On-surface synthesis of covalently bonded molecular structures on insulators

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The field of bottom-up fabrication of tailored organic molecular nanostructures on surfaces has shifted towards covalently bonded structures in recent years - among other reasons, because they are more stable and allow for a strong electronic coupling. A most prominent example is the bottom-up synthesis of atomically precise graphene nanoribbons. As in the on-surface chemical reactions employed so far the metal substrate played a key role in initiating the reaction, working on insulators requires new strategies for bond formation between organic molecules. However for applications in opto- and nano-electronics insulating surfaces are required. The aim of this project is to enable bottom-up fabrication of tailored organic molecular nanostructures also on insulating substrates under ultra-high-vacuum conditions. To this end, we will scrutinize two routes, namely Pd-catalyzed cross-coupling and light-induced radical formation followed by a chemical synthesis between radicals. The methods of choice to investigate the structures and possible intermediates will be scanning probe techniques including their spectroscopic modes of operation. The experimental studies will be supported by state-of-the-art theoretical analysis from our collaboration partner including density functional theory calculations, image simulations and non-adiabatic molecular dynamics with electronic transitions. We are convinced that this project - if funded - will provide completely novel routes in on-surface reactions and thereby create a platform for bottom-up synthesis on insulators.