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arXiv · 2108.11377

Infrared and NMR Spectroscopic Fingerprints of the Asymmetric H7+O3 Complex in Solution

Eve Kozari·Mark Sigalov·Dina Pines·Benjamin P. Fingerhut·Ehud Pines
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Abstract

Infrared (IR) absorption in the 1000-3700 cm-1 range and 1H NMR spectroscopy reveal the existence of an asymmetric protonated water trimer, H7+O3, in acetonitrile. The core H7+O3 motif persists in larger protonated water clusters in acetonitrile up to at least 8 water molecules. Quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) simulations reveal irreversible proton transport promoted by propagating the asymmetric H7+O3 structure in solution. The QM/MM calculations allow for the successful simulation of the measured IR absorption spectra of H7+O3 in the OH stretch region, which reaffirms the assignment of the H7+O3 spectra to a hybrid-complex structure: a protonated water dimer strongly hydrogen-bonded to a third water molecule with the proton exchanging between the two possible shared-proton Zundel-like centers. The H7+O3 structure lends itself to promoting irreversible proton transport in presence of even one additional water molecule. We demonstrate how continuously evolving H7+O3 structures may support proton transport within larger water solvates.

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Eve Kozari, Mark Sigalov, Dina Pines, Benjamin P. Fingerhut, Ehud Pines. 2021-08-25. Infrared and NMR Spectroscopic Fingerprints of the Asymmetric H7+O3 Complex in Solution. https://doi.org/10.1002/cphc.202001046

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