Observation of orientation-dependent electron transfer in molecule-surface collisions
Observation of orientation-dependent electron transfer in molecule-surface collisions
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DOI：
10.1073/pnas.1312200110
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发表时间：
2013-10-29
影响因子：
11.1
通讯作者：
Schaefer, Tim
中科院分区：
文献类型：
--
作者：
Bartels, Nils;Golibrzuch, Kai;Schaefer, Tim
分子通常必须指向特定的相对方向，才能有效地参与能量转移和反应。例如，Forster能量转移有利于每个分子的过渡偶极的特定相对方向[Forster T(1948)Ann Phys 2(1-2)：55-75]，而气相分子之间的电子转移通常取决于轨道的相对取向[Brooks PR，et al.(2007年)化学学报129(50)：15572-15580]。表面化学反应可能比它们的气相类似物快许多个数量级，这一事实突显了表面对催化的重要性。表面反应如此迅速的一个原因是氧化状态的不稳定变化，这种变化通常发生在吸附过程中，这是一个涉及固体金属和接近的分子之间的电子转移的过程。通过将电子转移到吸附体或从吸附体转移电子，启动了键减弱和/或断裂的过程，以化学方式激活反应物[Yoon B，等人]。(2005)科学307(5708)：403-407]。在这里，我们表明，NO的振动弛豫--一个由电子转移事件驱动的电子非绝热能量转移的例子[Gadzuk JW(1983)J Chem Phys 79(12)：6341-6348]--当分子接近Au(111)表面时，N原子朝向表面，振动弛豫显著增强。这是一个难得的机会来研究空间位阻对发生在表面上的电子转移反应的影响。
Molecules typically must point in specific relative directions to participate efficiently in energy transfer and reactions. For example, Forster energy transfer favors specific relative directions of each molecule's transition dipole [Forster T (1948) Ann Phys 2(1-2):55-75] and electron transfer between gas- phase molecules often depends on the relative orientation of orbitals [Brooks PR, et al. (2007) J Am Chem Soc 129(50):15572-15580]. Surface chemical reactions can be many orders of magnitude faster than their gas-phase analogs, a fact that underscores the importance of surfaces for catalysis. One reason surface reactions can be so fast is the labile change of oxidation state that commonly takes place upon adsorption, a process involving electron transfer between a solid metal and an approaching molecule. By transferring electrons to or from the adsorbate, the process of bond weakening and/or cleavage is initiated, chemically activating the reactant [Yoon B, et al. (2005) Science 307(5708):403-407]. Here, we show that the vibrational relaxation of NO-an example of electronically nonadiabatic energy transfer that is driven by an electron transfer event [Gadzuk JW (1983) J Chem Phys 79(12):6341-6348]-is dramatically enhanced when the molecule approaches an Au(111) surface with the N atom oriented toward the surface. This represents a rare opportunity to investigate the steric influences on an electron transfer reaction happening at a surface.