title: Experimental measurements of water molecule binding energies for the second and third solvation shells of [Ca(H2O)n]2+complexes.
abstract: Further understanding of the biological role of the Ca2+ion in an aqueous environment requires quantitative measurements of both the short- and long-range interactions experienced by the ion in an aqueous medium. Here, we present experimental measurements of binding energies for water molecules occupying the second and, quite possibly, the third solvation shell surrounding a central Ca2+ion in [Ca(H2O)n]2+complexes. Results for these large, previously inaccessible, complexes have come from the application of finite heat bath theory to kinetic energy measurements following unimolecular decay. Even atn= 20, the results show water molecules to be more strongly bound to Ca2+than would be expected just from the presence of an extended network of hydrogen bonds. Forn> 10, there is very good agreement between the experimental binding energies and recently published density functional theory calculations. Comparisons are made with similar data recorded for [Ca(NH3)n]2+and [Ca(CH3OH)n]2+complexes.
authors.affiliation: Department of Physical and Theoretical Chemistry, School of Chemistry , University of Nottingham , University Park, Nottingham NG7 2RD , UK.
authors.forename: E
authors.identifier: 0000-0002-8370-5094
authors.initials: E
authors.lastname: Bruzzi
authors.affiliation: Department of Physical and Theoretical Chemistry, School of Chemistry , University of Nottingham , University Park, Nottingham NG7 2RD , UK.
authors.forename: A J
authors.identifier: 0000-0001-5948-3623
authors.initials: AJ
authors.lastname: Stace
keywords: binding energy; calcium; solvation shell; water