Selection of conformational states in self-assembled surface structures formed from an oligo(naphthylene-ethynylene) 3-bit binary switch
Selection of conformational states in self-assembled surface structures formed from an oligo(naphthylene-ethynylene) 3-bit binary switch
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DOI：
10.1063/1.4908062
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发表时间：
2015-03-14
影响因子：
4.4
通讯作者：
Linderoth, T. R.
中科院分区：
文献类型：
--
作者：
Ning, Y.;Cramer, J. R.;Linderoth, T. R.
表面上的超分子自组装通常涉及分子构象柔性，其可以起到丰富所形成的结构的变化和复杂性的作用。然而，在表面自组装过程中如何选择分子构象状态的系统和明确的调查是相对稀缺的。在这里，我们使用高分辨率扫描隧道显微镜和密度泛函理论（DFT）计算相结合，以研究自组装的定制设计的分子能够假设八个不同的表面构象（四个对映体对）。构象的结果从二进制位置的n = 3萘单元的线性低聚（亚萘基-乙炔基）的骨干。在Au（111）表面，羧基和叔丁基苯基官能团的相互作用使分子形成了砖壁和片层两种有序相。这些结构各自涉及两种构象状态的分子，并且在两种类型的结构中涉及的构象异构体之间存在明显的分离。在Cu（111）上，通过羧酸-底物结合分离的单个分子显示出涉及所有可能的构象状态的分布。总之，这些观察意味着分子自组装时构象状态的选择和适应。从DFT模型和分子构象的统计分析，所观察到的构象状态的选择归因于萘单元之间的空间相互作用。本研究增强了我们的理解，如何有序和选择的分子构象是由分子间的相互作用控制在一个复杂的情况下，许多不同的构象状态的参与分子。(C)2015 AIP Publishing LLC.
Supra-molecular self-assembly on surfaces often involves molecular conformational flexibility which may act to enrich the variation and complexity of the structures formed. However, systematic and explicit investigations of how molecular conformational states are selected in surface self-assembly processes are relatively scarce. Here, we use a combination of high-resolution scanning tunneling microscopy and Density Functional Theory (DFT) calculations to investigate self-assembly for a custom-designed molecule capable of assuming eight distinct surface conformations (four enantiomeric pairs). The conformations result from binary positions of n = 3 naphtalene units on a linear oligo(naphthylene-ethynylene) backbone. On Au(111), inter-molecular interactions involving carboxyl and bulky tert-butyl-phenyl functional groups induce the molecules to form two ordered phases with brick-wall and lamella structure, respectively. These structures each involve molecules in two conformational states, and there is a clear separation between the conformers involved in the two types of structures. On Cu(111), individual molecules isolated by carboxylate-substrate binding show a distribution involving all possible conformational states. Together these observations imply selection and adaptation of conformational states upon molecular self-assembly. From DFT modeling and statistical analysis of the molecular conformations, the observed selection of conformational states is attributed to steric interaction between the naphthalene units. The present study enhances our understanding of how ordering and selection of molecular conformations is controlled by intermolecular interactions in a complex situation with many distinct conformational states for the participating molecules. (C) 2015 AIP Publishing LLC.