Lash Miller Chemical Laboratories, Department of Chemistry and Institute of Optical Sciences, University of Toronto, 80 St George Street, Toronto, Ontario M5S 3H6, Canada.
Nat Commun. 2016 Dec 9;7:13690. doi: 10.1038/ncomms13690.
Bond-selective reaction is central to heterogeneous catalysis. In heterogeneous catalysis, selectivity is found to depend on the chemical nature and morphology of the substrate. Here, however, we show a high degree of bond selectivity dependent only on adsorbate bond alignment. The system studied is the electron-induced reaction of meta-diiodobenzene physisorbed on Cu(110). Of the adsorbate's C-I bonds, C-I aligned 'Along' the copper row dissociates in 99.3% of the cases giving surface reaction, whereas C-I bond aligned 'Across' the rows dissociates in only 0.7% of the cases. A two-electronic-state molecular dynamics model attributes reaction to an initial transition to a repulsive state of an Along C-I, followed by directed recoil of C towards a Cu atom of the same row, forming C-Cu. A similar impulse on an Across C-I gives directed C that, moving across rows, does not encounter a Cu atom and hence exhibits markedly less reaction.
键选择性反应是多相催化的核心。在多相催化中，选择性被发现取决于底物的化学性质和形态。然而，在这里，我们展示了一种仅依赖于吸附物键排列的高度键选择性。所研究的系统是 meta-二碘苯物理吸附在 Cu(110)上的电子诱导反应。在吸附物的 C-I 键中，C-I 沿着铜排的方向排列的 C-I 以 99.3%的情况解离，产生表面反应，而 C-I 键横跨行排列的 C-I 仅以 0.7%的情况解离。一个双电子态分子动力学模型将反应归因于最初向沿 C-I 的排斥态的跃迁，随后 C 向同一行的 Cu 原子定向反冲，形成 C-Cu。对沿 C-I 的类似冲量会产生定向 C，它在穿过行时不会遇到 Cu 原子，因此表现出明显较少的反应。
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