Solvent Dependence of the Single Molecule Conductance of Oligoyne-Based Molecular Wires
Solvent Dependence of the Single Molecule Conductance of Oligoyne-Based Molecular Wires
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DOI：
10.1021/acs.jpcc.5b08877
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发表时间：
2016-07-28
影响因子：
3.7
通讯作者：
Garcia-Suarez, Victor M.
中科院分区：
文献类型：
--
作者：
Milan, David C.;Al-Owaedi, Oday A.;Garcia-Suarez, Victor M.
在同系寡炔系列 Me3Si-(C 相当于 C)(n)-SiMe3 (n = 2、3、4 或 5) 内，电导和电导衰减作为分子长度的函数，显示强烈依赖于溶剂介质。在均三甲苯 (MES)、1,2,4-三氯苯 (TCB) 和碳酸亚丙酯 (PC) 中，使用 I(s) 方法对 Me3Si-（C 相当于 C）(n)-SiMe3 (n = 2、3、4 和 5) 系列的每个成员进行了单分子结电导测量。在均三甲苯中，整个系列的电导较低，长度衰减较高（β 约为 1 nm(-1)）。相比之下，1,2,4-三氯苯和碳酸丙烯酯中的测量给出了更高的电导值和更低的长度衰减（β分别接近0.1和0.5 nm(-1)）。这种行为通过理论和计算研究得到了合理化，其中发现当接触费米能量接近 HOMO-LUMO 间隙的中间时，β 值较高，但当费米能量接近与占据或未占据的前沿轨道共振时，β 值降低。使用基于 DFT 的分子连接模型进一步探索了 MES、PC 和 TCB 之间的不同电导率和 β 值，其中包括与寡炔主链相互作用的溶剂分子。实验结果与这些“溶剂化”结模型之间取得了良好的一致性，为溶剂如何影响基于寡炔的单分子结中的电荷传输提供了新的见解。
The conductance and the decay of conductance as a function of molecular length within a homologous series of oligoynes, Me3Si-(C equivalent to C)(n)-SiMe3 (n = 2, 3, 4, or 5), is shown to depend strongly on the solvent medium. Single molecule junction conductance measurements have been made with the I(s) method for each member of the series Me3Si-(C equivalent to C)(n)-SiMe3 (n = 2, 3, 4, and 5) in mesitylene (MES), 1,2,4-trichlorobenzene (TCB), and propylene carbonate (PC). In mesitylene, a lower conductance is obtained across the whole series with a higher length decay (beta approximate to 1 nm(-1)). In contrast, measurements in 1,2,4-trichlorobenzene and propylene carbonate give higher conductance values with lower length decay (beta approximate to 0.1 and 0.5 nm(-1) respectively). This behavior is rationalized through theoretical and computational investigations, where beta values are found to be higher when the contact Fermi energies are dose to the middle of the HOMO-LUMO gap but decrease as the Fermi energies approach resonance with either the occupied or unoccupied frontier orbitals. The different conductance and beta values between MES, PC, and TCB have been further explored using DFT-based models of the molecular junction, which include solvent molecules interacting with the oligoyne backbone. Good agreement between the experimental results and these "solvated" junction models is achieved, giving new insights into how solvent can influence charge transport in oligoyne-based single molecule junctions.