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O: Fachverband Oberflächenphysik

O 87: Focus Session: Molecular Nanostructures on Surfaces: On-Surface Synthesis and Single-Molecule Manipulation III

O 87.1: Topical Talk

Thursday, March 21, 2024, 15:00–15:30, HE 101

Towards the third dimension: Organic molecular architectures synthesized on solid surfaces by means of solution-based click chemistry — •Michael Dürr — Institut für Angewandte Physik and Zentrum für Materialforschung, Justus-Liebig-Universität Giessen, Germany

In most on-surface reactions, the solid (metal) substrate acts both as a template as well as a catalyst. When we think on expanding the concept of on-surface synthesis into the third dimension, the coupling reactions will not be catalyzed by the substrate any more. Thus, either catalyst-free reaction schemes or new reaction strategies have to be applied. For the growth of 3D structures on silicon surfaces, we have followed two alternative routes: Using a carefully tuned enolether/tetrazine cycloaddition, a second layer of organic molecules was directly coupled under UHV conditions on a prefunctionalized Si(001) surface. As an alternative approach, we combined UHV-based surface functionalization with solution-based click chemistry. In this scheme, ordered multilayers of organic molecules were realized on the prefunctionalized Si(001) surface via a two-step reaction cycle in solution. In order to ensure a controlled layer-by-layer growth, two orthogonal alkyne-azide click reaction schemes based on asymmetric bifunctional molecular building blocks were employed. Each reaction step was monitored by means of XPS demonstrating a high selectivity of the reaction schemes in use. Our approach thus opens the road for the controlled synthesis of organic 3D structures on surfaces.

Keywords: click chemistry; silicon surface; alkyne-azide coupling; selectivity; organic functionalization