Dynamics of [Zn(D2O)6]2+ in [Zn(D2O)6][SiF6] crystal as studied by 1D, 2D spectra and spin-lattice relaxation time of 2H NMR

The dynamics of [Zn(D2O)6]2+ in [Zn(D2O)6][SiF6] was investigated by 2H NMR one-dimensional spectra, two-dimensional exchange spectra and spin-lattice relaxation time (T1). The lineshapes of those spectra and T1 were dominated by the 180° flip of the water molecules and the reorientation of [Zn(D2O)6]2+ about the C3 axis. The variation of lineshape of the one-dimensional spectrum below room temperature can be explained by only the 180° flip of the water molecules. The spectrum at room temperature showed a typical shape due to the rapid 180° flip of water molecules. The change in lineshape of the one-dimensional 2H NMR spectrum is caused by the three-site jump of [Zn(D2O)6]2+ about its C3 axis above 333 K. Information of the reorientation of [Zn(D2O)6]2+ below 333 K could not be obtained from the one-dimensional spectrum and T1. In this temperature range, the two-dimensional exchange spectrum was effective for analysis of molecular motion. The effects of multiple motions, the 180° flip of the water molecules and the reorientation of [Zn(D2O)6]2+ about the C3 axis, on the lineshape of the two-dimensional exchange spectrum were studied using spectral simulation.