Stereoelectronic Interactions in Molecular Systems

Stereoelectronic interactions are a class of orbital-driven forces that govern the shape, stability and reactivity of molecular systems. They emerge when filled and vacant molecular orbitals adopt specific spatial alignments, permitting stabilising donor–acceptor overlap or, conversely, destabilising interactions when filled orbitals clash. Classic examples include hyperconjugation, whereby electrons in σ-bonds interact with adjacent antibonding orbitals to influence bond lengths and rotational barriers, and the anomeric effect, in which lone-pair donation to σ* orbitals stabilises certain ring conformations in carbohydrates and heterocycles. The balance between these attractive orbital overlaps and repulsive forces such as Pauli repulsion shapes conformational equilibria in organic frameworks, guiding selectivity in synthesis and catalysis. Advances in computational methods, including natural bond orbital analysis and energy decomposition, have enabled quantitative elucidation of these effects, while spectroscopic techniques offer experimental validation. Through careful stereoelectronic tuning, chemists have achieved precise control over reaction pathways, engineered novel catalysts and designed functional materials. At a global level, understanding stereoelectronic principles underpins the development of pharmaceuticals with optimal binding geometries, next-generation polymers with tailored mechanical properties and efficient catalytic processes that reduce energy demands and waste.

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Recent computational and experimental studies have deepened our understanding of stereoelectronic phenomena across diverse molecular frameworks. A 2024 investigation of Schiff bases derived from aromatic aldehydes revealed a robust reverse anomeric effect in iminoaldoses, demonstrating that intramolecular hydrogen bonding can counteract classical exo-anomeric donation and invert conformational preferences irrespective of substituent hydrophobicity. Complementary quantum-chemical analyses of dihaloethanes have revisited the gauche effect, showing that hyperconjugative stabilisation is modulated by steric Pauli repulsion between halogen lone pairs, with larger halogens favouring anti conformers despite intrinsic orbital donation. In parallel, density functional and energy-decomposition studies on low-valent tetrylene ligands have highlighted how bidentate coordination by electron-rich phosphorus–carbon units can stabilise reactive silicon centres by up to 70 kcal mol−1, exemplifying the interplay between charge-transfer attraction and Pauli exchange repulsion in chelate-like binding. Together, these works illustrate the power of stereoelectronic design in controlling molecular architecture and reactivity.

Stereoelectronic Interactions in Molecular Systems publication trend

The graph below shows the total number of articles in stereoelectronic interactions in molecular systems across all publications each year (not limited to Nature Index journals).

Technical terms

Stereoelectronic interactions: Electronic stabilisation or destabilisation arising from the directional overlap of filled and vacant orbitals.

Hyperconjugation: Delocalisation of electrons from a filled σ-bonding orbital into an adjacent antibonding orbital.

Anomeric effect: Preference for an electronegative substituent on a cyclic system to adopt an axial orientation due to lone-pair donation into a σ* orbital.

Pauli repulsion: Destabilising interaction between filled orbitals that cannot occupy the same spatial region.

References

1. Exploring and Re-Assessing Reverse Anomeric Effect in 2-Iminoaldoses Derived from Mono- and Polynuclear Aromatic Aldehydes. Molecules (2024).
2. The Gauche Effect in XCH2CH2X Revisited. ChemPhysChem (2021).
3. In silico modelling of chelate stabilized tetrylene derivatives. RSC Advances (2024).