Chapter 4: Self-assembly on Crystalline Surfaces: From Phthalocyanines to Porphyrins

Self-assembled two-dimensional periodic structures of ordered monolayers are presented and discussed. These can be obtained experimentally after moderate annealing of in situ evaporated thin films of organic molecules on crystalline substrates in ultra-high vacuum (UHV). The systems focused here are various derivatives of phthalocyanines and porphyrins on substrates such as graphite [HOPG(0001)] and face-centered cubic (fcc) noble metals [Ag(111), Au(111), and Ag(110)]. The method of investigation is scanning tunneling microscopy (STM) performed in situ, which allows direct imaging in real space with submolecular resolution. The variety of structures observed is discussed comparatively where the experience collected with phthalocyanines helps in better understanding the situation encountered at porphyrins. In most cases, the concepts of direct and indirect intermolecular (i.e., adsorbate–adsorbate) interaction in competition with adsorbate–substrate interaction based on the electronic structure of these components allow interpretation of the results. Furthermore, approaches to single-molecule manipulation, heat-induced surface reactions, and possible self-healing effects in such systems are demonstrated, possibly offering new basic insights as well as promising applications.