Longitudinal nuclear spin relaxation studies in heteronuclear two-spin XH systems in triphenyl derivatives, (C6H5)(3)XH, with X = C-13, Si-29, and Sn-119 are reported. Spin-lattice relaxation times and nuclear Overhauser enhancement factors for the X nuclei have been measured using conventional, one-dimensional NMR experiments characterizing the reorientational dynamics of the three systems in solution. Two-dimensional exchange spectroscopy has been applied to the same systems to measure the interference effects between the dipole-dipole and chemical shift anisotropy (the cross-correlation rates) for both the X nuclei and the protons bonded to them. The results of the one- and two-dimensional experiments are compared and combined in order to estimate the anisotropies of the shielding tensors for the X nuclei and protons. For X = C-13 and Si-29, the shielding anisotropies from the liquid-state relaxation experiments are compared with the measurements on the solid powders.
Cross-correlation effects in two spin systems in (C6H6)3XH, and chemical shift anistropy for 1H and X=13C, 29Si, 119Sn
DI BARI, LORENZO;
1994-01-01
Abstract
Longitudinal nuclear spin relaxation studies in heteronuclear two-spin XH systems in triphenyl derivatives, (C6H5)(3)XH, with X = C-13, Si-29, and Sn-119 are reported. Spin-lattice relaxation times and nuclear Overhauser enhancement factors for the X nuclei have been measured using conventional, one-dimensional NMR experiments characterizing the reorientational dynamics of the three systems in solution. Two-dimensional exchange spectroscopy has been applied to the same systems to measure the interference effects between the dipole-dipole and chemical shift anisotropy (the cross-correlation rates) for both the X nuclei and the protons bonded to them. The results of the one- and two-dimensional experiments are compared and combined in order to estimate the anisotropies of the shielding tensors for the X nuclei and protons. For X = C-13 and Si-29, the shielding anisotropies from the liquid-state relaxation experiments are compared with the measurements on the solid powders.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
