Invited Paper SS2-TuM3
Structure, Bonding and Electronic Properties of Self-assembled 2D Organic Nanostructures at Surfaces: Negatively Charged TCNQ Networks and Other Systems
Interfaces between organic materials and inorganic supports are critical for the design and function of new organic-based technologies (e.g., OLEDs, organic photovoltaics, and molecular electronics) as well as novel routes to chemical sensors and catalysts. There are vast opportunities for designing structure-function relationships in these systems due to the immense library of organic compounds and metal-organic chemistries available. Molecular self-assembly at surfaces by covalent, metal-organic, ionic, and weaker interactions are active fields of research, but much remains to be determined with regard to the complex interplay of intermolecular and adsorbate-substrate interactions and how these impact structure and function. TCNQ undergoes a charge transfer from a Cu surface to adopt a bond conformation to the surface that enables stable adsorption and the self-assembly of highly ordered 2D structures via surface-mediated attractive interactions. These structures are stable at room temperature. Addition of Mn triggers a structural transformation to a highly-ordered porous network with Mn centers in a high spin state. These studies have allowed new insight into organic / metal interfaces by collaborative work involving high-resolution scanning tunneling microscopy, photoelectron spectroscopy methods, synchrotron measurements, other UHV surface experiments, and density functional theory calculations. Recent progress on other 2D and multilayer organic systems in our group lends further evidence to the significance of direct organic-surface interactions in such systems, the problems those interactions may pose, and solutions for balancing them at a desired level. We are making progress towards tailored chemical function by rational design of molecular architectures at surfaces and tuning such function through supramolecular design strategies.