Berlin 2024 – scientific programme

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O: Fachverband Oberflächenphysik

O 65: Poster: Molecular Nanostructures on Surfaces

O 65.15: Poster

Wednesday, March 20, 2024, 18:00–20:00, Poster C

On-surface degradation reactions of Pb(II)-tetraphenylporphyrin — •Cong Guo, Jan Herritsch, Lukas J. Heuplick, Stefan R. Kachel, Mark Hutter, and J. Michael Gottfried — Department of Chemistry, University of Marburg, 35043 Marburg, Germany

Metal-organic compounds of heavy main group elements are promising building blocks for the assembly of novel (opto-)electronic surface structures. However, dynamic processes of these compounds at surfaces or interfaces (i.e., chemical reactions or structural adaption upon adsorption) are largely unexplored, but can be crucial for the devices' performance. To fill this knowledge gap, we investigated the on-surface chemistry of lead(II) tetraphenylporphyrin (Pb(TPP)). On Cu(111), Pb(TPP) undergoes spontaneous transmetalation above 380 K, resulting in an exchange of the incorporated Pb ion by a Cu adatom.[1] However, a different reactivity was found for Pb(TPP) on Au(111). Here, a spontaneous demetalation of Pb(TPP) and formation of a free-base porphyrin was observed by XPS, STM, and TPD. Temperature-dependent XPS confirms the demetalation and reveals cyclodehydrogenation side-reactions of the porphyrin ligand starting above 450 K. At 720 K, re-metalation of the porphyrin with substrate Au atoms results in Au(II)-porphyrin. The observed de- and transmetalation reactions are practically relevant, because they alter the electronic and chemical properties of the metal-organic interface substantially. [1] J. Herritsch et al., Nanoscale 13, Nanoscale, 2021,13, 13241-13248 (2021).

Keywords: tetraphenylporphyrin; transmetalation; cyclodehydrogenation