2016. 57, 6 – UDC 548.73:543.422:541.49:546.562 CRYSTAL STRUCTURE DETERMINATION, AND DFT CALCULATIONS OF DICHLOROBIS(DIMETHYLSULFOXIDE-O)COPPER(II) H. Chebbi1,2, M. Chebbi3, A. Guesmi2, Y. Arfaoui3 1Preparatory Institute in the Studies of Engineers of Monastir, University of Monastir, Tunisia E-mail: chebhamouda@yahoo.fr 2Laboratory of Materials and Crystallochemistry, Department of Chemistry, Faculty of Science, University of Tunis El Manar, Tunisia 3Laboratory of Physical Chemistry of Condensed Materials, Department of Chemistry, Faculty of Science, University of Tunis El Manar, 2092, Tunisia Received June, 7, 2015 The crystal structure of dichlorobis(dimethylsulfoxide-O)copper(II), [CuCl2(DMSO)2] (I), previously determined by Willett and Chang, is reinvestigated. <...> In contrast to the previous investigation, all H atoms are placed at calculated positions. <...> In the title molecule, the CuII atom is five coordinated in a distorted square pyramidal geometry. <...> Thus, as reported previously, it can be shown that the crystal structure consists of [CuCl2(DMSO)2] molecules which, by virtue of long Cu—Cl interactions, are tied together to form chains parallel to the [100] direction. <...> The density functional theory (DFT) optimized structure at the B3LYP/6-311++G(2d,2p) level is compared with the experimentally determined molecular structure. <...> The HOMO—LUMO energy gap and other related molecular properties are also calculated. <...> Comprehensive experimental and theoretical structural studies on the studied complex are carried out by FT-IR and UV-visible spectroscopies. <...> The studied compound, [CuCl2(DMSO)2] (I), is an example of this class of materials. <...> Its structure determination was undertaken within a project on the preparation and structural investigation of new coordination compounds based on copper(II) halides and organic bases. <...> Our results are of a significantly higher precision in terms of bond lengths, angles, and R factors. <...> Moreover, with the aid of literature, it is clear that there is no quantum mechanical study on the title complex which has motivated us to perform a detailed quantum mechanical analysis in order to understand the vibrational modes and HOMO—LUMO properties. <...> The present paper reports a determination of the crystal structure of dichlorobis(dimethylsulfoxide-O)copper(II), with greater precision and accuracy. <...> Therefore, in the present <...>