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Issue 39, 2013
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The hydration structure of Cu2+: more tetrahedral than octahedral?

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Abstract

A comprehensive multi-technique approach has been used to address the controversial question of the preferred geometric form of the Cu2+ aqua-ion hydration shell. A combination of H/D isotopic substitution neutron scattering and X-ray scattering has been used to refine atomistic models of 0.5 m and 2.0 m solutions of Cu(ClO4)2, that have also been constrained to simultaneously reproduce detailed local structure information about the cation environment obtained by X-ray Absorption spectroscopy. The adoption of the Empirical Potential Structure Refinement (EPSR) technique as a single unified analytical framework minimises the chances for biasing the result in favour of a specific pre-conceived outcome. The results are consistent with an average coordination for each Cu2+ ion of 4.5 ± 0.6 water molecules that matches the more recent picture of five-fold coordination in a 2.0 m solution, but interestingly this combined study highlights that the preferred local geometry of the ion sites is found to have a mixed character of tetrahedral, trigonal bipyramidal and octahedral components. A further point to note is that this new model adds support to a largely ignored result in the literature relating to the linear electric field effect induced g-shifts observed in the electron paramagnetic resonance spectra of glassy Cu2+ complexes (Peisach and Mims, Chem. Phys. Lett., 1976, 37, 307–310) that first highlighted the importance of tetrahedral distortions in the cation's hydration shell structure.

Graphical abstract: The hydration structure of Cu2+: more tetrahedral than octahedral?

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Publication details

The article was received on 15 May 2013, accepted on 19 Jul 2013 and first published on 19 Jul 2013


Article type: Paper
DOI: 10.1039/C3RA42400F
Citation: RSC Adv., 2013,3, 17803-17812
  • Open access: Creative Commons BY license
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    The hydration structure of Cu2+: more tetrahedral than octahedral?

    D. T. Bowron, M. Amboage, R. Boada, A. Freeman, S. Hayama and S. Díaz-Moreno, RSC Adv., 2013, 3, 17803
    DOI: 10.1039/C3RA42400F

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