Highly conducting single-molecule topological insulators based on mono- and di-radical cations
Highly conducting single-molecule topological insulators based on mono- and di-radical cations
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DOI：
10.1038/s41557-022-00978-1
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发表时间：
2022-07-07
期刊：
影响因子：
21.8
通讯作者：
Venkataraman, Latha
中科院分区：
文献类型：
--
作者：
Li, Liang;Low, Jonathan Z.;Venkataraman, Latha
单分子拓扑绝缘体是一种很有希望的纳米尺度导线材料。一个关键的优点是它们表现出准金属传输的能力，与共轭分子线相反，共轭分子线通常表现出随着线长度增加而衰减的低电导。在这里，我们研究了一个家庭的oligophenylene-bridged双（三芳基胺）与可调和稳定的单或二-radicaloid字符。这些金属丝可以分别进行单电子和双电子化学氧化，生成相应的单阳离子和双阳离子。我们发现，氧化的电线表现出相反的电导随长度的增加而衰减，与预期的Su-Schrieffer-Heeger型一维拓扑绝缘体。这里报道的2.6 nm长的双阳离子显示出大于0.1G（0）的电导，其中G（0）是电导量子，比中性形式大5，400倍。所观察到的电导-长度关系在单阳离子和双阳离子系列之间是相似的。密度泛函理论计算阐明了自由基的前沿轨道和离域如何促进所观察到的非经典准金属行为。
Single-molecule topological insulators are promising candidates as conducting wires over nanometre length scales. A key advantage is their ability to exhibit quasi-metallic transport, in contrast to conjugated molecular wires which typically exhibit a low conductance that decays as the wire length increases. Here, we study a family of oligophenylene-bridged bis(triarylamines) with tunable and stable mono- or di-radicaloid character. These wires can undergo one- and two-electron chemical oxidations to the corresponding mono-cation and di-cation, respectively. We show that the oxidized wires exhibit reversed conductance decay with increasing length, consistent with the expectation for Su-Schrieffer-Heeger-type one-dimensional topological insulators. The 2.6-nm-long di-cation reported here displays a conductance greater than 0.1G(0), where G(0) is the conductance quantum, a factor of 5,400 greater than the neutral form. The observed conductance-length relationship is similar between the mono-cation and di-cation series. Density functional theory calculations elucidate how the frontier orbitals and delocalization of radicals facilitate the observed non-classical quasi-metallic behaviour.