单分子连接中交叉共轭和跳跃共轭分子的电子电导和热电势,The Journal of Physical Chemistry C

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单分子连接中交叉共轭和跳跃共轭分子的电子电导和热电势
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2023-07-06 , DOI: 10.1021/acs.jpcc.3c00742
Rebecca J Salthouse ₁ , Juan Hurtado-Gallego ₂ , Iain M Grace ₃ , Ross Davidson ₁ , Ohud Alshammari ₃ , Nicolás Agraït _{2,

4,

5} , Colin J Lambert ₃ , Martin R Bryce ₁

Affiliation

我们报告了一系列硫甲基（SMe）锚定的交叉共轭分子的综合实验和理论研究，这些分子具有无环中心桥酮及其类似的跳跃共轭醇衍生物。使用扫描隧道显微镜断裂连接技术对金|单分子|金连接中的这些分子进行研究，揭示了交叉共轭分子及其跳过共轭伙伴的相似电导 ( G ) 值。基于连接处最佳几何形状的分子的密度泛函理论的理论研究揭示了电导率相似的原因，因为醇系列化合物的预测电导率随倾斜角变化更大。热电势测量显示，交叉共轭酮分子相对于醇衍生物具有更高的塞贝克系数 ( S )，其中联苯衍生物3a的S特别高(−15.6 μV/K)，比其醇类似物增加了三倍。发现这一系列交叉共轭分子中量子干涉（QI）的预测行为是建设性的，尽管3a的破坏性 QI 特征的出现是由于 HOMO 轨道的简并性，并且可以解释该分子的S值。

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Electronic Conductance and Thermopower of Cross-Conjugated and Skipped-Conjugated Molecules in Single-Molecule Junctions

We report a combined experimental and theoretical study of a series of thiomethyl (SMe) anchored cross-conjugated molecules featuring an acyclic central bridging ketone and their analogous skipped-conjugated alcohol derivatives. Studies of these molecules in a gold|single-molecule|gold junction using scanning tunneling microscopy-break junction techniques reveal a similar conductance (G) value for both the cross-conjugated molecules and their skipped-conjugated partners. Theoretical studies based on density functional theory of the molecules in their optimum geometries in the junction reveal the reason for this similarity in conductance, as the predicted conductance for the alcohol series of compounds varies more with the tilt angle. Thermopower measurements reveal a higher Seebeck coefficient (S) for the cross-conjugated ketone molecules relative to the alcohol derivatives, with a particularly high S for the biphenyl derivative 3a (−15.6 μV/K), an increase of threefold compared to its alcohol analog. The predicted behavior of the quantum interference (QI) in this series of cross-conjugated molecules is found to be constructive, though the appearance of a destructive QI feature for 3a is due to the degeneracy of the HOMO orbital and may explain the enhancement of the value of S for this molecule.

更新日期：2023-07-06

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