Steering on-surface reactions through molecular steric hindrance and molecule-substrate van der Waals interactions

• Published in: Quantum frontiers Vol. 1; no. 1; p. 23
• Main Authors: Wang, Shiyong, Nishiuchi, Tomohiko, Pignedoli, Carlo A., Yao, Xuelin, Di Giovannantonio, Marco, Zhao, Yan, Narita, Akimitsu, Feng, Xinliang, Müllen, Klaus, Ruffieux, Pascal, Fasel, Roman
• Format: Journal Article
• Language: English
• Published: Singapore Springer Nature Singapore 01.01.2022
• Subjects: Condensed Matter Physics; Original; Original Article; Physics; Physics and Astronomy; Quantum Physics; Atomic force microscopy; Scanning tunneling spectroscopy; Chemoselectivity; On-surface synthesis; Graphene nanoribbons
• ISSN: 2731-6106; 2731-6106
• DOI: 10.1007/s44214-022-00023-9

On-surface synthesis is a rapidly developing field involving chemical reactions on well-defined solid surfaces to access synthesis of low-dimensional organic nanostructures which cannot be achieved via traditional solution chemistry. On-surface reactions critically depend on a high degree of chemoselectivity in order to achieve an optimum balance between target structure and possible side products. Here, we demonstrate synthesis of graphene nanoribbons with a large unit cell based on steric hindrance-induced complete chemoselectivity as revealed by scanning probe microscopy measurements and density functional theory calculations. Our results disclose that combined molecule-substrate van der Waals interactions and intermolecular steric hindrance promote a selective aryl-aryl coupling, giving rise to high-quality uniform graphene nanostructures. The established coupling strategy has been used to synthesize two types of graphene nanoribbons with different edge topologies inducing a pronounced variation of the electronic energy gaps. The demonstrated chemoselectivity is representative for n-anthryl precursor molecules and may be further exploited to synthesize graphene nanoribbons with novel electronic, topological and magnetic properties with implications for electronic and spintronic applications.