Emergence of Chirality in Hexagonally Packed Monolayers of Hexapentyloxytriphenylene on Au(111): A Joint Experimental and Theoretical Study
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- 作者：Piotr Sleczkowski ; Nathalie Katsonis ; Oleksiy Kapitanchuk ; Alexandr Marchenko ; Fabrice Mathevet ; Bernard Croset ; Emmanuelle Lacaze
- 刊名：Langmuir
- 出版年：2014
- 出版时间：November 11, 2014
- 年：2014
- 卷：30
- 期：44
- 页码：13275-13282
- 全文大小：555K
- ISSN：1520-5827
文摘
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鈥搒ubstrate 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鈥搒ubstrate 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鈥搒ubstrate 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鉄?10鉄? 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.