Zhang Jing, Li Bin, Cui Xuefeng, Wang Bing, Yang Jinlong, Hou J G
Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
J Am Chem Soc. 2009 Apr 29;131(16):5885-90. doi: 10.1021/ja9001986.
We have investigated the self-assembly of 2,4,6-tris(2-pyridyl)-1,3,5-triazine (TPTZ) molecule on Au(111) surface using an ultrahigh vacuum low-temperature scanning tunneling microscope. The TPTZ molecules form enantiomorphous domains composed of rhombic supercells with various periods depending on the coverage of molecules, that is, "1 x 1" and "2 x 2" structures at low coverages, and "6 x 6", "7 x 7", and "8 x 8" structures at higher coverages. In a unit cell of a certain enantiomer, the two triangular half-unit cells, consisting of adsorbed TPTZ molecules, are centrosymmetric to each other. The molecules inside each half-unit cell are bound to each other through a single -CH...N- hydrogen bond, while the molecules at the boundaries between half-unit cells are bound through double -CH...N- hydrogen bonds. The STM images and the DFT calculations reveal that the molecules in an enantiomorphous domain adopt the same adsorption orientation of either R-TPTZ or L-TPTZ, which indicates that the adsorbed TPTZ molecules on Au(111) undergo spontaneous chiral resolution. The subtle balance between the intermolecular interaction and the molecule-substrate interaction tunes the period of the superstructure. The total interaction energy densities obtained from the DFT calculations explain the experimental observations quantitatively.
我们使用超高真空低温扫描隧道显微镜研究了2,4,6-三（2-吡啶基）-1,3,5-三嗪（TPTZ）分子在Au(111)表面的自组装。TPTZ分子形成由菱形超胞组成的对映体畴，其周期根据分子覆盖率的不同而变化，即在低覆盖率下为“1×1”和“2×2”结构，在较高覆盖率下为“6×6”、“7×7”和“8×8”结构。在某一对映体的一个晶胞中，由吸附的TPTZ分子组成的两个三角形半晶胞彼此呈中心对称。每个半晶胞内的分子通过单-CH...N-氢键相互结合，而半晶胞之间边界处的分子通过双-CH...N-氢键相互结合。扫描隧道显微镜图像和密度泛函理论计算表明，对映体畴中的分子采用相同的R-TPTZ或L-TPTZ吸附取向，这表明在Au(111)上吸附的TPTZ分子发生了自发的手性拆分。分子间相互作用与分子-衬底相互作用之间的微妙平衡调节了超结构的周期。从密度泛函理论计算得到的总相互作用能密度定量地解释了实验观察结果。
