The hydration structure of Cu2+: More tetrahedral than octahedral?

Bowron, D. T. ; Amboage, M. ; Boada, R. ; Freeman, A. ; Hayama, S. ; Díaz-Moreno, S.

Resumen: 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.

Idioma: Inglés

DOI: 10.1039/c3ra42400f

Año: 2013

Publicado en: RSC Advances 3, 39 (2013), 17803-17812
ISSN: 2046-2069

Factor impacto JCR: 3.708 (2013)

Categ. JCR: CHEMISTRY, MULTIDISCIPLINARY rank: 35 / 148 = 0.236 (2013) - Q1 - T1

Tipo y forma: Artículo (Versión definitiva)