Shaporenko Andrey, Elbing Mark, Błaszczyk Alfred, von Hänisch Carsten, Mayor Marcel, Zharnikov Michael
Angewandte Physikalische Chemie, Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany.
J Phys Chem B. 2006 Mar 9;110(9):4307-17. doi: 10.1021/jp056833z.
A series of biphenyl-derived dithiol (BDDT) compounds with terminal acetyl-protected sulfur groups and different structural arrangements of both phenyl rings have been synthesized and fully characterized. The different arrangements were achieved by introducing hydrocarbon substituents in the 2 and 2' positions of the biphenyl backbone. The presented model compounds enable the investigation of the correlation between the intramolecular conformation and other physical properties of interest, like, e.g., molecular assembly or electronic transport properties. Here, the ability of these model compounds to form self-assembled monolayers (SAMs) on Au(111) and Ag(111) is investigated in details. The deprotection of the target molecules was performed in situ using either NH4OH or triethylamine (TEA) deprotection agent. The fabricated films were characterized by synchrotron-based high-resolution photoelectron spectroscopy and near-edge absorption fine structure spectroscopy. Whereas the deprotection by NH4OH was found to result in the formation of multilayer films, the deprotection by TEA allowed the preparation of densely packed BDDT SAMs with a noticeably higher orientational order and smaller molecular inclination on Ag than on Au. Introduction of the alkyl bridge between the individual rings of the biphenyl backbone did not lead to a noticeable change in the structure and packing density of the BDDT SAMs as long as the molecule had a planar conformation in the respective SAM. The deviation from this conformation resulted in the deterioration of the film quality and a decrease of the orientational order.
已经合成并全面表征了一系列具有末端乙酰基保护硫基团且两个苯环结构排列不同的联苯衍生二硫醇（BDDT）化合物。通过在联苯主链的2位和2'位引入烃取代基实现了不同的排列。所展示的模型化合物能够研究分子内构象与其他感兴趣的物理性质之间的相关性，例如分子组装或电子传输性质。在此，详细研究了这些模型化合物在Au(111)和Ag(111)上形成自组装单分子层（SAMs）的能力。使用NH₄OH或三乙胺（TEA）脱保护剂原位进行目标分子的脱保护。通过基于同步加速器的高分辨率光电子能谱和近边吸收精细结构光谱对制备的薄膜进行表征。虽然发现用NH₄OH脱保护会导致形成多层膜，但用TEA脱保护可以制备紧密堆积的BDDT SAMs，其在Ag上的取向有序度明显高于在Au上，且分子倾斜度更小。只要分子在各自的SAM中具有平面构象，在联苯主链的各个环之间引入烷基桥不会导致BDDT SAMs的结构和堆积密度发生明显变化。偏离这种构象会导致薄膜质量下降和取向有序度降低。
