Context-Dependent Significance of London Dispersion.

Area of Science:

• Physical Chemistry
• Supramolecular Chemistry
• Chemical Physics

Background:

• London dispersion forces are a key component of van der Waals interactions, arising from transient dipoles in atoms.
• Investigating these forces, especially in solution, is challenging due to their weak and competing nature.
• Solvation energetics and solvophobic effects significantly influence molecular recognition equilibria and kinetics.

Purpose of the Study:

• To elucidate the context-dependent significance of London dispersion forces in molecular recognition.
• To contrast experimental findings with existing research on dispersion force contributions.
• To explore how system and solvent choices impact the role of dispersion forces.

Main Methods:

• Utilized molecular balances, particularly intramolecular approaches, to experimentally measure dispersion interactions.
• Screened various solvents to assess their influence on dispersion force measurements.
• Analyzed experimental data in conjunction with theoretical considerations of steric hindrance and strain minimization.

Main Results:

• Dispersion interactions between functional groups are typically weak (<5 kJ mol⁻¹), often secondary to electrostatic and solvophobic effects.
• Competitive dispersion interactions with solvents are influenced by solvent bulk polarizability.
• Dispersion forces are highly distance-dependent, leading to context-specific outcomes and cautioning against attributing stability solely to dispersion.

Conclusions:

• The apparent role of London dispersion forces is highly dependent on the specific molecular system and surrounding solvent environment.
• Solvophobic effects and solvent's cohesive energy density can stabilize bulky group contacts.
• Careful consideration of steric effects, strain, and solvent interactions is crucial when interpreting the contribution of dispersion forces.