单分子结中交叉共轭系统的量子干涉对分子构型的依赖性,Molecular Systems Design & Engineering

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单分子结中交叉共轭系统的量子干涉对分子构型的依赖性
Molecular Systems Design & Engineering ( IF 3.2 ) Pub Date : 2022-07-07 , DOI: 10.1039/d2me00074a
Juan Hurtado-Gallego ₁ , Ross Davidson ₂ , Iain M. Grace ₃ , Laura Rincón-García ₁ , Andrei S. Batsanov ₂ , Martin R. Bryce ₂ , Colin J. Lambert ₃ , Nicolás Agraït _{1,

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Affiliation

我们报告了在中心烯烃位点用侧基（二苯基、9-芴基、9-噻吨或环己基）官能化的七种交叉共轭烯二炔衍生物以及受保护的硫代甲基 (SMe) 或硫代乙酸酯官能化的实验和计算研究硫醇，(SAc) 基团作为锚。电导 ( G ) 和塞贝克系数 ( S ) 的测量)的金|单分子|金结是使用改进的扫描隧道显微镜-断裂结(STM-BJ)技术获得的。结果表明，大多数分子给出了多个电导平台，这归因于结内的不同分子配置。较高的电导平台与芳基悬垂单元与金电极之一相互作用一致，从而避免了电子通过烯二炔系统的传输；较低的电导平台与终端 SMe 或 S 单元都锚定到电极上是一致的。大多数化合物在 3.7-12.7 μV K ^-1范围内显示S的正值，表明通过 HOMO 的电子传输，而其中一种化合物显示S的负值(-6.2 μV K ^-1 )表明LUMO在电子传输中的优势。使用密度泛函理论的理论计算表明，在较低电导平台的最高占据和最低未占据分子轨道（HOMO-LUMO 间隙）之间的间隙中存在破坏性量子干涉（DQI）特征，这支持了实验数据中观察到的趋势。

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Quantum interference dependence on molecular configurations for cross-conjugated systems in single-molecule junctions

We report a combined experimental and computational study of seven cross-conjugated enediyne derivatives functionalised with a pendant group (diphenyl, 9-fluorenyl, 9-thioxanthene or cyclohexyl) at the central alkene site, and with thiomethyl (SMe) or thioacetate, as protected thiol, (SAc) groups as anchors. Measurements of the conductance (G) and Seebeck coefficient (S) of gold|single-molecule|gold junctions were obtained using a modified scanning tunnelling microscope-break junction (STM-BJ) technique. It is shown that most of the molecules give multiple conductance plateaus ascribed to different molecular configurations inside the junction. The higher conductance plateaus are consistent with the aryl pendant units interacting with one of the gold electrodes, thereby circumventing transmission of electrons through the enediyne system; the lower conductance plateaus are consistent with anchoring of both of the terminal SMe or S units to the electrodes. Most of the compounds show a positive value of S in the range 3.7–12.7 μV K⁻¹ indicating electronic transport through the HOMO, while one of them presents a negative value of S (−6.2 μV K⁻¹) indicating a predominance of the LUMO in the electronic transport. Theoretical calculations using density functional theory show a destructive quantum interference (DQI) feature in the gap between the highest occupied and lowest unoccupied molecular orbitals (the HOMO–LUMO gap) for the lower conductance plateaus, supporting the trends observed in the experimental data.

更新日期：2022-07-07

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