On-Surface Synthesis of Indenofluorene Polymers by Oxidative Five-Membered Ring Formation

• Published in: Journal of the American Chemical Society Vol. 140; no. 10; pp. 3532 - 3536
• Main Authors: Di Giovannantonio, Marco, Urgel, José I, Beser, Uliana, Yakutovich, Aliaksandr V, Wilhelm, Jan, Pignedoli, Carlo A, Ruffieux, Pascal, Narita, Akimitsu, Müllen, Klaus, Fasel, Roman
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14.03.2018
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.8b00587

On-surface synthesis is a successful approach to the creation of carbon-based nanostructures that cannot be obtained via standard solution chemistry. In this framework, we have established a novel synthetic pathway to one-dimensional conjugated polymers composed of indenofluorene units. Our concept is based on the use of ortho-methyl groups on a poly­(para-phenylene) backbone. In this situation, surface-assisted oxidative ring closure between a methyl and the neighboring aryl moiety gives rise to a five-membered ring. The atomically precise structures and electronic properties of the obtained indenofluorene polymers have been unambiguously characterized by STM, nc-AFM, and STS, supported by theoretical calculations. This unprecedented synthetic protocol can potentially be extended to other polyphenylenes and eventually graphene nanoribbons, to incorporate five-membered rings at desired positions for the fine-tuning of electronic properties.