Sun Kewei, Li Donglin, Kaihara Takahito, Minakata Satoshi, Takeda Youhei, Kawai Shigeki
International Center for Young Scientists, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan.
Center for Basic Research on Materials, National Institute for Materials Science, 1-2-1 Segen, Tsukuba, Ibaraki, 305-0047, Japan.
Commun Chem. 2023 Oct 20;6(1):228. doi: 10.1038/s42004-023-01023-z.
On-surface synthesis is of importance to fabricate low dimensional carbon-based nanomaterials with atomic precision. Here, we synthesize nitrogen-doped nanographene with an [18]annulene pore and its dimer through sequential reactions of debromination, aryl-aryl coupling, cyclodehydrogenation and C-N coupling on Ag(111) from 3,12-dibromo-7,8-diaza[5]helicene. The inner structures of the products were characterized with scanning tunneling microscopy with a CO terminated tip at low temperature. Furthermore, the first four unoccupied electronic states of the nanographene were investigated with a combination of scanning tunneling spectroscopy and theoretical calculations. Except for the LUMO + 2 state observed at +1.3 V, the electronic states at 500 mV, 750 mV and 1.9 V were attributed to the superatom molecular orbitals at the [18]annulene pore, which were significantly shifted towards the Fermi level due to the hybridization with the confined surface state.
表面合成对于精确制备具有原子精度的低维碳基纳米材料具有重要意义。在此，我们通过在Ag(111)表面上，以3,12-二溴-7,8-二氮杂[5]螺旋烯为原料，依次进行脱溴、芳基-芳基偶联、环脱氢和C-N偶联反应，合成了具有[18]轮烯孔的氮掺杂纳米石墨烯及其二聚体。产物的内部结构在低温下用CO封端的扫描隧道显微镜进行了表征。此外，结合扫描隧道谱和理论计算研究了纳米石墨烯的前四个未占据电子态。除了在+1.3 V处观察到的LUMO + 2态外，500 mV、750 mV和1.9 V处的电子态归因于[18]轮烯孔处的超原子分子轨道，由于与受限表面态的杂化，这些轨道显著向费米能级移动。
