studying the behavior of reactive molecules at a surface in real-time and real-space in a dedicated Scanning Tunneling Microscope (STM) setup. We can image monolayers of molecules at submolecular resolution at the chemically relevant interface of a solid and a liquid, at room temperature. I will present in situ STM studies of oxidation reactions of manganese porphyrins at solid/liquid interfaces. When a monolayer of these porphyrins is exposed to an atmosphere of O2 or to a single oxygen donor, STM revealed that a variety of reactions can occur which are expressed as clear changes in catalyst signature in the STM topography images. The dynamics of these reactions can be followed for hours. I will demonstrate that this new STM approach to visualize chemical reactions at the single molecule level reveals unique mechanistic aspects that remain hidden in conventional ensemble measurements.