结构可控的二茂铁分子线的合成和单分子电子输运行为的研究

The molecular wire plays a key role in the nanoelectronic circuit as connecting line and device. Structurally well-defined non-optoelectronically active linear molecules (such as OPEs), have not "switching" capabilities, and their electron transfer was very difficult modulated by physical means. Molecular wires have "switching" capability and optical (electrical) activity, for example, anthraquinone-based molecular wires, which the electro-responsive group increases the length of the molecular line so that the ability of the molecular line to transmit electrons is attenuated, and the ability to regulate electron transport is also correspondingly weakened. In contrast, ferrocene group will enhance the ability of the molecular wire to transport electrons which can be further enhanced if ferrocene is oxidized to ferrocenium ions.The current project is to design a series of ferrocene-based molecular wires and control the length and angle of the molecular wires (that is the degree of rotation of the Cp rings) by means of chemical synthesis, self-assembly techniques and changing the distance between the nano-spacing electrodes. The MCBJ-SERS combination technology and STM-BJ technology were used to investigate the electron transfer of molecular wires and reveal the switching effects, quantum interference effects, and structure-activity relationships between molecular structures. Our research has high value to design the nanoelectronic devices.

具有开关效应的分子线，在纳电子线路中起着连线和器件的功能，是纳电子线路中的关键元件。非光电活性的线状分子（如OPE），虽然结构确定，但不具有“开关”能力，利用物理手段调控其电子传输的能力较弱；而具有“开关”能力和光（电）活性的分子线（如蒽醌），活性基团增加了分子线的长度使得分子线传输电子的能力衰减，调控电子传输的能力也相应减弱。与之相比，具有较高稳定性和“开关”能力的二茂铁分子线，二茂铁基团会增强分子线的电子输运能力，二茂铁氧化后分子线的电子输运能力又会进一步增强，但茂环容易旋转分子构型难以确定。本项目拟合成一系列二茂铁分子线，通过合成手段、自组装技术和改变纳米间隔电极距离等方法，调控分子线的长度和角度（茂环旋转程度），利用MCBJ-SERS联用技术和STM裂结技术系统考察分子线的电子输运性质，揭示开关效应、量子干涉效应和分子结构间的构效关系，我们的研究对纳电子器件的设计具有参考价值。

为揭示二茂铁分子线电子传输行为，我们设计、合成了一系列经C−C、C=C或C≡C连接、不同锚定基团、两茂环可自由旋转的同环和异环二取代二茂铁分子线，以及茂环旋转受限的伸展式和折叠式2-O-[3]和2-S-[3]二茂铁环番分子线，进而把研究扩展到与二茂铁类似结构的线状分子，合成了1-,1′-二茂钌分子线和η5-环戊二烯-η6-苯钌基配合物分子线；利用电子吸收光谱、循环伏安、扫描隧道显微裂结技术（STM-BJ），结合密度泛函理论计算，系统揭示其单分子尺度下的二茂铁分子线机械开关效应、电化学开关效应、量子干涉效应等电子传输行为和结构信息，并通过调制茂环的旋转实现对其电子传输行为和量子干涉效应的调控。我们的研究对揭示开关效应、分子结构和电学性质的关系，对设计具有“开关”效应的纳电子器件具有参考价值和提供理论依据。