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

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. (C) 2003 Elsevier B.V. All rights reserved.