Yin Xiaodong, Zang Yaping, Zhu Liangliang, Low Jonathan Z, Liu Zhen-Fei, Cui Jing, Neaton Jeffrey B, Venkataraman Latha, Campos Luis M
Department of Chemistry, Columbia University, New York, NY 10027, USA.
Department of Applied Physics, Columbia University, New York, NY 10027, USA.
Sci Adv. 2017 Oct 27;3(10):eaao2615. doi: 10.1126/sciadv.aao2615. eCollection 2017 Oct.
Single-molecule electronic devices provide researchers with an unprecedented ability to relate novel physical phenomena to molecular chemical structures. Typically, conjugated aromatic molecular backbones are relied upon to create electronic devices, where the aromaticity of the building blocks is used to enhance conductivity. We capitalize on the classical physical organic chemistry concept of Hückel antiaromaticity by demonstrating a single-molecule switch that exhibits low conductance in the neutral state and, upon electrochemical oxidation, reversibly switches to an antiaromatic high-conducting structure. We form single-molecule devices using the scanning tunneling microscope-based break-junction technique and observe an on/off ratio of ~70 for a thiophenylidene derivative that switches to an antiaromatic state with 6-4-6-π electrons. Through supporting nuclear magnetic resonance measurements, we show that the doubly oxidized core has antiaromatic character and we use density functional theory calculations to rationalize the origin of the high-conductance state for the oxidized single-molecule junction. Together, our work demonstrates how the concept of antiaromaticity can be exploited to create single-molecule devices that are highly conducting.
单分子电子器件为研究人员提供了前所未有的能力，将新颖的物理现象与分子化学结构联系起来。通常，共轭芳香分子主链被用于制造电子器件，其中构建单元的芳香性被用来提高导电性。我们通过展示一种单分子开关来利用休克尔反芳香性这一经典物理有机化学概念，该开关在中性状态下表现出低电导率，并且在电化学氧化时可逆地切换到反芳香性的高导电结构。我们使用基于扫描隧道显微镜的断接技术形成单分子器件，并观察到一种噻吩亚基衍生物的开/关比约为70，该衍生物切换到具有6-4-6-π电子的反芳香状态。通过辅助核磁共振测量，我们表明双氧化核心具有反芳香特性，并且我们使用密度泛函理论计算来合理化氧化单分子结高导电状态的起源。总之，我们的工作展示了如何利用反芳香性概念来制造高导电的单分子器件。
