Dynamic Chemistry of Isomerization Reactions

Dynamic chemistry of isomerization reactions encompasses processes by which molecules undergo structural rearrangements under equilibrium or upon external stimulus, enabling reversible conversion between distinct isomeric forms. This discipline includes constitutional isomerization—alteration of atomic connectivity—and configurational isomerization, in which stereochemical inversion occurs without bond cleavage. At its core is fluxional behaviour, whereby low-energy barriers facilitate rapid interconversion. These phenomena underpin applications ranging from photoswitchable materials and shapeshifting molecular scaffolds to adaptive catalysts and responsive sensors. Recent advances in synthetic strategies have delivered novel homoaromatic systems capable of photochemical switching via sigmatropic rearrangements and fluxional carbon cages that transmit stereochemical information through strain-assisted Cope rearrangements. Complementary progress in computational modelling and spectroscopic techniques has refined understanding of dynamic bond rearrangements, while strategic use of long-range non-covalent interactions allows precise control over isomer equilibria. Collectively, these developments highlight the global significance of isomerization dynamics in designing functional molecular assemblies and adaptive chemical systems.

Research from Nature Portfolio

Recent studies have demonstrated a class of neutral homoaromatic hydrocarbons that undergo reversible photochemical [1,11] sigmatropic rearrangements, enabling photoswitching between local and global aromatic states upon irradiation. Experimental evidence from NMR spectroscopy and X-ray crystallography, combined with computational analysis, has elucidated the mechanism and aromatic character changes during the switching cycle. In parallel, investigations into dynamic sp³-carbon stereochemistry have revealed fluxional carbon cages that invert configuration through strain-assisted Cope rearrangements. These systems emulate low-barrier stereodynamic motifs and can be modulated by external reagents or neighbouring stereocentres to start, stop or slow enantiomerization. Integration of such fluxional units into ligand frameworks has unlocked controlled transmission of stereochemical information, influencing catalytic activity and coordination environments.

Research from all publishers

A comprehensive guide to bullvalene stereodynamics has classified its elementary rearrangement steps and introduced a computational tool to predict isomer populations. Analysis of principal moments of inertia and exit vector plots has shown how shapeshifting valence isomerism in substituted bullvalenes affords a rich dynamic covalent library from a single scaffold. Another study coupled rapid constitutional rearrangements of a substituted bullvalene with remote E–Z configurational isomerization of a carbamate group, revealing long-range non-covalent interactions that bias the isomer equilibrium and enable correlated motion. Theoretical work on the 3D to 2D isomerization of hexaborane(12) has mapped the potential energy surface linking three-dimensional and planar forms, identifying key bond-breaking steps and energetic barriers that guide the design of planar borane molecules.

Dynamic Chemistry of Isomerization Reactions publication trend

The graph below shows the total number of articles in dynamic chemistry of isomerization reactions across all publications each year (not limited to Nature Index journals).

Technical terms

Isomerization: The process by which a molecule transforms into another molecule with the same formula but a different arrangement of atoms or stereochemistry.

Constitutional isomerization: Rearrangement of atoms that alters the connectivity within a molecule.

Configurational isomerization: Inversion of stereochemistry at a fixed connectivity without breaking the molecular framework.

Sigmatropic rearrangement: A concerted pericyclic reaction in which a sigma bond migrates across a conjugated system, changing connectivity.

Cope rearrangement: A specific [3,3]-sigmatropic rearrangement involving the migration of a six-membered transition state within a conjugated hydrocarbon framework.

Homoaromaticity: Aromatic stabilisation in a system where conjugation is interrupted by a non-conjugated atom or bond but maintained through through-space or through-bond interactions.

Fluxional behaviour: Rapid interconversion among isomeric forms due to low energy barriers, resulting in dynamic structural flux.

Dynamic covalent library: A collection of interconverting molecular species maintained in equilibrium through reversible covalent bond formation and cleavage.

References

1. Photoswitching neutral homoaromatic hydrocarbons. Nature Chemistry (2023).
2. Control of dynamic sp3-C stereochemistry. Nature Chemistry (2023).
3. A guide to bullvalene stereodynamics. Chemical Science (2024).
4. Correlated shapeshifting and configurational isomerization. Chemical Science (2024).
5. On the 3D → 2D Isomerization of Hexaborane(12). Chemistry (2021).