CORRELATION OF ~(51)V NMR PARAMETERS WITH LOCAL ENVIRONMENT OF VANADIUM SITES

摘要

~(51)V NMR parameters are obtained for Li, Cs, Sr, Ba, Al, La, Lu and Y orthovanadates, Sr, Ba and Zr pyrovanadates, as well as for some more complex vanadium compounds (K_3V_5O_(14), Rb_2V_6O_(16) Cs_2V_4O_(11)and VOPO_4). The relation between ~(51)V NMR parameters and vanadium local environment is examined using both new and literature ~(51)V NMR data. Correlation between CS anisotropy and QC constant is presented, and previously known correlation between anisotropy and asymmetry parameters of CS tensor is refined. Definite intervals of parameters characteristic for different types of vanadium environment may be found in these correlations. The correlations clearly indicate that for the characterization of vanadium sites with unknown structure the knowledge of both CS and QC tensors parameters is required. That the most informative are: CS anisotropy, QC constant and CS asymmetry parameter. For one metal, both CS anisotropy and QC constant are growing in the row M_3(VO_4)2, M_2V_2O7 H M(VO_3)_2. At the same time, quadrupole asymmetry parameter is not characteristic. The correlations obtained may be used for ~(51)V NMR studies of vanadium ions in solids, including supported vanadium catalysts.