Pulsed Neutron Diffraction Studies on Lanthanide(III)Hydration in Aqueous Perchlorate Solutions

Abstract

P u ls e d N e u tr o n D if fr a c tio n S tu d ie s o n L a n t h a n i d e ( I I I ) H y d r a tio n in A q u e o u s P e r c h lo r a te S o lu tio n s T. Yamaguchi, S. Tanaka, H. Wakita, M. Misawa1, I. Okada2, A. K. Soper3, and W. S. Howells3 Department of Chemistry, Faculty of Science, Fukuoka University, Nanakuma, Jonan-ku, Fukuoka 814-01, Japan Z. Naturforsch. 46a, 84-88 (1991); received August 1, 1990Dedicated to Dr. Karl Heinzinger on the occasion of his 60th birthday Pulsed neutron diffraction measurements are reported on 2 molar aqueous solutions of Pr3 + , Nd3 + , Tb3 + , Dy3 + , Tm3 + , and Yb3+ in D20 at room temperature. The first order difference technique on isomorphous ions is used to derive the metal ion pair correlation functions in these systems. The metal-oxygen and metal-deuterium distances and the hydration numbers are deter mined. The data indicate that the hydration number changes from ~ 10 for the lighter ions to ~8 for the heavier ones in the series. The water dipole is orientated on the average at an angle of 10 ~ 20 degrees to the metal-oxygen vector; these values are significantly smaller than those found for mono-and di-valent ions. The present results are compared with other results from neutron diffraction with isotope substitution, X-ray diffraction, and extended X-ray absorption fine structure.

Experimental and Molecular Dynamics Studies of Dysprosium(III) Salt Solutions for a Better Representation of the Microscopic Features Used within the Binding Mean Spherical Approximation Theory

“…This value is in good agreement with distances found from neutron diffraction studies. Cossy et al found d (Dy−O (1) ) = 0.239 ± 0.002 and 0.240 ± 0.002 nm, in agreement with Yamaguchi et al These measurements, conducted in D 2 O solvent, also provided values for d (Dy−D (1) ), the distance between Dy 3+ and a deuterium atom of the first D 2 O coordination sphere: Cossy et al found a d (Dy−D (1) ) value of 0.303 ± 0.002 nm, which is in reasonable agreement with the Yamaguchi et al d (Dy−D (1) ) value of 0.308 ± 0.003 nm. These distances, noticeably lower than our σ + (0) /2 value, show that the BIMSA hydrated cation diameter accounts for water molecules beyond the first layer, in agreement with the generally admitted picture that lanthanide(III) cations are surrounded by more than one hydration layer .…”

The thermodynamics of aqueous trivalent rare earth elements. Apparent molar heat capacities and volumes of Nd(ClO4)3(aq), Eu(ClO4)3(aq), Er(ClO4)3(aq), and Yb(ClO4)3(aq) from the temperatures 283 K to 328 K

“…(49) suggest that some features of ionic hydration may be quite constant across the series. However, the X-ray (30)(31)(32) and neutron diffraction (33)(34)(35) results and modelling investigations (36) strongly support Spedding's interpretation that the anomalies in the thermodynamic properties of the aquo ion arise from a change in hydration number. Several theoretical and semi-empirical models have been developed to link the structures of the hydrated ions to the thermodynamic properties.…”

“…X-ray (30)(31)(32) and neutron diffraction studies, (33)(34)(35) and modelling investigations (36) Our values of C°p ,2 for the six lanthanide perchlorates for each temperature are plotted as a function of ionic radius in figure 10, along with those for Al(ClO 4 ) 3 (aq) and Fe(ClO 4 ) 3 (aq). (37) The values for C°p ,2 {Al(ClO 4 ) 3 ,aq} were calculated from those for AlCl 3 (aq), (38,39) HClO 4 (aq), (21) and HCl(aq).…”

“…The structure of hydrated lanthanide ions has been investigated using X-ray (30)(31)(32)(41)(42)(43)(44)(45) and neutron diffraction, (33)(34)(35) extended X-ray absorption spectroscopy (EXAFS), (46) Raman spectroscopy, (9,47,48) n.m.r., (49) molecular dynamics simulations, (50) and quantum mechanical calculations. (36) Generally, the results from these investigations suggest that lighter lanthanide ions, from La 3+ (aq) to Nd 3+ (aq) in the series, have a hydration number of nine; those from Tb 3+ (aq) to Lu 3+ (aq) have a hydration number of eight; and those in the middle of the series have a fractional hydration number reflecting an equilibrium between the hydration numbers eight and nine.…”

Optical spectroscopy as a tool for studying the solution chemistry of neodymium(iii)

“…250 Both techniques have been used since the early days of lanthanide( iii ) solution chemistry. 254,255 Traditionally, luminescence has been used as the favoured technique. When it comes to speciation, this has recently been proven to be problematic as luminescence does not correlate directly to speciation.…”