Adélaïde Savoy


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Savoy

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Adélaïde

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0000-0002-5775-7261

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Publications 1 - 3 of 3
  • Solvation Free Energies of Ion Dissociations in Dichloromethane: En Route to Accurate Computations
    Item type: Journal Article
    Savoy, Adélaïde; Paenurk, Eno; Pollice, Robert; et al. (2025)
    The Journal of Physical Chemistry B
    Calculating accurate free energies for solution-phase reactions is notoriously difficult. In our previous joint experimental and computational studies, we observed a striking failure of quantum mechanical calculations with popular implicit solvent models to even qualitatively reproduce the experimental trends of dissociation free energies of numerous proton-bound pyridine dimers in organic solvents [; [. In this article, we expand the computational study of the dissociation of proton-bound pyridine dimers in the gas phase and in dichloromethane (DCM). In an effort to determine the prerequisites for reproducing the experimental trends and magnitudes of the dissociation free energies (Delta G diss) in solvent, we investigated the impact of accounting for the ensemble free energy, umbrella sampling, thermodynamic integration, and explicit solvation using semiempirical quantum mechanics and molecular mechanics. We estimated the effect of conformational free energy contributions with semiempirical quantum mechanics (SE). Molecular dynamics (MD) with explicit solvation and classical molecular mechanics (MM) was used as a method to treat not only the solute but also the solvent configurational entropy. We found that explicit solvation with MM is indeed capable of reproducing Delta G diss in DCM for our test system within an acceptable error margin. We analyze and discuss the results and limitations of our approach for calculating the solvation free energy.
  • London Dispersion versus Intramolecular Hydrogen Bond in Bis-Pyridines: How Accurate Is DFT for Competing Noncovalent Interactions in the Condensed Phase?
    Item type: Journal Article
    Savoy, Adélaïde; Gorbachev, Vladimir; Stindt , Charlotte N.; et al. (2025)
    Chemistry - A European Journal
    We report a systematic investigation of noncovalent interactions—particularly an intramolecular hydrogen bond and London Dispersion forces—in singly protonated bis-pyridines, studied across solution and crystalline states. Building on our previous gas-phase study, we combine variable-temperature 1H NMR spectroscopy, single-crystal X-ray diffraction, and density functional theory (DFT) calculations. The measured 1H NMR chemical shifts of the acidic proton serve as a solution-phase structural readout, which we correlate with an independent crystallographic metric. By systematically varying the linker (–CH2–, –O–, and –CH2CH2–) and the pendant substituents (H, methyl, tert-butyl), we examine how increasingly bulky “dispersion energy donors” affect both the intramolecular hydrogen bond and the accessible conformational states. In reference systems, where a single noncovalent interaction governs the geometry, even relatively simple computational models correctly reproduce the experimentally observed structures. However, for molecules featuring two competing noncovalent interactions, the tested, dispersion-corrected, DFT often fails to predict the relative energies of accessible conformers accurately, highlighting current limitations in predictive accuracy. We briefly discuss broader implications of currently achievable predictive accuracy for homogeneous catalysis.
  • Probing London Dispersion in Proton-Bound Onium Ions: Are Alkyl-Alkyl Steric Interactions Reliably Modeled?
    Item type: Journal Article
    Gorbachev, Vladimir; Savoy, Adélaïde; Tsybizova, Alexandra; et al. (2025)
    Journal of the American Chemical Society
    We report spectroscopic and spectrometric experiments that probe the London dispersion interaction between tert-butyl substituents in three series of covalently linked, protonated bis-pyridines in the gas phase. Molecular ions in the three test series, along with several reference molecules for control, were electrosprayed from solution into the gas phase and then probed by infrared multiphoton dissociation spectroscopy and trapped ion mobility spectrometry. The observed N-H stretching frequencies provided an experimental readout diagnostic of the ground-state geometry of each ion, which could be furthermore compared to a second, independent structural readout via the collision cross section. In each of the three series, the strength of a London dispersion interaction could be modulated systematically by a progressive increase in the size of substituents from H to Me to tert-Bu. Parallel to the experimental study, extensive dispersion-corrected density functional theory (DFT-D3BJ) calculations were performed with a range of exchange correlation functionals. A full analysis of the conformational space for the flexible members of the series, and an analysis of the vibrational spectra in the context of a general double-well potential, finds that DFT-D3BJ appears to significantly overbind alkyl-alkyl interactions, specifically interactions between tert-Bu groups, even failing to predict the minimum energy structures reliably in the case of molecules in which London dispersion competes with other noncovalent interactions such as hydrogen bonding.
Publications 1 - 3 of 3