Extended surface chirality from supramolecular assemblies of adsorbed chiral molecules
Extended surface chirality from supramolecular assemblies of adsorbed chiral molecules
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DOI：
10.1038/35006031
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发表时间：
2000-03-23
期刊：
影响因子：
64.8
通讯作者：
Raval, R
中科院分区：
文献类型：
--
作者：
Lorenzo, MO;Baddeley, CJ;Raval, R
化学和制药工业对对映体纯化合物的需求不断增长，刺激了一系列所谓的“手性技术”的发展（参考文献1），其目的是通过指导化学反应的对映体选择性来最终控制化学反应（2）。非均相对映选择性催化（3-5）是特别有吸引力的，因为它允许在仅使用少量催化剂的情况下生产和容易地分离大量手性产物。非均相对映体选择性通常通过将手性分子吸附到催化活性表面上来诱导（1，3 -7）。通过在Cu（110）表面上吸附（R，R）-酒石酸分子形成了一种此类催化剂的模拟物：这产生了多种表面相，其中只有一种具有潜在的催化活性（8），并留下了吸附的手性分子如何产生对映选择性的问题。在这里，我们表明，活性相由吸附的（R，R）-酒石酸，破坏现有的对称元素的基础金属和直接赋予手性的改性表面的扩展超分子组件。吸附的组件创建手性“通道”暴露裸露的金属原子，它是这些手性空间，我们认为是负责赋予对映体选择性，通过迫使反应物分子对接到催化活性金属位点的取向。我们的研究结果表明，它是可能的，以维持一个单一的手性域在整个扩展的表面-提供的反射域的相反的手性被删除的刚性和手性的局部吸附几何形状，和不等价的旋转域被删除的成功匹配的旋转对称性的吸附分子与底层金属表面。
The increasing demand of the chemical and pharmaceutical industries for enantiomerically pure compounds has spurred the development of a range of so-called 'chiral technologies' (ref. 1), which aim to exert the ultimate control over a chemical reaction by directing its enantioselectivity(2). Heterogeneous enantioselective catalysis(3-5) is particularly attractive because it allows the production and ready separation of large quantities of chiral product while using only small quantities of catalyst. Heterogeneous enantioselectivity is usually induced by adsorbing chiral molecules onto catalytically active surfaces(1,3-7). A mimic of one such catalyst is formed by adsorbing (R,R)-tartaric acid molecules on Cu(110) surfaces: this generates a variety of surface phases, of which only one is potentially catalytically active(8), and leaves the question of how adsorbed chiral molecules give rise to enantioselectivity. Here we show that the active phase consists of extended supramolecular assemblies of adsorbed (R,R)-tartaric acid, which destroy existing symmetry elements of the underlying metal and directly bestow chirality to the modified surface. The adsorbed assemblies create chiral 'channels' exposing bare metal atoms, and it is these chiral spaces that we believe to be responsible for imparting enantioselectivity, by forcing the orientation of reactant molecules docking onto catalytically active metal sites. Our findings demonstrate that it is possible to sustain a single chiral domain across an extended surface-provided that reflection domains of opposite handedness are removed by a rigid and chiral local adsorption geometry, and that inequivalent rotation domains are removed by successful matching of the rotational symmetry of the adsorbed molecule with that of the underlying metal surface.