Synthesis of covalently bonded molecular nano-architectures on surfaces modeled from first principles

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A wide variety of highly regular supramolecular architectures, based on noncovalent bonds, has been realized on single crystal metal surfaces over the past decade. Many potential applications, e.g., in bottom-up device technology, however, require a thermal and chemical stability that can only be provided by covalent bonding. In response to this need a number of attempts to fabricate covalently interlinked polymeric networks on single crystal metal surfaces have recently been made. Thereby it was noted that some reactions known from 3D chemistry occur differently when the reaction partners are confined to two dimensions and in some cases entirely novel reaction pathways were reported. Here we propose density-functional theory (DFT) calculations in order to explore in detail the influence of the surface on the thermodynamics and kinetics of chemical reactions. In particular we aim at identifying and exploring systems, where the substrate acts simultaneously as a template and a catalyst, as they seem especially promising for controllable reactions at surfaces. Thereby we focus on prototypical examples such as surface-supported tautomerization of pyrimidine groups, Ullmann couplings, imidization condensation of amines and anhydrides, esterification between boronic acid and diol groups, imine formation from aldehydes and amines, and the reaction of activated porphyrins on metal substrates. Various potential mechanisms like steric hindrances, electron transfer and screening effects, chemical interactions with the substrate as well as the direct involvement of substrate atoms in the reaction will be investigated for the coin metal (111), (110), and (001) surfaces in order to establish chemical trends and arrive at a deep and thorough understanding of the covalent synthesis at surfaces.