Figure: Triaza[5]triangulene, containing three graphitic nitrogen atoms synthesized on Au(111) through cyclodehydrogenation.64Substituting carbon with silicon in organic molecules and materials has long been an attractive way to modify their electronic structure and properties. Silicon-doped graphene-based materials are known to exhibit exotic properties, yet conjugated organic materials with atomically precise Si substitution have remained difficult to prepare. Here we present the on-surface synthesis of two-dimensional covalent organic frameworks (COFs) and one-dimensional graphene nanoribbons (GNRs), both incorporating 1,4-disilabenzene (C4Si2) units in their backbones. Silicon atoms were first deposited on a Au(111) surface, forming a AuSiX film on annealing. The subsequent deposition and annealing of a bromo-substituted polyaromatic hydrocarbon precursor (triphenylene or pyrene) on this surface led to the formation of the C4Si2-bridged networks, which were characterized by a combination of high-resolution scanning tunnelling microscopy (STM) and photoelectron spectroscopy supported by density functional theory calculations. Triangulenes as neutral radicals are becoming promising candidates for future applications such as spintronics and quantum technologies. Doping nitrogen atoms to the carbon structures tunes their electronic and magnetic properties, resulting in higher polyradicals. Here, we synthesize triaza[5]triangulene on Au(111) by cyclodehydrogenation, and its derivatives by cleaving C–N bonds.[1] Bond-resolved scanning tunneling microscopy and scanning tunneling spectroscopy provided detailed structural information and evidence for open-shell singlet ground state. The antiferromagnetic arrangement of the spins in positively doped triaza[5]triangulene was further confirmed by density function theory calculations. Our findings pave the way for the exploration of exotic low-dimensional quantum phases of matter in heteroatom doped organic systems.Poster Award NomineePoster Award NomineeP3-03On-Surface Synthesis of Silicon Incorporated Carbon Nanostructures Kewei Sun1 and Shigeki Kawai2,3 1 International Center for Young Scientists (ICYS), National Institute for Materials Science (NIMS) 2 Center for Basic Research on Materials, National Institute for Materials Science (NIMS) 3 Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan [1] Kewei Sun, Orlando J. Silveira, Yujing Ma, Yuri Hasegawa, Michio Matsumoto, Satoshi Kera, Ondřej Krejčí, Adam S. Foster, Shigeki Kawai. Nature Chemistry, 15, 136–142 (2023). P3-04On-surface Synthesis of Triaza[5]triangulene and its Magnetism Donglin Li1, O. J. Silveira2, H. Hayashi1, H. Maeda3, A. S. Foster2*, and S. Kawai1,4* 1 Center for Basic Research on Materials, National Institute for Materials Science (NIMS)2 Dep. Applied Physics, Aalto University, Espoo, Finland.3 Dep. Applied Chemistry, College of Life Sciences, Ritsumeikan University, Kusatsu 525-8577 Japan.4 Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 Japan. [1] D. Li, et al., Angew. Chem. Int. Ed., e202411893 (2024).
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