Synthesis,Characterization And Charge Transport Properties Of Molecular Wires Bridged By 1,3-benzene

Because the size of traditional electronic devices represented by silicon-based semiconductors is approaching the physical limit,researchers have turned their attention to the field of molecular electronics.The main content of their research is to build electronic devices via bottom-up method.Molecular devices include molecular wires,molecular rectifiers,molecular switches,etc.Molecular wires serve as a bridge between molecular devices and the macro world,so they have very important research significance.The most ideal way to study the electronic transport characteristics of molecular wires is to construct a "metal-molecule-metal" heterojunction and study its single-molecule conductance.It was found that due to the destructive quantum interference effect of the m-benzene molecular wire,the single-molecular conductance of 1,4-p-benzene molecular wire is up to two orders of magnitude higher than that of the 1,3-m-benzene molecular wire.Recently,the research groups of Hongwen Jing of Xiamen University,Tao Nongjian of Georgia Institute of Technology and Zhou Xiaoshun of Zhejiang Normal University have also found that electrochemical techniques can be used to electrochemically regulate the 1,3-m-benzene molecular wire to increase the single molecule conductance by two Orders of magnitude,making it possible to manufacture molecular switches with quantum interference effects with good performance.In order to systematically study the influence of substituent electronic properties and substitution position on the destructive quantum interference effect.We made the following inquiry:1.In order to systematically study the influence of different electronic substituents on the quantum interference effect of 1,3-m-benzene molecular wire,electron-withdrawing groups(-NO2,-CF3),electron-donating groups(-OCH3)and heteroatom N are introduced on the benzene ring,using STM-BJ technology to investigate its single molecule conductance.The results show that:The introduction of different electronic substituents will increases the conductance of the molecular wire by about two orders of magnitude,indicating that the introduction of the substituent can significantly weaken the molecular wire Destructive quantum interference effect of 1,3-m-benzene.Electrochemical regulation of the destructive quantum interference effect of 1,3-m-benzene molecular wire shows that:(1)When the electron-withdrawing nitro group is introduced at the 2-position and 4-position,the conductance changes gently,indicating its destructiveness quantum interference effect disappears.(2)When the electron-donating methoxy group is introduced at the 4-position,there is a destructive quantum interference characteristic,but the switching ratio is smaller than that of the meta-position BT.2.In order to study the effect of bi-ruthenium complexes at different substitution positions on the electron transmission behavior of molecular wires,we synthesized 1,2-,1,3-,and 1,4-three pairs of ruthenium metal molecular line.The effects of the position of the substituent on the electrochemical behavior and spectral behavior of the bimetallic center were investigated by voltammetry and infrared spectroelectrochemical techniques.The results show that:Different substituents have a significant effect on the electrochemical behavior and spectral behavior of the bimetallic center.3.In order to investigate the effect of substituent electronic properties on the destructive quantum interference of meta-biruthenium molecular wires,electronwithdrawing groups(-NO2,-CF3)and electron-donating groups(-OCH3)And heteroatom N were introduced to study its effect on the electrochemical behavior and spectral behavior of the bi-ruthenium center.The results show that:Introduction of electron-donating groups is conducive to the interaction of bi-ruthenium centers,and the introduction of electron-withdrawing groups is on the contrast of electron-donating groups.