Issue 46, 2022

Charge and adsorption height dependence of the self-metalation of porphyrins on ultrathin MgO(001) films

Abstract

We have experimentally determined the adsorption structure, charge state, and metalation state of porphin, the fundamental building block of porphyrins, on ultrathin Ag(001)-supported MgO(001) films by scanning tunneling microscopy and photoemission spectroscopy, supported by calculations based on density functional theory. By tuning the substrate work function to values below and above the critical work function for charging, we succeeded in the preparation of 2H-P monolayers which contain negatively charged and uncharged molecules. It is shown that the porphin molecules self-metalate at room temperature, forming the corresponding Mg–porphin, irrespective of their charge state. This is in contrast to self-metalation of tetraphenyl porphyrin (TPP), which occurs on planar MgO(001) only if the molecules are negatively charged. The different reactivity is explained by the reduced molecule-substrate distance of the planar porphin molecule compared to the bulkier TPP. The results of this study shed light on the mechanism of porphyrin self-metalation on oxides and highlight the role of the adsorption geometry on the chemical reactivity.

Graphical abstract: Charge and adsorption height dependence of the self-metalation of porphyrins on ultrathin MgO(001) films

Supplementary files

Article information

Article type
Paper
Submitted
07 okt 2022
Accepted
16 nov 2022
First published
17 nov 2022
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2022,24, 28540-28547

Charge and adsorption height dependence of the self-metalation of porphyrins on ultrathin MgO(001) films

F. Presel, C. S. Kern, T. G. Boné, F. Schwarz, P. Puschnig, M. G. Ramsey and M. Sterrer, Phys. Chem. Chem. Phys., 2022, 24, 28540 DOI: 10.1039/D2CP04688A

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