Chemical Activation of a Single Melamine Molecule via Isomerization Followed by Metalation with a Copper Atom.

Scanning probe methods have very successfully been used for inducing on-surface reactions and imaging with high resolution the reaction partners at the single-molecule level. However, the entire sequence of chemically activating an educt, identifying its reactive site, running a chemical reaction, and quantifying the involved forces and energies has been missing to date. Here, the organic molecule melamine adsorbed on Cu(100) serves as a single-molecule model system for activation via tautomerization and subsequent metalation with a single Cu atom. An atomic force microscope with a CO-decorated tip probes the most reactive intramolecular site of the tautomer, while a Cu-terminated tip transfers a single Cu atom to this site. Following the interaction between the mutually approached reaction partners up to the verge of chemical-bond formation enables access to the force and energy involved in the single-molecule metalation process. Total-energy calculations from density functional theory support the experimental findings and illustrate the structure of the reactants.