B. Kukovec, Diogo Vila-Viçosa, Marija Zbačnik
Aug 5, 2014
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Journal
Acta Crystallographica Section A
Abstract
Hydrothermal and mechanochemical syntheses are extensively used to obtain metal coordination polymers of different dimensionalities. Transition metal complexes with carboxylate based ligands e. g. 3-hydroxyquinoxaline-2-carboxylic acid (3- OHquinoxH) are interesting due to the possible formation of porous structures suitable for gas storage and separation. 1D coordination polymer {; ; ; [Cu2(3-OHquinox)2(SO4)(H2O)2]∙4DMSO}; ; ; n (1) was obtained by reaction of CuSO4 and 3-OHquinoxH in dimethyl sulfoxide (DMSO) solution at room temperature, while mononuclear complex [Cu(3- OHquinox)2(H2O)2]∙2DMSO (2) was formed in hydrothermal conditions. X-ray crystal structure analysis revealed two differently coordinated Cu(II) ions in 1. One Cu(II) ion in 1 is octahedrally coordinated by two bridging O, O'- bidentate 3-OHquinox ligands and two water molecules in trans position, while the second Cu(II) ion by two bridging N, O'-bidentate 3- OHquinox ligands and one O, O'-bidentate sulfate ion. The reaction mixture was also grinded in a ball mill in the presence of H2O, DMSO or their mixture and the products were identified by PXRD. The grinding in these conditions could not be used to prepare pure 1 nor 2, but rather a mixture of both 1, 2, reactants and new, still unidentified, phase. The complex 2 was also studied by DFT methods. The hypothetical complex with two O-bound DMSO molecules is more stable than 2 by 2.9 kcal mol-1. The preference for the formation of 2 must be assigned to the hydrogen bonds between coordinated water and solvated DMSO molecules in 2.