Configuration- and Conformation-Dependent Electronic-Structure Variations in 1,4-Disubstituted Cyclohexanes Enabled by a Carbon-to-Silicon Exchange
Configuration- and Conformation-Dependent Electronic-Structure Variations in 1,4-Disubstituted Cyclohexanes Enabled by a Carbon-to-Silicon Exchange
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DOI：
10.1002/chem.201402610
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发表时间：
2014-07-21
影响因子：
4.3
通讯作者：
Ottosson, Henrik
中科院分区：
文献类型：
--
作者：
Emanuelsson, Rikard;Lofas, Henrik;Ottosson, Henrik
环己烷具有明确定义的构象，如果其电子和光学性质在构象之间表现出实质性的差异，则可以成为理想的力控制分子开关。我们在环己烷（即环己硅烷）的较重类似物中使用sigma共轭，并表明1,4-二取代环己硅烷在这些性质上表现出构型和构象依赖的变化。顺式和反式-1,4-双（三甲基硅乙基）-环己硅烷的氧化电位相差0.11 V（计算值为0.11 V），最低紫外吸收相差0.34 eV（计算值为0.07 eV）。这与类似的全碳环己烷的相应性质的差异形成鲜明对比（分别计算为0.02 V和0.03 eV）。此外，环己硅烷反式异构体的两个椅子构象在电子结构相关性质上显示出很大的差异。这使得机械力控电导开关的计算设计成为可能，在零偏置电压下，计算出的单分子开/关比为213。
Cyclohexane, with its well-defined conformers, could be an ideal force-controlled molecular switch if it were to display substantial differences in electronic and optical properties between its conformers. We utilize sigma conjugation in heavier analogues of cyclohexanes (i.e. cyclohexasilanes) and show that 1,4-disubstituted cyclohexasilanes display configuration-and conformation-dependent variations in these properties. Cis- and trans-1,4-bis(trimethylsilylethynyl)-cyclohexasilanes display a 0.11 V difference in their oxidation potentials (computed 0.11 V) and a 0.34 eV difference in their lowest UV absorption (computed difference between first excitations 0.07 eV). This is in stark contrast to differences in the corresponding properties of analogous all-carbon cyclohexanes (computed 0.02 V and 0.03 eV, respectively). Moreover, the two chair conformers of the cyclohexasilane trans isomer display large differences in electronic-structure-related properties. This enables computational design of a mechanically force-controlled conductance switch with a calculated single-molecule ON/OFF ratio of 213 at zero-bias voltage.