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Electrostatic catalysis of a Diels-Alder reaction

机译：Diels-Alder反应的静电催化

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摘要

It is often thought that the ability to control reaction rates with an applied electrical potential gradient is unique to redox systems. However, recent theoretical studies suggest that oriented electric fields could affect the outcomes of a range of chemical reactions, regardless of whether a redox system is involved(1-4). This possibility arises because many formally covalent species can be stabilized via minor charge-separated resonance contributors. When an applied electric field is aligned in such a way as to electrostatically stabilize one of these minor forms, the degree of resonance increases, resulting in the overall stabilization of the molecule or transition state. This means that it should be possible to manipulate the kinetics and thermodynamics of non-redox processes using an external electric field, as long as the orientation of the approaching reactants with respect to the field stimulus can be controlled. Here, we provide experimental evidence that the formation of carboncarbon bonds is accelerated by an electric field. We have designed a surface model system to probe the Diels-Alder reaction, and coupled it with a scanning tunnelling microscopy break-junction approach(5-7). This technique, performed at the single-molecule level, is perfectly suited to deliver an electric-field stimulus across approaching reactants. We find a fivefold increase in the frequency of formation of single-molecule junctions, resulting from the reaction that occurs when the electric field is present and aligned so as to favour electron flow from the dienophile to the diene. Our results are qualitatively consistent with those predicted by quantum-chemical calculations in a theoretical model of this system, and herald a new approach to chemical catalysis.
机译：通常认为，通过施加的电势梯度控制反应速率的能力是氧化还原系统所独有的。但是，最近的理论研究表明，无论是否涉及氧化还原系统，定向电场都可能影响一系列化学反应的结果（1-4）。之所以出现这种可能性，是因为许多形式上共价的物质可以通过较小的电荷分离共振贡献子而稳定下来。当施加的电场以使这些次要形式之一静电稳定的方式排列时，共振度增加，导致分子或过渡态的整体稳定。这意味着，只要可以控制接近的反应物相对于电场刺激的取向，就应该有可能使用外部电场来控制非氧化还原过程的动力学和热力学。在这里，我们提供了实验证据，表明电场会加速碳-碳键的形成。我们设计了一个表面模型系统以探测Diels-Alder反应，并将其与扫描隧道显微镜断裂连接方法相结合（5-7）。该技术以单分子水平执行，非常适合在接近的反应物上传递电场刺激。我们发现单分子连接的形成频率增加了五倍，这是由电场存在并排列以利于电子从亲二烯体到二烯的流动而发生的。我们的结果与该系统理论模型中的量子化学计算所预测的结果在质量上是一致的，并预示着一种新的化学催化方法。

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  • 来源
    《Nature》 |2016年第7592期|88-91|共4页
  • 作者

    Aragones Albert C.; Aworth Naomi L. H.; Darwish Nadim; Iampi Simone C.; Bloomfield Nathaniel J.; Wallace Gordon G.; Diez-Perez Ismael; Coote Michelle L.;

  • 作者单位

    Univ Barcelona, Dept Quim Fis, Diagonal 645, E-08028 Barcelona, Catalonia, Spain|Inst Bioengn Catalunya IBEC, Baldiri Reixac 15-21, Barcelona 08028, Catalonia, Spain|Ctr Invest Biomed Red CIBER BBN, Campus Rio Ebro Edificio I D, Zaragoza 50018, Spain;

    Australian Natl Univ, Res Sch Chem, ARC Ctr Excellence Electromat Sci, Canberra, ACT 2601, Australia;

    Univ Barcelona, Dept Quim Fis, Diagonal 645, E-08028 Barcelona, Catalonia, Spain|Inst Bioengn Catalunya IBEC, Baldiri Reixac 15-21, Barcelona 08028, Catalonia, Spain;

    Univ Wollongong, Intelligent Polymer Res Inst, ARC Ctr Excellence Electromat Sci, Wollongong, NSW 2500, Australia;

    Australian Natl Univ, Res Sch Chem, ARC Ctr Excellence Electromat Sci, Canberra, ACT 2601, Australia;

    Univ Wollongong, Intelligent Polymer Res Inst, ARC Ctr Excellence Electromat Sci, Wollongong, NSW 2500, Australia;

    Univ Barcelona, Dept Quim Fis, Diagonal 645, E-08028 Barcelona, Catalonia, Spain|Inst Bioengn Catalunya IBEC, Baldiri Reixac 15-21, Barcelona 08028, Catalonia, Spain|Ctr Invest Biomed Red CIBER BBN, Campus Rio Ebro Edificio I D, Zaragoza 50018, Spain;

    Australian Natl Univ, Res Sch Chem, ARC Ctr Excellence Electromat Sci, Canberra, ACT 2601, Australia;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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