Highly Structure-Selective On-Surface Synthesis of Isokekulene Versus Kekulene
Zilin Ruan1, Qitang Fan1,2, Alexander Reichmann3
1Department of Chemistry, Marburg University, 35037, Marburg, Germany.
Angewandte Chemie (International Ed. in English)
|July 9, 2025
Summary
Copper nanoparticle facets control chemical reactions. Different crystal surfaces (Cu(110) and Cu(111)) selectively produce unique cycloarene molecules, offering new synthesis routes.
Area of Science:
- Materials Science
- Catalysis
- Organic Chemistry
Background:
- Heterogeneous catalysts' facet-dependent selectivity is key for targeted chemical synthesis.
- Transition-metal-catalyzed carbon-hydrogen (C-H) bond activation is vital for producing chemicals, materials, and pharmaceuticals.
Purpose of the Study:
- To investigate how different copper single crystal facets steer reaction pathways in intramolecular cyclodehydrogenation.
- To achieve orthogonal selectivity in synthesizing complex cycloarene molecules.
Main Methods:
- Utilized scanning tunneling microscopy with CO-functionalized tips.
- Employed density functional theory calculations.
- Combined in-solution and on-surface synthesis approaches.
Main Results:
- The Cu(110) surface selectively produced the novel cycloarene isokekulene (92% selectivity).
- The Cu(111) surface exclusively yielded kekulene (>99% selectivity).
- Identified two precursor adsorption geometries influencing product formation, with isokekulene's nonplanar configurations and strong molecule-substrate interactions favoring Cu(110).
Conclusions:
- Facet-dependent steering of reaction pathways by copper single crystals enables orthogonal selectivity in cycloarene synthesis.
- This approach provides an alternative route for synthesizing challenging molecules via controlled adsorption and reaction mechanisms.
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