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).


        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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