Syntheses of Heteroatom-Substituted and Three-Dimensional Nanocarbon Materials on Surfaces

I will present our recent studies on on-surface chemistry with high-resolution scanning probe microscopy operating at low temperature under ultra-high vacuum. We synthesized three-dimensional organometallic compound and graphene nanoribbon by coupling hexabromo substituted-propellane molecules on Au(111) and Ag(111). 1 In the structure, the C-Br bonds distant from the surface remained intact even after the reaction. The radical species were formed by tip-induced debromination and were also stabilized by either tip-manipulated Br atom or fullerene molecule. We also demonstrate systematic tip-induced isomerization via embedding a text of “NIMS” by following binary and ternary ascii cords, in which two chiral dehydroazulene and diradical units were used. 2 Among the three states, the diradical unit showed the spin coupling of 90 meV. For heteroatom substitution, we developed an on-surface reaction, which can synthesize graphene nanoribbon and covalent organic frameworks with silabenzene units by coupling Si atom and Br-substituted molecule. 3 The heavier congeners of cyclic aromatic compounds have been studied as an elusive target product for organic synthesis due to their high reactivity at ambient temperature and difficult isolation. Thus, this result shows the advantage of on-surface synthesis. Reference 1 S. Kawai, et al Sci. Adv. 6 , eaay8913 (2020). 2 S. Kawai, et al Nat. Commun. 14 , 7741 (2023). 3 K. Sun et al, Nat. Chem. 15 , 136 (2023).