The structure of solvated halide ions in dimethyl sulfoxide studied by Raman spectroscopy and X-ray diffraction

Abstract

The solvation structure of chloride, bromide, and iodide ions, X −, in dimethyl sulfoxide (DMSO) has been investigated by using Raman spectroscopy and large angle X-ray diffraction under ambient conditions. The positively charged sulfur atom in DMSO interacts with X − and slightly positively charged methyl groups in the coordinating molecules also interact with X −. The X −S, X −···C, and X −···O distances are determined as follows: Cl −S: 416, Cl −···C: 363, Cl −···O: 543, Br −S: 433, Br −···C: 372, Br −···O: 544, I −S: 437, I −···C: 374 and I −···O: 520 pm. The coordination numbers of DMSO molecules around the anions are six, seven and eight for Cl −, Br − and I − ions, respectively, with the uncertainty of ±1. Rather large uncertainties in the measured solvation numbers suggest large fluctuations in the solvation structure of the anions.