17O NMR Investigation of Water Structure and Dynamics

The structure and dynamics of the bound water in barium chlorate monohydrate were studied with O-17 nuclear magnetic resonance (NMR) spectroscopy in samples that are stationary and spinning at the magic-angle in magnetic fields ranging from 14.1 to 21.1 T. O-17 NMR parameters of the water were determined, and the effects of torsional oscillations of the water molecule on the O-17 quadrupolar coupling constant (C-Q) were delineated with variable temperature MAS NMR. With decreasing temperature and reduction of the librational motion, we observe an increase in the experimentally measured C-Q explaining the discrepancy between experiments and predictions from density functional theory. In addition, at low temperatures and in the absence of H-1 decoupling, we observe a well-resolved H-1-O-17 dipole splitting in, the spectra, which provides information on the structure of the H2O molecule. The splitting arises because of the homogeneous nature of the coupling between the two H-1-O-17 dipoles and the H-1-H-1 dipole.