Understanding the formation of metal-molecule contact at the microscopic level is the key towards controlling and manipulating atomic-scale devices. Employing two isomers of bipyridine, $4,4^{\prime }$ bipyridine and $2,2^{\prime }$ bipyridine between gold electrodes, here, we investigate the formation of a metal-molecule bond by studying charge transport through single molecular junctions using a mechanically controlled break junction technique at room temperature. While both molecules form molecular junctions during the breaking process, closing traces show the formation of molecular junctions unambiguously for $4,4^{\prime }$ bipyridine via a conductance jump from the tunneling regime, referred to as “jump to molecular contact,” being absent for $2,2^{\prime }$ bipyridine. Through statistical analysis of the data, along with molecular dynamics and first-principles calculations, we establish that contact formation is strongly connected with the molecular structure of the electrodes as well as how the junction is broken during the breaking process, providing important insights for using a single molecule in an electronic device.

中文翻译：

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通过电导跳跃在原子尺度上探测金属-分子接触

在微观层面了解金属-分子接触的形成是控制和操纵原子级设备的关键。采用联吡啶的两种异构体，$4,4^{\prime }$ 联吡啶和 $2,2^{\prime }$金电极之间的联吡啶，在这里，我们通过在室温下使用机械控制的断裂结技术研究通过单分子结的电荷传输来研究金属-分子键的形成。虽然两个分子在断裂过程中都形成了分子连接，但闭合的痕迹表明分子连接的形成明确地$4,4^{\prime }$ 联吡啶通过从隧道机制的电导跳跃，被称为“跳转到分子接触”，不存在 $2,2^{\prime }$联吡啶。通过对数据的统计分析，结合分子动力学和第一性原理计算，我们确定接触形成与电极的分子结构以及在断开过程中连接如何断开密切相关，为使用提供了重要的见解电子设备中的单个分子。