Richard Jarman - NMR Study of Water Reorientation  in Molydic Acids

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      Publication Details (including relevant citation   information):

      NMR Study of   Water Reorientation in Molydic Acids, R.H. Jarman and R.C.T.   Slade, J. Solid State Chem., 39, 387 (1981).

      Abstract:

        Proton NMR relaxation times (T2,    T1,    T1ϱ)   are reported for powder samples of MoO3    · 2H2O   and yellow MoO3    · H2O   in the temperature range 150–325 K and at 20 and 60 MHz. No   translation of hydrogen atoms is detected but the spin-lattice   relaxation behavior indicates reorientation of   H2O   molecules. The waters coordinated to Mo atoms undergo 180° flips   (about their   C2    axes) with similar motional parameters in both compounds. The   interlayer waters in MoO3    · 2H2O   undergo 180° flips with different parameters. An assumed   Arrhenius-type temperature dependence of correlation times leads   to preexponential factors which are “anomalously” low. The   possible involvement of temperature-dependent activation barriers   is discussed.

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