Atomic force microscopy is an impressive tool with which to directly resolve the bonding structure of organic compounds^1,2,3,4,5. The methodology usually involves chemical passivation of the probe-tip termination by attaching single molecules or atoms such as CO or Xe (refs ^1,6,7,8,9). However, these probe particles are only weakly connected to the metallic apex, which results in considerable dynamic deflection. This probe particle deflection leads to pronounced image distortions, systematic overestimation of bond lengths, and in some cases even spurious bond-like contrast features, thus inhibiting reliable data interpretation^8–12. Recently, an alternative approach to tip passivation has been used in which slightly indenting a tip into oxidized copper substrates and subsequent contrast analysis allows for the verification of an oxygen-terminated Cu tip^13,14,15. Here we show that, due to the covalently bound configuration of the terminal oxygen atom, this copper oxide tip (CuOx tip) has a high structural stability, allowing not only a quantitative determination of individual bond lengths and access to bond order effects, but also reliable intermolecular bond characterization. In particular, by removing the previous limitations of flexible probe particles, we are able to provide conclusive experimental evidence for an unusual intermolecular N–Au–N three-centre bond. Furthermore, we demonstrate that CuOx tips allow the characterization of the strength and configuration of individual hydrogen bonds within a molecular assembly.

原子力显微镜是一种令人印象深刻的工具，可用来直接解决有机化合物^1,2,3,4,5的键合结构。该方法通常涉及通过连接单个分子或原子（例如CO或Xe ）对探针末端进行化学钝化（参考文献^1,6,7,8,9）。然而，这些探针颗粒仅弱地连接到金属顶点，这导致相当大的动态偏转。这种探针粒子的偏转会导致明显的图像失真，对键长的系统性高估，甚至在某些情况下甚至会出现虚假的类似键的对比特征，从而阻碍了可靠的数据解释^8-12。最近，已经使用了另一种钝化钝头的方法，其中，将钝头略微压入氧化的铜基板中，然后进行对比分析，可以验证末端为氧的铜尖头^13,14,15。。在这里我们表明，由于末端氧原子的共价键构型，该氧化铜尖端（CuOx尖端）具有很高的结构稳定性，不仅可以定量确定各个键的长度和获得键序效应，而且还可以可靠的分子间键表征。特别是，通过消除柔性探针颗粒的先前限制，我们能够为不寻常的分子间N–Au–N三中心键提供确凿的实验证据。此外，我们证明了CuOx尖端可以表征分子组装体内单个氢键的强度和构型。