氧钝化铁上的金属卟啉：第一层之外的构象与有序性
Metalloporphyrins on Oxygen-Passivated Iron: Conformation and Order Beyond the First Layer
AI总结：
本研究利用光电子轨道断层扫描结合DFT计算，探究了ZnTPP和NiTPP在氧钝化铁表面的构象与电子结构，发现基底作用导致分子形变及HOMO能隙变化，证明该技术可探测多层膜分子结构。
摘要：
表面金属卟啉会发生电子和构象变化，这在决定分子层的化学反应性中起着至关重要的作用。因此，理解这些性质对于有机器件的设计与实现至关重要。在此，借助由密度泛函理论计算支持的光电子轨道断层扫描技术，我们研究了两种金属化四苯基卟啉（MTPP），即 ZnTPP 和 NiTPP，吸附在氧钝化的 Fe(100)-p(1x1)O 表面上的电子和几何结构。两种分子均与表面弱相互作用，未观察到电荷转移。对于 ZnTPP，我们的数据对应于适度扭曲的分子，而 NiTPP 则表现出严重的鞍形形变。通过对 NiTPP 多层膜的补充实验，我们得出结论：这种形变是与基底相互作用的结果，因为第二层的 NiTPP 大环最终是平坦的。我们进一步发现，MTPP 大环的形变伴随着最高占据分子轨道（HOMO 和 HOMO-1）之间能隙的增加。我们的结果表明，光电子轨道断层扫描能够同时探测复杂芳香族分子的能级排列、方位取向和吸附几何结构，即使在多层膜情况下也是如此。
英文摘要：
On-surface metal porphyrins can undergo electronic and conformational changes that play a crucial role in determining the chemical reactivity of the molecular layer. Therefore, understanding those properties is pivotal for the design and implementation of organic-based devices. Here, by means of photoemission orbital tomography supported by density functional theory calculations, we investigate the electronic and geometrical structure of two metallated tetraphenyl porphyrins (MTPPs), namely ZnTPP and NiTPP, adsorbed on the oxygen-passivated Fe(100)-p(1x1)O surface. Both molecules weakly interact with the surface as no charge transfer is observed. In the case of ZnTPP our data correspond to those of moderately distorted molecules, while NiTPP exhibits a severe saddle-shape deformation. From additional experiments on NiTPP multilayer films, we conclude that this distortion is a consequence of the interaction with the substrate, as the NiTPP macrocycle of the second layer turns out to be flat. We further find that distortions in the MTPP macrocycle are accompanied by an increasing energy gap between the highest occupied molecular orbitals (HOMO and HOMO-1). Our results demonstrate that photoemission orbital tomography can simultaneously probe the energy level alignment, the azimuthal orientation, and the adsorption geometry of complex aromatic molecules even in the multilayer regime.
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