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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