Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan.
Nanoscale. 2019 Mar 28;11(13):5951-5959. doi: 10.1039/c9nr00717b.
Understanding of the dynamics of the bonding states of molecules with electrodes while the molecular conformation is changed is particularly important for elucidating the details of electrochemical devices as well as molecular devices in which the reaction dynamics of the electrodes and molecules plays an important role, such as in fuel cells, catalysis and bioelectrochemical devices. However, it has been difficult to make measurements when the distance between counter electrodes is short, namely, the molecule is raised from a lying form, almost parallel and close to the electrodes, toward a standing form and vice versa. We previously have developed a method called the three-dimensional (3D) dynamic probe method, which enables conductance measurement while the conformation of a single-molecule junction is precisely controlled by scanning tunneling microscopy (STM) techniques. Here, by combining this method with density functional theory (DFT) calculations, it has become possible to simultaneously consider the effects of the dynamics of molecular structures and the bonding states at the electrodes on the local transmission pathways, local-bond contributions to conductance. Here, by performing an analysis on 1,4-benzenediamine (BDA) and 1,4-benzenedithiol (BDT) single molecule junctions, we have observed, for the first time, the effect of a change in the molecular conformations and bonding states on the local transmission pathways for a short Au electrode distance condition.
理解分子与电极之间的成键状态的动力学，同时分子构象发生变化，对于阐明电化学器件以及在电极和分子的反应动力学中起着重要作用的分子器件的细节尤为重要，例如在燃料电池、催化和生物电化学器件中。然而，当对电极之间的距离很短时，即分子从躺卧形式升高到几乎平行且靠近电极的站立形式，或者反之，进行测量是很困难的。我们之前已经开发了一种称为三维（3D）动态探针的方法，该方法可以通过扫描隧道显微镜（STM）技术精确控制单分子结的构象，同时进行电导测量。在这里，通过将这种方法与密度泛函理论（DFT）计算相结合，就有可能同时考虑分子结构动力学和电极上的成键状态对局部传输途径、电导的局部键贡献的影响。在这里，通过对 1,4-苯二胺（BDA）和 1,4-苯二硫醇（BDT）单分子结进行分析，我们首次观察到在短 Au 电极距离条件下，分子构象和成键状态的变化对局部传输途径的影响。
