Sleczkowski Piotr, Katsonis Nathalie, Kapitanchuk Oleksiy, Marchenko Alexandr, Mathevet Fabrice, Croset Bernard, Lacaze Emmanuelle
CNRS UMR7588, Institut des Nano-Sciences de Paris (INSP), 75252 Paris, France.
Langmuir. 2014 Nov 11;30(44):13275-82. doi: 10.1021/la5030058. Epub 2014 Oct 28.
We investigate the expression of chirality in a monolayer formed spontaneously by 2,3,6,7,10,11-pentyloxytriphenylene (H5T) on Au(111). We resolve its interface morphology by combining scanning tunneling microscopy (STM) with theoretical calculations of intermolecular and interfacial interaction potentials. We observe two commensurate structures. While both of them belong to a hexagonal space group, analogical to the triangular symmetry of the molecule and the hexagonal symmetry of the substrate surface, they surprisingly reveal a 2D chiral character. The corresponding breaking of symmetry arises for two reasons. First it is due to the establishment of a large molecular density on the substrate, which leads to a rotation of the molecules with respect to the molecular network crystallographic axes to avoid steric repulsion between neighboring alkoxy chains. Second it is due to the molecule-substrate interactions, leading to commensurable large crystallographic cells associated with the large size of the molecule. As a consequence, molecular networks disoriented with respect to the high symmetry directions of the substrate are induced. The high simplicity of the intermolecular and molecule-substrate van der Waals interactions leading to these observations suggests a generic character for this kind of symmetry breaking. We demonstrate that, for similar molecular densities, only two kinds of molecular networks are stabilized by the molecule-substrate interactions. The most stable network favors the interfacial interactions between terminal alkoxy tails and Au(111). The metastable one favors a specific orientation of the triphenylene core with its symmetry axes collinear to the Au⟨110⟩. This specific orientation of the triphenylene cores with respect to Au(111) appears associated with an energy advantage larger by at least 0.26 eV with respect to the disoriented core.
我们研究了2,3,6,7,10,11-戊氧基三亚苯（H5T）在Au(111)上自发形成的单层中的手性表达。我们通过将扫描隧道显微镜（STM）与分子间和界面相互作用势的理论计算相结合，解析了其界面形态。我们观察到两种共格结构。虽然它们都属于六方空间群，类似于分子的三角对称性和衬底表面的六方对称性，但令人惊讶的是，它们呈现出二维手性特征。相应的对称性破缺有两个原因。首先，这是由于在衬底上建立了较大的分子密度，这导致分子相对于分子网络结晶轴发生旋转，以避免相邻烷氧基链之间的空间排斥。其次，这是由于分子与衬底的相互作用，导致与分子的大尺寸相关的可公度大结晶胞。结果，诱导了相对于衬底高对称方向取向无序的分子网络。导致这些观察结果的分子间和分子与衬底之间范德华相互作用的高度简单性表明了这种对称性破缺的一般特征。我们证明，对于相似的分子密度，分子与衬底的相互作用仅稳定两种分子网络。最稳定的网络有利于末端烷氧基尾部与Au(111)之间的界面相互作用。亚稳的网络有利于三亚苯核心的特定取向，其对称轴与Au⟨110⟩共线。相对于取向无序的核心，三亚苯核心相对于Au(111)的这种特定取向似乎具有至少0.26 eV的能量优势。
