Interfacial charge rearrangement and intermolecular interactions: Density-functional theory study of free-base porphine adsorbed on Ag(111) and Cu(111)

TL;DR

This study uses dispersion-corrected density-functional theory to analyze how 2H-porphine molecules interact with Ag(111) and Cu(111) surfaces, revealing substrate-mediated van der Waals forces crucial for understanding self-assembly.

Contribution

It provides a detailed analysis of adsorbate-substrate and intermolecular interactions, highlighting the role of substrate-mediated van der Waals forces in molecular self-assembly.

Findings

Substrate-mediated van der Waals interactions are significant.

Direct dispersive interactions between molecules are negligible.

Single molecule adsorption is favored due to net repulsive interactions.

Abstract

We employ dispersion-corrected density-functional theory to study the adsorption of tetrapyrrole 2H-porphine (2H-P) at Cu(111) and Ag(111). Various contributions to adsorbate-substrate and adsorbate-adsorbate interactions are systematically extracted to analyze the self-assembly behavior of this basic building block to porphyrin-based metal-organic nanostructures. This analysis reveals a surprising importance of substrate-mediated van der Waals interactions between 2H-P molecules, in contrast to negligible direct dispersive interactions. The resulting net repulsive interactions rationalize the experimentally observed tendency for single molecule adsorption.