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Issue 17, 2012
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On the structure and dynamics of the hydrated sulfite ion in aqueous solution – an ab initio QMCF MD simulation and large angle X-ray scattering study

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Abstract

Theoretical ab initio quantum mechanical charge field molecular dynamics (QMCF MD) formalism has been applied in conjunction to experimental large angle X-ray scattering to study the structure and dynamics of the hydrated sulfite ion in aqueous solution. The results show that there is a considerable effect of the lone electron-pair on sulfur concerning structure and dynamics in comparison with the sulfate ion with higher oxidation number and symmetry of the hydration shell. The S–O bond distance in the hydrated sulfite ion has been determined to 1.53(1) Å by both methods. The hydrogen bonds between the three water molecules bound to each sulfite oxygen are only slightly stronger than those in bulk water. The sulfite ion can therefore be regarded as a weak structure maker. The water exchange rate is somewhat slower for the sulfite ion than for the sulfate ion, τ0.5 = 3.2 and 2.6 ps, respectively. An even more striking observation in the angular radial distribution (ARD) functions is that the for sulfite ion the water exchange takes place in close vicinity of the lone electron-pair directed at its sides, while in principle no water exchange did take place of the water molecules hydrogen bound to sulfite oxygens during the simulation time. This is also confirmed when detailed pathway analysis is conducted. The simulation showed that the water molecules hydrogen bound to the sulfite oxygens can move inside the hydration shell to the area outside the lone electron-pair and there be exchanged. On the other hand, for the hydrated sulfate ion in aqueous solution one can clearly see from the ARD that the distribution of exchange events is symmetrical around the entire hydration sphere.

Graphical abstract: On the structure and dynamics of the hydrated sulfite ion in aqueous solution – an ab initio QMCF MD simulation and large angle X-ray scattering study

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Publication details

The article was received on 21 Dec 2011, accepted on 15 Feb 2012 and first published on 14 Mar 2012


Article type: Paper
DOI: 10.1039/C2DT12467J
Dalton Trans., 2012,41, 5209-5216

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    On the structure and dynamics of the hydrated sulfite ion in aqueous solution – an ab initio QMCF MD simulation and large angle X-ray scattering study

    L. Eklund, T. S. Hofer, A. B. Pribil, B. M. Rode and I. Persson, Dalton Trans., 2012, 41, 5209
    DOI: 10.1039/C2DT12467J

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