Aryl halides are among the most important molecular precursors for on-surface synthesis. Their dehalogenative coupling – so called surface-assisted Ullmann-type coupling – represents a unique synthetic route for the bottom-up fabrication of extended low-dimensional covalent nanostructures that exhibit all benefits of strong carbon-carbon linkages.<br/><br/>Organometallic templating has proven an invaluable tool for improving the notoriously low structural quality of 2D covalent networks. Structural equilibration in the organometallic stage, where dehalogenated monomers form reticulated networks based on organometallic carbon-metal-carbon linkages, can promote the on-surface synthesis of regular and defined covalent networks. In these favorable cases, the order generated in the organometallic networks was transferred to the final covalent product by a thermally activated isostructural conversion. On the one hand, studying organometallic self-assembly is per se rewarding, since an advanced understanding of its mechanisms could contribute to further push its limits. On the other hand, the partial dehalogenation, as typically observed on silver surfaces, gives rise to new modes of supramolecular self-assembly, where both the split off and subsequently chemisorbed halogens and organometallic metal atoms represent dominating interaction sites.<br/><br/>In this contribution, we will discuss self-assembly of aryl halides on surfaces for various degrees of dehalogenation ranging from fully halogenated to fully dehalogenated. Moreover, we will demonstrate, how a detailed analysis of the stereochemical distribution of dehalogenated sites holds the potential for elucidating fundamental aspects of surface-assisted dehalogenative couplings.

Self-assembly of aryl halides for various degrees of dehalogenation

2019 Spring National Meeting

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