Site-selective functionalization of only one of two identical chemical groups within one molecule is highly challenging, which hinders the production of complex organic macromolecules. Here we demonstrate that adsorption of 4,4″-diamino-p-terphenyl on a metal surface leads to a dissymmetric binding affinity. With low temperature atomic force microscopy, using CO-tip functionalization, we reveal the asymmetric adsorption geometries of 4,4″-diamino-p-terphenyl on Cu(111), while on Au(111) the symmetry is retained. This symmetry breaking on Cu(111) is caused by a lattice mismatch and interactions with the subsurface atomic layer. The dissymmetry results in a change of the binding affinity of one of the amine groups, leading to a non-stationary behavior under the influence of the scanning tip. Finally, we exploit this dissymmetric binding affinity for on-surface self-assembly with 4,4″-diamino-p-terphenyl for side-preferential attachment of 2-triphenylenecarbaldehyde. Our findings provide a new route towards surface-induced dissymmetric activation of a symmetric compound.

中文翻译：

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通过晶格失配，在Cu（111）表面上的4,4“-二氨基-对-三联苯对称分解。

在一个分子中仅两个相同化学基团之一的位点选择性功能化就极具挑战性，这阻碍了复杂有机大分子的生产。在这里，我们证明了在金属表面吸附4,4''-二氨基-对-三联苯会导致不对称的结合亲和力。在低温原子力显微镜下，使用CO-尖端功能化技术，我们揭示了4,4''-二氨基-对-叔苯基在Cu（111）上的不对称吸附几何形状，而在Au（111）上则保持了对称性。Cu（111）上的这种对称性断裂是由晶格失配和与地下原子层的相互作用引起的。不对称导致胺基之一的结合亲和力改变，导致在扫描尖端的影响下的不稳定行为。最后，我们利用这种不对称的结合亲和力进行表面自组装，并以4,4''-二氨基-对-三联苯对2-三亚苯基甲醛进行侧向优先连接。我们的发现为表面诱导对称化合物的不对称活化提供了一条新途径。