Proton Transfer Dynamics in Carboxylic Acid Dimers

Proton transfer in carboxylic acid dimers constitutes a paradigmatic model for hydrogen‐bonded proton relays underpinning many chemical and biological processes. In these cyclic dimers, two carboxyl groups are linked by a pair of hydrogen bonds, enabling concerted or sequential transfer of protons between donor and acceptor sites. The interplay between the shape of the potential‐energy surface, anharmonic vibrational coupling and quantum tunnelling determines the rate and mechanism of transfer. Experimental techniques such as jet-cooled infrared and Raman spectroscopy provide high-resolution vibrational spectra that reveal tunnelling splittings and overtone transitions, while ab initio and density-functional calculations map out the multidimensional energy landscape. Recent advances in machine-learning potentials and tailored quantum-dynamics schemes have further refined our understanding of how mass, isotopic substitution and environmental perturbations influence the transfer dynamics. Insights from this prototypical system inform broader contexts, from proton conduction in materials to enzyme catalysis and atmospheric chemistry.

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Proton Transfer Dynamics in Carboxylic Acid Dimers publication trend

The graph below shows the total number of articles in proton transfer dynamics in carboxylic acid dimers across all publications each year (not limited to Nature Index journals).

Technical terms

Carboxylic acid dimer: A cyclic assembly of two carboxylic acid molecules held together by two hydrogen bonds.

Proton tunnelling: Quantum phenomenon allowing a proton to traverse an energy barrier lower than its classical kinetic energy would permit.

Potential‐energy surface: Multidimensional landscape describing how the energy of a molecular system varies with nuclear positions.

Vibrational exciton: Delocalised vibrational mode arising from coupling between identical oscillators in a molecular aggregate.

Tunnelling splitting: Energy separation between symmetric and antisymmetric tunnelling states resulting from quantum delocalisation of the proton.

References

1. Double Proton Transfer in the Dimer of Formic Acid: An Efficient Quantum Mechanical Scheme. Frontiers in Chemistry (2019).
2. High-dimensional neural network potentials for accurate vibrational frequencies: the formic acid dimer benchmark. Physical Chemistry Chemical Physics (2022).
3. Slow monomer vibrations in formic acid dimer: Stepping up the ladder with FTIR and Raman jet spectroscopy. The Journal of Chemical Physics (2021).