Quantum interference and heteroaromaticity of para- and meta-linked bridged biphenyl units in single molecular conductance measurements.
Quantum interference and heteroaromaticity of para- and meta-linked bridged biphenyl units in single molecular conductance measurements.
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DOI：
10.1038/s41598-017-01903-0
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发表时间：
2017-05-11
影响因子：
4.6
通讯作者：
Bryce MR
中科院分区：
文献类型：
--
作者：
Gantenbein M;Wang L;Al-Jobory AA;Ismael AK;Lambert CJ;Hong W;Bryce MR
分子核心的(杂化)芳香性与其在单个分子结中的电导之间是否存在关联？为了解决这个在分子电子学中具有重要意义的问题，合成了以二苯并噻吩苯、咔唑、二苯并呋喃和荧烯为核心单元的低聚(芳撑-乙炔)(OAE)分子线。为了比较，我们研究了联苯核。已得到两个同分异构体系列，其中4-乙炔基吡啶单元连接到核心，或者在对位(对位系列1-5)或偏位(对位系列6-10)。使用机械控制的断点测量和密度泛函理论计算的实验和计算相结合的研究表明，与元系相比，对位系列的电导始终更高：这与对位系列中π-体系的共轭增加是一致的。在对位系列中，电导按杂芳度(dibenzothiophene <； carbazole <； dibenzofuran).递减的顺序增加然而，元系列中的序列非常不同，其中dibenzothiophene ≈ dibenzofuran <； carbazole.电导值的理论值与实验值符合得很好。我们的研究表明，分子核心单元中的量子干涉和杂芳性在决定单分子结的电导中起着重要且相互关联的作用。
Is there a correlation between the (hetero)aromaticity of the core of a molecule and its conductance in a single molecular junction? To address this question, which is of fundamental interest in molecular electronics, oligo(arylene-ethynylene) (OAE) molecular wires have been synthesized with core units comprising dibenzothiophene, carbazole, dibenzofuran and fluorene. The biphenyl core has been studied for comparison. Two isomeric series have been obtained with 4-ethynylpyridine units linked to the core either at para-para positions (para series 1–5) or meta-meta positions (meta series 6–10). A combined experimental and computational study, using mechanically controlled break junction measurements and density functional theory calculations, demonstrates consistently higher conductance in the para series compared to the meta series: this is in agreement with increased conjugation of the π–system in the para series. Within the para series conductance increases in the order of decreasing heteroaromaticity (dibenzothiophene < carbazole < dibenzofuran). However, the sequence is very different in the meta series, where dibenzothiophene ≈ dibenzofuran < carbazole. Excellent agreement between theoretical and experimental conductance values is obtained. Our study establishes that both quantum interference and heteroaromaticity in the molecular core units play important and inter-related roles in determining the conductance of single molecular junctions.