Polycyclic aromates on close-packed metal surfaces: functionalization, molecular chemisorption and organic epitaxy
Polycyclic aromates on close-packed metal surfaces: functionalization, molecular chemisorption and organic epitaxy
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密排金属表面上的多环芳香族化合物：功能化、分子化学吸附和有机外延
DOI：
10.1088/1367-2630/6/1/004
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发表时间：
2004
影响因子：
3.3
通讯作者：
F. Tautz
中科院分区：
文献类型：
--
作者：
M. Eremtchenko;D. Bauer;J. Schaefer;F. Tautz
本文详细分析了二萘嵌苯和PTCDA与两种密排贵金属Ag（111）和Au（111）表面的成键机理，旨在阐明成键与界面结构之间的关系。我们的分析是基于高分辨率的电子能量损失光谱和第一性原理量子化学计算（密度泛函理论）的分子轨道和振动的组合。在实验上，关键的观察是在表面的对称性破缺激活某些完全对称的模式。详细分析计算的振动本征矢量和诱导的最低未占分子轨道的动力学畸变，我们提出了一个相互作用模型，根据该模型，在两个分子的中心碳环构成的分子化学吸附中心。在二萘嵌苯的情况下，其反应性相当小。然而，通过在芳族主链上引入官能团，可以在很宽的范围内调节反应活性，从而显著增强PTCDA/Ag（111）的分子-基底相互作用，如显著的界面外延所证明的。弱相互作用的PTCDA/Au（111）界面的例子说明了本化学吸附强度工程方案的局限性。最后，我们的研究结果的影响进行了讨论的吸附位点的详细测定。
In this paper we present a detailed analysis of the molecular mechanisms of perylene and PTCDA bonding to two close-packed noble metal surfaces, Ag(111) and Au(111), with the aim of elucidating the relation between bonding and interface structure. Our analysis is based on a combination of high-resolution electron energy-loss spectroscopy and first-principles quantum chemical calculations (density functional theory) of molecular orbitals and vibrations. Experimentally, the key observation is the activation of certain totally symmetric modes by symmetry breaking at the surface. Analysing calculated vibrational eigenvectors and the induced dynamic distortions of the lowest unoccupied molecular orbital in detail, we propose an interaction model according to which the central carbon ring in both molecules constitutes the molecular chemisorption centre. In the case of perylene, its reactivity is rather small. By the application of functional groups to the aromatic backbone, however, the reactivity can be tuned over a wide range, leading to a dramatic enhancement of the molecule–substrate interaction in the case of PTCDA/Ag(111), as testified by the remarkable interface epitaxy. The example of the weakly interacting PTCDA/Au(111) interface illustrates the limitations of the present scheme of chemisorption strength engineering. Finally, the implications of our results for a detailed determination of the adsorption site are discussed.