Quintero Sergio Moles, Van Nyvel Louis, Roig Nil, Casado Juan, Alonso Mercedes
Department of Physical Chemistry, University of Málaga, Campus de Teatinos s/n, Málaga 29071, Spain.
Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium.
J Phys Chem A. 2024 Aug 1;128(30):6140-6157. doi: 10.1021/acs.jpca.4c01588. Epub 2024 Jul 23.
Quantum interference (QI) effects offer unique opportunities to modulate charge transport through single molecules. In recent years, several transmission selection rules have been developed to determine constructive and destructive QIs in an intuitive and simple manner, although some of these rules fail for cross-conjugated systems. In this work, we evaluate the performance of distinct transmission rules on a broad series of anthracene and fluorene derivatives with distinctive structural features including linear-, broken-, and cross-conjugation, heteroatoms, and five-membered rings as such species affords a predictive challenge for the qualitative selection rules for QI effects. The electron transport properties and local transmission plots are first evaluated by combining DFT and the nonequilibrium Green function method allowing for an equal-footing comparison of the conductance of the different polycyclic compounds. Our findings are in line with experimental observations on the influence of the type of conjugation and the connectivity to the metallic electrodes on the transport properties. Thus, cross-conjugated systems exhibit reduced conductance values as compared to the linear-conjugated ones, although the transmission is enhanced in the -connected junctions. Remarkably, our study reveals that aromatic cores exhibit generally larger zero-bias conductance for a given connectivity, in contrast to the negative aromaticity-conductance relationship found in literature.
量子干涉（QI）效应为调控单分子中的电荷传输提供了独特的机会。近年来，已经开发了几种传输选择规则，以直观且简单的方式确定相长和相消量子干涉，尽管其中一些规则在交叉共轭体系中并不适用。在这项工作中，我们评估了不同传输规则在一系列具有独特结构特征的蒽和芴衍生物上的性能，这些特征包括线性共轭、断裂共轭和交叉共轭、杂原子以及五元环，因为这类物质对量子干涉效应的定性选择规则提出了预测挑战。首先通过结合密度泛函理论（DFT）和非平衡格林函数方法来评估电子传输性质和局部传输图，从而能够对不同多环化合物的电导进行公平比较。我们的研究结果与关于共轭类型和与金属电极连接性对传输性质影响的实验观察结果一致。因此，与线性共轭体系相比，交叉共轭体系的电导值降低，尽管在连接的结中传输增强。值得注意的是，我们的研究表明，对于给定的连接性，芳香核通常表现出更大的零偏置电导，这与文献中发现的负芳香性 - 电导关系形成对比。
