On-Surface Synthesis of Functionalized Honeycombene Macrocycles and Related Two-Dimensional Polymer Structures

• Applicants: Professor Dr. Michael Gottfried; Professor Dr. Gerhard Hilt
• Subject Area: Solid State and Surface Chemistry, Material Synthesis ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 290068185

• Final Report Year: 2021

Final Report Abstract

We  successfully  explored  the  on‐surface  synthesis  (OSS)  of  honeycombenes  and  related  nanographenes, nanoribbons, and 2D polymers. The results were published in high‐ranking journals  including Science (1), J. Am. Chem. Soc. (4), Nature Comm. (1), ACS Nano (5) and Chem. Comm. (1).  Mechanistic studies resulted in a thorough understanding of on‐surface reactivity as a solid basis for a  high degree of selectivity control. Deviations from the originally planned work were necessary to stay  competitive in a highly dynamic field of research.  Reaction control in on‐surface synthesis: We developed novel concepts for selective reaction control  in  OSS.  To  obtain  high  yields  of  macrocycles  in  OSS,  various  approaches  were  developed  including  thermodynamic  and  kinetic  control,  steric  control  through  precursor  design,  control  by  surface  interactions and surface structure, as well as 0D and 1D surface templates. These methods are partly  applied in combination. Extensive mechanistic studies of OSS reaction were performed to establish  and optimize the principles of reaction control and to maximize yields and selectivities. Moreover, we  expanded the tool box of reaction types in OSS, for example with the interpolymer dehydrofluorination  (HF‐zipping) reaction.  Macrocycles: We synthesized various π‐conjugated oligophenylene macrocycles such as the hexagonal  honeycombenes and related molecules with square, pentagonal and heptagonal symmetry. Detailed  mechanistic  studies  were  performed  to  understand  the  competition  of  ring  formation  versus  chain  growth  in  on‐surface  polymerization.  Novel  approaches  for  controlling  the  ring/chain  competition  were  introduced,  such  as  the  on‐surface  high‐dilution  principle,  on‐surface  templates,  and  other  kinetic  /  thermodynamic  principles.  Another  ground‐breaking  achievement  was  the  first  OSS  of  a  cycloarene.  This  hexagonal  nanographene  macrocycle  (C108H36)  and  a  related  compound  were  synthesized  by  cyclotrimerization  using  Ullmann  coupling,  followed  by  cyclodehydrogenation.  The  reaction was carefully controlled by precursor design and adsorbate‐substrate interactions. We also  achieved the first OSS of kekulene as a prototypical cycloarene. The reaction proceeds with very high  yield  and  selectivity,  resulting  in  ordered  monolayers  of  kekulene.  The  sample  quality  was  even  sufficient  for  orbital  tomography  experiments,  which  confirmed  the  Clar  model  of  aromaticity  for  kekulene.  Using  OSS,  we  also  achieved  the  first  synthesis  of  a  superphthalocyanine  (superPC)  derivative  without  uranium.  In  solution,  the  ‐extended  superPCs  form  only  with  uranium  and  decompose  on  attempts  to  exchange  the  metal  center.  Using  the  2D  confinement  and  template  effects, made the first Gd‐superPC derivative. In addition, various other organometallic macrocycles  were synthesized and used e.g. for studying the ring/chain competition in on‐surface reactions.  Nanoribbons and 2D carbon materials: We synthesized the first planar all‐sp2 carbon allotrope besides  graphene. This new material, biphenylene network, contains 4‐, 6‐, and 8‐membered rings and was  made on a gold surface using a novel reaction type (inter‐polymer dehydrofluorination). Before, we  succeeded in making the first azulene‐based carbon nanoribbons with 4‐, 5‐, 6‐, and 7‐membered rings  (phagraphene,  TPH‐graphene).  Due  to  their  non‐benzenoid  and/or  non‐alternant  topology,  these  carbon  materials  have  unique  properties  that  are  very  different  from  those  of  graphene,  such  as  metallicity at very small dimensions.   Some of our results received considerable attention in the media, social networks, and the scientific  literature.

Publications

• Confined Synthesis of Organometallic Chains and Macrocycles by Cu–O Surface Templating. ACS Nano 10 (2016) 3747‐3754
  Q. Fan, J. Dai, T. Wang, J. Kuttner, G. Hilt, J.M. Gottfried, J.F. Zhu
  
• The role of the substrate structure in the on‐surface synthesis of organometallic and covalent oligophenylene chains. Phys. Chem. Chem. Phys. 18 (2016) 20627‐20634
  J. Dai, Q. Fan, T. Wang, J. Kuttner, G. Hilt, J.M. Gottfried, J.F. Zhu
  
• On‐Surface Pseudo‐High Dilution Synthesis of Macrocycles: Principle and Mechanism. ACS Nano 11 (2017) 5070‐5079
  Q.T. Fan, T. Wang, J. Dai, J. Kuttner, G. Hilt, J. M. Gottfried, J. F. Zhu
  
• On‐Surface Synthesis and Characterization of Honeycombene Oligophenylene Macrocycles. ACS Nano 11 (2017) 134‐143
  M. Chen, J. Shang, Y. Wang, K. Wu, J. Kuttner, G. Hilt, W. Hieringer, J.M. Gottfried
  
• Precise Mono‐Selective Aromatic C‐H Bond Activation by Chemisorption of Meta‐Aryne on a Metal Surface. J. Am. Chem. Soc. 140 (2018) 7526‐7532
  Q.T. Fan, S. Werner, J. Tschakert, D. Ebeling, A. Schirmeisen, G. Hilt, W. Hieringer, J.M. Gottfried
  
• Surface Adatom Mediated Structural Transformation in Bromoarene Monolayers: Precursor Phases in Surface Ullmann Reaction. ACS Nano 12 (2018) 2267‐2274
  Q.T. Fan, L. Liu, J. Dai, T. Wang, H. Ju, J. Zhao, J. Kuttner, G. Hilt, J. M. Gottfried, J.F. Zhu
  
• Nanoribbons with Non‐Alternant Topology from Fusion of Polyazulene: Carbon Allotropes Beyond Graphene. J. Am. Chem. Soc. 141 (2019) 17713‐17720
  Q.T. Fan, D. Martin‐Jimenez, D. Ebeling, C.K. Krug, L. Brechmann, C. Kohlmeyer, G. Hilt, W. Hieringer, A. Schirmeisen, J.M. Gottfried
  
• Template‐Controlled On‐Surface Synthesis of a Lanthanide Supernaphthalocyanine and its Open‐Chain Polycyanine Counterpart. Nature Comm. 10 (2019) 5049
  Q.T. Fan, J.‐N. Luy, M. Liebold, K. Greulich, M. Zugermeier, J. Sundermeyer, R. Tonner, J.M. Gottfried
  
• On‐Surface Synthesis and Characterization of a Cycloarene: C108 Graphene Ring. J. Am. Chem. Soc. 142 (2020) 894‐899
  Q.T. Fan, D. Martin‐Jimnez, S. Werner, D. Ebeling, T. Koehler, T. Vollgraff, J. Sundermeyer, W. Hieringer, A. Schirmeisen, J.M. Gottfried
  
• Biphenylene Network: A Nonbenzenoid Carbon Allotrope. Science 372 (2021) 852‐856
  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