Study On The Control Of Molecular Assembly Structure On Solid Surface By Chiral Recognition And Manipulation

In this paper,the control of molecular assembly structure by two-dimensional chiral recognition of aromatic compounds 1H,5H-benzo?1,2-d:4,5-d'?bistriazole?H₂bbta?molecules were studied by room temperature ultra-high vacuum scanning tunneling microscopy?STM?on Ag?111?,Ag?110?and Ag?100?surface.It was found that the assembly structure of H₂bbta molecules on the surface of Ag?111?and Ag?100?formed two self-assembled structures which were mirror images and had no correlation with heat treatment temperature under the action of chiral self-recognition.In addition,it was also observed that the assembly structure of H₂bbta molecules on the surface of Ag?110?was gradually regulated with the recognition of chirality.When the annealing temperature of the sample increased from 300K to 333K,and it was observed that the H₂bbta molecule with the same chirality gradually formed a large area of ordered structure.When the sample was annealed at 355K,the pure chiral structure changed into the coexistence structure containing mixed chirality.Density functional theory?DFT?calculations showed that the thermal drive and intermolecular interactions jointly induced the H₂bbta molecular chiral self-recognition and formed a mirrored H₂bbta self-assembled structure,in which N-H···N hydrogen bonds and C-H···N hydrogen bonds were the main forces.In addition,the competition between the interaction between molecules and the interaction between molecules and substrates led to the formation of mixed chirality.The self-assembled structure of fullerene(C₆₀)molecules before and after annealing on Cu?111?surface and the manipulation of the adsorption orientation of individual C₆₀ molecules after annealing were studied using room temperature scanning tunneling microscopy and low temperature scanning tunneling microscopy.It was found in the experiment that C₆₀ molecules adsorbed to Cu?111?surface by thermal deposition presented the circular and three-lobed conformations under the bias of+2V?voltage added to the sample?,and there were different adsorption orientations in the three-lobed conformation.After the sample was annealed at 473K,most of the adsorption conformations of C₆₀ molecules were converted to the three-lobe conformation,and two 4×4 ordered self-assembly structures with different adsorption orientations were formed.DFT calculations show that the up-three-lobed and down-three-lobed conformations are the two equivalent adsorption conformations with the lowest energy.The experiment also found that the three-lobed conformation after annealing can be converted into a circular conformation by the tip of STM.In addition,a single C₆₀ molecule,under the manipulation of the tip,can switch back and forth in two three-lobe conformations with different adsorption orientations,thus forming a molecular switch...