Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University , Beijing 100871, China.
Department of Applied Physics, University of Tokyo , Hongo, Tokyo 113-8656, Japan.
Nano Lett. 2017 Feb 8;17(2):856-861. doi: 10.1021/acs.nanolett.6b04139. Epub 2017 Jan 12.
Biphenyl, as the elementary unit of organic functional materials, has been widely used in electronic and optoelectronic devices. However, over decades little has been fundamentally understood regarding how the intramolecular conformation of biphenyl dynamically affects its transport properties at the single-molecule level. Here, we establish the stereoelectronic effect of biphenyl on its electrical conductance based on the platform of graphene-molecule single-molecule junctions, where a specifically designed hexaphenyl aromatic chain molecule is covalently sandwiched between nanogapped graphene point contacts to create stable single-molecule junctions. Both theoretical and temperature-dependent experimental results consistently demonstrate that phenyl twisting in the aromatic chain molecule produces different microstates with different degrees of conjugation, thus leading to stochastic switching between high- and low-conductance states. These investigations offer new molecular design insights into building functional single-molecule electrical devices.
联苯作为有机功能材料的基本单元，已被广泛应用于电子和光电设备中。然而，几十年来，人们对于联苯的分子内构象如何动态影响其在单分子水平上的输运性质，几乎没有从根本上理解。在这里，我们基于石墨烯-分子单分子结的平台，建立了联苯对其电导率的立体电子效应，其中一个特别设计的六苯基芳香链分子通过共价键夹在纳米间隙的石墨烯点接触之间，以创建稳定的单分子结。理论和温度相关的实验结果都一致表明，芳香链分子中的苯基扭曲产生了不同程度共轭的不同微观状态，从而导致高电导态和低电导态之间的随机切换。这些研究为构建功能单分子电子器件提供了新的分子设计思路。
