NCAFM2023 Programme Booklet

Wang Lulu 1 , Peng Xinnan 1 , Su Jie 1 , Aurelio Gallardo 2 , Yang Hui 1 , Chen Qifan 2 , Lyu Pin 1 , Pavel Jelínek 2 , Liu Junzhi *3 , Wong Ming Wah *1 , Lu Jiong *1,4 1 Department of Chemistry, National University of Singapore, 117543 Singapore 2 Institute of Physics, The Czech Academy of Sciences, 16200 Prague, Czech Republic 3 Department of Chemistry and State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, 999077 Hong Kong, China 4 Centre for Advanced 2D Materials (CA2DM), National University of Singapore, 117546 Singapore SELECTIVE ON-SURFACE RING-OPENING OF AROMATIC AZULENE MOIETY VIA STRAIN-INDUCED RING REARRANGEMENT AND DEAROMATIZATION The controllable ring-opening of polycyclic aromatic hydrocarbons is essential in many chemical and biological processes. However, breaking aromatic covalent structures usually requires a harsh environment with the presence of particular catalysts. Here, we first report a precise ring-opening of the seven-membered ring in the aromatic azulene moiety with high selectivity. The chemical structures of the products are identified by bond-resolved scanning probe microscopy and non-contact atomic force microscopy. With the help of density functional theory calculations, the ring-opening reaction mechanism and its chemical driving force have been revealed. The aromatic azulene moiety could be opened by steering the molecular internal strain and local aromaticity. Our findings would inspire new schemes for the manipulation and reconstruction of aromatic polycyclic aromatic hydrocarbons. Email: chmluj@nus.edu.sg

Fig. Aromaticity-modulated ring-opening of azulene moiety. (a-b) Schematic illustration of the aromaticity-driven ring-opening of azulene moiety. The blue color bar represents the level of aromaticity of the rings. (c) Large-scale STM image of the precursor molecule deposited on Au(111) before thermal annealing. (d) Magnified high-resolution STM image of an individual precursor. (e) Large-scale STM image of the products on Au(111) after thermal annealing at 400 K. (f) High-resolution nc-AFM image of the major product acquired with a CO-functionalized tip.

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