Surface-Confined Supramolecular Coordination Chemistry

The non-covalent synthesis of coordination compounds and networks provides promising avenues towards metal-containing supermolecules and nanostructured materials with ultimate feature definition. An important factor for their further development, and their integration and exploitation in nanoscale functional systems, is the capability to prepare or organize them at well-defined substrates or templated environments. Supra-molecular engineering on atomistically controlled surfaces has been propelled by the direct insight into low-dimensional coordination systems provided by scanning tunneling microscopy observations. Here we discuss the principles of surface-confined supramolecular coordination chemistry, emphasizing self-assembly protocols conducted on surface atomic lattices employing metal centers to direct the organization of molecular ligands and the template-induced organization of prefabricated metallosupramolecular species. The presented exemplary molecular-level studies elucidate the arrangement of organic adsorbates and transition metal adatoms on low-index metal and graphite surfaces. They reveal the interplay between molecule-adatom, intermolecular, and adsorbate-substrate interactions, which need to be balanced for the fabrication of low-dimensional nanostructures. The control and understanding of both the nature of metal-ligand interactions and the resulting supramolecular organization on solid surfaces is decisive for the design of advanced architectures with concomitant functions. The realized metallosupramolecular compounds and arrays combine the properties of their constituent metal ions and organic ligands, and feature versatile structural characteristics as well as attractive functional aspects: their redox, magnetic, spin-state, and electronic transitions.