Heavy atom tunneling: When molecules disobey the reactivity textbook

DIPC Seminars

Speaker

Sebastian Kozuch
Ben-Gurion University of the Negev, Israel

When

2024/06/24
16:00

Place

Donostia International Physics Center (Hybrid Seminar)

Host

Bo Chen

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Quantum mechanical tunneling of “heavy” atoms1 (i.e. heavier than hydrogen) is extremely atypical, but also exceptionally rich chemistry, especially at cryogenic conditions. The only requirements are a rather low activation energy and, much more important, a narrow barrier. From all the cryptic effects can appear in such regime, we will consider:
I. Quantum tunneling instability,2 where supposedly stable hypothetical molecules can swiftly decompose, even when trying to keep them close to the absolute zero.
II. Isotope controlled selectivity,3 where the product of a reaction can be dictated by the presence of deuterium.
III. Reassessment of activation energies, where your ultra-accurate computed barriers might still be missing an important component.4
IV. Degenerate rearrangements, where the molecules just cannot stay put.  bond shifting,5 fluorine tunneling,6 transition metal complexes,7 heavy atom tunneling might appear just around the corner.
V. Tunneling inside Diamonds

1 W. T. Borden, Reactions that involve tunneling by carbon and the role that calculations have played in their study, WIREs Comput. Mol. Sci., 2016, 6, 20–46.
2 A. Frenklach, H. Amlani and S. Kozuch, Quantum Tunneling Instability in Pericyclic Reactions, J. Am. Chem. Soc., 2024, 146, 11823–11834.
3 A. Nandi, D. Gerbig, P. R. Schreiner, W. T. Borden and S. Kozuch, Isotope-Controlled Selectivity by Quantum Tunneling: Hydrogen Migration versus Ring Expansion in Cyclopropylmethylcarbenes, J. Am. Chem. Soc., 2017, 139, 9097–9099.
4 S. Kozuch, T. Schleif and A. Karton, Quantum mechanical tunnelling: the missing term to achieve sub-kJ mol−1 barrier heights, Phys. Chem. Chem. Phys., 2021, 23, 10888–10898.
5 A. Nandi, E. Solel and S. Kozuch, Carbon Tunneling in the Automerization of Cyclo[18]carbon, Chem. Eur. J., 2020, 26, 625–628.
6 I. Sedgi and S. Kozuch, Heavy atom tunnelling on XeF6 pseudorotation, Phys. Chem. Chem. Phys., 2020, 22, 17725–17730.
7 I. Sedgi and S. Kozuch, Heavy-atom tunnelling in Cu(II)N6 complexes: theoretical predictions and experimental manifestation, Chem. Sci., 2020, 11, 2828–2833.
8 I. Sedgi and S. Kozuch, A Playground for Heavy Atom Tunnelling: Neutral Substitutional Defect Rearrangement from Diamondoids to Diamonds, Chem. Eur. J., 2023, 29, e202300673.

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