Chiral segregation driven by a dynamical response of the adsorption footprint to the local adsorption environment: bitartrate on Cu(110).
Chiral segregation driven by a dynamical response of the adsorption footprint to the local adsorption environment: bitartrate on Cu(110).
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DOI：
10.1039/c7cp00622e
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发表时间：
2017-03
期刊：
影响因子：
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通讯作者：
G. Darling;M. Forster;C. Lin;N. Liu;R. Raval;A. Hodgson
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文献类型：
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作者：
G. Darling;M. Forster;C. Lin;N. Liu;R. Raval;A. Hodgson
手性分子在表面的局部或整体有序化是手性分离和多相不对称催化的关键步骤。使用密度泛函理论和扫描探针显微镜的结果，我们发现，公认的结构模型为众所周知的酒石酸氢铜（110）手性系统不能解释所观察到的手性分离。相反，我们表明，这种强烈的约束，手性吸附物改变其吸附足迹在响应当地环境。灵活的吸附几何形状允许酒石酸氢盐形成稳定的纯手性三聚体链，其中中心分子从矩形重组为倾斜足迹，打破其内部氢键，以便与相邻吸附物形成强分子间氢键。含有混合对映异构体的外消旋结构不形成强氢键，为实验观察到的手性分离提供热力学驱动力。这一结果表明，在指导手性组装和分离的分子吸附足迹在表面的动力学响应的重要性。强化学吸附的对映异构体的能力，改变足迹取决于当地的吸附环境表明，超分子组装在表面可能会表现出更复杂的动力学行为比迄今为止怀疑，这最终可以定制，导致环境和刺激响应的手性表面。
Local or global ordering of chiral molecules at a surface is a key step in both chiral separation and heterogeneous enantioselective catalysis. Using density functional theory and scanning probe microscopy results, we find that the accepted structural model for the well known bitartrate on Cu(110) chiral system cannot account for the chiral segregation observed. Instead, we show that this strongly bound, chiral adsorbate changes its adsorption footprint in response to the local environment. The flexible adsorption geometry allows bitartrate to form stable homochiral trimer chains in which the central molecule restructures from a rectangular to an oblique footprint, breaking its internal hydrogen bonds in order to form strong intermolecular hydrogen bonds to neighbouring adsorbates. Racemic structures containing mixed enantiomers do not form strong hydrogen bonds, providing the thermodynamic driving force for the chiral separation that is observed experimentally. This result shows the importance of considering the dynamical response of molecular adsorption footprints at the surface in directing chiral assembly and segregation. The ability of strongly-chemisorbed enantiomers to change footprint depending on the local adsorption environment indicates that supramolecular assemblies at surfaces may exhibit more complex dynamical behaviour than hitherto suspected, which, ultimately, could be tailored to lead to environment and stimuli-responsive chiral surfaces.