Structural Investigation of the Aqueous Eu²⁺ Ion:  Comparison with Sr²⁺ Using the XAFS Technique

Abstract

Structural parameters of the Sr 2+ and, for the first time, of the Eu 2+ ions in aqueous solution were determined by the XAFS method. For the Sr 2+ , the use of an improved theoretical approach led to a first shell coordination number of 8.0 (3), a Sr-O distance of 2.600 (3) Å and a Debye-Waller factor of σ 2 ) 0.0126 (5)

Solution X-ray Absorption Fine Structure Study of the Eu2+and Sr2+Ions: Unexpected Solvent and Metal Ion Dependencies of the Solvation Numbers

“…6.2 Å -1 ( Figure 2). As in the case of the Eu 2+ aqua ion, 1 we attribute this sharp contribution to a 2p4d double-electron transition.…”

“…1 In solvents such as DMSO, the contribution of the second shell of scatterers is not negligible and can be used to extract information about the configuration of the coordinated ligands. 28 Among these contributions, it has been shown that only the contributions of the M‚‚‚S single scattering (SS) and of the M-O-S multiple scattering (MS) pathways are significant.…”

“…It is made of one-dimensional chains along the a axis ( Figure 6) with the metal cation lying on a binary axis. 1 In aqueous solutions, it is well established that the triflate ion does not enter the first coordination sphere of solvated metal ions. In the nonaqueous DMF, DMSO, and MeCN solvents with smaller dielectric constants than water, it is important to ensure that no inner sphere ion pairing occurs between the metal and the triflate ions.…”

Structural Investigation of Pd(II) in Concentrated Nitric and Perchloric Acid Solutions by XAFS

“…The single-shell XAFS spectra were fitted using the singlescattering curved-wave formalism in a way similar to the one used in ref 21. The SS contributions, related to the first shell, were singled out by the back FT with phase and amplitude corrections in the interval 1.5-2.5 Å.…”

“…Unfortunately, there is a difficulty in regard to the inclusions of hydrogen atoms in the FEFF code. 6,21,26,27 This difficulty exists because the O-H bond is much shorter than the Pd-O distance, and for the oxygen and hydrogen it is difficult to determine a good muffin-tin radius: FEFF code gives unrealistic muffin-tin radii and an overestimation of the backscattering contribution. 21,26,27 Here, to resolve this problem, we have used a known approximation by substituting the backscatter with the next chemical element.…”