Isolating the Spectroscopic Signature of a Hydration Shell With the Use of Clusters: Superoxide Tetrahydrate

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Science  31 Mar 2000:
Vol. 287, Issue 5462, pp. 2461-2463
DOI: 10.1126/science.287.5462.2461

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Cluster spectroscopy, aided by ab initio theory, was used to determine the detailed structure of a complete hydration shell around an anion. Infrared spectra of size-selected O2 · (H2O)n(n = 1 to 4) cluster ions were obtained by photoevaporation of an argon nanomatrix. Four water molecules are required to complete the coordination shell. The simple spectrum of the tetrahydrate reveals a structure in which each water molecule is engaged in a single hydrogen bond to one of the four lobes of the π* orbital of the superoxide, whereas the water molecules bind together in pairs. This illustrates how water networks deform upon accommodating a solute ion to create a distinct supramolecular species.

  • * Present address: Institute of Physics and Astronomy, Aarhus Center for Advanced Physics, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark.

  • Present address: Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Post Office Box 999, Richland, WA 99352, USA.

  • To whom correspondence should be addressed. E-mail: mark.johnson{at}

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