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Identifying on-surface site-selective chemical conversions by theory-aided NEXAFS spectroscopy: The case of free-base corroles on Ag(111).

Research paper by Hazem H Aldahhak, Mateusz M Paszkiewicz, Eva E Rauls, Francesco F Allegretti, Stefano S Tebi, Anthoula A Papageorgiou, Yiqi Y Zhang, Liding L Zhang, Tao T Lin, Tobias T Paintner, Reinhold R Koch, Wolf Gero WG Schmidt, Johannes J Barth, Wolfgang W Schöfberger, Stefan S Müllegger, et al.

Indexed on: 02 Mar '18Published on: 02 Mar '18Published in: Chemistry - A European Journal



Abstract

It is demonstrated that theory-assisted near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy enables the site-sensitive monitoring of on-surface chemical reactions, thus, providing information not accessible to other techniques. As a prototype example we use free-base 5,10,15-tris(pentafluorophenyl)-corroles (3H-TpFPC) adsorbed on Ag(111) and present a detailed investigation of the angle-dependent NEXAFS of this molecular species as well as of their thermally induced derivatives. For this, we record experimental C and N K-edge NEXAFS spectra and interpret them based on XAS cross section calculations using a continuous fraction approach and core-hole including multi-projector PAW pseudopotentials within density functional theory (DFT). We characterize the as-deposited low temperature (200 K) phase and unravel the subsequent changes induced by dehydrogenation (at 330 K) and ring-closure reactions (at 430 K). By exemplarily obtaining profound insight into the on-surface chemistry of free-base corrolic species adsorbed on a noble metal this work highlights how angle-dependent X-ray absorption spectroscopy combined with accurate theoretical modeling can serve for the investigation of on-surface reactions, whereby even highly similar molecular structures, such as tautomers and isomers, can be distinguished. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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