Competition between Hydrogen Bonds and Coordination Bonds Steered by the Surface Molecular Coverage

Abstract

In addition to the choices of metal atoms/molecular linkers and surfaces, several crucial parameters, including surface temperature, molecular stoichiometric ratio, electrical stimulation, concentration, and solvent effect for liquid/solid interfaces, have been demonstrated to play key roles in the formation of on-surface self-assembled supramolecular architectures. Moreover, self-assembled structural transformations frequently occur in response to a delicate control over those parameters, which, in most cases, involve either conversions from relatively weak interactions to stronger ones (e.g., hydrogen bonds to coordination bonds) or transformations between the comparable interactions (e.g., different coordination binding modes or hydrogen bonding configurations). However, intermolecular bond conversions from relatively strong coordination bonds to weak hydrogen bonds were rarely reported. Moreover, to our knowledge, a reversible conversion between hydrogen bonds and coordination bonds has not been demonstrated before. Herein, we have demonstrated a facile strategy for the regulation of stepwise intermolecular bond conversions from the metal-organic coordination bond (Cu-N) to the weak hydrogen bond (CH···N) by increasing the surface molecular coverage. From the DFT calculations we quantify that the loss in intermolecular interaction energy is compensated by the increased molecular adsorption energy at higher molecular coverage. Moreover, we achieved a reversible conversion from the weak hydrogen bond to the coordination bond by decreasing the surface molecular coverage.

Synthesis and Local Probe Gating of a Monolayer Metal‐Organic Framework

“…The proper annealing temperature is vital for the formation of a uniform monolayer 2D MOF, since the coordination bonds are relatively weak and reversible. [32,33] The networks are structurally robust, which is evidenced by the fact that they grow seamlessly across step edges of the underlying Ir(111) substrate (see Figure 1b). Annealing at a higher temperature (>70°C) yields a new phase of close-packed DCA molecules and large Cu islands (see Figure S2b, Supporting Information).…”

Covalent organic frameworks from a monomer with reduced symmetry: polymorphism and Sierpiński triangles

“…14,42 In ultrahigh vacuum conditions similar coverage-dependent polymorphism has been identified in the supramolecular ST systems. 29,32,43 For example, the V-shaped molecule 4,4″-dibromo-1,1′:3′,1″-terphenyl (B3Pb) can form honeycomb-like networks and ST structures depending on the molecular coverage on Ag(111). 29 Importantly, the surface density of ST-n patterns decreases rapidly with increasing n order.…”

The Sub‐Nanometer Scale as a New Focus in Nanoscience

“…The surface coverage might also influence the structures of the ligand. Xu et al found that the self‐assembling behavior of [1,1′‐biphenyl]‐4,4′‐dicarbonitrile or [1,1′:3′,1″‐TERphenyl]‐4,4′‐dicarbonitrile on a Cu substrate can be dramatically tuned by the surface coverage of the building blocks . When the coverage was low, the binding of building blocks with the Cu substrate through coordination bonds was more pronounced, and loose hexagonal or triangular superlattice were the main structure.…”