On-Surface Synthesis and Characterization of a High-Spin Aza-[5]-Triangulene
On-Surface Synthesis and Characterization of a High-Spin Aza-[5]-Triangulene
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高自旋氮杂-[5]-三角烯的表面合成与表征
DOI：
10.1002/ange.202307884
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发表时间：
2023
影响因子：
--
通讯作者：
Vilas-Varela M
中科院分区：
文献类型：
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作者：
Vilas-Varela M
三角烯是一类总自旋随尺寸增大而增加的开壳三角形石墨烯薄片。在过去的几年里，表面合成策略已经允许以原子精度制造和工程各种尺寸和结构的三角烯。然而，总自旋随着它们的大小而增加的直接证据仍然难以捉摸。在这项工作中，我们报道了在Au（111）表面上结合溶液和表面合成了一个大的氮掺杂三角烯（aza - [5] - triangulene），并检测了它的高自旋基态。键分辨扫描隧道显微镜图像揭示了沿之字形边缘分布的自由基态，在扫描隧道光谱中检测到弱零偏共振。这些光谱特征揭示了高自旋态的部分近藤筛选。通过几种模拟工具的组合，我们发现观察到的自由基态分布可以用一个五元基态（S=2）来解释，而不是中性物质预期的四元态（S=3/2）。这证实了电子向金属衬底的转移提高了基态的自旋。我们进一步定性描述了N -取代引起的（反）芳香性的变化，以及它在表面电荷稳定中的作用，从而导致Au上的anS=2 aza -三角烯（111）。
Triangulenes are a class of open‐shell triangular graphene flakes with total spin increasing with their size. In the last years, on‐surface‐synthesis strategies have permitted fabricating and engineering triangulenes of various sizes and structures with atomic precision. However, direct proof of the increasing total spin with their size remains elusive. In this work, we report the combined in‐solution and on‐surface synthesis of a large nitrogen‐doped triangulene (aza‐[5]‐triangulene) on a Au(111) surface, and the detection of its high‐spin ground state. Bond‐resolved scanning tunneling microscopy images uncovered radical states distributed along the zigzag edges, which were detected as weak zero‐bias resonances in scanning tunneling spectra. These spectral features reveal the partial Kondo screening of a high‐spin state. Through a combination of several simulation tools, we find that the observed distribution of radical states is explained by a quintet ground state (S=2), instead of the quartet state (S=3/2) expected for the neutral species. This confirms that electron transfer to the metal substrate raises the spin of the ground state. We further provide a qualitative description of the change of (anti)aromaticity introduced by N‐substitution, and its role in the charge stabilization on a surface, resulting in anS=2 aza‐triangulene on Au(111).