N-heterocyclic carbenes (NHCs) have recently proven to be powerful ligands for planar surface modification in terms of chemical and electronic properties due to their structural diversity, property tunability, and high affinity for a diverse array of elements. However, the utilization of NHCs for planar surface modification has almost exclusively been limited to bulk substrates. Here, we investigate the adsorption of NHCs on a two-dimensional (2D) metal (i.e., borophene) using combined single-molecule optical/electronic spectroscopy. Tip-enhanced Raman spectroscopy reveals two distinct interfacial states between individual NHCs and borophene, which correspond to covalent (boron–carbon bonding) and van-der-Waals-type interactions. Furthermore, the impact of NHC modification on borophene’s electronic properties is demonstrated by local work function reductions, as measured by scanning tunneling spectroscopy. In addition to providing novel insight into NHC–substrate interactions in the 2D regime, this study opens up an avenue for investigations of single-molecule NHC chemistry.

N-杂环卡宾（NHC）最近被证明是化学和电子性质方面平面表面改性的强大配体，因为它们具有结构多样性、性质可调性以及对多种元素的高亲和力。然而，利用 NHC 进行平面表面改性几乎完全局限于块状基材。在这里，我们使用组合单分子光学/电子光谱研究了 NHC 在二维 (2D) 金属（即硼烯）上的吸附。尖端增强拉曼光谱揭示了单个 NHC 和硼烯之间的两种不同的界面态，这对应于共价（硼-碳键合）和范德华型相互作用。此外，通过扫描隧道光谱测量，局部逸出功的降低证明了 NHC 改性对硼烯电子特性的影响。除了提供对二维体系中 NHC-底物相互作用的新见解外，这项研究还为单分子 NHC 化学的研究开辟了一条途径。