Triptycene Tripods for the Formation of Highly Uniform and Densely Packed Self-Assembled Monolayers with Controlled Molecular Orientation
Triptycene Tripods for the Formation of Highly Uniform and Densely Packed Self-Assembled Monolayers with Controlled Molecular Orientation
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DOI：
10.1021/jacs.9b00950
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发表时间：
2019-04-10
影响因子：
15
通讯作者：
Fukushima, Takanori
中科院分区：
文献类型：
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作者：
Ishiwari, Fumitaka;Nascimbeni, Giulia;Fukushima, Takanori
当采用自组装单层 (SAM) 来调节表面和界面特性时，非常需要能够与基材牢固结合、大面积结构均匀性、官能团精确排列以及控制其密度的有机分子。为了实现这些目标，已经开发了具有多个键合位点的三脚架系统作为传统单齿系统的替代品。然而，所有三个位点的结合几乎没有实现，因此三足 SAM 中的结构均匀性和取向顺序通常很差。为了克服这个问题，我们设计了1,8,13-三巯基甲基三蝶烯（T1）和1,8,13-三巯基三蝶烯（T2）作为潜在的三足SAM前驱体，并结合多种先进的实验技术和最先进的理论模拟研究了它们在Au(111)上的吸附行为。两种 SAM 均采用致密的嵌套六边形结构，但其吸附构型和结构均匀性有所不同。虽然基于 T2 的 SAM 表现出较低的有序度，并且与所需的三足锚定存在明显偏差，但 T1 的所有三个锚定基团都以硫醇盐的形式同等地键合到表面，导致苯环几乎垂直方向和大面积结构均匀性。这些优异的性能归因于锚定基团上构象灵活的亚甲基连接体的作用，而 T2 则不存在这种作用。两种 SAM 都显示出有趣的电子特性，并且考虑到三蝶烯框架可以通过不同位置和高度对准的尾基进行功能化，特别是 T1 似乎是复杂和高功能分子薄膜的理想对接平台。
When employing self-assembled monolayers (SAMs) for tuning surface and interface properties, organic molecules that enable strong binding to the substrate, large-area structural uniformity, precise alignment of functional groups, and control of their density are highly desirable. To achieve these goals, tripod systems bearing multiple bonding sites have been developed as an alternative to conventional monodentate systems. Bonding of all three sites has, however, hardly been achieved, with the consequence that structural uniformity and orientational order in tripodal SAMs are usually quite poor. To overcome that problem, we designed 1,8,13-trimercaptomethyltriptycene (T1) and 1,8,13-trimercaptotriptycene (T2) as potential tripodal SAM precursors and investigated their adsorption behavior on Au(111) combining several advanced experimental techniques and state-of-the-art theoretical simulations. Both SAMs adopt dense, nested hexagonal structures but differ in their adsorption configurations and structural uniformity. While the T2-based SAM exhibits a low degree of order and noticeable deviation from the desired tripodal anchoring, all three anchoring groups of T1 are equally bonded to the surface as thiolates, resulting in an almost upright orientation of the benzene rings and large-area structural uniformity. These superior properties are attributed to the effect of conformationally flexible methylene linkers at the anchoring groups, absent in the case of T2. Both SAMs display interesting electronic properties, and, bearing in mind that the triptycene framework can be functionalized by tail groups in various positions and with high degree of alignment, especially T1 appears as an ideal docking platform for complex and highly functional molecular films.