Abstract:
London dispersion (LD) is the weakest non-covalent interaction, historically overlooked due to its small magnitude in individual pairwise interactions. Recently, it has gained attention with the proposed dispersion energy donors (DEDs) concept, implying the utilization of polarizable moieties, providing a substantial number of these small stabilizing contacts to steer reactivity. However, most of the studies on LD have been performed in solution, where a significant part of the London forces is screened out. The adequate treatment of solvation per se, along with the ambiguity associated with dispersion corrections in electronic structure calculations, presents twofold computational challenges when studying LD in media. Consequently, a quantitative assessment of the attractive dispersion interactions necessarily requires the utilization of gas-phase experimental techniques to eliminate environmental factors and provide direct and easy access for benchmarking computational methods.
We present a comprehensive investigation of onium ions analyzed using gas-phase techniques, including energy-resolved collision-induced dissociation cross-sections, collision cross-sections from trapped ion mobility spectrometry (TIMS), and spectroscopic methods such as cryogenic ion vibrational predissociation (CIVP) and infrared multiple photon dissociation (IRMPD). Our findings reveal limitations in widely-used dispersion-corrected DFT-D3/D4 methods, which do not accurately describe the potential between alkyl groups.1-2 In contrast, most dispersion-correction DFT methods reproduce dissociation energies of face-to-face π-stacking dimers more reliably. Our work suggests that the anisotropy of the London dispersion interaction is not reliably captured by current computational methods and is likely a major source of their inconsistent accuracy.3-5
[1] V. Gorbachev, A. Savoy, A. Tsybizova, R. Pollice, L. van Tetering, J. Martens, J. Oomens, G. Berden, P. Chen, J. Am. Chem. Soc.,2024, 147, 5, 4308–4323.
[2] A. Savoy, V. Gorbachev, S. Stindt, P. Chen, Chem. Eur. J., 2025, e02745.
[3] M. Bot, V. Gorbachev, A. Tsybizova, P. Chen, J. Phys. Chem. A, 2020, 124, 8692-8707.
[4] V. Gorbachev, PhD thesis, «Unraveling London Dispersion in the Gas Phase» (ETH Zurich, 2023).
[5] V. Gorbachev, A. Spadea, A. Tsybizova, P. Chen, 2026, (unpublished).
After the colloquium there will pizza and drinks.
