title: Hydration of Hg2+ in aqueous solution studied by neutron diffraction with isotopic substitution.
abstract: The structural parameters of Hg2+ hydration were studied in 0.225 mol/L solutions of Hg2+ in DNO3/D2O by means of neutron diffraction with isotopic substitution of 199Hg for natHg. It was found that Hg2+ is hydrated by a first solvation shell of six water molecules. The observed Hg-O and Hg-H distances are equal to 2.48+/-0.05 and 3.08+/-0.05 A, respectively. The angle phi between the plane of the water molecule and the cation-water oxygen axis is approximately 35 degrees . The solvation of Hg2+ therefore mimics very closely that of Ca2+ (the Ca-O and Ca-H distances are 2.40 and 3.03 A, respectively) and helps to account for the extreme toxicity of mercury(II). We note also that the Hg-O distance obtained in the neutron diffraction experiment is larger by approximately 0.1 A than that obtained by X-ray diffraction. This difference is consistent with a shift of the oxygen electron density toward the mercury cation due to the covalency of the Hg-O interaction.
authors.affiliation: LGIT, University of Grenoble and CNRS, BP 53, 38041 Grenoble, France. Oleg.SOBOLEV@ujf-grenoble.fr
authors.forename: Oleg
authors.initials: O
authors.lastname: Sobolev
authors.forename: Gabriel J
authors.initials: GJ
authors.lastname: Cuello
authors.forename: Gabriela
authors.initials: G
authors.lastname: Román-Ross
authors.forename: Neal T
authors.initials: NT
authors.lastname: Skipper
authors.forename: Laurent
authors.initials: L
authors.lastname: Charlet
mesh_terms: D003903:Deuterium; D007477:Ions; D008628:Mercury / Q000737:chemistry*; D008629:Mercury Isotopes / Q000737:chemistry; D033363:Neutron Diffraction; D010100:Oxygen / Q000737:chemistry; D010316:Particle Size; D012996:Solutions / Q000737:chemistry; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D007477:Ions; D008629:Mercury Isotopes; D012996:Solutions; D014867:Water; D003903:Deuterium; D008628:Mercury; D010100:Oxygen