Creating chiral surfaces for enantioselective heterogeneous catalysis:: R,R-Tartaric acid on Cu(110)
Creating chiral surfaces for enantioselective heterogeneous catalysis:: R,R-Tartaric acid on Cu(110)
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DOI：
10.1021/jp992188i
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发表时间：
1999-12-02
影响因子：
3.3
通讯作者：
Baddeley, CJ
中科院分区：
文献类型：
--
作者：
Lorenzo, MO;Haq, S;Baddeley, CJ
在多相催化体系中诱导对映选择性的最成功的方法之一是通过在活性金属表面上吸附手性“改性剂”分子。然而，很少有人知道的性质的活性位点上存在的改性的金属表面上，以及如何这样的改性剂赋予手性的非手性金属表面。在本文中，我们使用高分辨率表面分析技术报道了R，R-酒石酸在Cu（110）表面的吸附行为。已知R，R-酒石酸是一种非常成功的改性剂分子，用于将乙酰乙酸甲酯（最简单的β-酮酯）对映选择性氢化为产物分子S-羟基丁酸甲酯的R-对映体。低能电子衍射（LEED），扫描隧道显微镜（STM），和傅里叶变换反射吸收红外光谱（FT-RAIRS）技术的组合，使我们能够证明，一个复杂的吸附相图存在于这个系统。产生了丰富多样的有序的覆盖层结构，其中采用了优选的分子形式、键合和手性分子的取向，这取决于覆盖率、温度和时间。这些不同的吸附层在对映选择性反应中显然起着不同的作用。特别令人感兴趣的是，在某些条件下，IZ，R-酒石酸吸附层的2维顺序破坏了表面的所有对称元素，导致产生扩展的手性表面！这样的手性表面可能是一个重要的因素，在确定活性位点的非均相对映选择性反应。
One of the most successful ways of inducing enantioselectivity in a heterogeneous catalytic system is by the adsorption of chiral "modifier" molecules on the reactive metal surface. However, little is known about the nature of the active sites present on the modified metal surface and how such modifiers bestow chirality to an achiral metal surface. In this paper we report the behavior of R,R-tartaric acid adsorption on a Cu(110) surface using high-resolution surface analytical techniques. R,R-Tartaric acid is known to be an extremely successful modifier molecule for the enantioselective hydrogenation of methyl acetoacetate, the simplest beta-keto ester, to the R-enantiomer of the product molecule methyl S-hydroxybutyrate. A combination of low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and Fourier transform reflection-absorption infrared spectroscopy (FT-RAIRS) techniques has allowed us to demonstrate that a complicated adsorption phase diagram exists for this system. A rich variety of ordered overlayer structures are produced, in which preferred molecular forms, bonding and orientations of the chiral molecules are adopted, dependent on coverage, temperature and time. These different adlayers will clearly play a different role in the enantioselective reaction. Of particular interest is the fact that under certain conditions, the 2-dimensional order of the IZ,R-tartaric acid adlayer destroys all symmetry elements at the surface, leading to the creation of extended chiral surfaces! Such chiral surfaces may be an important factor in defining the active site in heterogeneous enantioselective reactions.