title: The structure of the lanthanide aquo ions in solution as studied by 17O NMR spectroscopy and DFT calculations.
abstract: The (17)O NMR shifts of aqueous samples of lanthanide triflates were measured and analysed. In these systems the triflate anion does not enter the first coordination sphere. The contact contribution to the shifts showed a break at Eu(III), which reflects a change in the number of water molecules in the first coordination sphere of the Ln(III) ion from 9 for La-Sm to 8 for the heavier lanthanides. This change in hydration number is accompanied by a change in the parameters governing the pseudo-contact shifts. Fitting of the data with tricapped trigonal prism and square antiprismatic geometries obtained by DFT (density function theory) calculations showed that the crystal field parameters for these geometries differ by an order of magnitude. The hyperfine coupling constant for both geometries was determined to be A/(Planck's constant)= -4.2 x 10(6) rad s(-1).
authors.affiliation: Biocatalysis and Organic Chemistry, Department of Biotechnology, Delft University of Technology, Julianalaan 136, 2628, BL Delft, The Netherlands. K.Djanashvili@tudelft.nl
authors.forename: Kristina
authors.initials: K
authors.lastname: Djanashvili
authors.forename: Carlos
authors.initials: C
authors.lastname: Platas-Iglesias
authors.forename: Joop A
authors.initials: JA
authors.lastname: Peters
mesh_terms: D003198:Computer Simulation; D007477:Ions / Q000737:chemistry; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D010103:Oxygen Isotopes; D012996:Solutions; D014867:Water / Q000737:chemistry*
chemical_list: D007477:Ions; D028581:Lanthanoid Series Elements; D010103:Oxygen Isotopes; D012996:Solutions; D014867:Water