Characterization of the Room-Temperature Structure of SnP2O7 by 31P Through-Space and Through-Bond NMR Correlation Spectroscopy

The room-temperature structure of SnP2O7 has been investigated using various one- and two-dimensional (1- and 2D) magic-angle spinning (MAS) NMR experiments. We show that 31P homonuclear through-bond and through-space correlation NMR spectroscopies allow us to discriminate between the 12 possible space group symmetries of the structure. In particular, the 31P 2D refocused INADEQUATE experiment allows us to resolve an impressive number of distinct 31P resonances, showing that the asymmetric unit contains at least 49 different P2O7 groups with two inequivalent P sites. The results suggest that the symmetry of the SnP2O7 room-temperature structure is monoclinic with space group P21 or Pc.