Asymmetric Catalysis at the Mesoscale: Gold Nanoclusters Embedded in Chiral Self-Assembled Monolayer as Heterogeneous Catalyst for Asymmetric Reactions
Asymmetric Catalysis at the Mesoscale: Gold Nanoclusters Embedded in Chiral Self-Assembled Monolayer as Heterogeneous Catalyst for Asymmetric Reactions
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DOI：
10.1021/ja310640b
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发表时间：
2013-03-13
影响因子：
15
通讯作者：
Somorjai, Gabor A.
中科院分区：
文献类型：
--
作者：
Gross, Elad;Liu, Jack H.;Somorjai, Gabor A.
开发用于不对称有机转化的高度通用的手性非均相催化剂而不淬灭催化反应性的研究取得了有限的成功。虽然手性超分子结构，通过弱键连接，是高活性的均相不对称催化，它们在多相催化的应用是罕见的。本工作通过将金属纳米团簇包裹在手性自组装单分子膜中，固定在介孔SiO2载体上，制备了不对称催化剂。以烯烃环丙烷化反应为例，证明了通过控制SAM的性质，嵌入手性SAM中的Au团簇可以催化不对称反应。高达50%的对映体选择性与高非对映体选择性，而采用Au纳米团簇包覆SAM肽作为非均相催化剂的环丙烷含产品的形成。光谱测量相关的手性SAM中的氢键网络的形成，提高对映选择性。这些结果证明了催化活性金属位点和周围手性SAM的协同效应，用于形成介观尺度的对映选择性催化剂。
Research to develop highly versatile, chiral, heterogeneous catalysts for asymmetric organic transformations, without quenching the catalytic reactivity, has met with limited success. While chiral supramolecular structures, connected by weak bonds, are highly active for homogeneous asymmetric catalysis, their application in heterogeneous catalysis is rare. In this work, asymmetric catalyst was prepared by encapsulating metallic nanoclusters in chiral self-assembled monolayer (SAM), immobilized on mesoporous SiO2 support. Using olefin cyclopropanation as an example, it was demonstrated that by controlling the SAM properties, asymmetric reactions can be catalyzed by Au clusters embedded in chiral SAM. Up to 50% enantioselectivity with high diastereoselectivity were obtained while employing Au nanoclusters coated with SAM peptides as heterogeneous catalyst for the formation of cyclopropane-containing products. Spectroscopic measurements correlated the improved enantioselectivity with the formation of a hydrogen-bonding network in the chiral SAM. These results demonstrate the synergetic effect of the catalytically active metallic sites and the surrounding chiral SAM for the formation of a mesoscale enantioselective catalyst.