Exploring the RIDEr ligation at supported PORPHyrins using a combined theory and experiment atomic-scale approach_RIDEPORPH
Zusammenfassung der Projektergebnisse
The main question triggering this project was if deformed, surface-adsorbed tetrapyrroles (such as porphyrins, porphines, and phthalocyanines) are responsible for an enhanced ligation of di-atomic molecules. Accordingly, the starting point of the project was the exploration of the so-called paired rider ligation of CO molecules on metalloporphyrins anchored to different supports. The project started with the exploration of the non-classical ligation properties of metal porphyrins once they are adsorbed onto a support. Indeed, saddle-shaped porphyrins immobilized onto coinage surfaces can bind two molecules of CO in a paired bridge position midway between the Co metal and the pointing-down N atoms of the pyrroles. This multiple and off-center ligation mode offers novel perspectives in the nanodesign of future specific gas sensors. It was therefore of crucial interest to investigate similar interfaces. In this project, we decided to change one parameter at a time in a systematic approach: e.g., replace Co by Fe centers, replace CO ligands by O2, NO or Fe adatom ligands, replace the Ag surface by an epitaxial graphene layer supported on a Cu surface. This project was dual, one part of the systems results from combined surface science experiments (STM, TUM) and theory (DFT, ENS Lyon) and the second part proposed interfaces resulting exclusively from massive quantum calculations, which partially still await an experimental validation. In a second phase of the project, high-resolution STM, STS, and IETS combined with first principles simulations was employed to unveil the ligation properties of hybrid systems on the single-molecule level. Specifically, we addressed vibrational properties of the NO/CoTPP/Ag system. While usually no chemical sensitivity is provided by STM imaging, IETS allowed one to gain a fingerprint of the NO ligation to the porphyrin, with a characteristic inelastic signal emerging at 30 mV. The computation of the inelastic spectra performed by the partner team at ENS Lyon has required extensive supercomputing time but permitted to solve the exact nature of the vibrational mode involving the NO ligand and the Co center. Furthermore, we demonstrated that the site-selective adsorption of Fe atoms on the saddleshaped CoTPP can restore the Co magnetic moment, which was quenched upon surface adsorption. Additionally, we showed that the Fe/CoTPP/Ag system represents an atomic-scale switch operated by STM manipulation at low temperature, with the characteristics of the switch rationalized by first principle calculations. Overall, our results do confirm the decisive role of the structural deformation of the porphyrin macrocycle. We not only introduced and characterized tetrapyrrole-based complexes with unique properties, but also predicted fascinating new ligation modes, e.g., for CO on dehydrogenated porphines covalently anchored to graphene sheets, which remain to be implemented experimentally, thus opening perspectives for exciting future research endeavours.
Projektbezogene Publikationen (Auswahl)
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Probing Nitrosyl Ligation of Surface-Confined Metalloporphyrins by Inelastic Electron Tunneling Spectroscopy. ACS Nano, 2013, 7(6), 5273-5281
Shiri R. Burema, Knud Seufert, Willi Auwärter, Johannes V. Barth, and Marie-Laure Bocquet
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Cycloaddition of metal porphines on metal-supported graphene: a computational study J. Phys. Chem. C, 2015, 119 (17), 9234-9241
Marie Lattelais and Marie-Laure Bocquet
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Restoring the Co Magnetic Moments at Interfacial Co-Porphyrin Arrays by Site-Selective Uptake of Iron. ACS Nano, 2015, 9 (4), 3605-3616
Saranyan Vijayaraghavan, Willi Auwärter, David Ecija, Knud Seufert, Stefano Rusponi, Torsten Houwaart, Philippe Sautet, Marie-Laure Bocquet, Pardeep Thakur, Sebastian Stepanow, Uta Schlickum, Markus Etzkorn, Harald Brune, and Johannes V. Barth
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Scrutinizing individual CoTPP molecules adsorbed on coinage metal surfaces from the interplay of STM experiment and theory, Surface Science, 2015, 635, 108-114
Torsten Houwaart, Tangui Le Bahers, Philippe Sautet, Willi Auwärter, Knud Seufert, Johannes V. Barth, Marie-Laure Bocquet
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Fusing tetrapyrroles to graphene edges by surface-assisted covalent coupling, Nature Chemistry, (2017), 9, 33-38
Yuanqin He, Manuela Garnica, Felix Bischoff, Jacob Ducke, Marie-Laure Bocquet, Matthias Batzill, Willi Auwärter, and Johannes V. Barth
