Science2014-01-07 10:37 PM

Direct Imaging of Covalent Bond Structure in Single-Molecule Chemical Reactions 单分子化学反应中共价键结构的直接成像

Abstract
Observing the intricate chemical transformation of an individual molecule as it undergoes a complex reaction is a long-standing challenge in molecular imaging. Advances in scanning probe microscopy now provide the tools to visualize not only the frontier orbitals of chemical reaction partners and products, but their internal covalent bond configurations as well. We used noncontact atomic force microscopy to investigate reaction-induced changes in the detailed internal bond structure of individual oligo-(phenylene-1,2-ethynylenes) on a (100) oriented silver surface as they underwent a series of cyclization processes. Our images reveal the complex surface reaction mechanisms underlying thermally induced cyclization cascades of enediynes. Calculations using ab initio density functional theory provide additional support for the proposed reaction pathways. 摘要摘要 在分子影像学领域由于单个分子经历着复杂的反应过程,使得观察单个分子中错综复杂的化学变化长期以来一直是一个挑战。现在,高级扫描探针显微镜已成为使观察过程可视化的工具,不但可以观察到化学反应物和产物的前线轨道中,而且也能观察到内部共价键的构型。这里,我们证实了用非接触原子力显微镜观察单个的(亚苯基-1,2-次乙炔基)低聚物在银表面由于发生一系列环化反应过程而引起的内部化学键结构变化。图像从根本上提示了热致环化级联烯二炔分子过程中复杂的表面反应机理,所提出的反应路径的附加证据利用从头计算密度泛函理论得以获得。

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