Control of Metal Catalyst Selectivity through Specific Noncovalent Molecular Interactions
Control of Metal Catalyst Selectivity through Specific Noncovalent Molecular Interactions
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DOI：
10.1021/ja411973p
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发表时间：
2014-01-08
影响因子：
15
通讯作者：
Medlin, J. Will
中科院分区：
文献类型：
--
作者：
Kahsar, Karl R.;Schwartz, Daniel K.;Medlin, J. Will
通过利用非共价相互作用来指导反应物结合几何形状，可以潜在地改善在固体催化剂上进行的化学反应的特异性。在这里，我们应用硫醇盐自组装单分子膜（SAMs）与适当的结构，Pt/Al 2 O3催化剂选择性地定向反应物分子肉桂醛在与氢化所需的产品肉桂醇的配置。虽然表面活性位点上的非特异性作用被证明通常提高选择性，肉桂醛和苯基化SAM的苯环之间的特定芳香族堆积相互作用允许调节反应选择性而不损害所需产物形成的速率。红外光谱表明，增加的选择性是由于反应物在催化剂表面上的有利取向。相比之下，氢化不含苯环的不饱和醛显示出不可调的选择性改善，表明硫醇自组装膜可以通过非特异性表面效应和配体特异性近表面效应的组合来改善反应选择性。
The specificity of chemical reactions conducted over solid catalysts can potentially be improved by utilizing noncovalent interactions to direct reactant binding geometry. Here we apply thiolate self-assembled monolayers (SAMs) with an appropriate structure to Pt/Al2O3 catalysts to selectively orient the reactant molecule cinnamaldehyde in a configuration associated with hydrogenation to the desired product cinnamyl alcohol. While nonspecific effects on the surface active site were shown to generally enhance selectivity, specific aromatic stacking interactions between the phenyl ring of cinnamaldehyde and phenylated SAMs allowed tuning of reaction selectivity without compromising the rate of desired product formation. Infrared spectroscopy showed that increased selectivity was a result of favorable orientation of the reactant on the catalyst surface. In contrast, hydrogenation of an unsaturated aldehyde without a phenyl ring showed a nontunable improvement in selectivity, indicating that thiol SAMs can improve reaction selectivity through a combination of nonspecific surface effects and ligand-specific near-surface effects.