Bonding Motifs in Metal–Organic Compounds on Surfaces

Abstract

The bonds in metal organic networks on surfaces govern the resulting geometry as well as the electronic properties. Here, we study the nature of these bonds by forming phenazine-copper complexes on a copper surface by means of atomic manipulation. The structures are characterized by a combination of scanning probe microscopy and density functional theory calculations. We observed an increase of the molecule-substrate distance upon covalent bond formation and an out-of-plane geometry that is in direct contradiction with the common expectation that these networks are steered by coordination bonds. Instead, we find that a complex energy balance of hybridization with the substrate, inhomogeneous Pauli repulsion, and elastic deformation drives the phenazine-copper interaction. Most remarkably, this attractive interaction is not driven by electron acceptor properties of copper but is of completely different donation/back-donation mechanism between molecular π-like orbitals and sp-like metal states. Our findings show that the nature of bonds between constituents adsorbed on surfaces does not have to follow the common categories.

Guide for Atomic Force Microscopy Image Analysis To Discriminate Heteroatoms in Aromatic Molecules

“…For instance, the bonding motifs formed between N and copper adatoms on the surface have been reported. 48 Built upon the adsorption geometry determination by AFM originally introduced by Schuler et al on aromatic hydrocarbons, 49 a robust determination of the adsorption geometry of heterocycles would be needed for broader applications, especially in catalysis and surface sciences. As noted above, in the AFM image of DBT, the contrast at the far end at the outer CC bonds (labeled as AB and CD) is noticeably higher than the side near the S atom and the molecule seems to be tilted with S closer to the Au (111) substrate (Figure 1c).…”

Strain‐Induced Isomerization in One‐Dimensional Metal–Organic Chains

“…[13] Thes trongest Pauli repulsion occurs over regions of high electron density (for example,chemical bonds), which allows organic and metal-organic nanostructures to be imaged with submolecular resolution. [14][15][16][17] Figure 2s hows Nc-AFM images acquired with al arger tip-sample distance indicated that the methyl groups exhibited the strongest Pauli repulsion (Figures 2c,h). Thef aint lines linking adjacent molecules via the carbon atoms originally bound to Br (1 and 5) exhibit the highest STM contrast.…”

Strain‐Induced Isomerization in One‐Dimensional Metal–Organic Chains

“…The nc‐AFM imaging strategy used in this work relies on the functionalization of the tip with a CO molecule and the operation of the microscope in constant height mode in the short‐range Pauli repulsion regime . The strongest Pauli repulsion occurs over regions of high electron density (for example, chemical bonds), which allows organic and metal–organic nanostructures to be imaged with submolecular resolution . Figure shows STM topography, constant height current, and nc‐AFM images of the strained homochiral (Figures a–e) and heterochiral (Figures f,j) MOC junctions.…”