Hydration Dynamics and IR Spectroscopy of 4-Fluorophenol

Seyedeh Maryam Salehi; Silvan Käser; Kai Töpfer; Polydefkis Diamantis; Rolf Pfister; Peter Hamm; Ursula Röthlisberger; Markus Meuwly

arXiv · 2206.10463

Hydration Dynamics and IR Spectroscopy of 4-Fluorophenol

Seyedeh Maryam Salehi·Silvan Käser·Kai Töpfer·Polydefkis Diamantis·Rolf Pfister·Peter Hamm·Ursula Röthlisberger·Markus Meuwly

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Abstract

Halogenated groups are relevant in pharmaceutical applications and potentially useful spectroscopic probes for infrared spectroscopy. In this work, the structural dynamics and infrared spectroscopy of $para$-fluorophenol (F-PhOH) and phenol (PhOH) is investigated in the gas phase and in water using a combination of experiment and molecular dynamics (MD) simulations. The gas phase and solvent dynamics around F-PhOH and PhOH is characterized from atomistic simulations using empirical energy functions with point charges or multipoles for the electrostatics, Machine-Learning (ML) based parametrization and with full $\textit{ab initio}$ (QM) and mixed Quantum Mechanical/Molecular Mechanics (QM/MM) simulations with a particular focus on the CF- and OH-stretch region. The CF-stretch band is heavily mixed with other modes whereas the OH-stretch in solution displays a characteristic high-frequency peak around 3600 cm$^{-1}$ most likely associated with the -OH group of PhOH and F-PhOH together with a characteristic progression below 3000 cm$^{-1}$ due to coupling with water modes which is also reproduced by several of the simulations. Solvent and radial distribution functions indicate that the CF-site is largely hydrophobic except for simulations using point charges which renders them unsuited for correctly describing hydration and dynamics around fluorinated sites.

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Seyedeh Maryam Salehi, Silvan Käser, Kai Töpfer, Polydefkis Diamantis, Rolf Pfister, Peter Hamm, Ursula Röthlisberger, Markus Meuwly. 2022-06-21. Hydration Dynamics and IR Spectroscopy of 4-Fluorophenol. https://arxiv.org/abs/2206.10463

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