03 October

On-Surface Synthesis as a Versatile Route to Novel Non-Benzenoid Carbon Allotropes

Monday 03 October 2022, 12:00pm

ICN2 Seminar Room, Campus UAB

By J. Michael Gottfried, Department of Chemistry, Philipps-Universität Marburg, Germany

Hosted by Prof. Stephan Roche, Theoretical and Computational Nanoscience Group Leader at ICN2. 

Abstract: The quest for planar sp2-hybridized carbon allotropes other than graphene, such as phagraphene, graphenylene, and biphenylene network, has stimulated substantial research efforts because of the materials' predicted unique mechanical, electronic, and transport properties. However, their syntheses remain challenging due to the lack of reliable protocols for generating non-hexagonal rings during the in-plane tiling of carbon atoms. We have developed an on-surface synthesis strategy by which we first generate straight polymer chains, which then link to form the non-benzenoid graphene isomers. Using this approach, we achieved the bottom-up growth of ultraflat biphenylene network with periodically arranged four-, six-, and eight-membered rings of sp2-hybridized carbon atoms, through on-surface inter-polymer dehydrofluorination (HF-zipping) reaction (Figure 1a). Apart from graphene, biphenylene network is the only experimentally known planar sp2 carbon so far. Its characterization by scanning probe methods (STM, AFM, STS) confirms the non-benzenoid nature and reveals that it is metallic rather than a dielectric already at very small dimensions [1]. While HF-zipping generates the four- and eight-membered rings during the on-surface reaction, the non-benzenoid structural elements may already be contained in the precursor: using an azulene-based precursor, we achieved sp2 carbon nanostructures with odd-numbered rings, such as phagraphene nanoribbons containing five-, six- and seven-membered rings (Figure 1b). Additional non-benzenoid four- and seven-membered rings can be formed during dehydrogenative C-C coupling of the intermediate 2,6-polyazulene chains, resulting in tetra-penta-hepta(TPH)-graphene (Figure 1c) with metallic properties [2]. 


 [1] Q.T. Fan, L.H. Yan, M.W. Tripp, O. Krejči, S. Dimosthenous, S.R. Kachel, M.Y. Chen, A.S. Foster, U. Koert, P. Liljeroth, J.M. Gottfried, Science 372, 852-856 (2021).

[2] Q.T. Fan, D. Martin-Jimenez, D. Ebeling, C.K. Krug, L. Brechmann, C. Kohlmeyer, G. Hilt, W. Hieringer, A. Schirmeisen, J.M. Gottfried, J. Am. Chem. Soc. 141, 17713-17720 (2019).

Bio:J. Michael Gottfried is a professor of Physical Chemistry at the University of Marburg, Germany. His current research interests encompass on-surface synthesis, cyclic nanographenes, synthetic carbon allotropes, non-benzenoid aromatic systems, and porphyrin-based materials, which are generated and studied using advanced surface-science techniques. He received his PhD degree in 2003 from Free University of Berlin, Germany. After postdoctoral research at the University of Washington, USA, and a habilitation at the University of Erlangen-Nuremberg, Germany, he was appointed to his current position in 2011. The held a guest professor¬ship at the University of Science and Technology of China and received the International Partnership Award for Young Scientists of the Chinese Academy of Sciences and the SCS Lectureship of the Swiss Chemical Society, among other awards. He is the vice-spokesperson of CRC 1083 “Structure and Dynamics of Internal Interfaces”.