Quantum Chemical Characterization of Strained Organic Molecules

Strained organic molecules are defined by bond angles and lengths that depart significantly from their ideal values, endowing such frameworks with unique electronic, thermodynamic and kinetic properties. Quantum chemical characterisation employs theoretical methods to quantify strain energies, analyse frontier molecular orbitals and predict reaction pathways. Ab initio approaches and density functional theory (DFT) have advanced to deliver high precision in evaluating the energetic cost of geometric deformation, revealing how electronic delocalisation can mitigate strain. These techniques have illuminated the stability of small cage compounds such as tetrahedranes, propellanes and cyclopropanes, as well as heteroatom-substituted analogues. By mapping intrinsic reaction coordinates and calculating transition-state barriers at levels like CCSD(T) and DFT with dispersion corrections, researchers have gained predictive power over the synthesis and reactivity of highly strained systems. The global significance of this work spans the design of molecular springs for nanomechanical devices, understanding of mechanochemical transformations in polymers and the synthesis of collision-resistant pharmaceuticals. Integration of quantum chemical data with crystallographic and spectroscopic characterisation continues to drive the discovery of unprecedented strained architectures with tailored properties.

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Quantum Chemical Characterization of Strained Organic Molecules publication trend

The graph below shows the total number of articles in quantum chemical characterization of strained organic molecules across all publications each year (not limited to Nature Index journals).

Technical terms

Strain energy: The excess potential energy stored when bond angles or lengths deviate from their equilibrium values.

Density functional theory (DFT): A quantum mechanical method that determines electronic structure using electron density rather than wavefunctions.

Ab initio methods: First-principles computational approaches that solve the Schrödinger equation without empirical parameters.

Transition state: The highest-energy point along a reaction coordinate representing the barrier between reactants and products.

Frontier molecular orbitals: The highest occupied and lowest unoccupied orbitals central to determining reactivity and electronic interactions.

References

1. Isolation of an elusive phosphatetrahedrane. Science Advances (2020).
2. Carbene Routes to Cyclopropatetrahedrane. The Journal of Organic Chemistry (2022).
3. Cyclobutane dication, (CH2)42+: a model for a two-electron four-center (2e-4c) Woodward–Hoffmann frozen transition state. Beilstein Journal of Organic Chemistry (2019).