TY - JOUR
T1 - The nature and transport mechanism of hydrated hydroxide ions in aqueous solution
AU - Tuckerman, Mark E.
AU - Marx, Dominik
AU - Parrinello, Michele
N1 - Funding Information:
M.E.T. was supported by the National Science Foundation (NSF) and Research Corporation.
Funding Information:
We thank E. Turner, J. Winn and R. Barkana for discussions. This work was supported in part by grants from the NSF and NASA. J.S.B.W. is supported by a Hubble Fellowship.
PY - 2002/6/27
Y1 - 2002/6/27
N2 - Compared to other ions, protons (H+) and hydroxide ions (OH−) exhibit anomalously high mobilities in aqueous solutions. On a qualitative level, this behaviour has long been explained by 'structural diffusion' - the continuous interconversion between hydration complexes driven by fluctuations in the solvation shell of the hydrated ions. Detailed investigations have led to a clear understanding of the proton transport mechanism at the molecular level2-8. In contrast, hydroxide ion mobility in basic solutions has received far less attention2, 3, 9, 10, even though bases and base catalysis play important roles in many organic and biochemical reactions and in the chemical industry. The reason for this may be attributed to the century-old notion11 that a hydrated OH− can be regarded as a water molecule missing a proton, and that the transport mechanism of such a 'proton hole' can be inferred from that of an excess proton by simply reversing hydrogen bond polarities11-18. However, recent studies2, 3 have identified OH− hydration complexes that bear little structural similarity to proton hydration complexes. Here we report the solution structures and transport mechanisms of hydrated hydroxide, which we obtained from first-principles computer simulations that explicitly treat quantum and thermal fluctuations of all nuclei19-21. We find that the transport mechanism, which differs significantly from the proton hole picture, involves an interplay between the previously identified hydration complexes2, 3 and is strongly influenced by nuclear quantum effects.
AB - Compared to other ions, protons (H+) and hydroxide ions (OH−) exhibit anomalously high mobilities in aqueous solutions. On a qualitative level, this behaviour has long been explained by 'structural diffusion' - the continuous interconversion between hydration complexes driven by fluctuations in the solvation shell of the hydrated ions. Detailed investigations have led to a clear understanding of the proton transport mechanism at the molecular level2-8. In contrast, hydroxide ion mobility in basic solutions has received far less attention2, 3, 9, 10, even though bases and base catalysis play important roles in many organic and biochemical reactions and in the chemical industry. The reason for this may be attributed to the century-old notion11 that a hydrated OH− can be regarded as a water molecule missing a proton, and that the transport mechanism of such a 'proton hole' can be inferred from that of an excess proton by simply reversing hydrogen bond polarities11-18. However, recent studies2, 3 have identified OH− hydration complexes that bear little structural similarity to proton hydration complexes. Here we report the solution structures and transport mechanisms of hydrated hydroxide, which we obtained from first-principles computer simulations that explicitly treat quantum and thermal fluctuations of all nuclei19-21. We find that the transport mechanism, which differs significantly from the proton hole picture, involves an interplay between the previously identified hydration complexes2, 3 and is strongly influenced by nuclear quantum effects.
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U2 - 10.1038/nature00797
DO - 10.1038/nature00797
M3 - Article
C2 - 12087398
AN - SCOPUS:0037182850
VL - 417
SP - 925
EP - 929
JO - Nature Cell Biology
JF - Nature Cell Biology
SN - 1465-7392
IS - 6892
ER -