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

Area of Science:

• Supramolecular Chemistry
• Surface Science
• Materials Chemistry

Background:

• On-surface self-assembly relies on various parameters like temperature and concentration.
• Structural transformations often involve shifts from weaker to stronger interactions.
• Reversible conversions between strong coordination bonds and weak hydrogen bonds are rare.

Purpose of the Study:

• To demonstrate a facile strategy for controlling stepwise intermolecular bond conversions.
• To investigate the reversible conversion between metal-organic coordination bonds and hydrogen bonds.
• To understand the energetic compensation during bond conversion.

Main Methods:

• On-surface self-assembly experiments.
• Systematic variation of surface molecular coverage.
• Density Functional Theory (DFT) calculations.

Main Results:

• Achieved stepwise conversion from Cu-N coordination bonds to CH···N hydrogen bonds by increasing molecular coverage.
• DFT calculations quantified energy compensation: reduced intermolecular energy offset by increased adsorption energy.
• Demonstrated reversible conversion from hydrogen bonds back to coordination bonds by decreasing molecular coverage.

Conclusions:

• Molecular coverage is a key parameter for regulating intermolecular bond types in self-assembled architectures.
• Reversible switching between coordination and hydrogen bonds is feasible.
• Energetic balance drives the observed structural transformations.