In-Depth XANES and EXAFS Characterization of the Ag Ion Coordination in Dimethyl Sulfoxide Solution.

X-ray absorption near-edge structure (XANES) spectroscopy has been used, in conjunction with extended X-ray absorption fine structure (EXAFS), to determine the coordination structure of the Ag ion in a dimethyl sulfoxide (DMSO) solution. From the EXAFS data analysis, the Ag-O first shell distance in DMSO was found to be 2.31(3) Å, with 4.1(5) oxygen atoms surrounding the Ag ion, in fair agreement with previous results. This technique did not allow us to determine the geometry of the 4-fold coordination complex and a quantitative analysis of the XANES region was carried out to shed light on this issue. The XANES data analysis confirmed the presence of a four-coordinated complex, unambiguously showing that a regular tetrahedral [Ag(DMSO)] complex is formed when silver triflate is dissolved in DMSO solution.