1 NanoChemistry, Department of Chemistry, Technical University of Denmark2 Department of Chemistry, Technical University of Denmark3 Department of Physics, Technical University of Denmark4 Theoretical Atomic-scale Physics, Department of Physics, Technical University of Denmark5 Chalmers University of Technology6 Center for Atomic-scale Materials Design, Center, Technical University of Denmark7 Chinese Academy of Sciences8 Center for Nanostructured Graphene, Center, Technical University of Denmark
Coordination chemistry has been a consistently active branch of chemistry since Werner's seminal theory of coordination compounds inaugurated in 1893, with the central focus on transition metal complexes. However, control and measurement of metal-ligand interactions at the single-molecule level remain a daunting challenge. Here we demonstrate an interdisciplinary and systematic approach that enables measurement and modulation of the coordinative bonding forces in a transition metal complex. Terpyridine is derived with a thiol linker, facilitating covalent attachment of this ligand on both gold substrate surfaces and gold-coated atomic force microscopy tips. The coordination and bond breaking between terpyridine and osmium are followed in situ by electrochemically controlled atomic force microscopy at the single-molecule level. The redox state of the central metal atom is found to have a significant impact on the metal-ligand interactions. The present approach represents a major advancement in unravelling the nature of metal-ligand interactions and could have broad implications in coordination chemistry.