Yamane Aoshi, Fujii Shintaro, Nishino Tomoaki
Department of Chemistry, School of Science, Institute of Science Tokyo, 2-12-1 W4-10 Ookayama, Meguro-ku, Tokyo 152-8551, Japan.
ACS Omega. 2025 Sep 1;10(36):42102-42108. doi: 10.1021/acsomega.5c08235. eCollection 2025 Sep 16.
Destructive quantum interference (DQI) in single-molecule junctions can drastically suppress electron transmission, offering a powerful mechanism for modulating molecular conductance. While DQI is often dominated by molecular connectivity, it is also sensitive to molecule-electrode coupling geometry. In this study, we investigate the impact of molecule-electrode coupling geometry, especially those induced by different anchoring motifs, on the manifestation of DQI using naphthalene derivatives substituted at the 2,6- or 2,7-positions and terminated with thiolate or nitrile groups. Conductance measurement using the break junction method revealed that the 2,7-substituted thiolate-anchored molecular junction exhibited strong DQI, while the corresponding nitrile-anchored molecular junction did not, showing conductance level comparable to the 2,6-isomer. Flicker noise analysis and density functional theory-based transmission calculations suggest that the suppression of DQI in the nitrile system arises from a face-on adsorption geometry, which induces direct π-system overlap between the molecule and the Au electrodes. This overlap effectively introduces a through-space conduction pathway that bypasses DQI features present in the through-bond channel. Our findings demonstrate that subtle variations in molecule-electrode geometry can strongly influence quantum interference and provide valuable guidelines for designing molecular devices with tailored transport properties.
单分子结中的破坏性量子干涉（DQI）能够极大地抑制电子传输，为调节分子电导提供了一种强大的机制。虽然DQI通常由分子连接性主导，但它也对分子-电极耦合几何结构敏感。在本研究中，我们使用在2,6-或2,7-位取代并以硫醇盐或腈基终止的萘衍生物，研究分子-电极耦合几何结构，特别是由不同锚定基序诱导的几何结构，对DQI表现的影响。使用断结法进行的电导测量表明，2,7-取代的硫醇盐锚定分子结表现出强烈的DQI，而相应的腈基锚定分子结则没有，其电导水平与2,6-异构体相当。闪烁噪声分析和基于密度泛函理论的传输计算表明，腈基体系中DQI的抑制源于面对面的吸附几何结构，这种结构会诱导分子与金电极之间的直接π-体系重叠。这种重叠有效地引入了一条穿越空间的传导路径，绕过了通过键通道中存在的DQI特征。我们的研究结果表明，分子-电极几何结构的细微变化会强烈影响量子干涉，并为设计具有定制传输特性的分子器件提供有价值的指导。
