# Local adsorption structure and bonding of porphine on Cu(111) before and after self-metalation

## TL;DR

This study combines experimental photoelectron diffraction and DFT calculations to analyze the adsorption structure and bonding of porphine molecules on Cu(111), revealing how metalation affects molecular geometry and surface interactions.

## Contribution

It provides the first combined experimental and theoretical analysis of porphine adsorption and metalation on Cu(111), highlighting structural changes and adsorption behavior.

## Key findings

- Adsorption occurs with the molecule center above a surface bridge site.
- Metalation changes the corrugation of nitrogen atoms in the macrocycle.
- The N atom height increases from 2H-P to cobalt porphine, with an inverse relation to adsorption strength.

## Abstract

We have experimentally determined the lateral registry and geometric structure of free-base porphine (2H-P) and copper-metalated porphine (Cu-P) adsorbed on Cu(111), by means of energy-scanned photoelectron diffraction (PhD), and compared the experimental results to density functional theory (DFT) calculations that included van der Waals corrections within the Tkatchenko-Scheffler approach. Both 2H-P and Cu-P adsorb with their center above a surface bridge site. Consistency is obtained between the experimental and DFT-predicted structural models, with a characteristic change in the corrugation of the four N atoms of the molecule's macrocycle following metalation. Interestingly, comparison with previously published data for cobalt porphine adsorbed on the same surface evidences a distinct increase in the average height of the N atoms above the surface through the series 2H-P, Cu-P, cobalt porphine. Such an increase strikingly anti-correlates the DFT-predicted adsorption strength, with 2H-P having the smallest adsorption height despite the weakest calculated adsorption energy. In addition, our findings suggest that for these macrocyclic compounds, substrate-to-molecule charge transfer and adsorption strength may not be univocally correlated.

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Source: https://tomesphere.com/paper/1905.02339