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Bottom up fabrication of a metal supported oxo-metal porphyrin

DOI: 10.1021/acs.jpcc.9b08661 DOI Help

Authors: David A. Duncan (Technical University of Munich; Diamond Light Source) , Peter S. Deimel (Technical University of Munich) , Alissa Wiengarten (Technical University of Munich) , Mateusz Paszkiewicz (Technical University of Munich) , Pablo Casado Aguilar (Technical University of Munich) , Robert G. Acres (Elettra-Sincrotrone Trieste) , Florian Klappenberger (Technical University of Munich) , Willi Auwärter (Technical University of Munich) , Ari Paavo Seitsonen (École Normale Supérieure; Sorbonne Université) , Johannes V. Barth (Technical University of Munich) , Francesco Allegretti (Technical University of Munich)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: The Journal Of Physical Chemistry C

State: Published (Approved)
Published: November 2019

Abstract: In situ preparation of oxotitanium tetraphenylporphyrin (TiO-TPP) on Ag(111) under ultra-high vacuum conditions was achieved in a multi-step procedure starting from adsorbed free-base tetraphenylporphyrin (2H-TPP). The final product as well as the intermediate titanium tetraphenylporphyrin (Ti-TPP) were characterized by a suite of surface-sensitive spectroscopic tools combined with scanning tunneling microscopy and density functional theory (DFT), and compared against the parent 2H-TPP species. Facile oxidation of Ti-TPP with molecular oxygen was observed at 300 K, with X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS) from the Ti 2p core levels supporting a change in the oxidation state from Ti2+ to Ti4+. N K-edge and Ti L-edge NEXAFS suggest that the tetrapyrrole macrocycle conformation is modified upon binding to oxygen, in agreement with DFT calculations that predict a marked change of the local environment of the Ti centers upon oxygen attachment. O K-edge NEXAFS and O 1s energy-scanned photoelectron diffraction from the resulting TiO-TPP monolayer provide strong evidence for the presence of a titanium-oxygen double bond, with the latter technique yielding a bond length of 1.56 ± 0.02 Å. The majority of adsorbed TiO-TPP species have the oxo group pointing away from the surface rather than towards it, and thus the oxygen atom can potentially interact coordinatively with external species. Both the highly reactive, intermediate Ti TPP species and the final product TiO-TPP are of great interest for catalytic applications.

Journal Keywords: X-ray absorption near edge spectroscopy; Binding energy; Molecules; Energy; Scanning tunneling microscopy

Subject Areas: Chemistry, Materials

Facility: BESSY-II; ELETTRA

Added On: 02/12/2019 14:21

Discipline Tags:

Catalysis Physical Chemistry Materials Science Metallurgy Chemistry Organometallic Chemistry

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