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

Abstract

Structural parameters of the Sr 2+ and, for the first time, of the Eu 2+ ions in nonaqueous solutions were determined by the X-ray absorption fine structure (XAFS) method and compared with those of the aqua ions. For both Eu 2+ and Sr 2+ ions, a decrease in coordination number (N) and metal-to-solvent distances was found along the increasingly solvating MeCN < H 2 O , DMF < DMSO solvent series: for strontium, N ) 8 with [Sr (MeCN)

Apparent molar volumes and compressibilities of alkaline earth metal ions in methanol and dimethylsulfoxide

“…The structure of hydrated and solvated alkaline earth metal cations have been investigated by large angle X-ray scattering (LAXS), extended X-ray absorption fine structure techniques (EXAFS), crystallography, infrared and Raman spectroscopy [13][14][15][16]. Moreover, the structures of hydrated alkaline earth metal ions have been studied by theoretical calculations [17,18].…”

“…Beryllium (II) ion, because of its small ionic radius, is able to accommodate a maximum of four solvent molecules in its complexes [16]. The coordination number of calcium (II) and strontium (II) ions varies from six to eight depending on solvent [13,15].…”

Solid‐State Models of Ion Solvation: Crystal Structures of Dimethyl Sulfoxide Solvates of Alkaline Earth Cations

“…The structure determined for the Sr compound ( Figure 3) 14 . The presence of a water ligand may simply reflect the use of solvents which were not completely dried and may mean that different species could be obtained under different crystallisation conditions, but the particular phase presently obtained is nonetheless of interest, even if it only exemplifies possible structures.…”

“…[13] Possibly significantly, however, is the eight-coordination for Sr II , accompanied by anion coordination, is seen in solid [Sr(dmso-O) 2 (CF 3 SO 3 ) 2 ]. [14] The exploration of such subtleties by structural work can therefore be seen as providing an important contribution to the development of more sophisticated molecular models for electrolyte solutions. Following the suggestion of a referee, we note that one particular use of single-crystal data is to provide a coordination number associated with a given mean metalϪdonor atom distance, since solution X-ray measurements (LAXS, XAFS, EXAFS) frequently provide precise values for the latter but imprecise values for the former.…”

Characterization of Metal Ions in Coordinating Solvent Mixtures by Means of Raman Spectroscopy

“…27 On the other hand, the strontium ion is seven-solvated in DMF and DMSO, while it is eight-solvated in acetonitrile. 28 Individual solvation numbers of alkaline earth metal ions in the DMF-DMA mixture determined by titration Raman spectroscopy are shown in Fig. 4.…”