Surface cis Effect: Influence of an Axial Ligand on Molecular Self-Assembly
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- 作者：Thomas Knaak ; Thiruvancheril G. Gopakumar ; Bettina Schwager ; Felix Tuczek ; Roberto Robles ; Nicolás Lorente ; Richard Berndt
- 刊名：Journal of the American Chemical Society
- 出版年：2016
- 出版时间：June 22, 2016
- 年：2016
- 卷：138
- 期：24
- 页码：7544-7550
- 全文大小：498K
- 年卷期：0
- ISSN：1520-5126
文摘
Adding ligands to molecules can have drastic and unforeseen consequences in the final products of a reaction. Recently a surface trans effect due to the weakening of a molecule–surface bond was reported. Here, we show a surface cis effect where an axial ligand at adsorbed transition-metal complexes enables lateral bonding among the molecules. In the absence of this ligand, the intermolecular interaction is repulsive and supramolecular patterns are not observed. Fe-tetramethyl-tetraazaannulene on Au(111) was investigated using low-temperature scanning tunneling microscopy and spectroscopy along with density functional theory calculations. At low coverages, the molecules remain isolated. Exposure to CO leads to axial CO bonding and induces reordering into extended clusters of chiral molecular trimers. The changed self-assembly pattern is due to a CO-induced modification of the molecular structure and the corresponding charge transfer between the molecule and the substrate, which in turn changes the lateral intermolecular forces.