We propose transition metal carbene complexes as novel active centers of materials suitable for application in molecular electronics. More specifically, metals that can undergo spin or oxidation state changes such as iron, cobalt, and ruthenium will be bound to N-heterocyclic carbenes.
Such ligands have a very high potential in molecular electronic applications, since they combine a variety of advantageous properties, viz. strong complexation through ?-donation, potential for ligand tuning through wingtip substitution, ligand functionalization for secondary properties such as incoporation of recognition sites or hierarchical organization, and a certain extent of ?-delocalization that allows for some metal-to-ligand ?-backbonding. This latter feature will be particularly important for molecular electronics applications, since ?-delocalization is predicted to substantially increase electron mobility along the metal-ligand framework.
We aims at demonstrating that such metal-carbene units are particularly suitable components for electronic applications. In a first step towards this goal, monometallic complexes will be synthesized in order to assess the ligand features that determine the metal’s electronic properties.
Subsequently, we will incorporate the most suitable metal-carbene units into bimetallic systems, in which the two metal sites are electronically coupled. Such a setup provides organometallic switches with three distinct states (off-off, off-on, on-on), which may be appropriate for simple logic gate processing. Various switching methods will be used, including electrochemical redox changes, thermally induced spin state transitions, and chemical switching. Finally, suitable bimetallic switches will be assembled into two- and three-dimensional arrays, thus fabricating real devices. As techniques for inducing self-assembly, we prefer monolayering on solid surfaces, and Langmuir-Blodgett film preparation at liquid-gas interfaces. We propose such devices in order to analyze possible lateral effects due to intermetallic cooperativity in such a rigid supramolecular arrangement, leading to signal amplification and hence to a significant increase in sensitivity compared to homogenous or anisotropically structured materials. According to this methodology, p- and n-doped materials for semiconductor application may be accessible, thus offers a new approach to multifunctional electronically active materials.