Fernández Cynthia C, Franke Matthias, Steinrück Hans-Peter, Lytken Ole, Williams Federico J
Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
Instituto de Química Física de los Materiales, Medio Ambiente y Energía INQUIMAE, CONICET, Universidad de Buenos Aires, Buenos Aires, Argentina.
Langmuir. 2021 Jan 19;37(2):852-857. doi: 10.1021/acs.langmuir.0c03197. Epub 2021 Jan 5.
Understanding the factors that control the demetalation of surface porphyrins at the solid-liquid interface is important as the molecular properties of porphyrins are largely determined by their metal centers. In this work, we used X-ray photoelectron spectroscopy (XPS) to follow the demetalation of Zn and Cd tetraphenylporphyrin molecules (ZnTPP and CdTPP) adsorbed as three-monolayer-thin multilayer films on Au(111), by exposing the molecular layers to acidic aqueous solutions. We found that porphyrin molecules at the solid-liquid interface are less prone to lose their metal center than molecules in solution. We propose that this behavior is due to either the incoming protons provided by the solution or the outgoing metal ion having to pass through the hydrophobic porphyrin multilayers where they cannot be solvated. Our results are relevant for the design of molecular devices based on porphyrin molecules adsorbed on solid surfaces.
了解控制卟啉在固液界面脱金属的因素非常重要，因为卟啉的分子性质很大程度上由其金属中心决定。在这项工作中，我们通过将分子层暴露于酸性水溶液中，利用X射线光电子能谱（XPS）跟踪吸附在Au(111)上的三层单层厚多层膜中的锌和镉四苯基卟啉分子（ZnTPP和CdTPP）的脱金属过程。我们发现，固液界面处的卟啉分子比溶液中的分子更不容易失去其金属中心。我们认为，这种行为是由于溶液提供的进入质子或离去的金属离子必须穿过疏水性卟啉多层膜，而在那里它们无法被溶剂化。我们的结果与基于吸附在固体表面的卟啉分子的分子器件设计相关。
