Department of Chemistry and Biochemistry, University of Bern , Freiestrasse 3, CH-3012 Bern, Switzerland.
J Am Chem Soc. 2015 Feb 18;137(6):2318-27. doi: 10.1021/ja511271e. Epub 2015 Feb 4.
Single molecule charge transport characteristics of buckminsterfullerene-capped symmetric fluorene-based dumbbell-type compound 1 were investigated by scanning tunneling microscopy break junction (STM-BJ), current sensing atomic force microscopy break junction (CS-AFM-BJ), and mechanically controlled break junction (MCBJ) techniques, under ambient conditions. We also show that compound 1 is able to form highly organized defect-free surface adlayers, allowing the molecules on the surface to be addressed specifically. Two distinct single molecule conductance states (called high G(H)(1) and low G(L)(1)) were observed, depending on the pressure exerted by the probe on the junction, thus allowing molecule 1 to function as a mechanically driven molecular switch. These two distinct conductance states were attributed to the electron tunneling through the buckminsterfullerene anchoring group and fully extended molecule 1, respectively. The assignment of conductance features to these configurations was further confirmed by control experiments with asymmetrically designed buckminsterfullerene derivative 2 as well as pristine buckminsterfullerene 3, both lacking the G(L) feature.
采用扫描隧道显微镜断键（STM-BJ）、电流感应原子力显微镜断键（CS-AFM-BJ）和机械控制断键（MCBJ）技术，在环境条件下研究了富勒烯封端的对称芴基哑铃型化合物 1 的单分子电荷输运特性。我们还表明，化合物 1 能够形成高度有序且无缺陷的表面覆盖层，从而能够对表面上的分子进行特异性寻址。根据探针对结施加的压力，观察到两种不同的单分子电导状态（称为高电导 G(H)(1)和低电导 G(L)(1)），从而使分子 1 能够用作机械驱动的分子开关。这两种不同的电导状态分别归因于电子通过富勒烯锚定基团和完全伸展的分子 1 的隧道跃迁。通过用不对称设计的富勒烯衍生物 2 和缺少 G(L)特征的原始富勒烯 3 进行对照实验，进一步证实了电导特征与这些构型的对应关系。
