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London Dispersion Governs Stereochemistry, Stability, and Self-Sorting in a System of M4L4 Cages.
Itai Massad1, James T F Dobson1, Paula C P Teeuwen1
1Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, U.K.
Journal of the American Chemical Society
|May 21, 2026
Summary
Steric attraction from London dispersion forces drives the stability and structure of metal-organic cages. These forces optimize cage formation over other factors, demonstrating their significant role in molecular design.
Area of Science:
- Supramolecular Chemistry
- Materials Science
- Physical Chemistry
Background:
- London dispersion forces, arising from temporary fluctuations in electron distribution, are crucial in molecular interactions.
- Steric attraction, a consequence of these forces between alkyl groups, is proposed as a molecular design principle but requires further validation.
- Understanding the balance between steric attraction and other forces like steric hindrance and solvophobic effects is key in supramolecular chemistry.
Purpose of the Study:
- To investigate the role and magnitude of steric attraction in dictating the stereochemistry and stability of metal-organic cages.
- To demonstrate that London dispersion forces can outweigh competing energetic and entropic factors in molecular assembly.
- To establish metal-organic cages as a viable platform for studying fundamental non-covalent interactions.
Main Methods:
- Synthesis and characterization of four tetrahedral M4L4 cages with varying metal (FeII, ZnII) and alkyl (Me, Et) substituents.
- Analysis of cage stability in solution and gas phase under different conditions.
- Observation of self-sorting behavior in mixtures of cages to infer stability trends based on alkyl-alkyl interactions.
Main Results:
- The synthesized M4L4 cages exhibit stability dictated by the optimization of London dispersion forces between confined alkyl groups.
- Steric attraction was shown to be the predominant driving force, overriding steric hindrance, strain, solvophobic effects, and metal-ligand bond strength.
- Self-sorting experiments revealed preferential formation of cages with optimal alkyl-alkyl contacts, defying entropic preferences for statistical mixtures.
Conclusions:
- Metal-organic cages effectively demonstrate and exploit steric attraction driven by London dispersion forces.
- These forces play a dominant role in determining the stereochemistry and stability of complex molecular architectures.
- Metal-organic cages provide a powerful platform for the fundamental study and application of non-covalent interactions in molecular design.
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