Lesnard Hervé, Bocquet Marie-Laure, Lorente Nicolas
Laboratoire de Chimie, UMR 5182, ENS Lyon, 46 allée d'Italie, 69364 Lyon, France.
J Am Chem Soc. 2007 Apr 11;129(14):4298-305. doi: 10.1021/ja067442g. Epub 2007 Mar 16.
We have performed a theoretical study on the dehydrogenation of benzene and pyridine molecules on Cu(100) induced by a scanning tunneling microscope (STM). Density functional theory calculations have been used to characterize benzene, pyridine, and different dehydrogenation products. The adiabatic pathways for single and double dehydrogenation have been evaluated with the nudge elastic band method. After identification of the transition states, the analysis of the electronic structure along the reaction pathway yields interesting information on the electronic process that leads to H-scission. The adiabatic barriers show that the formation of double dehydrogenated fragments is difficult and probably beyond reach under the actual experimental conditions. However, nonadiabatic processes cannot be ruled out. Hence, in order to identify the final dehydrogenation products, the inelastic spectra are simulated and compared with the experimental ones. We can then assign phenyl (C6H5) and alpha-pyridil (alpha-C5H4N) as the STM-induced dehydrogenation products of benzene and pyridine, respectively. Our simulations permit us to understand why phenyl, pyridine, and alpha-pyridil present tunneling-active C-H stretch modes in opposition to benzene.
我们利用扫描隧道显微镜（STM）对Cu(100)表面苯和吡啶分子的脱氢反应进行了理论研究。采用密度泛函理论计算对苯、吡啶及不同脱氢产物进行了表征。用推挤弹性带方法评估了单脱氢和双脱氢的绝热路径。在确定过渡态之后，沿着反应路径对电子结构进行分析，得到了关于导致氢原子断裂的电子过程的有趣信息。绝热势垒表明，在实际实验条件下，双脱氢片段的形成很困难，可能无法实现。然而，非绝热过程不能排除。因此，为了确定最终的脱氢产物，我们模拟了非弹性光谱并与实验光谱进行比较。然后我们可以分别将苯基（C6H5）和α-吡啶基（α-C5H4N）指定为STM诱导的苯和吡啶的脱氢产物。我们的模拟使我们能够理解为什么苯基、吡啶和α-吡啶基呈现出与苯相反的隧穿活性C-H伸缩模式。
