Infrared spectroscopic study of Cs2Ni(XO4)2•6H2O (X = S, Se) and of NH4+ ions included in M2Ni(XO4)2•6H2O (M = Rb, Cs; X = S, Se) and crystal structures of (M,NH4)2Ni(XO4)2•6H2O (M = Rb, Cs; X = S, Se) mixed crystals

Author(s): Veronika Karadjova, Manfred Wildner, Donka Stoilova
Abstract: The soly. in the three-?component Cs2SO4-?NiSO4-?H2O system was studied at 25°C. It has been established that a double salt, Cs2Ni(SO4)?2·6H2O, crystallizes within a wide concn. range. IR spectra of neat Tutton compds. Cs2Ni(XO4)?2·6H2O (X = S, Se) as well as those of ammonium doped rubidium and cesium sulfate and selenate matrixes are presented and discussed with respect to the normal modes of the tetrahedral ions and water librations. The ammonium ions included in the sulfates exhibit three bands corresponding to the asym. bending modes ?4 in agreement with the low site symmetry C1 of the host cesium and rubidium cations. However, the inclusion of ammonium ions in the rubidium and cesium selenates leads to the appearance of four bands in the region of ?4. At that stage of our knowledge we assume that some kind of disorder of the ammonium ions included in the selenates occurs due to the strong proton acceptor capability of the SeO42- (stronger than that of SO42-?)?, thus facilitating the formation of polyfurcate hydrogen bonds by the ammonium ions in the selenate matrixes. The strength of the hydrogen bonds formed in the mixed crystals M1.85(NH4)?0.15Ni(XO4)?2·6H2O (M = Rb, Cs; X = S, Se) as deduced from the frequencies of the water librations is discussed. The spectroscopic expts. reveal that the water mols. in the mixed crystals form weaker hydrogen bonds than those in the neat rubidium and cesium Tutton salts due to decreasing in the proton acceptor strength of the SO42- and SeO42- ions as a result of the formation of hydrogen bonds between the host anions and the NH4+ guest cations (anti-?cooperative or proton acceptor competitive effect)?. Crystal structure investigations of several (M,?NH4)?2Ni(XO4)?2·6H2O (M = Rb, Cs; X = S, Se) mixed crystals reveal significant changes in the environment of the monovalent cations as well as in the hydrogen bonding systems of the water mols. upon incorporation of ammonium ions. Disorder of NH4 groups and the formation of polyfurcate N-?H···O hydrogen bonds have not been obsd., but neither can be excluded by the X-?ray diffraction expts., esp. not for rather low ammonium contents.
Organisation(s): Department of Mineralogy and Crystallography
External organisation(s): University of Chemical Technology and Metallurgy, Bulgarian Academy of Sciences (BAS)
Journal: International Research Journal of Pure and Applied Chemistry
Volume: 5
Pages: 245-262
No. of pages: 18
ISSN: 2231-3443
DOI: https://doi.org/10.9734/IRJPAC/2015/14426
Publication date: 12-2014
Peer reviewed: Yes
Austrian Fields of Science 2012: 105116 Mineralogy, 104011 Materials chemistry, 105113 Crystallography, 104003 Inorganic chemistry
Keywords
Portal url: https://ucrisportal.univie.ac.at/en/publications/infrared-spectroscopic-study-of-cs2nixo426h2o-x--s-se-and-of-nh4-ions-included-in-m2nixo426h2o-m--rb-cs-x--s-se-and-crystal-structures-of-mnh42nixo426h2o-m--rb-cs-x--s-se-mixed-crystals(960b1c35-b685-40fa-8c17-38599eeb7ce5).html

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