CESIUM-133 NMR-STUDY OF CSCD(SCN)(3) - RELATIVE ORIENTATION OF THE CHEMICAL-SHIFT AND ELECTRIC-FIELD GRADIENT TENSORS

Single-crystal NMR was used to characterize the cesium-133 chemical sh ift and electric field gradient (EFG) tensors in CsCd(SCN)(3). The pri ncipal axes of the two interaction tensors are not coincident, a refle ction of the general positioning of cesium nuclei within the unit cell . Relative orientations of the chemical shift and EFG tensors have bee n determined, but assignment of the two magnetically distinct sites re mains elusive. The span of the chemical shift, 94.4 ppm, is moderate i n comparison with other cesium salts, and the magnitude of the nuclear quadrupole coupling constant, 148 kHz, is in the midrange of those re ported for cesium compounds. Excellent agreement is observed between e xperimental Cs-133 NMR spectra of a stationary powder sample and spect ra calculated using NMR parameters from the single-crystal analysis. M oreover, simulations indicate that the static line shape is very sensi tive to the relative orientation of the chemical shift and EFG tensors . Experimental Cs-133 NMR spectra obtained with magic-angle and variab le-angle spinning are well reproduced by calculations utilizing single -crystal NMR data.