Rao B V, Kwon K Y, Zhang J, Liu A, Bartels L
Pierce Hall, University of California, Riverside, California 92521, USA.
Langmuir. 2004 May 25;20(11):4406-12. doi: 10.1021/la030364f.
We present a low-temperature scanning tunneling microscopy study of increasing coverages of 2,5-dichlorothiophenol, an asymmetrically halo-substituted aromatic thiol, on Cu(111). At low coverage, deprotonation of the thiol occurs spontaneously upon adsorption at 80 K. Albeit the low deposition temperature, we find the formation of adsorbate islands at low coverage, which coalesce into a well-ordered film of horizontally adsorbed molecules at increasing coverage. This behavior indicates (i) significant mobility of the thiols on Cu(111) even at low temperatures and (ii) attractive adsorbate-adsorbate interactions. At higher coverages intermolecular interactions prevent long-range diffusion of adsorbates and thermal activation of the S-H bond becomes necessary. A close analysis of the molecular films reveals chiral recognition between neighboring molecules, which leads to the formation of enantiopure areas on the surface. Upright orientation of individual molecules starts at the boundaries between such phases and can be induced by scanning tunneling microscopy.
我们展示了一项关于2,5-二氯苯硫酚（一种不对称卤代取代的芳香硫醇）在Cu(111)表面覆盖度增加的低温扫描隧道显微镜研究。在低覆盖度下，硫醇在80 K吸附时会自发发生去质子化。尽管沉积温度较低，但我们发现在低覆盖度下会形成吸附质岛，随着覆盖度增加，这些岛聚合并形成由水平吸附分子组成的有序薄膜。这种行为表明：(i) 即使在低温下，硫醇在Cu(111)表面也具有显著的迁移率；(ii) 吸附质 - 吸附质之间存在吸引相互作用。在较高覆盖度下，分子间相互作用会阻止吸附质的长程扩散，此时S - H键的热活化变得必要。对分子薄膜的仔细分析揭示了相邻分子之间的手性识别，这导致表面上形成对映体纯区域。单个分子的直立取向始于这些相之间的边界，并且可以通过扫描隧道显微镜诱导。
