Combined ab initio Computational and Solid-State17O MAS NMR Studies of Crystalline P2O5.

Abstract

Ab initio calculations of the 1 7 O electrical field gradient (EFG) tensor quadrupolar coupling constant (C Q ) and asymmetry parameter (η Q ), along with the 1 7 O NMR isotropic chemical shift (δ i s o ) for the three crystalline polymorphs of P 2 O 5 are presented. These computational results are compared with experimental values for crystalline h-P 2 O 5 (hexagonal-form) obtained using a combination of solid-state 1 7 O magic angle spinning (MAS) NMR at three different magnetic field strengths (9.4, 14.1, and 19.6 T), two-dimensional (2D) multiple-quantum (MQ)MAS NMR, and 2D satellite-transition (ST)MAS NMR experiments. In addition ab initio studies of the model H 4 P 2 O 7 cluster allowed empirical correlations between the bridging oxygen EFG parameters and the P-O-P bond angle to be developed.