Single-Molecule Junctions Based on Bipyridine: Impact of an Unusual Reorganization on Charge Transport
Single-Molecule Junctions Based on Bipyridine: Impact of an Unusual Reorganization on Charge Transport
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DOI：
10.1021/jp412675k
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发表时间：
2014-04-24
影响因子：
3.7
通讯作者：
Baldea, Ioan
中科院分区：
文献类型：
--
作者：
Baldea, Ioan
(4，4‘)-联吡啶分子(44bpy)在分子电子学方面引起了人们的极大兴趣，因为单分子结可以通过氮-金的亲和力直接形成，从而不需要了解额外的锚定基团对分子的侵袭效应。在最近的一项研究中，通过强调环境(溶剂与环境条件)的基本作用，解决了与44bpy结的运输有关的一个明显的难题。在这篇论文中，我们通过引入分子内重组作为分析中的一个新的和基本的元素，证明了该研究结论的稳健性。鉴于最近的研究引起了人们对44bpy分子内重组的不同寻常的特性的关注，这种扩展是必要的，因为44bpy分子具有松软的、高度非谐的自由度，它与主导电荷传输的分子轨道强烈和非线性耦合。作为与显著和不寻常的分子内重组有关的另一个重要影响，我们调查了过剩(散粒)噪声，发现其值比到目前为止测量到的分子结的情况下要大得多。噪声功率和Fano因子的计算证明了能量依赖传输的重要性，这一事实在解释迄今所研究的纳米结和分子结的实验数据时被忽略了。根据这里报道的理论结果，对于比现有实验中探索的更大的偏压，分子内重组应该对44bpy中的电荷传输有更显著的总体影响，但不会太大而变得令人望而却步。这些发现应该会激励相关的实验研究朝着这个方向发展。
The (4,4')-bipyridine molecule (44bpy) has attracted particular interest in molecular electronics because single-molecule junctions can be directly formed via nitrogen-gold affinity, obviating the need of understanding nontrivial invasive effects due to extra anchoring groups. In a recent study, an apparent conundrum related to the transport through 44bpy junctions has been resolved by emphasizing the essential role of the environment (solvent vs ambient conditions). In the present paper, we demonstrate the robustness of the conclusion of that study, by introducing intramolecular reorganization as a new and essential element in the analysis. This extension is necessary in the light of recent investigations drawing attention to the unusual character of intramolecular reorganization in 44bpy as a molecule possessing a floppy, highly anharmonic degree of freedom, which is strongly and nonlinearly coupled to the molecular orbital dominating the charge transport. As a further important effect related to the significant and unusual intramolecular reorganization, we investigate the excess (shot) noise and find values substantially larger than in cases of molecular junctions wherein it has been measured so far. The noise power and Fano factor calculations demonstrate the importance of energy-dependent transmission, a fact disregarded in the interpretation of experimental data for nanojunctions and molecular junctions investigated so far. According to the theoretical results reported here, the intramolecular reorganization should have a more pronounced overall impact on the charge transport in 44bpy for bias voltages larger than those explored in existing experiments, but not much larger to become prohibitive. These findings should motivate companion experimental investigations in this direction.