Study On Single Molecular Conductance Of Helicene Molecules Spin Molecules And Weak Intermolecular Interactions

Molecular electronics is a sub-discipline of organic electronics,which aims to use a single molecule or a certain number of molecular units to create functional circuits.It is not only expected to solve the miniaturization of traditional silicon-based materials,but also provides a necessary platform for exploring the intrinsic properties of materials at the molecular level.The inherent properties of single molecule such as nanometer-size,low cost,conjugated structure,and self-assembly make it a perfect complement to traditional silicon-based material electronics.With the development of single-molecule electrical characterization technology,the molecular junction dynamic junction technology represented by Scanning Probe Microscopy Break Junction(SPM-BJ)and Mechanical Controlled Break Junction(MCBJ)has become the main research method for the characterization of single-molecule electrical properties.Understanding and controlling the electrical transport properties of the main body that is molecular junction of molecular electronics has attracted attention in the scientific community.In this paper,the single-molecule electrical transport properties in three special structures of helical aromatic fused ring molecules,supramolecular based on weak intermolecular interactions,and spin molecules are studied.The research contents and results of this thesis are as follows.1.The spiral molecular wires with [6]helicene skeleton and two kinds of connecting conformations(outward and inward)of pyridine anchoring groups were designed and synthesized.Using STM-BJ technology,the unique charge transport characteristics brought by the helical structure of helicene molecules were explored,and the charge transport modes of different connection conformations were compared.By changing the phase switching frequency of the applied bias voltage,the single-molecule inductance and capacitance performance based on the ring current and the vertical current is studied.2.We designed and synthesized a monomer molecule based on 7-azaindole double hydrogen bonds.Using the STM-BJ testing platform,a dynamic double hydrogen bond supramolecular junction based on 4-thiomethyl-7-azaindole was constructed at the single molecule level.The electrical transport properties of the dynamic hydrogen bond supramolecular were analyzed and studied.At the same time,based on the pyridine supramolecular dimer assembly model,the single molecular conductance was characterized under different solvent systems,and the pyridine dimer assembly mode was clarified.3.We designed and synthesized a kind of spin molecular wire containing spin centers.Its conductivity was measured in the STM-BJ conductivity measurement platform.The experimental results show that it can still maintain the open shell characteristics between the metal electrodes and is stable in the atmospheric environment.We study the influence of spin center and steric hindrance on molecular conductance in detail.